Aerobic Cellular Respiration

Question 1

Cellular Respiration

Answer 1

• it is a process by which cells use chemical energy stored in organic molecules to regenerate ATP, which powers work
• it includes both aerobic (oxygen present) and anaerobic respiration (lacks oxygen)
• aerobic respiration is the most efficient catabolic pathway in which oxygen is consumed as a reactanct along with the organic fuel

Question 2

What are the four distinct regions of the mitochondria and what processes of aerobic respiration occur here?

Answer 2

• two major processes of aerobic respiration, the Krebs Cycle and Oxidative Phosphorylation, occur in the mitochondria
• the four distinct areas include:

1. outer membrane: consists of double layer of phospholipids
2. intermembrane space: narrow area between inner and outer membranes
3. inner membrane: also has double phospholipid bilayer, has convolutions called cristae which are infoldings that increase surface area; oxidative phosphorylation occurs here
4. matrix: fluid material that fills the area inside the inner membrane; the Krebs Cycle and the conversion of pyruvate to acetyl CoA occur here

Question 3

3 Stages of Cellular Respiration Overview

Answer 3

1. Glycolysis:

• means “sugar splitting”
• breaks down glucose into two molecules of pyruvate
• occurs in the cytosol
• substrate level phosphorylation

2. Citric Acid Cycle/Krebs Cycle:

• completes the breakdown of glucose, oxidizing the organic fuel derived from pyruvate
• CO2 is released
• occurs in mitochondrial matrix
• substrate level phosphorylation

3. Oxidative Phosphorylation:

• occurs in the mitochondria
• powered by redox reactions of the electron transport chain located in the cristae of mitochondria
• accounts for most of ATP synthesis

Question 4

What are the roles of electron carriers?

Answer 4

• transport electrons from glucose in the cytosol to the mitochondrion and also transport from one part of the mitochondrion to another
• the carriers alternate reduced and oxidized states as they accept and donate electrons during cellular respiration
• NAD+ and FAD: coenzymes and electron shuttles, oxidizing agents
• NADH and FADH2 are the reduced forms

Question 5

What is Substrate Level Phosphorylation?

Answer 5

• type of chemical reaction that results in the formation of ATP by the direct transfer of a phosphate group to ADP from a reactive intermediate
• it serves as a fast source of ATP independent of external electron acceptors
• occurs primarily in the cytoplasm during glycolysis under aerobic and anaerobic conditions, but also occurs in mitochondria during Krebs Cycle
• oxidation and phosphorylation are not coupled

Question 6

What are the ins and outs of Glycolysis?

Answer 6

• substrate level phosphorylation that occurs in the cytosol
• ins include glucose, 2 ATP, and 2 NAD+
• outs include 2 ATP, 2 NADH, 2 Pyruvate
• ultimately a net gain of 2 ATP

Question 7

Conversion of Pyruvate into Acetyl CoA, an intermediate process

Answer 7

• pyruvate enters the mitochondria
• CO2 is released
• pyruvate gives up 2 electrons to NAD+ which is reduced to NADH
• coenzyme A binds to what is left of pyruvate to result in Acetyl CoA (highly reactive compound), which then enters the Krebs cycle for further oxidation

Question 8

What is the Citric Acid Cycle/ Krebs Cycle?

Answer 8

• substrate level phosphorylation that occurs in mitochondrial matrix
• the cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn
• CO2 is a waste product
• includes 8 steps each catalyzed by a specific enzyme
• the first step: the acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate
• the next seven steps decompose the citrate back to oxaloacetate
• for one molecule of glucose, there are two turns of the Krebs cycle, one for each pyruvate

Question 9

Oxidative Phosphorylation

Answer 9

• a metabolic pathway that uses energy released by the oxidation of nutrients to produce ATP
• involves the electron transport chain on the inner membrane of the mitochondria (ETC is in the cristae)
• accounts for most of ATP synthesis
• uses electrons carried by NADH and FADH2- alternate reduced and oxidized states as they accept and donate electrons
• ETC’s main components are multiprotein complexes
• Electron transfer in the ETC causes proteins to pump H+ from the matrix to the intermembrane space, forming a proton gradient and electric charge gradient
• H+ then moves back across the membrane passing through channels in ATP synthase, which drives phosphorylation of ATP
• water is final product
• can produce up to about 32-34 ATP

Question 10

Chemiosmosis and a proton-motive force

Answer 10

• chemiosmosis is the use of energy in a H+ gradient to drive cellular work; an example of this is when ATP synthase uses the exergonic flow of H+ to drive phosphorylation of ATP during aerobic respiration
• the H+ gradient is referred to as a proton-motive force, emphasizing its capacity to do work

Question 11

About how many ATP can be created from energy from one NADH?

Answer 11

3

Question 12

About how many ATP can be created from energy from one FADH2?

Answer 12

2

Question 13

About how much ATP can be produced from each step of aerobic respiration?

Answer 13

1. glycolysis: 2
2. citric acid cycle: 2
3. oxidative phosphorylation: about 32 or 34

Question 14

Which step of aerobic respiration has water as its final product?

Answer 14

oxidative phosphorylation

Question 15

During Cellular Respiration glucose is ________, and oxygen is _________.

Answer 15

oxidized, reduced

Question 16

who are the main players in aerobic respiration?

Answer 16

• glucose
• mitochondria
• electron carriers (NAD+ and FAD)
• ATP
• Coenzyme A (binds to acetate to form acetyl CoA