Biology 1020
Biology 1020
Cell Theory: The principle stating that all organisms of one or more cells, which are the smallest living things and that all cells come from preexisting cells. Cell is the smallest unit of life. (Some organisms are single celled) Tissue is a group of similar cells that perform a function. Organs are several tissues joined together. An organ system is various organs that work together. Complex organisms are a collection of organ systems. Genes allow cells and organisms to reproduce. DNA contains the hereditary information that directs cell structure of the cell and its metabolism. Biodiversity encompasses the total number of species, the variability of their genes and the ecosystems they live in.
Classification: Domain Archea: Capable of living in extreme locations. Aquatic environments that lack oxygen or are too salty, too hot or too acidic for most other organisms. (Unicellular Prokaryotes.)
Domain Bacteria: Found almost everywhere. Found in water, air, soil, atmosphere along with our skin and digestive tracts. (Unicellular Prokaryotes.)
Domain Eukarya:
1. Protista: Complex single cellular and sometimes multicellular. Absorb, photosynthesize or ingest food. (Protozoan, algae, water molds, slime molds.) 2. Fungi: Some unicellular, most multicellular filamentous forms with specialized complex cells. Absorb food. (Molds, yeasts and mushrooms.) 3. Plantae: Multicellular form with specialized cells. Photosynthesize foods. (Mosses, ferns, non-woody and woody flowering plants.) 4. Anamalia: Multicellular form with specialized complex cells. Ingest food. (Invertebrates, fishes, reptiles, amphibians, birds and mammals.)
Cell Anatomy Plasma Membrane: Semi permeable membrane that consists of phospholipid bilayer in which some protein molecules are imbedded. Regulates the entrance and exit of molecules into and out of the cytoplasm.
Cytoplasm: Jelly like fluid (semi fluid medium) inside the cell that holds the cell’s organelles within the cell in place.
Prokaryotic Cells Cell Wall: Located outside of the plasma membrane, contains peptidoglycan, a complex molecule that is unique to bacteria and composed of chains of disaccharides joined by peptide chains. Protects the bacteria.
Capsule/Slime Layer: Surrounds the cell wall. Flagella: Rotating filament, which pushes the cell forward. Fimbrae: Hair like bristles that allow adhesion to surfaces. Nucleoid: A single chromosome located within a region of cytoplasm. It is not bound by any sort of membrane.
Plasmid: Small accessory rings of DNA. Ribsomes: Used in the synthesis of proteins. Thykaloids: Photosynthetic cyanobacteria have light-sensitive pigments usually within the membranes, which resemble flattened disks.
Eukaryotic Cells Cell Walls: Permeable but protective cell wall, in addition to a plasma membrane. Plant cells often have a primary and secondary cell wall. Cellulose molecules make up the cell wall. Secondary cell wall, which forms within the first cell wall, consists of lignin. Often cell walls could consist of chitin.
Nucleus: Prominent structure. Stores genetic material such as DNA, which governs the characteristics and metabolic information for the cell.
Chromatin: DNA and associated proteins. Appears grainy material but is threadlike in structure and undergoes coiling to form chromosomes. Chromatin is immersed in a semi fluid medium known as the nucleoplasm.
Nucleolus: RNA is stored here, called rRNA (ribosomal RNA. Nuclear Envelope: A membrane surrounding the nucleus that separates the nucleus from the cytoplasm.
Nuclear Pores: Small pores that allow proteins to pass through into the nucleus and allows the ribosomal units to pass out.
Ribosomes: Composed of two types of units, small and large. rRNA and protein molecules which comprise ribosomes can be found individually in ribosome form in the cytoplasm. They can also be found in groups called polyribosomes. Ribosomes are often found attached to endoplasmic reticulum. Proteins synthesized and attached to the endoplasmic reticulum have different destinations than those floating freely in the cytoplasm.
Endoplasmic Reticulum: Complicated system of membranous channels and saccules. Continuous with the outer membrane of the nuclear envelope. Rough ER is studded with ribosomes on the side of the membrane that faces the cytoplasm. Proteins are synthesized here and enter the ER interior where modification and processing begin, without the protein in the proper place the cell is unable to regulate itself resulting in various symptoms of diseases. Smooth ER is continuous off the rough ER does not have ribosomes. Smooth ER synthesizes the phospholipids that occur in membranes and performs
various other functions depending on the particular cell. ER also forms vesicles which products are transported to the Golgi Apparatus.
