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4. Exocytosis:
- The process by which cells release substances (like waste or proteins) to the outside by forming a vesicle that fuses with the cell membrane.
5. Endocytosis:
- The process by which cells take in substances from the outside by engulfing them into a vesicle.
6. Tonicity:
- Describes the concentration of solutes in a solution compared to another solution.
- Isotonic: Equal solute concentration inside and outside the cell.
- Hypotonic: Lower solute concentration outside the cell, so water enters the cell.
- Hypertonic: Higher solute concentration outside the cell, so water leaves the cell.
7. Osmosis:
- The movement of water across a semipermeable membrane from an area of low solute concentration to an area of high solute concentration.
8. Diffusion:
- The movement of molecules (like gases or small particles) from an area of high concentration to an area of low concentration.
9. Extracellular Fluid:
- The fluid outside the cells, including blood plasma and interstitial fluid.
10. Intracellular Fluid:
- The fluid inside the cells, also called cytoplasm.
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### Study Guide Questions:
1. Describe the structure of the cell membrane.
The cell membrane is made up of a phospholipid bilayer, with phospholipids arranged so that their hydrophilic "heads" face the outside and inside of the cell (toward water), while their hydrophobic "tails" face each other, away from water. This creates a semi-permeable barrier. The membrane also contains proteins, cholesterol, and other molecules.
2. How does the structure of the cell membrane affect its function? What IS its function?
The structure of the cell membrane allows it to be semi-permeable, meaning it controls what enters and leaves the cell. The phospholipid bilayer is flexible and fluid, allowing the membrane to adjust and interact with different substances. The function of the membrane is to protect the cell, communicate with other cells, and regulate the flow of materials into and out of the cell.
3. Why is the cell membrane said to be a fluid mosaic?
The cell membrane is called a fluid mosaic because it is flexible (fluid) and made up of many different components (mosaic), such as phospholipids, proteins, and cholesterol, all moving around within the layer.
4. What roles do proteins play in the cell membrane?
Proteins in the cell membrane have several roles:
- Transport proteins help move substances across the membrane.
- Receptor proteins receive signals from outside the cell.
- Enzymatic proteins catalyze chemical reactions.
- Structural proteins help maintain the cell’s shape.
5. What roles does cholesterol play in the cell membrane?
Cholesterol helps stabilize the cell membrane by preventing it from becoming too rigid or too fluid. It helps the membrane maintain its flexibility across different temperatures.
6. How do substances get into and out of the cell?
Substances move into and out of the cell through different mechanisms:
- Passive transport (no energy required) includes diffusion and osmosis.
- Active transport (requires energy) uses transport proteins to move substances against a concentration gradient.
7. Compare and contrast active and passive transport.
- Passive Transport: Moves substances from high to low concentration without using energy (e.g., diffusion, osmosis).
- Active Transport: Moves substances from low to high concentration, requiring energy (ATP) (e.g., sodium-potassium pump).
8. Compare and contrast simple diffusion and facilitated diffusion.
- Simple Diffusion: Small molecules, like oxygen or carbon dioxide, move directly through the membrane from high to low concentration.
- Facilitated Diffusion: Larger or charged molecules move through the membrane with the help of a protein channel (still from high to low concentration, but with help).
9. Compare and contrast endocytosis and exocytosis.
- Endocytosis: The cell takes in substances by engulfing them into a vesicle (e.g., when cells take in nutrients).
- Exocytosis: The cell expels substances by vesicles fusing with the membrane (e.g., releasing waste or proteins outside the cell).
10. Define osmosis.
Osmosis is the movement of water across a semipermeable membrane from an area of low solute concentration to an area of high solute concentration.
11. Describe the concept of tonicity.
- Isotonic: Same solute concentration inside and outside the cell (no water movement).
- Hypotonic: Lower solute concentration outside the cell, water moves into the cell (cell may swell).
- Hypertonic: Higher solute concentration outside the cell, water moves out of the cell (cell may shrink).
12. Given a specific example, be able to determine if and in which direction water and/or solutes would flow between two compartments divided by a semipermeable membrane.
- Example: If you have a hypotonic solution on the outside of the cell and higher solute concentration inside the cell, water will flow into the cell to balance the concentrations.
- If you have a hypertonic solution outside the cell, water will flow out of the cell to balance the solute concentration.
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### Vocabulary Definitions:
1. Mitochondrion:
- Outer membrane: The outer boundary of the mitochondrion.
- Inner membrane: The membrane inside the mitochondrion, where the electron transport chain (ETC) and ATP synthase are located.
- Intermembrane space: The space between the outer and inner membranes of the mitochondrion.
- Matrix: The fluid-filled space inside the inner membrane where the Krebs cycle takes place.
2. Glycolysis:
- The breakdown of glucose (6-carbon molecule) into two molecules of pyruvate (3-carbon molecules), producing small amounts of ATP and NADH in the cytoplasm.
