Chapter 6 - Cellular Respiration

Question 1

Do plants go through cellular respiration?

Answer 1

Yes, plants experience both photosynthesis and cellular respiration.

Question 2

What is the chemical equation for photosynthesis and cellular respiration?

Answer 2

Photosynthesis:
Light energy +6CO2 + 6H2O —–> C6H12O6 + 6O2
Respiration:
C6H12O6 + 6O2 —–> 6CO2 + 6H2O + Energy (ATP + heat)

Question 3

Can energy be recycled? Can chemicals from cellular respiration be recycled?

Answer 3

No, energy makes a one-way trip through an ecosystem.
Yes, chemicals are recycled.

Question 4

What organelle does cellular respiration take place in?

Answer 4

Mitochondria 🔥THE POWERHOUSE OF THE CELL️‍🔥 (and glycolysis in the cytoplasm)

Question 5

Define cellular respiration.

Answer 5

The oxygen requiring harvesting of energy from food molecules by cells.

Question 6

Is cellular respiration and breathing the same thing? Explain.

Answer 6

No, but they are related. Breathing supplies the oxygen (via blood) and disposed of the CO2 necessary for cellular respiration.

Question 7

What is a kilocalorie (kcal)? What do we measure in kilocalories?

Answer 7

The amount of heat required to raise the temperature of 1 kg of water by 1 degree celsius. Can be used to measure energy in food or how much energy certain activities use up.

Question 8

What is the energy staircase?

Answer 8

Cellular respiration can be described as a controlled descent of electrons down an energy staircase (from glucose to oxygen), with small amounts of energy being released at various steps

Question 9

What are REDOX reactions? Example?

Answer 9

Chemical reactions that involve a transfer of electrons.
One reactant is reduced while the other is oxidized, (one does not happen without the other).
i.e. Cellular respiration.

Question 10

What does the acronym OIL RIG mean?
How are hydrogen atoms related to this?

Answer 10

Oxidation Is Losing electrons;
Reduction Is Gaining electrons.
We can generally follow these electrons by seeing where their associated protons (H) end up.
Hydrogen = electrons

Question 11

What is NAD+ and what is its primary function in cellular respiration? What is it reduced to? Where does this fit in the energy staircase?

Answer 11

NAD+ is a coenzyme that cells make from the vitamin niacin. It is used to shuttle electrons (two at a time) in redox reactions, becoming reduced to NADH + H+
The first step.

Question 12

What is FAD? What does it reduce to?

Answer 12

An electron acceptor, not nearly as abundant as NAD+, also carries/transfers 2 electrons.
FAD is reduced to FADH2

Question 13

What’s the difference between ATP and NADH + H+ (in terms of energy)?

Answer 13

ATP is readily usable energy.
The energy stored in the NADH + H+ is potential energy that will be used in oxidative phosphorylation to generate a lot more ATP.

Question 14

______ is the final electron acceptor in cellular respiration.

Answer 14

Oxygen.

Question 15

What are the key steps of cellular respiration (3)?

Answer 15

Glycolysis, the Citric Acid Cycle, and Oxidative Phosphorylation (+mini step between glycolysis and the Citric Acid cycle)

Question 16

What steps of cellular respiration occur in all cells?

Answer 16

Glycolysis occurs in the cytoplasm of ALL cells, plant, animal, bacterial, etc.

Question 17

What do aerobic and anaerobic mean? What step of cellular respiration is anaerobic?

Answer 17

Aerobic = with oxygen.
Anaerobic = without oxygen.
Glycolysis is anaerobic.

Question 18

Where in the cell does glycolysis occur? What substrate does it start with and what is produced at the end?

Answer 18

Glycolysis occurs in the cytoplasm (liquid interior) of the cell. One 6C glucose molecule becomes 2 3C molecules (pyruvate)
Produces 2 ATP and reduces 2NAD+ to 2NADH + 2H+

Question 19

How many steps does glycolysis actually have? How much ATP is used and produced by glycolysis?

Answer 19

9 steps split into two stages:
- 4 steps turn 6C glucose into 2 3C molecules of G3P
- 5 steps turn G3P into 2 3C pyruvate
2 ATP are invested; 4 are produced for a net gain of 2 ATP.

Question 20

What happens to the products of glycolysis before the citric acid cycle? How many NAD are used here?

Answer 20

The pyruvate (2 3C) enters the mitochondrial matrix and is oxidized to become Acetyl Co-enzyme A (2 2C, Acetyl CoA) + 2 CO2.
One NADH + H+ is made per pyruvate (so 2 more NADH + H+ per glucose)

Question 21

Where does the citric acid cycle occur?

Answer 21

In the mitochondrial matrix/ within the inner membrane of the mitochondrion (cristae/folds).

Question 22

During the Citric Acid Cycle, how many NAD+ and FAD are reduced?
How many ATP are made per Acetyl CoA? What does the Acetyl-CoA become? What is produced per glucose molecule?

