Cell Respiration (2.8 & 8.2)

Question 1

What is Cell Respiration?

Answer 1

Cell respiration is the controlled release of energy from organic compounds (principally glucose) to produce ATP within cells

Question 2

How do organic molecules (glucose) store energy?

Answer 2

Within chemical bonds where the energy is not readily accessible to cells

Question 3

ATP’s Function

Answer 3

• Immediate energy source (readily accessible)
• considered energy currency of cells

Question 4

ATP Structure

Answer 4

• It consists of a nucleoside linked to three phosphates via high energy bonds
• When ATP is hydrolyzed to ADP (+ Pi ), the energy contained is released for use

Question 5

Anerobic Respiration (summary)

Answer 5

Partial breakdown of organic molecules for a small ATP yield

Question 6

Aerobic Respiration (summary)

Answer 6

Complete breakdown of organic molecules for a large ATP yield

Question 7

Anarobic respiration (description)

Answer 7

• Partial breakdown of organic molecules for a small ATP yield (x2 ATP)
• Done through glycolysis
• Turns glucose into x2 pyruvate
• net gain of x2 ATP
• oxidized carrier molecules (NAD+) are reduced to form two hydrogen carrier molecules (NADH)

Question 8

Aerobic Respiration (description)

Answer 8

• Complete breakdown of organic molecules for a large ATP yield
• Requires oxygen and occurs in the mitochondria
• Hydrogen carriers are made in large quantities
• These hydrogen carriers (NADH) are used to
  produce significant amounts of ATP (net = 36)
  via the process of oxidative phosphorylation

Question 9

Anaerobic vs Aerobic (reactants)

Answer 9

Anaerobic = glucose
Aerobic = glucose and oxygen

Question 10

Anaerobic vs Aerobic (combustion)

Answer 10

Anaerobic = partial
Aerobic = complete

Question 11

Anaerobic vs Aerobic (energy yield)

Answer 11

Anaerobic = x2 ATP
Aerobic = x36 ATP

Question 12

Anaerobic vs Aerobic (products)

Answer 12

Anaerobic = pyruvate
Aerobic = CO2 and H2O

Question 13

Anaerobic vs Aerobic (location)

Answer 13

Anaerobic = cytosol
Aerobic = cytosol and mitochondria

Question 14

Fermentation

Answer 14

Fermentation involves the reversible conversion of pyruvate into intermediate
forms via the oxidation of hydrogen carrier molecules (under anaerobic conditions)
- This restores stocks of the precursor (NAD+), allowing glycolysis to continue

Question 15

Fermentation (Animals)

Answer 15

• In animals (including humans), fermentation converts pyruvate into lactic acid
• A build-up of lactic acid (lactate) within muscle tissue leads to muscle fatigue (when excercising)

Question 16

Fermentation (Plants and Yeast)

Answer 16

• In plants and yeasts, pyruvate is fermented to form ethanol and carbon dioxide
• Ethanol is used in alcoholic beverages while CO2 causes leavening in bread

Question 17

Energy Conversions

Answer 17

• Chemical energy can be released through cell respiration
• energy can be converted into immediate ATP energy
• energy can be converted into a transitional source (Hydrogen carriers)

Question 18

Redox

Answer 18

• Reduction is a gain in hydrogen and electrons or a loss of oxygen
• Oxidation is a loss in hydrogen and electrons or a gain of oxygen

Question 19

Aerobic Respiration stages

Answer 19

Aerobic Respiration: It releases energy stored within hydrogen carriers for a greater ATP yield

• Glycolysis – Carbohydrates are partially broken down anaerobically
• Link Reaction – Products are transferred to the mitochondria
• Krebs Cycle – Products are completely broken down (⬆︎ hydrogen carriers)
• Electron Transport Chain – ATP produced from hydrogen carriers

Question 20

Key events of Glycolysis

Answer 20

Glycolysis: glucose (6C) is broken down into two pyruvate molecules (3C)

• ATP expenditure – Glucose is phosphorylated by two ATP
• Lysis – The phosphorylated molecule is split into two
• Oxidation – The two triose phosphates are oxidized
• Hydrogen carriers formed – Two NADH molecules released
• ATP production – Four ATP molecules formed (net gain = 2)

Question 21

Key events of Link Reaction

Answer 21

Link Reaction: connects anaerobic process in the cytoplasm (glycolysis) with the anaerobic events in the mitochondria

• Pyruvate is transported from the cytoplasm to the mitochondrial matrix
• Pyruvate is oxidized to produce a reduced hydrogen carrier (NADH)
• Pyruvate is decarboxylated to form an acetyl compound (CO2 is produced)
• The acetyl compound is attached to coenzyme A (to form acetyl CoA)

Question 22

Key events of Krebs Cycle

Answer 22

Krebs cycle: series of oxidation and decarboxylation that occur in the mitochondrial matrix

• Acetyl CoA combines with a 4C compound to make a 6C compound
• The 6C compound is broken back down into the original 4C compound
• This involves the formation of ATP (1 per cycle) and carbon dioxide (2 per cycle)
• It also produces a large amount of hydrogen carriers (3 NADH + 1 FADH2 per cycle)

Question 23

Electron Transport Chain

Answer 23

• Hydrogen carriers produced by prior reactions (glycolysis, link reaction, Krebs cycle) are transported to the mitochondrial cristae (i.e. the inner mitochondrial membrane)
• This is the location of the electron transport chain (and ATP synthase)

Question 24

Establishing a Proton Gradient

Answer 24

• Hydrogen carriers transfer high energy electrons to the electron transport chain
• The electrons lose energy as they are shuttled between electron carriers
  which is used to pump protons into the intermembrane space (from matrix)

Question 25

Chemiosmosis

Answer 25

- The build up of protons within the intermembrane space creates an electrochemical gradient - The protons return to the matrix via a transmembrane enzyme called ATP synthase (catalyzes ATP synthesis) - This formation of ATP is called oxidative phosphorylation because it was coupled to oxidation of hydrogen carriers

Question 26

Role of Oxygen in Aerobic Respiration

Answer 26

- Aerobic respiration requires oxygen to proceed - Oxygen is final proton acceptor in e- transport chain (de-energized e- must be removed) - Oxygen also binds to hydrogen ions in the matrix to maintain a proton gradient (chemiosmosis requires a higher proton concentration in intermembrane space) - Oxygen combines with the electrons and protons to form water molecules

Question 27

Mitochondrion Role

Answer 27

The mitochondrion is the organelle responsible for aerobic respiration and has a highly specialized structure in order to best perform this function

Question 28

Mitochondrion 4 Structural features and their function

Answer 28

- Cristae – The inner membrane is highly folded to increase the SA:Vol ratio (the inner membrane is the site of the electron transport chain) - Intermembrane Space – There is a very small space between the membranes (maximizes the gradient upon proton accumulation) - Matrix – Contains appropriate enzymes and suitable pH for the Krebs cycle - Outer membrane – Contains transport proteins for the shuttling of pyruvate

Question 29

Electron Tomography Description

Answer 29

Electron tomography models internal structures of cells by generating images at different angles with TEM and then compiling a 3D representation

Question 30

What does Electron Tomography produce?

Answer 30

- The intermembrane space is shown to be a consistent width throughout a mitochondrion - Cristae are shown to be continuous infoldings of the inner mitochondrial membrane