3. Krebs/Citric Acid Cycle:
- A cycle of reactions in the mitochondria that processes acetyl-CoA (derived from pyruvate) to produce NADH, FADH2, ATP, and carbon dioxide (CO2).
4. Oxidative Phosphorylation:
- The final stage of cellular respiration, involving the electron transport chain (ETC) and chemiosmosis, where ATP is produced using energy from electrons carried by NADH and FADH2. Oxygen acts as the final electron acceptor.
5. NADH, FADH2:
- NADH and FADH2 are electron carriers that transport electrons to the electron transport chain during cellular respiration.
6. Glucose/Pyruvate/Acetyl-CoA:
- Glucose: A simple sugar that is the starting point for cellular respiration.
- Pyruvate: The product of glycolysis, a 3-carbon molecule that is further processed into acetyl-CoA.
- Acetyl-CoA: The molecule that enters the Krebs cycle after pyruvate is converted.
7. ATP Synthase:
- An enzyme that synthesizes ATP from ADP and inorganic phosphate (Pi) during oxidative phosphorylation, using the energy from a proton gradient (H+).
8. Fermentation:
- An anaerobic process that allows cells to generate ATP without oxygen, typically producing lactic acid (in animals) or ethanol and CO2 (in yeast).
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### Study Guide Questions:
1. What is the chemical equation that describes cellular respiration?
The general equation for cellular respiration is:
\[ \text{Glucose (C}_6\text{H}_12\text{O}_6\text{) + 6O}_2 \rightarrow 6CO_2 + 6H_2O + \text{ATP} \]
2. What are the reactants and what are the products of cellular respiration overall?
- Reactants: Glucose (C6H12O6) and oxygen (O2).
- Products: Carbon dioxide (CO2), water (H2O), and ATP (energy).
3. Where does each stage of cellular respiration take place?
- Glycolysis: In the cytoplasm.
- Acetyl-CoA formation: In the mitochondrial matrix.
- Krebs cycle: In the mitochondrial matrix.
- Oxidative phosphorylation: Across the inner mitochondrial membrane (electron transport chain and ATP synthase).
4. Name and describe the function of the electron carriers in cellular respiration.
- NADH: Carries electrons from glycolysis and the Krebs cycle to the electron transport chain.
- FADH2: Carries electrons from the Krebs cycle to the electron transport chain. These electron carriers are crucial for oxidative phosphorylation and ATP production.
5. Be able to do "energy accounting" for each stage of cellular respiration: account for the electron carriers and ATP molecules.
- Glycolysis:
- Produces 2 ATP (net) and 2 NADH.
- The 2 NADH will carry electrons to the electron transport chain.
- Acetyl-CoA formation:
- Produces 2 NADH (for each glucose molecule).
- Krebs cycle:
- Produces 2 ATP, 6 NADH, and 2 FADH2 (per glucose).
- These electron carriers will go to the electron transport chain.
- Oxidative phosphorylation:
- ATP is generated via chemiosmosis (about 34 ATP).
- NADH and FADH2 donate electrons to the electron transport chain, where energy is used to pump protons, and ATP is synthesized.
6. Explain the functional role of oxygen in cellular respiration.
- Oxygen acts as the final electron acceptor in the electron transport chain. It combines with electrons and protons to form water (H2O), which is a byproduct of cellular respiration. Without oxygen, the electron transport chain would stop, halting ATP production.
7. Glucose is used in cellular respiration. Where does it come from?
- Glucose comes from the food we eat, primarily carbohydrates like starch and sugars. It is absorbed into the bloodstream during digestion and transported to cells for energy production.
8. Oxygen is used in cellular respiration. Where does it come from? What is the oxygen used for?
- Oxygen comes from the air we breathe. It is used at the end of the electron transport chain to accept electrons and protons, forming water (H2O).
9. Water is produced in cellular respiration. In which step of the process is it created?
- Water is produced during oxidative phosphorylation when oxygen acts as the final electron acceptor in the electron transport chain and combines with electrons and protons.
10. Carbon dioxide is produced in cellular respiration. In which step of the process is it created?
- Carbon dioxide is produced during the Krebs cycle (also called the citric acid cycle). Each turn of the cycle generates 2 molecules of CO2 as a waste product.
11. What role do hydrogen ions play in the process?
- Hydrogen ions (H+) are pumped across the inner mitochondrial membrane during oxidative phosphorylation. This creates a proton gradient, which is used by ATP synthase to produce ATP.
12. Is feeding glucose into glycolysis the only way to reap the benefits of oxidative phosphorylation?
- No, glucose is not the only molecule that can feed into glycolysis. Fatty acids and proteins can also be broken down into molecules (like acetyl-CoA) that enter the Krebs cycle, which then allows oxidative phosphorylation to occur.