Cellular Respiration Flashcards
(49 cards)
Define and relate the terms oxidation and reduction as they relate to chemical reactions
Oxidation is the loss of electrons; Reduction is the gain of electrons
Describe the energy changes associated with oxidation-reduction (redox) reactions
- Reduction (gain electron) ===> increase in energy because you gain an electron which contains high amounts of energy
i.e., NAD+ –> NADH (low energy –> high energy) - Oxidation(lose electron) ===> decrease in energy because you lose an electron
As an electron flows through this series of reactions, where is its associated free energy the highest? Where is it the lowest?
- Free energy highest in the reduced state because electrons in the reduced form have higher potential energy
- Free energy is lowest in the oxidized state because oxidation releases energy when it loses an electron
Discuss what happens to matter and energy through overall process of cellular respiration
As the cell converts food molecules into CO2, free energy is released, transformed, and used to make ATP from ADP + Pi
What are the different stages of cellular respiration?
Stage 1: Glycolysis
Stage 2: Pyruvate oxidation
Stage 3: Citric Acid Cycle
Stage 4: Oxidative phoshorylation
Where does glycolysis occur? Describe its process.
Where: Cytoplasm
Process:
- 2 ATPs are used to break down glucose into 2 PGAL (3 Carbons + Phosphate) molecules
- Turn into 2 pyruvates
- Produces a net gain of 2 ATPs and 2 NADH (from NAD+).
- Does not require oxygen
Where does pyruvate oxidation occur? Describe its process.
Where: It occurs in the mitochondria
Process:
- Each pyruvate from glycolysis enters the mitochondrial matrix.
- One CO₂ is released.
- The remaining 2-carbon molecule is attached to Coenzyme A, forming acetyl-CoA.
- The molecule is oxidized, and electrons are transferred to NAD⁺, forming NADH.
- This step links glycolysis to the citric acid cycle.
Why is the creation of acetyl CoA important for the citric acid cycle?
Acetyl CoA serves as fuel for the citric acid cycle in the next stage of cellular respiration
Where does the Citric Acid Cycle occur? Describe its process.
Where: mitochondrial matrix
Process:
- The citric acid cycle breaks down acetyl-CoA to release carbon dioxide and produce ATP, NADH, and FADH₂.
- Acetyl-CoA (2C) joins oxaloacetate (4C) → forms citrate (6C)
- Citrate gradually oxidized -> 2 CO₂ are released
- 3 NADH, 1 FADH₂, and 1 ATP are made per acetyl-CoA
- Oxaloacetate is regenerated to keep the cycle going
Where does the ETC & Oxidative Phosphorylation occur? Describe its
process.
Where: Inner Mitochondrial Membrane
Process:
- NADH and FADH₂ donate electrons to the ETC.
- Electrons move through protein complexes, releasing energy.
- This energy is used to pump protons (H⁺) into the intermembrane space, creating a proton gradient.
- Protons flow back into the matrix through ATP synthase — this flow powers the production of ATP.
- At the end, oxygen accepts electrons and H⁺ to form water.
What happens to NAD+ and FAD in Oxidative Phosphorylation?
- In oxidative phosphorylation, NADH and FADH₂ donate their electrons to the electron transport chain.
- As they give up electrons, they are oxidized back into NAD⁺ and FAD.
- These regenerated NAD⁺ and FAD are recycled and return to earlier steps (like glycolysis and the Krebs cycle) to pick up more electrons.
What is Oxidative Phosphorylation?
a cellular process that harnesses the reduction of oxygen to generate ATP
What is the electron transport chain (ETC)?
It is a collection of membrane-embedded proteins and organic molecules. In the ETC, electrons are passed from one molecule to another, and the energy released in these electron transfers is used to form an electrochemical gradient.
What roles do energy and enzymes play in glycolysis?
- Enzymes lower activation energy, allowing glycolysis to proceed rapidly at body temperature.
- Regulation of enzymes (e.g., PFK-1) controls energy production based on cellular needs (ATP/AMP levels).
- Without enzymes, glycolysis would be too slow to meet energy demands.
Describe the structure and function of ATP synthase
- Sits across the phospholipid membrane
- Uses proton gradient created by the electron transport chain
- Protons flow through the ATP synthase from the intermembrane space to the matrix
- This flow spins part of the enzyme, which drives the conversion of ADP + Pi -> ATP
What is ATP synthase?
It is an enzyme in the mitochondria and chloroplasts that produces ATP
Compare and contrast the generation of ATP in the presence or absence of oxygen
With oxygen: aerobic
- Cells use the full process of cellular respiration to make lots of ATP
- glucose + oxygen -> CO2 + H2O
Without oxygen: anaerobic
- Only glycolysis works, followed by fermentation
- glucose -> lactic acid
What is fermentation?
An anaerobic process where energy is released from glucose (or other sugars) without the use of an electron transport chain
What is fermentation’s role in glycolysis?
- Fermentation allows glycolysis to continue when oxygen is not available.
- During glycolysis, NAD⁺ is reduced to NADH.
- Fermentation regenerates NAD⁺ by transferring electrons from NADH to pyruvate or its derivatives.
- This keeps the supply of NAD⁺ available so ATP can keep being made through glycolysis.
- Without fermentation, NAD⁺ would run out, and glycolysis would stop.
Relate the metabolism of different molecules to cellular respiration
Amino acids, lipids, and other carbohydrates can be converted to various intermediates of glycolysis and the citric acid cycle, allowing them to slip into the cellular respiration pathway through a multitude of side doors.
How do proteins enter cellular respiration?
- Proteins are broken down into amino acids
- Some amino acids will get broken down for energy via cellular respiration
- To enter cellular respiration, amino acids must first have their amino group removed
- Once they’ve been deaminated, different amino acids enter the cellular respiration pathways at different stages
How do carbohydrates enter cellular respiration?
- Most enter during glycolysis
- glucose polymer broken down into individual glucose molecules
How do lipids enter the pathway?
- They can be broken down into glycerol and fatty acids
- Glycerol enters glycolysis while fatty acids undergo beta-oxidation to form acetyl-CoA which enters the citric acid cycle
Explain how cellular respiration can be regulated by inhibiting or activating PFK?
When ATP levels are high:
- ATP binds to PFK, acting as an allosteric inhibitor
- Slows down glycolysis → less glucose is broken down
- Prevents wasteful overproduction of ATP
When ATP is low (high ADP or AMP):
- PFK is activated
- Speeds up glycolysis → more ATP is made
