C1.2 cell respiration

Question 1

what do organic molecules have stored?

Answer 1

they contain energy stored in their molecular structures. Each covalent bond in a molecule of glucose, an amino acid, or a fatty acid represents stored chemical energy

Question 2

How doe cells release energy from organic nutrients like glucose?

Answer 2

cells break down nutrients by slow oxidation using enzymes that catalyze a series of reactions, breaking covalent bonds one at a time and releasing energy

Question 3

What is the purpose of breaking down organic molecules in a controlled way?

Answer 3

To release energy gradually and store it in the form of ATP molecules for controlled use by the cell

Question 4

What happens if glucose is not available for cellular energy?

Answer 4

the cell can use other organic molecules like fatty acids or amino acids as substitutes

Question 5

Why is ATP classified as a nucleotide?

Answer 5

Because it contains a 5-carbon sugar (ribose), a nitrogenous base (adenine), and three phosphate groups.

Question 6

What makes ATP useful as the energy currency of the cell?

Answer 6

The last two phosphate bonds in ATP are high-energy bonds, which release energy when broken, powering cellular processes

Question 7

How does breaking the high-energy phosphate bonds in ATP release energy for cellular processes?

Answer 7

When a high-energy bond between phosphate groups in ATP is broken, ATP is converted to ADP + P. This reaction releases energy, which is then used to power cellular process like muscle contraction, active transport, and synthesis of macromolecules.

Question 8

Why are ATP’s phosphate bonds called ‘high-energy’ bonds?

Answer 8

the phosphate groups are negatively charged, therefore repelling eachother, making the covalent bonds between them unstable. This instability gives them high potential energy and makes them easy to break

Question 9

How is energy released from ATP and used by the cell?

Answer 9

The high-energy phosphate bonds are easily broken by hydrolysis, a reaction with low activation energy. This reaction is exergonic, meaning it releases energy, which the cell uses to perform work

Question 10

Cellular work carried out using the energy released from the high-energy bonds of ATP include:

Answer 10

• Active transport across cell membranes
• synthesis of macromolecules by anabolism
• movement of the whol cell by cilia or flagellum action
• movement within the cell of cell components, such as chromosome movement in mitosis or meiosis.

Question 11

Through what process is ATP often broken down with?

Answer 11

It usually used hydrolysis, this process adds H2O to the equation. This adds the H20 lost from the condesation reaction, which occured when transforming ADP + P to ATP

Question 12

What process is most commen for ATP to form from ADP + P?

Answer 12

condensation reactionmost commonly occurs. This reaction takes out H20, the one added by the hydrolysis reaction.

Question 13

Why is ATP synthesis an endergonic reaction and ATP hydrolysis and exergonic reaction?

Answer 13

ATP synthesis from ADP + P requires energy, which is stored in the high-energy bond between the second and third phosphate. This energy input makes it an endergonic reaction. When ATP is broken down (hydrolyzed) into ADP + P, energy is released, making it an exergonic reaction

Question 15

Compare and contrast cell respiration and gas exchange

Answer 15

Cell respiration:
- A metabolic process that releases energy from glucose in cells
- to produce ATP for cellular activities
- In the mitochondria
- does not always require oxygen
- produces ATP
- a chemical reaction

Gas exchange:
- the movement of gases across a membrane by diffusion
- to supply oxygen for respiration and remove co2 waste
- in the lungs in humans; across membranes in organisms
- always involves oxygen intake and/or CO2 release
- does not produce energy, however it enables respiration
- a physical process

Question 16

What is cellular respiration?

Answer 16

Is the process by which most organisms on earth synthesize ATP for cellular functions. It involves the release of energy from carbon compounds, especially for glucose (C6H1206) and fatty acids. Carbohydrates, proteins and many other carbon-containing compounds can also be used in respiration.

Question 17

Equation for aerobic cellular respiration

Answer 17

C6H1206 (1) + 602 (2) -> 6c02(3) + 6h20(4) + energy
- Oxidation occurs from 1 and 3
- Reduction occurs from 2 and 4

Question 18

What is the first stage of both aerobic and anaerobic respiration?

