Enzymes
What part of an enzyme binds to the substrate?
The active site
What is the main pigment involved in capturing light energy?
Chlorophyll a.
What is the net gain of ATP from glycolysis?
2 ATP
What form of energy is used by cells to do work?
ATP
What conserved process provides evidence for a common ancestor among all living things?
Glycolysis
Enzymes speed up reactions by lowering what?
The activation energy.
Where do the light-dependent reactions occur?
In the thylakoid membranes.
In which organelle does the Krebs cycle take place?
The mitochondrial matrix.
What law of thermodynamics explains why energy conversions are never 100% efficient?
The second law of thermodynamics.
How is ATP synthase similar in mitochondria and chloroplasts?
Both use a proton gradient across a membrane to generate ATP
What is the term for the model that describes how enzymes fit the substrate?
Lock and Key Fit
What are the two main products of the light reactions that fuel the Calvin cycle?
ATP and NADPH
What happens to electrons at the end of the electron transport chain?
They combine with oxygen and hydrogen ions to form water.
What kind of reaction requires energy input—endergonic or exergonic?
Endergonic.
How does cellular respiration support the concept of fitness?
Organisms with more efficient ATP production have greater survival and reproductive success.
How does a noncompetitive inhibitor differ from a competitive inhibitor?
Noncompetitive inhibitors bind to an allosteric site and change enzyme shape; competitive inhibitors bind to the active site.
How do plants balance photosynthesis and water loss on hot, dry days?
They close their stomata to save water, but that limits CO₂ intake, which slows photosynthesis.
What builds up across the inner mitochondrial membrane to power ATP synthase?
A concentration gradient of hydrogen ions (H⁺).
When ATP is broken down, what does it become and what is released?
It becomes ADP + phosphate, and energy is released.
Why do both plants and animals perform cellular respiration?
To convert glucose into usable ATP energy for cellular processes.
Why does enzyme activity decrease sharply beyond the optimal temperature?
The enzyme denatures due to disruption of hydrogen bonds and loss of tertiary structure.
How does the structure of the chloroplast optimize the light-dependent and light-independent reactions?
Thylakoid membranes provide a large surface area for embedded pigments and electron transport chains that create an H⁺ gradient; the stroma contains enzymes of the Calvin cycle that use ATP and NADPH produced in the thylakoids, keeping pathways spatially separated yet metabolically linked.
How much ATP does aerobic respiration make compared to fermentation?
Aerobic respiration makes about 36–38 ATP per glucose; fermentation makes only 2 ATP
Why do cells need a constant supply of energy?
To keep up cell functions like transport, growth, and repair—without energy, cells can’t maintain homeostasis.
Explain how photosynthesis and respiration demonstrate energy flow through ecosystems.
Photosynthesis captures solar energy in glucose; respiration releases that energy to power life processes.