Golgi Apparatus: Named for Camillo Golgi who discovered it in 1898. The Golgi consists of 3 – 20 stacked slightly curved saccules. This organelle is used for the collecting, sorting and distributing proteins and lipids within the cell. The Golgi receives proteins and lipid filled vesicles from the ER and then passes through the Golgi Apparatus and the proteins and lipids are modified before they are repackaged into vesicles. Repackaging occurs in the form of secretory vesicles, which travel to the plasma membrane where they discharge their contents.
Lysosomes: Membrane bound vesicles produced by the Golgi Apparatus, they contain hydrolytic digestive enzymes.
Vacuole: A large membranous sac. Larger than a vesicles, very prominent in plant cells which stores substances. Often they contain pigments, which is responsible for the coloring of the plant, or they contents could be toxic substances which help protect the plant from herbivorous animals.
Peroxisomes: Are similar to Lysosomes in regards to being a membranebounded vesicle with enclosed enzymes. However, the enzymes in peroxisomes are synthesized by the cytoplasmic ribsomes and transported to the peroxisome by carrier proteins. Peroxisomes enzyme actions often result in hydrogen peroxide. Hydrogen Peroxide is immediately broken down to water and oxygen peroxisomal enzyme called catalase. However, the enzyme present in the peroxisome depends on the function of the cell.
Chloroplasts: Specialize in converting energy to a form the (plant) cell can use. Bounded by two membranes that enclose a fluid filled place known as the stroma. The membrane inside the stroma is organized into interconnected flattened sacs called thykaloids. The thykaloids are stacked up in structures called grana, often there are hundreds of grana inside of the cell. Chloroplasts are used to synthesize carbohydrates, which are then broken down in the mitochondria.
Mitochondria: Bounded by a double membrane. The inner fluid filled area is called the matrix, it contains DNA, ribosomes and enzymes that break down carbohydrate products releasing energy to be used for ATP production. The inner membrane opens to form cristae which increases surface area to accommodate the protein complexes and other participants that produce ATP.
Cytoskeleton: The protein components of the cytoskeleton are interconnected and extend from the nucleus to the plasma membrane. The cytoskeleton contains actin filaments, intermediate filaments and microtubules which maintain the shape of the cell and allows the organelles and the cell to move.
Actin Filament: long extremely thin yet flexible fibers that occur in bundles or meshlike networks. Play a structural role when they form a dense complex web just under the plasma membrane; they are anchored here by special proteins. They are also seen as Microvilli that project from intestinal cells.
Intermediate Filaments: Intermediate in size between actin filaments and microtubules, they perform a structural role in the cell. They are a ropelike assembly of fibrous polypeptides. Intermediate filaments support the nuclear envelope while others support the plasma membrane.
Microtubules: Small hollow cylinders, made up of the globular protein tubulin. They have 13 rows of tubulin dimmers, surrounding what appears to be an empty core. The microtubule-organizing centre is in the centrosome of most cells, which lies near the nucleus. They radiate from the centrosome helping maintain the shape of the cell and acting as tracks along which organelles can move. Before the cell divides microtubules disassemble and reassemble into the structure called the spindle that distributes the chromosomes in an orderly manner, at the end of cell division the spindle disassembles and the reassembles into microtubules.
Centrioles: Short cylinders with a 9+0 patter in microtubule triplets. (A ring has nine sets of triplets with none in the middle) In animal cells
centrosomes contain 2 centrioles lying at right angles to one another. The centrosome is the major microtubule-organizing centre for the cell. During division centrosomes function to organize and function to organize the meiotic spindle. Plant cells have the equivalent of a centrosome but it does not contain centrioles since they are not necessary to the assembly of cytoplasmic microtubules.
Cilia/Flagella: Hair like projections that can move either in an undulating fashion like a whip or stiffly like an oar. Cells, which have these organelles, are capable of movement. Both cilia and flagella are membrane bound cylinders enclosing a matrix area. In the matrix there are 9 microtubules surrounding 2 central microtubules. Cilia and Flagella move when the microtubule doublets slide past one another.
