Exam 2 Learning Objectives with Answers

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Nov 24, 2024

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Exam 2 Learning Objectives with Answers: Chapter 4 1. Be able to explain the differences between a eukaryotic cell and a prokaryotic cell Eukaryotic cells have a defined nucleus and internal membranes (organelles). Prokaryotic cells have no nuclear membrane. Instead, they have a “nucleoid” region, where the DNA is found on a single chromosome. And prokaryotes have no internal membranes (organelles) 2. Know what the nucleoid is and where it is found Nucleoid is found in a prokaryotic cell, in the center of the cytoplasm, and this is where the DNA is located on a single chromosome. 3. Be able to explain the function of the following organelles: Nucleus Contains the DNA in a cell and is the control center. Endoplasmic Reticulum (smooth and rough) Smooth ER makes lipids, including phospholipids and hormones. Rough ER contains ribosomes on its surface, and makes proteins. Golgi Complex This is the shipping / receiving organelle in the cell. Receives vesicles from the ER and ships them to the appropriate places in the cell. Lysosome Very acidic. Used to destroy anything the cell needs to break down. Used for recycling. Ribosome This is where proteins get made. These are protein synthesis machines. Vessicles Packages made of membrane that allow for transport within the cell. Chloroplast Organelle where photosynthesis occurs. Only found in plant cells, some bacteria, and algae. Mitochondria Where cellular respiration occurs. Where food gets broken down to make ATP energy for the cell. Nucleolus The center of the nucleus. Where ribosomes are assembled (made). 4. Be able to describe the structure of the nuclear membrane / envelope The nuclear envelope is a double phospholipid bilayer, meaning there are 4 layers of phospholipids. 5. Be able to describe what chromosomes are made of Chromosomes are made of DNA attached to proteins. 6. Know which organelles are part of the endomembrane system Nucleus, Smooth and the Rough ER, Golgi Apparatus, and the Lysosomes 7. Be able to describe the pathway of a secretory protein Protein gets made on ribosomes on the rough ER membrane. Then it inserts itself into the rough ER and gets enclosed in a vesicle. It then travels in the vesicle to the Golgi Apparatus where it is modified and re-packaged in another vesicle, before being sent to the membrane for exocytosis. 8. Be able to explain how mitochondria and chloroplasts are similar to prokaryotic cells Both of these organelles are semi-autonomous, which means they function almost independently of the cell. Both have ribosomes and DNA, and both organelles make some of their own proteins. Chapter 5
1. What are the 4 functions of the cell membrane: a. Isolate the cell environment b. Communicate c. Exchange d. identify 2. What 2 lines of evidence suggest that the cell membrane is a phospholipid bilayer with proteins associated with it? Phospholipid content of a red blood cells has just enough to cover the cell with 2 layers. Since these cells do not have any internal membranes, then all of the phospholipids have to make up the plasma membrane. Membranes collected from red blood cells contain proteins in addition to lipids 3. Why is the cell membrane described as a fluid-mosaic? Fluid: Because it behaves a lot like a liquid. These phospholipids move around a good bit, similar to the way molecules move within a liquid. Mosaic: There are numerous different proteins, and glycoproteins associated with the membrane. It is composed of several different ingredients. 4. Which directions do phospholipids move, and how often? Phospholipids move laterally 10,000,000 times per second Move transverse, or flip-flop (this means they move from one layer of the phospholipids to the other). Only happens about once a month 5. What are 3 main functions of membrane proteins? Communication, Identification and transport 6. What are glycoproteins, and what are they mainly used for? This is a combination of a sugar/carbohydrate and a protein. Used for cell identification (like an ID tag for a cell) 7. What are some examples and characteristics of passive transport? Passive transport means it does NOT require energy Examples: diffusion, facilitated diffusion, and osmosis Movement is from greater concentration to lesser concentration
The greater the concentration difference, the faster the diffusion Net movement continues until the system reaches equilibrium. Usually occurs over short distances 8. What are the factors that determine the permeability of the membrane to a molecule? Solubility characteristics: the membrane is MOSTLY nonpolar. So anything that is polar or charged, will not cross the membrane without some assistance. Are there any facilitated diffusion mechanisms available? (carrier proteins) 9. What are aquaporins, and why are they necessary? Water channels. Protein channels in the membrane that are permeable to water. Water is too polar to cross the membrane in large quantities on its own (through simple diffusion) 10. List and describe 3 mechanisms for facilitated diffusion. Bind and release: involves a carrier protein that changes shape and transports something down its gradient across the membrane Gated channel: Protein channel in the membrane that has a gate that has to be TOLD to open. It’s not open all the time. Some stimulus has to open it. Selective channel: Protein channel in the membrane that has a pore that only certain things can pass through. 11. Understand everything about osmosis and be able to predict what happens to cells when placed in different environments and why. Osmosis is diffusion of water from an area of low solute / high water to an area of high solute / low water. Water essentially moves from a hypotonic area to a hypertonic area. If a cell loses water, its mass will decrease and it will shrivel. If a cell gains water, its mass will increase and it will swell. 12. Be able to understand relative terms describing solutions of different concentrations (iso, hyper, hypo) Relative terms. Always compares one solution to another. An isotonic solution has the same solute concentration as another solution. A hypertonic solution has a higher solute concentration than another solution. A hypotonic solution has a lower solution concentration than another solution. 13. What is active transport, and what is required for it?