Answer 18

Glycolysis, which breaks down glucose (6c) into two molecules of pyruvate (3c), occurs in the cytoplasm and does not require oxygen

Question 19

What happens to pyruvate in anaerobic respiration in humans?

Answer 19

Pyruvate is converted to lactate (lactic acid) in a process called lactic acid fermentation, which allows glycolysis to continue when oxygen is unavailable

Question 20

How many ATP are produced in anaerobic respiration?

Answer 20

A net gain of 2 ATP per glucose molecule, all coming from glycolysis.

Question 21

Why is lactic acid fermentation important in anaerobic conditions?

Answer 21

It prevents pyruvate buildup and regenerates NAD+, allowing glycolysis (and ATP production) to continue without oxygen

Question 22

What are the 4 main stages of aerobic cellular respiration

Answer 22

1. glycolysis
2. link reaction
3. krebs cycle
4. electron transport chain

Question 23

Where does glycolysis occur and what does it produce?

Answer 23

Glycolysis occurs in the cytoplasm.
it produces: 2 pyruvates, 2 ATP (net gain), and 2 NADH

Question 24

What happens in the link reaction?

Answer 24

Each pyruvate (3c) is converted to acetyl CoA (2c) in the mitochondrial matrix. CO2 is released and NADH is produced

Question 25

Where does the krebs cycle occur and what is produced?

Answer 25

Takes place in the **mitochondrial matrix** Per glucose, it produces: 2 ATP, 2 NADH, 2 FADH2, and 4CO2

Question 26

What is the function of the eclectron transport chain (ETC)?

Answer 26

The ETC uses electron from NADH and FADH2 to power ATP production. It occurs in the **cristae** of mitochondria and produces 30-34 ATP. Oxygen is the final electron acceptor, forming water

Question 27

What is the total ATP yield from aerobic respiration per glucose molecule?

Answer 27

Approximately 36-38 ATP, depending on cell type and shuttle efficiency

Question 28

What is the role of oxygen in aerobic respiration?

Answer 28

Oxygen acts as a final electron acceptor in the ETC, combining with electrons and protons to form water

Question 29

Characteristics of anaerobic cell respiration

Answer 29

- Does **not** require oxygen but does require glucose - takes place in the cytoplasm of the cell - glucos is split into two molecules of pyruvate - if the oxygen supply is inadequate, in humans, pyruvate is made into lactic acid. This fermentation will occur in the cytoplasm - No mitochondria needed - Net gain of 2 ATP's - final product is lactic acid and ATP

Question 30

Characteristics of aerobic cell respiration

Answer 30

- requires oxygen and glucose - begins in the cytoplasm - the product of the first part of respiration is two molecules of pyruvate made from glucose - if oxygen supply is adequate, pyruvate will move into the mitochondria - Pyruvate is converted into a 2-carbon compound in the matrix of the mitochondria - The 2-carbon compound enters the krebs cycle, also in mitochondrial matrix - Carbon dioxide is produced as a waste of product of the krebs cycle - 30-34 ATP's are produced in the cristae of the mitochondria - final products is carbon dioxide, water, and ATP

Question 31

What is **oxidation**?

Answer 31

is the **loss of electrons, the loss of hydrogen, or the gain of oxygen** by a molecule, atom, or ion during a chemical reaction. Results in many C-O bonds. Results in a compound with lower potential energy

Question 32

What is **reduction**?

Answer 32

Is the **gain of electrons, the gain of hydrogen, or the loss of oxygen** by a molecule, atom, or ion during a chemical reaction. Results in many C-H bonds, results in a compound with higher potential energy

Question 33

What affects the overall rate of respiration?