Labs Lab 1 Workplace Hazardous Material Information System (WHMIS) Material Safety Data Sheet (MSDS)
Lab 3 1. What are the chemical constitutions of the plasma membrane and how are they arranged? The chemical composition of the Plasma membrane is: Proteins Lipids Carbohydrates Enzymes Water It is composed of a phospholipid bilayer with the hydrophilic/polar heads of the of the phospholipids facing outward and the hydrophobic/nonpolar tails facing inward. There is an array of amphipathic proteins used in cell to cell recognition,transport via passive or active transport, etc.There are glycoproteins mainly facing the extracelluar matrix and some cholestrol molecules to maintain the membranes fluidity.
2. Give three functions of the plasma membrane. a.
Controls materials that move in and out of the cell
b. Maintains cell shape and stabilizes the location of certain membrane proteins c.
Cell communication and recognition
3. What is the concentration gradient? A concentration gradient is when there is an uneven distribution of a substance across a border. For example, think of a balloon. The air inside the balloon is more concentrated than the air outside of it. There is a concentration gradient because of the differences in concentration. And what happens when you release the tip of the balloon? The air inside the balloon shoots out because things like it when the concentration is equal everywhere. So when something moves against its concentration gradient, it is being forced from an area where it is less concentrated into a place where it is more concentrated. Conversely, when something moves down its concentration gradient, it is going from a place where it is more concentrated to
where it is less concentrated. However, it is important to note that energy must be expended for something to go against the concentration gradient, but no energy needs to be used to move something down its concentration gradient.
4. Name one physical process that may limit the size at which a cell can grow. The ratio of volume to cell surface, if it gets too big, it will take too long or become unable to transport necessary molecules and nutrients throughout the cell as needed.
5. What is a semi-permeable membrane? A semipermeable membrane, also termed a selectively permeable membrane or a differentially permeable membrane, is a membrane which will allow certain molecules or ions to pass through it by diffusion and occasionally specialised "facilitated diffusion". The rate of passage depends on the pressure, concentration and temperature of the molecules or solutes on either side, as well as the permeability of the membrane to each solute. Depending on the membrane and the solute, permeability may depend on solute size, solubility properties, or chemistry. An example of a semi-permeable membrane is a lipid bilayer, on which is based the plasma membrane that surrounds all biological cells. Many natural and synthetic materials thicker than a membrane are also semipermeable. An example of this is the thin film on the inside of an egg.
6. What is osmosis? Osmosis is the diffusion of the movement of water from a region of higher concentration to a region of lower concentration through a cell membrane or other semi-permeable membrane until an equilibrium is reached. It is a special case of diffusion (passive transport).
7. What is osmotic pressure? Osmotic pressure is the hydrostatic pressure produced by a solution in a space divided by a semipermeable membrane due to a differential in the concentrations of solute. Osmotic potential is the opposite of water potential with the former meaning the degree to which a solvent (usually water) would want to stay in a liquid. When a biological cell is in a hypotonic environment (the cell interior contains a lower concentration of water and a higher concentration of other molecules than its exterior), water flows across the cell membrane into the cell, causing it to expand due to osmotic pressure. In plant cells, the cell wall restricts the expansion, resulting in pressure on the cell wall from within called turgor pressure. The osmotic pressure π of a dilute solution can be calculated using the formula
π = iMRT, where i is the van 't Hoff factor M is the molarity R is the gas constant, where R = 0.08206 L · atm · mol-1 · K-1 T is the thermodynamic temperature (formerly called absolute temperature)
8. Describe the “fluid mosaic” concept of membrane structure. The fluid mosaic model states that proteins float in a sea of lipids. A cell membrane is composed of lipids arranged with their hydrophobic tails touching each other, with proteins scattered throughout. The proteins may either be integral, meaning that they span the entire membrane, or peripheral, meaning they stay outside of the cell only loosely associated with the membrane. This membrane fluidity can be experimentally showed using a technique called FRAP (florescent recovery after photobleaching). Things that effect membrane fluidity include: a.
lipid tail length - shorter tails = more fluid at low temps
b. degree of saturation - less saturation = more fluid at lower temps Also, cholesterol tends to keep membranes at an intermediate fluidity.
9. What is the difference between active and passive transport? Give oneway by which active transport might be brought about? Active transport is the movement of molecules across a membrane requiring energy to be expanded by the cell. ACTIVE TRANSPORT REQUIRES ENERGY. Passive transport is diffusion across a membrane requiring only random motion of molecules with no energy expanded by the cell. Osmosis is an example of this. PASSIVE TRANSPORT REQUIRES NO ENERGY
10. List some factors, which affect permeability of substances through living membranes? a.
· Molecular size of the solute as the permeability mostly decreases with increasing size.
b. Lipid solubility’s permeability usually increases with increasing fat or oil solubility. c.
