Integration of Whole Body Metabolism Flashcards
How much glucose does the brain use daily? [1 mark]
100-120g
What is >50% of the energy the brain consumes used for? [3 marks]
for Na+/K+ transport
- to maintain membrane potential
- to synthesis neurotransmitters
At what point does the plasma glucose concentration become dangerously low? [1 mark]
2.2mM
Where are fats a major energy source? [1 mark]
Cardiac muscle
Where is glucose a major energy source? [2 marks]
- Muscles
- Brain
How is energy stored in adipose tissue? [1 mark]
As triglycerides (mainly synthesised in the liver)
Which glucose transporter is found in adipose tissue? [1 mark]
GLUT4
Which organ contributes to the half of blood glucose during starvation? [1 mark]
The kidneys (via gluconeogenesis)
How does the liver get its energy? [1 mark]
Via alpha keto acids (e.g. pyruvate)
Difference between hexokinase and glucokinase? [5 marks]
- Km (H: low, G: high)
- Location (H: all tissue, G: hepatic tissue)
- Allosteric (H: yes, G: no)
- Induction by insulin (H: no, G: yes)
- Inhibition by G6P (H: yes, G: no)
What is GLUT2 driven by and what does this mean as a result [2 marks]
- Driven by concentration gradient of glucose.
- This means that GLUT2 is bidrectional.
What does glucokinase do to GLUT2 and why? [2 marks]
- Phosphorylate it.
- To facilitate storage of glucose as glycogen.
What does glucose-6-phosphatase do? [1 mark]
Converts G6P to glucose
What is creatine phosphate? [1 mark]
It’s a reservoir of phosphate to donate to ADP.
Which form of respiration is more efficient? [1 mark]
Aerobic respiration
Advantage and disadvantage of fatty acids as a soure of energy? [2 marks]
ADVANTAGE: It’s a large source of energy.
DISADVANTAGE: Fatty acid oxidation is slow.
Where does pyruvate come from in the Cori cycle? [2 marks]
- Lactate from muscles
- Alanine from muscles
Where does G6P come from in the Cori cycle? [2 marks]
- Gluconeogenesis (using pyruvate)
- Glycogenolysis
What can alanine be used for? [1 mark]
Gluconeogenesis
What are the levels of glucose, hormones and enzyme activity in the post absorptive state? [5 marks]
LOW: blood glucose, low insulin, glucose uptake
HIGH: glucagon, phosphorylase a activity, glucogen breakdown
What happens in early starvation? [5 marks]
- Gluconeogenesis and glycogenolysis
- Mobilisation of fatty acids from adipose tissue
- Muscle switches to fatty acid oxidation
- Less GLUT4 expression so less glucose uptake
- After 12 hrs, 45% of resting energy comes from fatty acids and 40% come from glucose
What happens in intermediate starvation? [5 marks]
HIGH: lipolysis, ketogensis, gluconeogenesis
LOW: glycogen stores
- After 60 hrs, fatty acids account for 75% of energy provision.
- After 8 days, concentration of beta hydroxybutyrate (ketone body) is raised 50 fold
- Kidney takes over gluconeogensis from the liver
What happens in prolonged starvation? [6 marks]
- Beta hydroxybutyrate concetration plateaus at 20 days
- Brain switches its metabolism to ketone bodies
- Gluconeogenesis from lactate and glycerol
- Proteins are broken down
