study questions topic 7 and 8 Flashcards
(7 cards)
Draw the anatomy of a mitochondrion including the outer and inner membrane,
intermembrane space, and matrix. Identify what reactions of cellular respiration
occur in which parts of the mitochondrion.
Outer Membrane: The outermost layer, a smooth, relatively permeable barrier.
Intermembrane Space: The region between the outer and inner membranes.
Inner Membrane: The folded membrane forming cristae, which increases surface area.
Matrix: The innermost compartment, a gel-like substance containing enzymes, DNA, and ribosomes.
Krebs Cycle (Citric Acid Cycle): Occurs in the mitochondrial matrix.
Electron Transport Chain: Embedded in the inner mitochondrial membrane, using both the inner membrane and intermembrane space to generate a proton gradient for ATP synthesis.
Oxidative Phosphorylation: Occurs in the inner mitochondrial membrane and involves the electron transport chain and ATP synthase.
Pyruvate Oxidation: Occurs in the mitochondrial matrix.
Describe how oxidative phosphorylation produces ATP in cellular respiration. Identify
the electron donors, electron acceptor, and mechanism of ATP synthesis
Oxidative phosphorylation produces ATP by using the energy released from electrons transferred through the electron transport chain (ETC) to create a proton gradient, which then drives ATP synthesis via ATP synthase.
Describe when a cell would perform fermentation instead of aerobic cellular
respiration. What are some examples of products of fermentation? Give specific
examples of cells/organisms that perform fermentation reactions
A cell will perform fermentation instead of aerobic cellular respiration when oxygen is unavailable or in limited supply. This occurs because oxygen serves as the final electron acceptor in the electron transport chain (ETC) during aerobic respiration. Without oxygen, the ETC cannot function, and NADH cannot be oxidized back into NAD⁺, which is necessary for glycolysis to continue. To regenerate NAD⁺, cells use fermentation pathways.
Lactic Acid Fermentation
Process: Pyruvate is converted into lactic acid (lactate), regenerating NAD⁺.
Example Organisms:
Muscle cells: During strenuous exercise, oxygen demand exceeds supply, so muscle cells switch to lactic acid fermentation to produce ATP. This can lead to muscle fatigue.
Lactic acid bacteria (e.g., Lactobacillus): Used in the production of yogurt, cheese, and sourdough bread.
Alcohol Fermentation
Process: Pyruvate is converted into ethanol and CO₂, regenerating NAD⁺.
Example Organisms:
Yeast (e.g., Saccharomyces cerevisiae): Used in baking (CO₂ causes dough to rise) and brewing (ethanol in alcoholic beverages).
Some bacteria: Certain microbes in oxygen-deprived environments perform alcohol fermentation.
Diagram the light-dependent reactions of photosynthesis. Identify where it
happens in the plant cell, what is used, and what is produced at this stage
The light-dependent reactions of photosynthesis, which occur in the thylakoid membranes of chloroplasts, convert light energy into chemical energy in the form of ATP and NADPH, using water and releasing oxygen as a byproduct
ATP is produced: move hydrogen ions across the thykaloid membrane
NADPH; carries electrons and is use din the next stage of photosynthesis
Oxygen: released as a byproduct of the splitting of water molecules
What is the purpose of fermentation and how is energy generated in organisms
performing fermentation?
The purpose of fermentation is to regenerate NAD⁺ so that glycolysis can continue producing ATP in the absence of oxygen. Energy is generated through substrate-level phosphorylation in glycolysis, where glucose is broken down into pyruvate, yielding 2 ATP per glucose molecule. In fermentation, pyruvate is converted into lactic acid (in animals) or ethanol and CO₂ (in yeast), allowing NADH to be oxidized back into NAD⁺ for continued ATP production.
When analyzing photosynthetic microorganisms in a lake you often find that the
photosynthetic microorganisms growing at the very surface are green, while
photosynthetic microorganisms growing deeper are often purple. What is the
energetic and molecular reasoning for the purple coloring in the lower levels?
The purple photosynthetic microorganisms in deeper water absorb different wavelengths of light due to the filtering effect of water, which absorbs high-energy blue and red light more strongly. These microorganisms contain bacteriochlorophylls or other pigments that efficiently absorb the remaining wavelengths, such as far-red and infrared light, giving them a purple appearance. This adaptation allows them to maximize energy capture for photosynthesis in low-light conditions where chlorophyll-based green photosynthesis is less efficient.
Describe photorespiration and why it is a problem for plants. Four sentences or less.
Photorespiration occurs when the enzyme Rubisco mistakenly binds to O₂ instead of CO₂, leading to the production of a toxic byproduct instead of useful sugars in the Calvin cycle. This process wastes energy and carbon by consuming ATP and reducing organic carbon availability, ultimately decreasing photosynthetic efficiency. It becomes a major issue in hot, dry environments where plants close their stomata to conserve water, reducing CO₂ levels and increasing O₂ concentrations inside the leaf. To minimize photorespiration, C4 and CAM plants have evolved specialized mechanisms to efficiently capture and store CO₂.