The degree of ionization as permeability mostly decreases with increased ionization.
d. The pH and temperature also have great effect on the permeability of the plasma membrane.
11. Understand the terms Phagocytosis and Pinocytosis. The main difference between Phagocytosis and Pinocytosis is that Phagocytosis occurs when the small vesicle engulfs around a solid particle, but Pinocytosis, which can also be referred to as being "cell drinking", occurs when the small vesicle engulfs a liquid particle.
12. Understand the terms of isomotic (isotonic), hypoosmotic (hypotonic), and hyperosmotic (hypertonic). Isotonic – it means that the solution does not change the volume of the cell Hypotonic – it means that the solution causes a cell to swell Hypertonic – it means that the solution causes a cell to shrink
13. What happens to a cell placed in a hypertonic (hypersmotic) solution? In a hypotonic (hyposmotic)? What can you ay about the flow of water across the membrane of a cell placed in an isosomotic (isotonic) solution? 14. What is a vacuole? Is there any difference between plant and animal cells with respect to the vacuole? Plant cell vacuoles are a Permanent feature. One central vacuole occupies 60%-90% of the cell space depending on how much water it contains at a given time. Animal cell vacuoles are smaller any many in number and are temporary or disappear at times. They help digest food.
15. Name as many structures possible that are found inside the nuclear membrane? 16. What are the main functions of the nucleus? The nucleus is the information center for the cell and the storehouse of the genetic information (DNA) that directs all of the activities of a living eukaryotic cell it also
controls enzymes. It also controls the cell when to duplicate itself. It is usually the largest organelle in a eukaryotic cell and contains the chromosomes.
17. What effect does the cell wall have on the results of placing a plant cell in the hypoosmothic (hypotonic) solution? Plant cells are enclosed by a rigid cell wall. When the plant cell is placed in a hypotonic solution, it takes up water by osmosis and starts to swell, but the cell wall prevents it from bursting. The plant cell is said to have become "turgid" i.e. swollen and hard. The pressure inside the cell rises until this internal pressure is equal to the pressure outside. This liquid or hydrostatic pressure called the turgor pressure prevents further net intake of water. Turgidity is very important to plants as it helps in the maintenance of rigidity and stability of plant tissue and as each cell exerts a turgor pressure on its neighbor adding up to plant tissue tension which allows the green parts of the plant to "stand up" into the sunlight.
18. What is a turgid cell? What is turgor pressure? A plasmolyzed cell? turgid = swollen There is a limit to the amount of water that can enter the cell. The cell reaches this limit when the osmotic pressure attracting water into the vacuole is countered by the inward mechanical pressure exerted by the cell wall. A turgid cell is a plant cell whose vacuole contains the maximum amount of water. The water has entered by osmosis, because the vacuole is hypertonic to the solution outside the cell. Turgor pressure is accomplished when there is a sufficient amount of water entering a plant cell. This happens by inward osmosis and increases when a plant cell is in a hypotonic environment. a plasmolyzed cell is a cell that has been placed in a hypertonic solution and most of the water has left. Thus, it looks like a shriveled up prune or raisin due to the water loss.
19. What is the difference between the plasma membrane and the cell wall of a plant cell? The membrane is thin bi-lipid (two-fat) layer that blocks out water. The cell wall is a rigid cube like structure that surrounds a plant cell and gives it rigidity
20. List as many organelles as you can that would be found in a typical plant cell but not in an animal cell. Draw a typical plant cell. Plant cells have two organelles that animal cells do not have: a large central vacuole and chloroplasts & Plastids.
21. List as many organelles as you can that would be found in the a typical animal cell but not in a typical plant cell. Draw a typical animal cell. Animal cells have centrioles & a cytoskeleton.
