Metabolism (Week 4)

Question 1

What is Metabolism?

Answer 1

All biochemical reactions that occur in living organisms in order to maintain life allows generation of energy for our cells

Question 2

What are the two categories of Metabolism?

Answer 2

1. Anabolism
2. Catabolism

Question 3

What is Anabolism?

Answer 3

When substances are synthesized or built up from smaller substances.

Example - building a new protein from amino acids.

Question 4

What is Catabolism?

Answer 4

The process of breaking down complex structures into simpler ones.

Example - involved in energy generation in the cells.

Question 5

What are the three Stages of Metabolism?

Answer 5

1. Digestion and absorption of dietary nutrients
2. Nutrients built into lipids, protein or glycogen via anabolism OR broken down into pyruvic acid and acetyl CoA for ATP production
3. Mitochondria: ATP produced, oxygen is required to complete breakdown of nutrients (catabolism)

Question 6

What is Cellular Respiration?

Answer 6

Metabolic reactions and processes that take place in a cell or across the cell membrane to get biochemical energy from fuel molecules

Includes glycolysis, citric acid cycle, and the electron transport chain

NADH and FADH2 store energy released by oxidation of fuel molecules (energy released in the form of electrons)

NADH and FADH2 transport electrons into the electron transport chain

All cellular respiration reactions are catabolic reactions

Final product of cellular respiration is ~36 ATP from one glucose molecule

Question 7

What is the process of Glycolysis?

Answer 7

Occurs in the cytoplasm of the cell

Glucose converted to two pyruvate molecules so it can diffuse across the mitochondrial membrane

For each glucose molecule converted to pyruvate, cell gains 2 ATP molecules

Question 8

What is the Citric Acid Cycle (CAC) (Krebs cycle or Tricarboxylic acid cycle)?

Answer 8

Occurs in the mitochondrial matrix

Series of 8 enzyme-catalysed reactions

Acetyl CoA enters the cycle and NADH and FADH2 are produced

Very little ATP is produced in the CAC

Purpose of the citric acid cycle is to produce high-energy electron carriers that can then enter the electron transport chain.

Process after Glucose

Question 9

What is the Electron transport chain (ETC)?

Answer 9

NADH and FADH2 pass through a series of proteins on the inner mitochondrial membrane

As this occurs, they lose energy and protons are pumped into the intermembrane space

The inner membrane of the mitochondria is folded into cristae which holds the enzymes and coenzymes required for the ETC

Hydrogen ions diffuse to ATP synthase where ATP is produced by adding an inorganic phosphate to an ADP molecule

Question 10

What’s the equation that summarises the process of Cellular Respiration?

Answer 10

Glucose + Oxygen = produces Water, Carbon Dioxide and ATP

Question 11

What are the three processes and the final outcome of Cellular Respiration?

Answer 11

Cellular Respiration processes:

• Glycolysis,
• Citric acid cycle
• Electron transport chain

Cellular Respiration final outcome:
Is the production of approximately 36 ATP from one glucose molecule.

Question 12

What is Aerobic Respiration?

Answer 12

The process of producing cellular energy in the presence of oxygen

Complete catabolism of glucose requires oxygen, and is therefore an aerobic process

Question 13

What is Anaerobic Respiration?

Answer 13

The process of producing cellular energy in the absence of oxygen

During exercise when there is insufficient oxygen present, glycolysis occurs but pyruvic acid cannot enter the citric acid cycle or generate ATP from the electron transport chain.

Pyruvate that doesn’t enter the citric acid cycle undergoes fermentation which results in the production of lactic acid

Question 14

What is the process from Glucose to Glycogen to Glycogenesis?

Answer 14

When glucose is available and oxygen present it will be oxidized and catabolized fully and then our cells will create as much ATP as possible.

Glucose that is surplus to requirements will be stored as glycogen.

Once glycogen storage capacity is reached, any extra glucose is then stored as fat.

The generation of glycogen from glucose is called glycogenesis.

Question 15

What happens when Blood Glucose Levels Increase and Decrease?

Answer 15

The use and storage of glucose is regulated by the endocrine system and the release of insulin and glucagon from the pancreas.

Normal blood glucose is four to six millimoles per litre, but this will fluctuate throughout the day depending on the intake of glucose or level of activity.

These fluctuations stimulate the release of insulin when blood glucose increases and glucagon when blood glucose decreases.

Question 16

What is a Fed State?

Answer 16

Follows the consumption of food - blood glucose will increase from normal or homeostatic level.

Question 17

What is the process of Carbohydrate metabolism in the Fed state?

Answer 17

1. Absorption of glucose from food
2. Blood glucose rises from homeostatic level
3. Pancreatic islet cells to release insulin
4. Insulin enables cells to uptake glucose from blood and promotes the storage of glucose as glycogen through a process called glycogenesis, and also as triglycerides in adipose tissue
5. Blood glucose levels will decrease back to normal
6. Circulating insulin decreases via negative feedback

Question 18

What is the process of Fat metabolism in Fed state?

Answer 18

Both unused fats from the diet and excess glucose will be stored as triglycerides in adipose tissue through a process called lipogenesis.

This occurs when daily energy intake exceeds total energy demands.

Question 19

What is a Fasted State?

Answer 19

Follows period of time without food (such as between meals, during exercise, or during sleep)

Question 20

What is the process of Carbohydrate metabolism in Fasted state?

Answer 20

1. Blood glucose levels will decrease
2. Glucagon released from pancreatic alpha cells
3. Glucagon stimulates the release of glucose from glycogen stores into the blood to increase blood glucose through a process called glycogenolysis.
4. It also mobilizes fats from adipose tissue as well allowing glucose to be generated from fat through a process called gluconeogenesis, which is the synthesis of glucose from fats and proteins
5. Blood glucose levels return to normal
6. Glucagon levels decrease

Question 21

What is the process of Fat Metabolism in Fasted state?

Answer 21

1. Lipolysis occurs - which is the breakdown of stored fats (triglycerides) into glycerol and fatty acids.
2. Glycerol undergoes glycolysis - to from ATP while the
3. Fatty acids undergo beta oxidation - to form ATP.

Question 22

What is the process of Protein metabolism?

Answer 22

In extreme cases, amino acids from proteins can also be converted to glucose for energy through gluconeogenesis.

It is preferable not to use protein stores such as muscle for energy production because protein is an important structural and functional component of cells, proteins are difficult to break apart, and protein breakdown produces toxic by-products (such as ammonia)