Answer 33

-** Temperature:** the optimum temperature for rate of respiration is 20-30 degrees -** Carbon dioxide concentration:** an increase in concentration adversly affects the rate of cell respiration **- Oxygen concentration: **lower concentrations of oxygen lower rate of respiration. The absence of oxygen also results in anaerobic respiration - **glucose concentration**: low levels of glucose in the cell will decrease the rate of cell respiration **- type of cell:** some types of cells require more energy than others. Those that require more energy have higher cell respiration rates

Question 34

How can factors affecting cell respiration be determined?

Answer 34

The can be determined experimentally by calculating the rate of cell respiration using raw or secondary data. **respirometers** are often used to calculate the rate of cell respiration.

Question 35

What is the role of NAD in cell respiration, and how does it relate to oxidation and reduction?

Answer 35

NAD (nicotinamide adenine dinucleotide) is a **coenzyme** and **hydrogen barrier** used in cell respiration. - When **hydrogen is added** to NAD, it is **reduced** (forms NADH) - when **hydrogen is removed**, the molecule is oxidixe or dehydrogenated (forms NAD+)

Question 36

How is energy released during the breakdown of glucose in cellular respiration, and what role does NAD play?

Answer 36

As glucose is oxidized, it loses hydrogen atoms to become CO2. Oxygen is reduced by gaining hydrogen to form H2O. This movement of electrons is **energy-releasing**. The coenzyme NAD+ captures this energy by becoming NADH, which then carries high-energy electrons to help drive ATP production in later stages of respiration

Question 37

What is a **coenzyme?**

Answer 37

Is a non-protein, organic molecule that assists enzymes by transferring chemical groups or electrons during metabolic reactions

Question 38

**steps** of glycolysis

Answer 38

1. two molecules of ATP are used to begin glycolysis. First reaction is **phosphorylation**, the two phosphates from the ATP molecules are added to glucose to from fructose-1,6-biphosphate. This creates a less stable molecule. (2ATP -> 2ADP + 2 Pi), this is added to 6-carbon compound 2. The less stable 6-carbon phosphorylated fructose is split, **lysis**, into two 3-carbon sugars called triose phosphate (PT). 3. Each TP molecule undergoes oxidation to form a reduced molecule of NADH. As reduced NAD is formed, released energy is used to add an Pi to remaining 3-carbon compound. This results in a compound with 2 phosphate groups. Enzymes then remove the phosphate groups so that they can be added to ADP to produce ATP. The result is the formation of 4 molecules of ATP, two molecules of NADH, and 2 molecules of pyruvate. Pyruvate is the ionized (electrically charged) form of pyruvic acid

Question 39

What happens to pyruvate and NADH during anaerobic respiration in humans, and why is this important?

Answer 39

In the absence of oxygen, pyruvate remains in the **cytoplasm** and is converted to **lactate**. **NADH donates** its hydrogen and electrons to pyruvate, regenerating NAD+, which is essential to keep glycolysis running. This allows for the continued production of ATP, which is the only energy source during anaerobic respiration

Question 40

How does alcoholic fermentation work in yeast, and what are its products?

Answer 40

In the absence of oxygen, yeast undergoes **alcoholic fermentation** - glucose is broken down by glycolysis, producing 2 pyruvates and a net gain of 2 ATP - each pyruvate loses a carbon (as CO2) and becomes acetaldehyde (2C) - NADH donates its electrons and hydrogen to acetaldehyde, producing ethanol (2c) and regenerating NAD + products: ethanol, carbon dioxide, NAD+

Question 42

What are the key events in the krebs cycle, and what is the role of citrate and oxaloacetate?

Answer 42

- The krebs cycle occurs in the mitochondrial matrix - acetyl-CoA (2C) combines with oxaloacetate (4c) to form citrate (6c) - two decarboxylation reactions remove two carbon atoms as C02, returning the molecule to a 4c compound - the cycle produces NADH, FADH2, and ATP, and regenerates oxaloacetate - Citrate and oxaloacetate are key intermediates; citrate starts the cycle, oxaloacetate ends it and restarts the cycle

Question 43

What are the **total** products of the krebs cycle per **glucose**molecule?