22. Be able to distinguish between prokaryotic cells and eukaryotic cells.
- Prokaryotic cells do not have a nucleus and eukaryotic cells do. - Prokaryotic cells lack some organelles and eukaryotic cells do not. - Prokaryotic cells are not found in humans and eukaryotic cells are. - Prokaryotic cells are always unicellular and eukaryotic cells are often multicellular. - Prokaryotic cells reproduce/divide by binary fission and eukaryotic cells reproduce/divide by mitosis/meiosis
Cell Theory: The principle stating that all organisms of one or more cells, which are the smallest living things and that all cells come from preexisting cells. Cell is the smallest unit of life. (Some organisms are single celled) Tissue is a group of similar cells that perform a function. Organs are several tissues joined together. An organ system is various organs that work together. Complex organisms are a collection of organ systems. Genes allow cells and organisms to reproduce. DNA contains the hereditary information that directs cell structure of the cell and its metabolism. Biodiversity encompasses the total number of species, the variability of their genes and the ecosystems they live in.
Classification: Domain Archea: Capable of living in extreme locations. Aquatic environments that lack oxygen or are too salty, too hot or too acidic for most other organisms. (Unicellular Prokaryotes.)
Domain Bacteria: Found almost everywhere. Found in water, air, soil, atmosphere along with our skin and digestive tracts. (Unicellular Prokaryotes.)
Domain Eukarya:
1. Protista: Complex single cellular and sometimes multicellular. Absorb, photosynthesize or ingest food. (Protozoan, algae, water molds, slime molds.) 2. Fungi: Some unicellular, most multicellular filamentous forms with specialized complex cells. Absorb food. (Molds, yeasts and mushrooms.) 3. Plantae: Multicellular form with specialized cells. Photosynthesize foods. (Mosses, ferns, non-woody and woody flowering plants.) 4. Anamalia: Multicellular form with specialized complex cells. Ingest food. (Invertebrates, fishes, reptiles, amphibians, birds and mammals.)
Cell Anatomy Plasma Membrane: Semi permeable membrane that consists of phospholipid bilayer in which some protein molecules are imbedded. Regulates the entrance and exit of molecules into and out of the cytoplasm.
Cytoplasm: Jelly like fluid (semi fluid medium) inside the cell that holds the cell’s organelles within the cell in place.
Prokaryotic Cells Cell Wall: Located outside of the plasma membrane, contains peptidoglycan, a complex molecule that is unique to bacteria and composed of chains of disaccharides joined by peptide chains. Protects the bacteria.
Capsule/Slime Layer: Surrounds the cell wall. Flagella: Rotating filament, which pushes the cell forward. Fimbrae: Hair like bristles that allow adhesion to surfaces. Nucleoid: A single chromosome located within a region of cytoplasm. It is not bound by any sort of membrane.
Plasmid: Small accessory rings of DNA. Ribsomes: Used in the synthesis of proteins. Thykaloids: Photosynthetic cyanobacteria have light-sensitive pigments usually within the membranes, which resemble flattened disks.
Eukaryotic Cells Cell Walls: Permeable but protective cell wall, in addition to a plasma membrane. Plant cells often have a primary and secondary cell wall. Cellulose molecules make up the cell wall. Secondary cell wall, which forms within the first cell wall, consists of lignin. Often cell walls could consist of chitin.
Nucleus: Prominent structure. Stores genetic material such as DNA, which governs the characteristics and metabolic information for the cell.
Chromatin: DNA and associated proteins. Appears grainy material but is threadlike in structure and undergoes coiling to form chromosomes. Chromatin is immersed in a semi fluid medium known as the nucleoplasm.
Nucleolus: RNA is stored here, called rRNA (ribosomal RNA. Nuclear Envelope: A membrane surrounding the nucleus that separates the nucleus from the cytoplasm.
Nuclear Pores: Small pores that allow proteins to pass through into the nucleus and allows the ribosomal units to pass out.
Ribosomes: Composed of two types of units, small and large. rRNA and protein molecules which comprise ribosomes can be found individually in ribosome form in the cytoplasm. They can also be found in groups called polyribosomes. Ribosomes are often found attached to endoplasmic reticulum. Proteins synthesized and attached to the endoplasmic reticulum have different destinations than those floating freely in the cytoplasm.
Endoplasmic Reticulum: Complicated system of membranous channels and saccules. Continuous with the outer membrane of the nuclear envelope. Rough ER is studded with ribosomes on the side of the membrane that faces the cytoplasm. Proteins are synthesized here and enter the ER interior where modification and processing begin, without the protein in the proper place the cell is unable to regulate itself resulting in various symptoms of diseases. Smooth ER is continuous off the rough ER does not have ribosomes. Smooth ER synthesizes the phospholipids that occur in membranes and performs
various other functions depending on the particular cell. ER also forms vesicles which products are transported to the Golgi Apparatus.
