L6 - Importance of glucose metabolism

Question 1

Carbon metabolism pathways

Answer 1

Glucose may undergo glycolysis and can ‘choose’ to be metabolised into various pathways:
* TCA cycle
* Fats/triglyceride production
* Ketone production
* Protein production

There are certain set points of these pathways, that prevent movement to different pathways

Question 2

Fatty acid/triacylglycerol production from glucose

Answer 2

Glucose->pyruvate->acetyl CoA->fatty acid

Glucose->DHAP->glycerol-3P->triglyceride

Question 3

Daily minimum calorie intake

Answer 3

1000-2000

Question 4

Carbohydrates, lipid, and protein composition in diet and body stores

Answer 4

C - 40-45% diet, 0.5% of body stores
L - 40% diet and 80% body stores
P - 15-20% and 19.5% body stores

Question 5

Why are carbohydrates less present in stores while lipids are much more prevalent?

Answer 5

Carbohydrates - hydrated, hard to store efficiently

Lipids - can be compressed

Question 6

Bee flight

Answer 6

Uses futile cycling (synthesising and breaking down glucose) as a means to produce heat and warm up the muscles to ~40°C, which allows them to contract more efficiently and allows flight to occur

Question 7

Glucose production: what cells are it necessary in,

Answer 7

RBCs - no mitochondria, need to use glucose for energy
Neurones - no mitochondria, need to use glucose for energy (???)
Kidney medulla - no mitochondria, need to use glucose for energy
Brain - blood/brain barrier, lipids travelling through the blood with proteins cannot pass this barrier, glucose must be used

Question 8

Metabolic Integration gone wrong:

Diabetes and obesity

Answer 8

Diabetes - insulin and glucose, lipid, protein and nucleic acid

Obesity – central satiety centre and setting of metabolic balance

Question 9

Carbohydrate metabolism:

Glycolysis, gluconeogenesis, glycogen turnover, pentose phosphate pathway

Answer 9

Synthesis of glucose

Uses ATP, uses precursors

Breakdown of glucose

makes ATP, makes pyruvate

Question 10

Glucose permease: what is its other name, how many forms does it have, and what do they do?

Answer 10

Glucose translocase (GLUT)

• GLUT1 - muscle-located glucose transporter (weakly insulin receptive)
• GLUT2 - liver-located glucose transported
• GLUT3 - glucose transporter in various tissues
• GLUT4 - muscle/adipose tissue located glucose transporter (sensitive to insulin)
• GLUT5 - fructose transporter in various tissues

Question 11

What is the rate-limiting event for glucose metabolism?

Answer 11

Entry into the cell - the second it enters the cell it gets immediately metabolised by G6P (this is why there is practically no glucose present in cells)

Question 12

GLUTs: what are they, what is their structure, what do they do, and where are they located?

Answer 12

Glucose translocases

12 transmembrane-spanning proteins

Sugar uptake (glucose/fructose)

GLUT 2/3/5 - present at the membrane
GLUT 1(?)/4 - In vesicles within cells until insulin activates them and causes their translocation to the membrane