Answer 43

since **one glucose molecule** produces 2 **pyruvates,** the krebs cycle runs twice per glucose. total products: - 2 ATP - 6 NADH - 2 FADH2 - 4 CO2 these products go on to fuel the **ETC** or are released as waste

Question 44

What role do NADH coenzymes play in cellular respiration?

Answer 44

NADH carries high-energy electrons and protons (and hydrogen atoms) from glycolysis, the link reaction, and the krebs cycle to the electron transport chain. These electrons are used to generate ATP

Question 45

Where does the electron transport chain occur in the mitochondria?

Answer 45

it occurs in the **inner mitochondrial membrane**, specifically on the membranes of the cristae

Question 46

What happens to the hydrogen atoms carried by NADH?

Answer 46

The hydrogen atoms are split into a proton and an electron. The electron enters the electron transport chain, and the proton contributes to creating a proton gradient

Question 47

What happens to NADH after it donates its electrons to the electron transport chain?

Answer 47

NADH is oxidized back into NAD+, which can be reused in earlier stages of cellular respiration

Question 48

What is the electron transport chain and where does it occur?

Answer 48

is a series of electron carriers located in the inner mitochondrial membrane. It transfers high-energy electrons from NADH and FADH2 to oxygen, releasing energy to make ATP.

Question 49

What happens to the electrons from NADH and FADH2 in the electron transport chain?

Answer 49

They are passed from one carrier molecule to the next, losing energy at each step. This energy is used to pump protons and produce ATP

Question 50

What is the final electron acceptor in the electron transport chain?

Answer 50

**Oxygen** is the final electron acceptor. It combines with electrons and protons to form water

Question 51

What is **chemiosmosis?**

Answer 51

is the process by which ATP is produced using the energy from a proton (H+) gradient across the inner mitochondrial membrane. Protons flow from the intermembrane space back into the mitochondrial matrix through ATP synthase. This flow releases energy, which is used to convert ADP + Pi to ATP

Question 52

How does the ETC and chemiosmosis work together to produce ATP?

Answer 52

As electrons move through the ETC, energy is released and used to pump protons from the mitochondrial matrix into the intermembrane space, creating a proton gradient. Protons then diffuse back into the matrix through ATP synthase. This flow of proton powers ATP synthase to convert ADP + Pi into ATP. This process is called chemiosmosis

Question 53

What are the steps involved in ATP production through ETC and chemiosmosis?

Answer 53

1. NADH and FADH2 donate high-energy electrons to the ETC in the inner mitochondrial membrane 2. electrons move through protein carriers in the ETC, releasing small amounts of energy at each step 3. this energy is used to pump protons from the mitochondrial matrix into the intermembrane space, creating a proton gradient 4. a high concentration of proton builds up in the intermembrane space (low in matrix) 5. protons diffuse back into the matric through ATP synthase (a channel protein) 6. the flow of protons powers ATP synthase to convert ADP + Pi into ATP 7. the final electron acceptor is oxygen, which combines with electrons and protons to form water

Question 54

What is the final electron acceptor in the ETC, and what is the result?

Answer 54

Oxygen is the final electron acceptor. It combines with electrons and 2 protons from the mitochondrial matrix to form water. This water is known as **water of metabolism**. Oxygen's role in accepting electrons allows the electron transport chain to continue functioning

Question 55

How can lipids and proteins be used in aerobic respiration?

Answer 55

Lipids (especially triglycerides) are broken down into glycerol and fatty acids - glycerol can be converted into an intermediate of glycolysis - fatty acids are oxidized in the mitochondrial matrix to form multiple 2-carbon acetyl groups, which bind with CoA to form acetyl-Coa and enter the krebs cycle - due to their many C-H bonds, fatty acids produce about 20% more ATP than carbohydrates proteins (amino acids) can also be used: - some are converted to pyruvate - others become acetyl-CoA or enter directly into the krebs cycle as intermediates