Golgi Apparatus: Named for Camillo Golgi who discovered it in 1898. The Golgi consists of 3 – 20 stacked slightly curved saccules. This organelle is used for the collecting, sorting and distributing proteins and lipids within the cell. The Golgi receives proteins and lipid filled vesicles from the ER and then passes through the Golgi Apparatus and the proteins and lipids are modified before they are repackaged into vesicles. Repackaging occurs in the form of secretory vesicles, which travel to the plasma membrane where they discharge their contents.
Lysosomes: Membrane bound vesicles produced by the Golgi Apparatus, they contain hydrolytic digestive enzymes.
Vacuole: A large membranous sac. Larger than a vesicles, very prominent in plant cells which stores substances. Often they contain pigments, which is responsible for the coloring of the plant, or they contents could be toxic substances which help protect the plant from herbivorous animals.
Peroxisomes: Are similar to Lysosomes in regards to being a membranebounded vesicle with enclosed enzymes. However, the enzymes in peroxisomes are synthesized by the cytoplasmic ribsomes and transported to the peroxisome by carrier proteins. Peroxisomes enzyme actions often result in hydrogen peroxide. Hydrogen Peroxide is immediately broken down to water and oxygen peroxisomal enzyme called catalase. However, the enzyme present in the peroxisome depends on the function of the cell.
Chloroplasts: Specialize in converting energy to a form the (plant) cell can use. Bounded by two membranes that enclose a fluid filled place known as the stroma. The membrane inside the stroma is organized into interconnected flattened sacs called thykaloids. The thykaloids are stacked up in structures called grana, often there are hundreds of grana inside of the cell. Chloroplasts are used to synthesize carbohydrates, which are then broken down in the mitochondria.
Mitochondria: Bounded by a double membrane. The inner fluid filled area is called the matrix, it contains DNA, ribosomes and enzymes that break down carbohydrate products releasing energy to be used for ATP production. The inner membrane opens to form cristae which increases surface area to accommodate the protein complexes and other participants that produce ATP.
Cytoskeleton: The protein components of the cytoskeleton are interconnected and extend from the nucleus to the plasma membrane. The cytoskeleton contains actin filaments, intermediate filaments and microtubules which maintain the shape of the cell and allows the organelles and the cell to move.
Actin Filament: long extremely thin yet flexible fibers that occur in bundles or meshlike networks. Play a structural role when they form a dense complex web just under the plasma membrane; they are anchored here by special proteins. They are also seen as Microvilli that project from intestinal cells.
Intermediate Filaments: Intermediate in size between actin filaments and microtubules, they perform a structural role in the cell. They are a ropelike assembly of fibrous polypeptides. Intermediate filaments support the nuclear envelope while others support the plasma membrane.
Microtubules: Small hollow cylinders, made up of the globular protein tubulin. They have 13 rows of tubulin dimmers, surrounding what appears to be an empty core. The microtubule-organizing centre is in the centrosome of most cells, which lies near the nucleus. They radiate from the centrosome helping maintain the shape of the cell and acting as tracks along which organelles can move. Before the cell divides microtubules disassemble and reassemble into the structure called the spindle that distributes the chromosomes in an orderly manner, at the end of cell division the spindle disassembles and the reassembles into microtubules.
Centrioles: Short cylinders with a 9+0 patter in microtubule triplets. (A ring has nine sets of triplets with none in the middle) In animal cells
centrosomes contain 2 centrioles lying at right angles to one another. The centrosome is the major microtubule-organizing centre for the cell. During division centrosomes function to organize and function to organize the meiotic spindle. Plant cells have the equivalent of a centrosome but it does not contain centrioles since they are not necessary to the assembly of cytoplasmic microtubules.
Cilia/Flagella: Hair like projections that can move either in an undulating fashion like a whip or stiffly like an oar. Cells, which have these organelles, are capable of movement. Both cilia and flagella are membrane bound cylinders enclosing a matrix area. In the matrix there are 9 microtubules surrounding 2 central microtubules. Cilia and Flagella move when the microtubule doublets slide past one another.
