Carbs 1

Question 1

stage 1 of catabolism

Answer 1

converts nutrients to a form that can be taken into cells.
extracellular (GI tract)
building block molecules produces are then absorbed into circulation
no energy produced

Question 2

stage 2 catabolism

Answer 2

building block molecules broken down into smaller intermediates
intracellular (cytosolic and mitochondrial)
oxidative
some energy produced

Question 3

stage 3 metabolism

Answer 3

mitochondrial 
TCA cycle 
oxidative 
energy produced 
acetyl converted to 2CO2

Question 4

stage 4 catabolism

Answer 4

mitochondrial 
e- transport and ATP synthesis 
NADH & FAD2H re-oxidised
O2 required 
large amount of ATP produced

Question 5

what cells have an absolute requirement for glucose

Answer 5

RBC
neutrophils
innermost cells of kidney medulla
lens of the eye

Question 6

enzymes involved in stage 1 catabolism

Answer 6

saliva-amylase. this breaks down starch and glycogen to dextrins
pancreas-amylase. dextrins to monosaccharides
small intestine- dissacharidases specifically looking for disaccharides to complete digestion into monosaccharides. e.g lactase, sucrase, pancreatic amylase (a1-4 bonds),isomaltase(a1-6 bonds)

Question 7

why isn’t cellulose digested

Answer 7

no enzyme to break done b1-4 bonds

Question 8

primary lactase deficiency

Answer 8

absence of lactase persistence allele

only in adults

Question 9

secondary lactase deficiency

Answer 9

caused by injury to SI

e.g gastroenteritis, coeliac disease, Crohn’s disease, ulcerative colitis

Question 10

congenital lactase deficiency

Answer 10

autosomal recessive defect in lactase gene

cannot digest breast milk

Question 11

symptoms of lactose intolerance

Answer 11

Bloating/cramps
flatulence 
diarrhoea
vomiting 
rumbling stomach

Question 12

how are monosaccharides absorbed

Answer 12

active transport by SGLT1 into intestinal epithelial cells and then passive transport via GLUT 2 into blood supply
glucose uptake into cells from blood is via facilitated diffusion using GLUTs

Question 13

functions of glycolysis

Answer 13

oxidation of glucose
NADH production
synthesis of ATP from ADP
produces C6 and C3 intermediates

Question 14

important enzymes of glycolysis

Answer 14

1. hexokinase(glucokinase in liver)-makes the sugar anionic preventing it from crossing the plasma membrane. increases the reactivity of the sugar.
2. phosphofructokinase-1 - converts fructose-6-P into fructose 1,6-bis-P
3. pyruvate kinase- converts phosphophoenolpyruvate to pyruvate.

Question 15

features of glycolysis

Answer 15

central pathway of carbohydrate catabolism
occurs in all tissues 9cytosol)
exergonic
c6—->c3
only pathway that can operate anaerobically
irreversible pathway

Question 16

important glycolysis intermediates

Answer 16

glycerol phosphate- from dihydroacetone phosphate (DHAP) in adipose tissue and liver. important to triglyceride and phospholipid biosynthesis. enzyme needed is glycerol 3-phosphate dehydrogenase

2,3-bisphosphoglycerate- from 1,3-bisphosphoglycerate. produced in RBC. important regulator of O2 affinity of haemoglobin

Question 17

glycolysis in cancer

Answer 17

rate is 200 times greater