3A3 Biochemistry of Life

Question 1

What is cellular respiration?

Answer 1

The process by which cells convert glucose into energy.

Cellular respiration generates ATP by breaking down glucose molecules, with or without oxygen.

Question 2

What are the two main types of cellular respiration?

Answer 2

1. Aerobic Respiration
2. Anaerobic Respiration

Aerobic respiration requires oxygen and occurs in plants, animals, and fungi. Anaerobic respiration occurs without oxygen, and usually occurs in bacteria, archea, and other small microorganisms.

However, in situations of low oxygen, humans and plant cells can undergo anaerobic respiration.

Question 3

What is the primary energy carrier molecule produced during respiration?

Answer 3

ATP

(Adenosine Triphosphate)

This molecule provides energy for cellular processes.

Question 4

Fill in the blank:

Aerobic respiration occurs in the __________.

Answer 4

mitochondria

Aerobic respiration primarily takes place in the mitochondria where oxygen is utilized for ATP production.

Question 5

True or False:

Anaerobic respiration occurs in the mitochondria.

Answer 5

False

Anaerobic respiration occurs in the cytoplasm since it does not require the organelles involved in oxygen-dependent processes.

Question 6

What is the main purpose of aerobic respiration?

Answer 6

To produce ATP using oxygen.

This process is highly efficient, yielding up to 38 ATP molecules per glucose molecule.

Question 7

What is the main purpose of anaerobic respiration?

Answer 7

To generate energy without oxygen.

This process produces less ATP (2 ATP per glucose) but is faster than aerobic respiration.

Question 8

What is the chemical equation for aerobic respiration?

Answer 8

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP

Glucose and oxygen are converted into carbon dioxide, water, and energy in the form of ATP.

Question 9

Fill in the blank:

Anaerobic respiration produces _____ or ______ as by-products.

Answer 9

lactic acid ; ethanol

Ethanol and CO₂ are by-products in yeast. When humans (and other animals) exercise strenuously, the cells do not have enough oxygen to produce energy, so lactic acid is produced.

Question 10

What are the 3 stages of aerobic respiration?

Answer 10

• Glycolysis
• The Krebs cycle
• Electron Transport Chain

These stages collectively produce ATP and require oxygen.

Question 11

What is glycolysis?

Answer 11

The breakdown of glucose into pyruvate.

It occurs in the cytoplasm and is the first step in both aerobic and anaerobic respiration.

Question 12

True or False:

Glycolysis requires oxygen.

Answer 12

False

Glycolysis is an anaerobic process and can occur with or without oxygen, which is why it is the first step for both aerobic and anaerobic respiration.

Question 13

Where does the Krebs cycle occur in the cell?

Answer 13

In the mitochondrial matrix.

This cycle processes pyruvate to produce energy-rich molecules like NADH and FADH₂.

Question 14

What is the main role of the electron transport chain?

Answer 14

To generate ATP using high-energy electrons.

This step uses oxygen as the final electron acceptor to produce ATP.

Question 15

Fill in the blank:

Oxygen acts as the final ________ ________ in the electron transport chain.

Answer 15

electron acceptor

Oxygen combines with electrons and protons to form water, completing the process. This explains why oxygen is necessary for aerobic respiration.

Question 16

What is fermentation?

Answer 16

An anaerobic process that generates energy without oxygen.

This process is a type of anaerobic respiration seen in organisms like yeast and muscle cells under low oxygen conditions.

Question 17

What is the ATP yield of anaerobic respiration?

Answer 17

2 ATP per glucose molecule.

Anaerobic respiration makes less energy when compared to aerobic respiration, but is a much quicker process.

Question 18

What gas is released during aerobic respiration?

Answer 18

Carbon dioxide

(CO₂)

CO₂ is released during the Krebs cycle and is expelled during exhalation.

Question 19

What happens to pyruvate in aerobic respiration?

Answer 19

It enters the Krebs cycle.

In aerobic conditions, pyruvate is converted to acetyl-CoA and processed further in the mitochondria.

Question 20

What is photosynthesis?

Answer 20

The process by which plants convert sunlight into chemical energy.

This process occurs in chloroplasts, using light, water, and carbon dioxide to produce glucose and oxygen.

Question 21

Where does photosynthesis primarily occur in plants?

Answer 21

In the chloroplasts of leaf cells.

Chloroplasts contain chlorophyll, which captures light energy essential for photosynthesis.

Question 22

True or False:

The oxygen released during photosynthesis comes from carbon dioxide.

Answer 22

False

The oxygen released during photosynthesis originates from water molecules. During the light-dependent reactions, water is split through a process called photolysis, producing oxygen as a byproduct.

Question 23

What is the main molecule that absorbs light energy for photosynthesis?

Answer 23

Chlorophyll

This molecule absorbs light, primarily in the blue and red wavelengths, while reflecting green light.

Question 24

Fill in the blank:

The primary products of photosynthesis are glucose and ________.

Answer 24

oxygen

Glucose is stored as energy, while oxygen is released into the atmosphere as a byproduct.

Question 25

What are the two main **stages** of photosynthesis?

Answer 25

1. Light-dependent reactions 2. The Calvin cycle ## Footnote Light-dependent reactions occur in the thylakoid membranes, while the Calvin cycle occurs in the stroma.