Labs Lab 1 Workplace Hazardous Material Information System (WHMIS) Material Safety Data Sheet (MSDS)
Lab 3 1. What are the chemical constitutions of the plasma membrane and how are they arranged? The chemical composition of the Plasma membrane is: Proteins Lipids Carbohydrates Enzymes Water It is composed of a phospholipid bilayer with the hydrophilic/polar heads of the of the phospholipids facing outward and the hydrophobic/nonpolar tails facing inward. There is an array of amphipathic proteins used in cell to cell recognition,transport via passive or active transport, etc.There are glycoproteins mainly facing the extracelluar matrix and some cholestrol molecules to maintain the membranes fluidity.
2. Give three functions of the plasma membrane. a.
Controls materials that move in and out of the cell
b. Maintains cell shape and stabilizes the location of certain membrane proteins c.
Cell communication and recognition
3. What is the concentration gradient? A concentration gradient is when there is an uneven distribution of a substance across a border. For example, think of a balloon. The air inside the balloon is more concentrated than the air outside of it. There is a concentration gradient because of the differences in concentration. And what happens when you release the tip of the balloon? The air inside the balloon shoots out because things like it when the concentration is equal everywhere. So when something moves against its concentration gradient, it is being forced from an area where it is less concentrated into a place where it is more concentrated. Conversely, when something moves down its concentration gradient, it is going from a place where it is more concentrated to
where it is less concentrated. However, it is important to note that energy must be expended for something to go against the concentration gradient, but no energy needs to be used to move something down its concentration gradient.
4. Name one physical process that may limit the size at which a cell can grow. The ratio of volume to cell surface, if it gets too big, it will take too long or become unable to transport necessary molecules and nutrients throughout the cell as needed.
5. What is a semi-permeable membrane? A semipermeable membrane, also termed a selectively permeable membrane or a differentially permeable membrane, is a membrane which will allow certain molecules or ions to pass through it by diffusion and occasionally specialised "facilitated diffusion". The rate of passage depends on the pressure, concentration and temperature of the molecules or solutes on either side, as well as the permeability of the membrane to each solute. Depending on the membrane and the solute, permeability may depend on solute size, solubility properties, or chemistry. An example of a semi-permeable membrane is a lipid bilayer, on which is based the plasma membrane that surrounds all biological cells. Many natural and synthetic materials thicker than a membrane are also semipermeable. An example of this is the thin film on the inside of an egg.
6. What is osmosis? Osmosis is the diffusion of the movement of water from a region of higher concentration to a region of lower concentration through a cell membrane or other semi-permeable membrane until an equilibrium is reached. It is a special case of diffusion (passive transport).
7. What is osmotic pressure? Osmotic pressure is the hydrostatic pressure produced by a solution in a space divided by a semipermeable membrane due to a differential in the concentrations of solute. Osmotic potential is the opposite of water potential with the former meaning the degree to which a solvent (usually water) would want to stay in a liquid. When a biological cell is in a hypotonic environment (the cell interior contains a lower concentration of water and a higher concentration of other molecules than its exterior), water flows across the cell membrane into the cell, causing it to expand due to osmotic pressure. In plant cells, the cell wall restricts the expansion, resulting in pressure on the cell wall from within called turgor pressure. The osmotic pressure π of a dilute solution can be calculated using the formula
π = iMRT, where i is the van 't Hoff factor M is the molarity R is the gas constant, where R = 0.08206 L · atm · mol-1 · K-1 T is the thermodynamic temperature (formerly called absolute temperature)
8. Describe the “fluid mosaic” concept of membrane structure. The fluid mosaic model states that proteins float in a sea of lipids. A cell membrane is composed of lipids arranged with their hydrophobic tails touching each other, with proteins scattered throughout. The proteins may either be integral, meaning that they span the entire membrane, or peripheral, meaning they stay outside of the cell only loosely associated with the membrane. This membrane fluidity can be experimentally showed using a technique called FRAP (florescent recovery after photobleaching). Things that effect membrane fluidity include: a.
lipid tail length - shorter tails = more fluid at low temps
b. degree of saturation - less saturation = more fluid at lower temps Also, cholesterol tends to keep membranes at an intermediate fluidity.
9. What is the difference between active and passive transport? Give oneway by which active transport might be brought about? Active transport is the movement of molecules across a membrane requiring energy to be expanded by the cell. ACTIVE TRANSPORT REQUIRES ENERGY. Passive transport is diffusion across a membrane requiring only random motion of molecules with no energy expanded by the cell. Osmosis is an example of this. PASSIVE TRANSPORT REQUIRES NO ENERGY
10. List some factors, which affect permeability of substances through living membranes? a.
· Molecular size of the solute as the permeability mostly decreases with increasing size.
b. Lipid solubility’s permeability usually increases with increasing fat or oil solubility. c.