Answer 22

3 NAD are reduced to 3NADH + 3H+, one FAD is reduced to FADH2 and 1 ATP is produced per Acetyl-CoA.
One Acetyl-CoA becomes 2 CO2.
2 Acetyl-CoA are made per glucose so 2 ATP, 6 NADH + 6 H+ and 2 FADH2 are produced (and 4 CO2).

Question 23

Which substance is regenerated in the citric acid cycle which makes it a cycle.

Answer 23

4C Oxaloacetate
It joins with the 2C Acetyl Co-A at the beginning and is regenerated by the end of the cycle.

Question 24

What is chemiosmosis? How is it related to ADP/ATP?

Answer 24

An energy coupling mechanism that uses the energy of hydrogen ion gradients across membranes to drive cellular work, such as the phosphorylation of ADP to ATP.

Question 25

What are the net products of glycolysis and the citric acid cycle from one molecule of glucose?

Answer 25

4 ATP, 10 NADH + 10 H+ and 2 FADH2.

Question 26

Does the citric acid cycle consume oxygen?

Answer 26

No oxygen is consumed in this cycle. (But also it is a process that cannot occur without the presence of oxygen. idk why)

Question 27

By the end of the citric acid cycle, how many electrons are available to enter the electron transport chain during oxidative phosphorylation?

Answer 27

24 electrons/hydrogen.
These are from the 10 NADH + 10 H+ and 2 FADH2 that have been produced so far.

Question 28

Where in the mitochondrion does oxidative phosphorylation take place? What are the two parts of this process?

Answer 28

Entirely within the inner membrane (cristae/folds) of the mitochondrion.
The electron transport chain and chemiosmosis.

Question 29

Three transmembrane carrier protein complexes in the electron transport chain actively pump H+ across the membrane from where it is _______ concentrated in the ________ ________ to where it is ______ concentrated in the ________ _______. Where does the energy required for this come from?

Answer 29

Less concentrated (in the mitochondrial matrix) to where it is more concentrated (in the
intermembrane space).
The energy required for this is in the exergonic process of electrons “falling” towards oxygen.

Question 30

Why is it important that the inner membrane of the mitochondrion is highly folded into cristae?

Answer 30

This dramatically increases the surface area of the inner membrane, which makes space for many copies of the enzymes.

Question 31

Hydrogen ions fall down their concentration gradient through a particular enzyme. What is it called and what does it do? Where does the hydrogen fall from and to?

Answer 31

ATP synthase (like a turbine!).
It is used to add a phosphate group to (aka. phosphorylate) ADP to make ATP.
Hydrogen falls from the intermembrane space to the matrix.

Question 32

What are the products of oxidative phosphorylation?

Answer 32

About 28 more ATP are made and oxygen is reduced to water.

Question 33

How many ATP can be produced every second in a working muscle cell?

Answer 33

10 million!!!

Question 34

In cellular respiration, how much ATP is made by substrate-level phosphorylation compared with oxidative phosphorylation?

Answer 34

4 ATP are made by substrate-level phosphorylation during glycolysis and the citric acid cycle.
About 28 ATP are made by oxidative phosphorylation.

Question 35

If there were no oxygen for electrons to fall to, how would this affect the ability of cells to produce ATP?

Answer 35

The whole system would back up and the majority of the ATP production would stop. This would starve your cells of energy.

Question 36

How can things like carbon monoxide and poisons interrupt cellular respiration? What are uncouplers?

Answer 36

CO stops the flow of electrons, no H+ is pumped and no ATP can be
made.
Poisons, called uncouplers, work by making the membrane leaky to H+ ions so the gradient is destroyed.

Question 37

Other than glucose, what can enter cellular respiration to create energy?

Answer 37

Starches and glycogen can be broken down into glucose, fats are broken into glycerol that enters glycolysis as (G3P) and fatty acid chains are broken into 2 carbon fragments that enter the citric acid cycle as acetyl Co-A.

Question 38

The first prokaryotes evolved in the absence of oxygen – so how did they obtain energy?

Answer 38

They got energy from glycolysis alone and there are still many prokaryotic organisms that are still capable of living anaerobically.

Question 39

How does NADH + H+ get oxidized back to NAD if there is no oxygen? What are two examples?

Answer 39

Fermentation ☺
NADH + H+ becomes oxidized again by reducing pyruvate to either lactate or ethanol.
Lactic acid (muscles, yogurt, cheese) and alcohol fermentation (bread, wine, beer)

Question 40

What are facultative anaerobes?
What are obligate anaerobes?

Answer 40

FA: make ATP by fermentation or oxidative phosphorylation, depending on if oxygen is available.
OA: Require anaerobic conditions to survive. Oxygen is toxic to them.

Question 41

Why will a facultative anaerobe prefer to use oxidative phosphorylation to make ATP instead of fermentation?

Answer 41

Oxidative phosphorylation releases far more ATP (28 ATP instead of 2 from just glycolysis).

Question 42

How do bacteria carry out the citric acid cycle and oxidative phosphorylation without mitochondria?

Answer 42

Citric acid cycle occurs within the cytoplasm of the cell.
OP uses the plasma membrane and creates an H+ concentration outside the cell which falls back inside.