Question 26

# True or False: The Calvin cycle **requires** light to function.

Answer 26

False ## Footnote This cycle is light-independent but depends on energy (ATP and NADPH) produced during the light-dependent reactions.

Question 27

# Fill in the blank: During the Calvin cycle, carbon dioxide is **converted** into \_\_\_\_\_\_\_\_.

Answer 27

glucose ## Footnote The Calvin cycle uses ATP and NADPH to fix carbon dioxide and synthesize glucose.

Question 28

What **molecule** transports high-energy electrons during photosynthesis?

Answer 28

NADPH ## Footnote This molecule is produced in the light-dependent reactions and provides the reducing power needed for the Calvin cycle.

Question 29

How is ATP **produced** during the light-dependent reactions?

Answer 29

By **chemiosmosis** through ATP synthase. ## Footnote Chemiosmosis involves hydrogen ions moving across the semipermeable membrane down their electrochemical gradient. This creates free energy that is used by ATP synthase to convert ADP into ATP.

Question 30

What **enzyme** is responsible for fixing carbon dioxide in the Calvin cycle?

Answer 30

RuBisCO ## Footnote This enzyme catalyzes the reaction between carbon dioxide and RuBP, initiating the Calvin cycle.

Question 31

What are **biological molecules**?

Answer 31

Molecules that are **essential** for life. ## Footnote This *includes* nucleic acids, carbohydrates, proteins, and lipids, which perform various functions such as storing genetic information, providing energy, and forming cell structures.

Question 32

What are **nucleic acids** responsible for?

Answer 32

Storing and transmitting **genetic** information. ## Footnote Nucleic acids, like DNA and RNA, carry the genetic blueprint for all living organisms.

Question 33

What are the **building blocks** of nucleic acids?

Answer 33

Nucleotides ## Footnote They consist of a sugar, a phosphate group, and a nitrogenous base. DNA and RNA are polymers of nucleotides.

Question 34

# Fill in the blank: The two **types** of nucleic acids are \_\_\_\_\_ and \_\_\_\_\_.

Answer 34

DNA ; RNA ## Footnote DNA stores genetic information, while RNA plays a key role in protein synthesis.

Question 35

What are carbohydrates **used** for in living organisms?

Answer 35

Providing energy and structural support. ## Footnote Carbohydrates, such as sugars and starches, are vital for energy storage and structural components in plants and animals.

Question 36

What is the basic **unit** of carbohydrates?

Answer 36

Monosaccharides ## Footnote Examples include glucose and fructose, which are simple sugars that can form more complex carbohydrates.

Question 37

# True or False: Starch is a type of **protein**.

Answer 37

False ## Footnote Starch is a **carbohydrate** and serves as a storage form of energy in plants.

Question 38

# Fill in the blank: The **polymer** of glucose that is used by animals for energy storage is \_\_\_\_\_\_\_\_.

Answer 38

glycogen ## Footnote It is a polysaccharide stored primarily in the liver and muscles in animals.

Question 39

# Define: Cellulose

Answer 39

A **carbohydrate** that provides structural support in plant cell walls. ## Footnote Cellulose is a *polysaccharide* made of glucose units, and it is crucial for maintaining the strength and rigidity of plant cells.

Question 40

What are **proteins** made of?

Answer 40

Amino acids ## Footnote Proteins are polymers of amino acids, and their sequence determines their structure and function.

Question 41

What are the **functions** of proteins?

Answer 41

* Catalyzing reactions. * Providing structure. * Regulating body processes. ## Footnote Proteins are involved in almost all cellular functions, including enzyme catalysis and immune response.

Question 42

# True or False: All **proteins** are enzymes.

Answer 42

False ## Footnote While enzymes are proteins, *not all* proteins function as enzymes. Many proteins have structural or regulatory roles.

Question 43

What are lipids primarily **used** for in organisms?

Answer 43

**Storing long-term energy** and forming cell membranes. ## Footnote Lipids, such as fats and phospholipids, are important for energy storage and creating the structure of cell membranes.

Question 44

What are the **building blocks** of lipids?

Answer 44

Fatty acids and glycerol. ## Footnote They are made up of glycerol and fatty acid chains, forming triglycerides or phospholipids.

Question 45

# True or False: All lipids are **hydrophobic**.

Answer 45

True ## Footnote Lipids are generally **nonpolar** and do not dissolve in water, making them hydrophobic.

Question 46

# Fill in the blank: The most common **form** of lipid used for energy storage is \_\_\_\_\_\_\_\_\_.

Answer 46

triglycerides ## Footnote These lipids are made of three fatty acids bonded to a glycerol molecule and are stored in fat cells.

Question 47

What is the **role** of cholesterol in the body?

Answer 47

* Stabilize cell membranes * Produce hormones ## Footnote Cholesterol is a type of lipid that helps maintain membrane fluidity and is used to synthesize hormones like estrogen and testosterone.

Question 48

What type of **bond** forms between amino acids in a protein?

Answer 48

Peptide ## Footnote *Peptide bonds* are covalent bonds that link the amino group of one amino acid to the carboxyl group of another.

Question 49

# True or False: Enzymes are **consumed** in the reactions they catalyze.

Answer 49

False ## Footnote **Enzymes** are not consumed in reactions; they can be reused multiple times to catalyze the same reaction.