The degree of ionization as permeability mostly decreases with increased ionization.
d. The pH and temperature also have great effect on the permeability of the plasma membrane.
11. Understand the terms Phagocytosis and Pinocytosis. The main difference between Phagocytosis and Pinocytosis is that Phagocytosis occurs when the small vesicle engulfs around a solid particle, but Pinocytosis, which can also be referred to as being "cell drinking", occurs when the small vesicle engulfs a liquid particle.
12. Understand the terms of isomotic (isotonic), hypoosmotic (hypotonic), and hyperosmotic (hypertonic). Isotonic – it means that the solution does not change the volume of the cell Hypotonic – it means that the solution causes a cell to swell Hypertonic – it means that the solution causes a cell to shrink
13. What happens to a cell placed in a hypertonic (hypersmotic) solution? In a hypotonic (hyposmotic)? What can you ay about the flow of water across the membrane of a cell placed in an isosomotic (isotonic) solution? 14. What is a vacuole? Is there any difference between plant and animal cells with respect to the vacuole? Plant cell vacuoles are a Permanent feature. One central vacuole occupies 60%-90% of the cell space depending on how much water it contains at a given time. Animal cell vacuoles are smaller any many in number and are temporary or disappear at times. They help digest food.
15. Name as many structures possible that are found inside the nuclear membrane? 16. What are the main functions of the nucleus? The nucleus is the information center for the cell and the storehouse of the genetic information (DNA) that directs all of the activities of a living eukaryotic cell it also
controls enzymes. It also controls the cell when to duplicate itself. It is usually the largest organelle in a eukaryotic cell and contains the chromosomes.
17. What effect does the cell wall have on the results of placing a plant cell in the hypoosmothic (hypotonic) solution? Plant cells are enclosed by a rigid cell wall. When the plant cell is placed in a hypotonic solution, it takes up water by osmosis and starts to swell, but the cell wall prevents it from bursting. The plant cell is said to have become "turgid" i.e. swollen and hard. The pressure inside the cell rises until this internal pressure is equal to the pressure outside. This liquid or hydrostatic pressure called the turgor pressure prevents further net intake of water. Turgidity is very important to plants as it helps in the maintenance of rigidity and stability of plant tissue and as each cell exerts a turgor pressure on its neighbor adding up to plant tissue tension which allows the green parts of the plant to "stand up" into the sunlight.
18. What is a turgid cell? What is turgor pressure? A plasmolyzed cell? turgid = swollen There is a limit to the amount of water that can enter the cell. The cell reaches this limit when the osmotic pressure attracting water into the vacuole is countered by the inward mechanical pressure exerted by the cell wall. A turgid cell is a plant cell whose vacuole contains the maximum amount of water. The water has entered by osmosis, because the vacuole is hypertonic to the solution outside the cell. Turgor pressure is accomplished when there is a sufficient amount of water entering a plant cell. This happens by inward osmosis and increases when a plant cell is in a hypotonic environment. a plasmolyzed cell is a cell that has been placed in a hypertonic solution and most of the water has left. Thus, it looks like a shriveled up prune or raisin due to the water loss.
19. What is the difference between the plasma membrane and the cell wall of a plant cell? The membrane is thin bi-lipid (two-fat) layer that blocks out water. The cell wall is a rigid cube like structure that surrounds a plant cell and gives it rigidity
20. List as many organelles as you can that would be found in a typical plant cell but not in an animal cell. Draw a typical plant cell. Plant cells have two organelles that animal cells do not have: a large central vacuole and chloroplasts & Plastids.
21. List as many organelles as you can that would be found in the a typical animal cell but not in a typical plant cell. Draw a typical animal cell. Animal cells have centrioles & a cytoskeleton.
22. Be able to distinguish between prokaryotic cells and eukaryotic cells.
- Prokaryotic cells do not have a nucleus and eukaryotic cells do. - Prokaryotic cells lack some organelles and eukaryotic cells do not. - Prokaryotic cells are not found in humans and eukaryotic cells are. - Prokaryotic cells are always unicellular and eukaryotic cells are often multicellular. - Prokaryotic cells reproduce/divide by binary fission and eukaryotic cells reproduce/divide by mitosis/meiosis
