Sel Respirasie

Question 1

What are the two main types of cellular respiration?

Answer 1

Cellular respiration can be divided into aerobic and anaerobic respiration.

Question 2

What are the three key stages of aerobic cellular respiration?

Answer 2

The three key stages of aerobic cellular respiration are glycolysis, the Krebs cycle, and oxidative phosphorylation.

Question 3

Where does glycolysis take place?

Answer 3

Glycolysis takes place in the cytosol, which is the cytoplasm that sits around the mitochondria.

It is an anaerobic process, meaning it occurs in the absence of oxygen.

Question 4

What is the main goal of glycolysis?

Answer 4

The main goal of glycolysis is to take a sugar molecule (glucose) and cut it up (lysis).

Question 5

How does glycolysis make the glucose molecule unstable?

Answer 5

Glycolysis makes the glucose molecule unstable by adding phosphate groups to the ends of the molecule.

This process is called phosphorylation.

Question 6

What molecule is formed after phosphorylation in glycolysis?

Answer 6

After adding two phosphates, the molecule is called glucose diphosphate.

Question 7

What does glucose diphosphate break down into?

Answer 7

Glucose diphosphate breaks down into two pyruvic acids.

Each pyruvic acid molecule has three carbons and one phosphate.

Question 8

Does oxygen need to be present for glycolysis to occur?

Answer 8

No, glycolysis takes place with no oxygen present.

This is something that many people get wrong in exams.

Question 9

What happens to pyruvic acid if oxygen is present after glycolysis?

Answer 9

If oxygen is present, the pyruvic acid enters a step before the Krebs cycle where it is prepared.

Question 10

What substance is formed from pyruvic acid in the presence of oxygen before the Krebs cycle?

Answer 10

Pyruvic acid is turned into acetyl in the presence of oxygen.

Question 11

How many carbons are in an acetyl molecule?

Answer 11

An acetyl molecule has two carbons.

Question 12

What is lost when pyruvic acid is converted to acetyl?

Answer 12

When pyruvic acid is converted to acetyl, hydrogen, ATP, and carbon dioxide are lost.

Question 13

What molecule helps transport acetyl into the Krebs cycle?

Answer 13

Coenzyme A helps transport acetyl by combining with it to form acetyl coenzyme A.

Coenzyme A acts like a wheelbarrow, picking up acetyl and carrying it to the mitochondria.

Question 14

Where does the Krebs cycle take place?

Answer 14

The Krebs cycle takes place inside the matrix of the mitochondria.

Question 15

What is the main purpose of the Krebs cycle?

Answer 15

The purpose of the Krebs cycle is to harvest the hydrogen molecules that were made accessible in glycolysis.

Question 16

What happens to acetyl coenzyme A as it enters the Krebs cycle?

Answer 16

As acetyl coenzyme A enters the mitochondria, the acetyl breaks off, leaving a two-carbon structure, and coenzyme A leaves to pick up another acetyl molecule.

Question 17

What does the two-carbon acetyl compound combine with at the beginning of the Krebs cycle?

Answer 17

The two-carbon compound is joined by a four-carbon compound, forming a six-carbon compound.

Question 18

What happens to the six-carbon compound in the Krebs cycle?

Answer 18

The six-carbon compound is broken down.

It loses carbon atoms, which form carbon dioxide (breathed out), and it loses hydrogen atoms (harvested). This process repeats, leading to a five-carbon and then a four-carbon compound.

Question 19

What molecule carries the harvested hydrogen atoms from the Krebs cycle?

Answer 19

NAD acts as a hydrogen carrier and picks up hydrogen, forming NADH.

Question 20

Where does oxidative phosphorylation take place?

Answer 20

Oxidative phosphorylation takes place on the inner membrane of the mitochondria, specifically on the folds called cristae.

Question 21

What is the purpose of oxidative phosphorylation?

Answer 21

The purpose of oxidative phosphorylation is to use the harvested hydrogens to produce ATP molecules.

Question 22

What are cytochromes and what do they do in oxidative phosphorylation?

Answer 22

Cytochromes are large protein channels embedded in the inner mitochondrial membrane.

They assist in the production of ATP by passing along hydrogen electrons.

Question 23

How does hydrogen help produce ATP in oxidative phosphorylation?

Answer 23

As hydrogen moves through the cytochromes, it provides energy that allows a phosphate to join with ADP to create ATP.

This process can be visualized as hydrogen dropping in energy level as it moves down a ‘flight of stairs’ (representing the inner membrane).

Question 24

What is the final acceptor of hydrogen in oxidative phosphorylation?

Answer 24

Oxygen is the final acceptor of the hydrogen molecule.

Question 25

What is produced when oxygen accepts hydrogen at the end of oxidative phosphorylation?

Answer 25

Water is produced when oxygen accepts hydrogen. ## Footnote This water is a byproduct.

Question 26

Roughly how many ATP molecules are produced during the entire process of aerobic cellular respiration?

Answer 26

Roughly 32 ATP molecules are made throughout the whole cellular respiration cycle.

Question 27

What happens in anaerobic respiration in animal cells (like during strenuous exercise)?

Answer 27

In the absence of sufficient oxygen, glycolysis still occurs, breaking down glucose into pyruvic acid and releasing a small amount of energy (ATP). ## Footnote The pyruvic acid is then converted into lactic acid.

Question 28

What is lactic acid and what does it cause?

Answer 28

Lactic acid is a toxic substance that leads to muscle stiffness and pain.

Question 29

How is lactic acid removed?

Answer 29

Oxygen is needed to convert lactic acid back into pyruvic acid. ## Footnote Moderate exercise with deep breathing provides the necessary oxygen to muscle cells.

Question 30

What happens in anaerobic respiration in plant cells and certain fungi?

Answer 30

Glycolysis occurs, breaking down glucose into pyruvic acid and releasing a small amount of energy (ATP). ## Footnote The pyruvic acid is further broken down, releasing carbon dioxide and forming alcohol (ethanol).

Question 31

What is the name of this process in plant cells and certain fungi?

Answer 31

This process is called alcoholic fermentation.

Question 32

What are some industrial applications of anaerobic respiration?

Answer 32

Yeast and other fungi are used to produce alcoholic beverages (beer and wine). ## Footnote Yeast is also used to make bread rise. Certain bacteria are used to produce cheese, yogurt, and sour milk.

Question 33

What are some similarities between aerobic and anaerobic respiration?

Answer 33

Both processes use glucose as a raw material, both release carbon dioxide, and both release energy.

Question 34

What are the key differences between aerobic and anaerobic respiration?

Answer 34

Aerobic respiration requires oxygen, while anaerobic respiration does not. ## Footnote Aerobic respiration produces carbon dioxide and water, while anaerobic respiration produces lactic acid (in animals) or carbon dioxide and alcohol (in plants).