WEEK 8: 8.8

Question 1

define metabolism

Answer 1

the sum of all chemical reactions in the body involved in maintaining life, including energy production, synthesis of molecules, and breakdown of substances

all chemical reactions in the body

Question 2

define intermediary metabolism

Answer 2

the complex network of chemical reactions that occur within cells to convert nutrients into energy and building blocks, involving carbs, fats and proteins being processed for energy/synthesis

detailed steps of processing nutrients in cells

Question 3

define catabolism

Answer 3

the breakdown of complex molecules like glucose, fats or proteins into simpler ones, releasing energy

breaking down for energy

Question 4

define anabolism

Answer 4

the synthesis of complex molecules from simpler ones, which requires energy

building up for energy

Question 5

after nutrients are absorbed from the digestive tract into the bloodstream, describe the first of three main fates they can follow

Answer 5

1. enter the metabolic pool
   absorbed molecules like glucose, amino acids and fatty acids enter the MP, where they are used for ATP, used as building blocks for synthesis of other molecules

Question 6

after nutrients are absorbed from the digestive tract into the bloodstream, describe the second of three main fates they can follow

Answer 6

2. stored for later use
   fuel is stored
   glucose -> glycogen
   fatty acids -> triglycerides in adipose
   amino acids -> converted to fat or used to build proteins

Question 7

after nutrients are absorbed from the digestive tract into the bloodstream, describe the third of three main fates they can follow

Answer 7

Utilised (oxidised for energy)
broken down to produce ATP, CO2 and water
glucose -> via glycolysis

Question 8

What is glycolysis?

Answer 8

breakdown of glucose into pyruvate
occurs in cytoplasm and does not require oxygen
produces ATP and NADH

Question 9

what is glycogenesis?

Answer 9

conversion of glucose to glycogen for storage

Question 10

what is glycogenolysis?

Answer 10

breakdown of glycogen to glucose when body needs energy

Question 11

what is gluconeogenesis?

Answer 11

formation of new glucose from non-carbohydrate sources (amino acids, lactate)
occurs in liver

Question 12

what is lipogenesis

Answer 12

conversion of excess glucose/amino acids into fat

Question 13

what is lipolysis

Answer 13

breakdown of triglycerides into glycerol and free fatty acids

Question 14

what is protein catabolism

Answer 14

breakdown of proteins into amino acids

Question 15

how is energy in the form of ATP extracted from carbohydrates ?

Answer 15

glycolysis (in cytoplasm):
glucose –> pyruvate to produce 2 ATP and NADH
pyruvate is oxidised -> Acetyl-CoA
citric acid cycle (TCA/Krebs Cycle):
Acetyl-Coa -> CO2
PRODUCES NADH, FADH2, 2ATP/glucose
ETC cycle:
NADH and FADH2 donate electrons
Drive ATP synthesis via oxidative phosphorylation
produce 32 ATP per glucose

Question 16

how is energy in the form of ATP extracted from fats ?

Answer 16

beta-oxidation:
fatty acids –> acetylcoa
produce NADH and FADH2
Acetyl-CoA enters TCA cycle -> ETC
high amount of ATP

Question 17

how is energy in the form of ATP extracted from proteins?

Answer 17

Deamination:
amino acid group removed -> carbon skeleton used
—> pyruvate, acetyl-coa
TCA cycle —> ETC cycle
produces ATP

Question 18

What key hormone is released in a fed (high blood glucose) state?

Answer 18

Insulin

Question 19

What is insulin’s primary targets and actions in the liver?

Answer 19

Store glucose as glycogen
Stop making new glucose by inhibiting gluconeogenesis (making glucose from amino acids)
Convert glucose into fat (lipogenesis)

Question 20

What is insulin’s primary targets and actions in the muscle?

Answer 20

Take in glucose from the blood into muscle cells by increasing GLUT4 transporters
Store glucose as muscle glycogen
Build protein - stimulate protein synthesis

Question 21

What is insulin’s primary targets and actions in the adipose tissue?

Answer 21

Take in glucose: fat cells take in glucose from the blood
Store fat: insulin promotes conversion of glucose into triglycerides (fat molecules) for long-term energy storage
Prevent fat breakdown: it inhibits lipolysis

Question 22

When is glucagon released

Answer 22

When in a fasted state, and blood glucose levels drop

Question 23

What are glucagon’s primary targets and actions in the liver?

Answer 23

Break down stored glycogen by stimulating glycogenolysis
Create new glucose - trigger gluconeogenesis
Produce ketones- ketogenesis- conversion of fatty acids into ketones to use for energy

Question 24

What are glucagon’s primary targets and actions in the adipose tissue?

Answer 24

Break down fat: glucagon stimulates lipolysis - where fats are broken down into fatty acids and glycerol

Question 25

What crucial role does the liver play when you're fed?

Answer 25

It acts as a storage unit, removing glucose from the blood and storing it/converting it into fat

Question 26

What crucial role does the liver play when you're fasting?

Answer 26

the liver becomes a supplier, it releases glucose back into the blood, either from stored glycogen or by creating new glucose through gluconeogenesis

Question 27

What is basal metabolic rate?

Answer 27

the amount of energy your body uses at rest, in a fasted state and in a thermoneutral environment to perform basic functions that keep you alive

Question 28

What factors influence energy requirements?

Answer 28

- basal metabolic rate (higher BMR=higher energy requirement) - physical activity level - growth and development - body size and composition: larger bodies require more energy - age -sex -health status and illness -thermic effect of food

Question 29

how does glucagon convert glycogen into glucose?

Answer 29

1. blood glucose drops, pancreas releases glucagon 2. glucagon binds to hepatocytes (liver cells) 3. activates a signaling pathway involving adenylate cyclase , increases levels of cyclic AMP (cAMP) -> activate protein kinase A (PKA) 4. PKA stimulates enzymes glycogen phosphorylase breaks glycogen into glucose-1-phosphate phosphoglucomutase converts glucose-1-phosphate---> glucose-6-phosphate 5. liver cells convert glucose-6-phosphate --> free glucose

Question 30

Why is ketone production increased in diabetes?

Answer 30

In normal conditions, insulin prevents fat breakdown (lipolysis) and prevents free fatty acid release from adipose tissue however, in diabetes, FFas are released from triglycerides, travel to liver and are converted to ketones (another fuel when glucose is not used, also a process known as ketogenesis) Hence, ketone levels increase in the blood, leading to diabetic ketoacidosis (DKA)