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Movement of a substance across the membrane from an area of low concentration to an area of high concentration. Active transport always requires energy. 14. Be able to define and understand mechanisms for transport of large molecules across membranes (pinocytosis, phagocytosis, exocytosis, receptor-mediated). Phagocytosis (cell eating) any random solid molecule being transported into the cell. Pinocytosis (cell drinking) any random liquid being transported into the cell. Receptor-mediated a SPECIFIC molecule is being transported (usually a hormone or a neurotransmitter) that can recognize and bind to a receptor on the membrane. Exocytosis is anything large being transported OUT of the cell. 15. Be able to define and understand connections between cells. Desmosomes: holds cells together Tight junctions: used for when the connection needs to be water-tight. Can’t leak. Gap junctions are connections between animal cells. Plasmodesmata are connections between plant cells. Chapter 6 1. What are the different types of energy and what are examples of each? Potential energy: energy based on location, or energy found in chemical bonds. Ex: water at the top of a waterfall, or a sugar molecule. Kinetic: energy of movement. Ball rolling down a hill, or a windmill spinning. 2. Be able to explain the first 2 laws of thermodynamics. a. Energy cannot be created or destroyed. There’s a limited amount of energy in the universe. And that number is not changing. b. Every time energy gets transferred or transformed, heat gets released. In terms of usable energy, heat isn’t very useful. Heat cannot usually do work. 3. Is our planet an open energy system or a closed energy system? Why? Open. That means that energy is constantly being resupplied by the sun. Kind of like a laptop plugged into a power outlet. A closed system would be the laptop unplugged, running on just the battery. 4. Know and completely understand everything about endergonic and exergonic reactions, including examples of each.
Endergonic: the products have more energy than the reactants. Energy has to be added for an endergonic reaction to occur. Photosynthesis is one of the most important endergonic reactions on the planet. Exergonic: the reactants have more energy than the products. Energy is released as these reactions occur. Cellular respiration (the breakdown of glucose) is an exergonic reaction. 5. What is activation energy? Which type of reactions requires activation energy? How is this affected by enzymes? Activation energy is the small amount of “starter energy” needed to begin a reaction. ALL reactions require activation energy. Enzymes lower activation energy. 6. What are enzymes? What are they used for? Enzymes are biological catalysts. They are proteins that are used to speed up reactions. They do so by lowering activation energy. They are not destroyed by a reaction. And they have no effect on the energy of the reactants or the products. 7. Explain what happens in coupled reactions. An exergonic reaction (like the breakdown of ATP) releases energy that can be used to power an endergonic reaction (like protein synthesis). 8. Metabolism includes which processes? The sum total of ALL chemical reactions in an organism. Anabolic: builds larger molecules from smaller ones. Requires energy. Catabolic: breaks down larger molecules into smaller ones. Releases energy 9. What is the difference between an anabolic and a catabolic reaction? What are examples of each? Anabolic reactions require energy to BUILD molecules. Example: Photosynthesis Catabolic reactions release energy while BREAKING DOWN molecules. Example: Cellular respiration 10. What is a substrate? Where does the substrate bind the enzyme? A substrate is a reactant in a reaction that gets bound by an enzyme. Binding between the substrate and the enzyme takes place at the active site of the enzyme
11. What are examples of coenzymes? What do they do? Vitamins. Coenzymes are small non-protein molecules that help enzymes function 12. What happens during feedback inhibition? Too much of anything can be harmful to the cell. So we don’t want anything accumulating too much in the cell. It can become toxic. So if a product begins to build up in the cell, that actual product can inhibit an enzyme earlier in the pathway, and stop its own production. 13. What are allosteric enzymes? Where are they usually found? How are they regulated? Allosteric enzymes are enzymes that have an allosteric site to which a regulatory molecule can bind. These are enzymes that are controlled by molecules that bind somewhere on the enzyme OTHER than the active site, and shut it off. These enzymes are usually found in the intermediate steps of a metabolic pathway (In a series of reactions, the intermediate steps are the ones in the middle) 14. What is a competitive inhibitor? How does it affect enzyme activity? A competitive inhibitor is one that binds to the active site. It physically out-competes the substrate for the active site. When the active site is occupied, the substrate can’t bind. So the enzyme is effectively turned “OFF”
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