9- Metabolism 1 - glycolysis Flashcards
what is anabolism?
assimilation of molecules & complex structures from the building blocks of life
= requires energy
what is catabolism?
breakdown of molecules to obtain the anabolic “building blocks” of life and substrates for energy
= breakdown of molecules to yield energy
what is metabolism a balance between?
anabolism & catabolism
is anabolism
a) endergonic or exergonic?
b) reductive or oxidative?
a) endergonic
b) reductive
is catabolism
a) endergonic or exergonic?
b) reductive or oxidative?
a) exergonic
b) oxidative
what happens in anabolism?
it takes oxidised precursors (products of catabolism) and with NADPH and H+ assembles them together to make biosynthetic products and NADP+ which can be used in catabolism
= anabolism is essential for process of growth & storage
what happens in catabolism?
reduced fuel is broken down into oxidised products and NADH and H+ is used for oxidative phosphorylation of O2 to H2O which helps make energy
what does metabolism always require?
- precursor→product
- reducing equivalent (that either accepts or donates electrons) to drive process forward
what glucose molecules are in plants & animals?
plants = starch & cellulose
animals = glycogen
what cells require glucose as an energy source?
- erythrocytes
- retina
- renal medulla
- brain (the brain accounts of about 20% of the oxygen requirement in a resting person even though only 2% of body weight of an individual - highly oxidative organ)
- all cancer cells
what is structure of glucose?
6 carbon carbohydrate
- not naturally in linear form, usually circular
oxygen at top right corner - can think that it holds it in shape and holds likke spring so if you remove that O and do in controlled way you can release energy (glycolysis = breaking of glucose)
what are disaccharides?
2 glucose that join together very easily, in lots of different orientations making a family
lactose, maltose, sucrose, cellabiose
why is lactose so good for newborns?
it’s very easily broken down so good for supporting metabolism in newborn baby
what are polysaccharides?
lots of glucose joined together
cellulose = glucose molecules linked in carbon 1-4 orientation
glycogen = glucose linked together, can make branches which means you can pack together so have ready source of glucose that can be tapped into in times of starvation
if oxygen starved - what happens to pyruvate?
pyruvate converted to lactate
what are the 3 different pathways of glucose?
- converted to PYRUVATE by oxidation through aerobic glycolysis
- converted to LACTATE by fermentation by anaerobic glycolysis
- converted to RIBOSE-5-PHOSPHATE by oxidation through the pentose phosphate pathway
what is ribose-5-phosphate?
precursor for nucleotide synthesis & DNA repair = essential for growth (ties into warburg effect of cancer cells = glucose use for cancerous tumours is double whammy; for providing energy & for precursor of growth
how is glucose transported into cell?
via Na+/glucose symporters
what are examples of glucose symports?
GLUT 1 = in brain, low Km
GLUT 2 = in liver and B cells, high Km & insulin dependant
GLUT 3 = in brain, low Km
GLUT 4 = in muscle and adipose tissue, insulin dependant
GLUT 5 = in gut, fructose transport
what is process of GLUT 1 transporter?
- binding of glucose to the outside triggers conformational change
- binding site faces inwards
- glucose can be released in the inside
- Conformational change regenerates the binding site on the outside
what is process of stage 1 of glycolysis?
2 ATP →2 ADP energy helps convert glucose to fructose-1,6-biphosphate
- 1 ATP used by hexokinase for glucose →glucose-6-phosphate and (phosphoglucose isomerase →fructose-6-phosphate)
- 1 ATP used by phosphofructokinase to make fructose-1,6-biphosphate
what is the net gain of ATP in glycolysis?
2 ATP (2 used at start and then 4 made so 4-2 = 2)
what happens in stage 2 of glycolysis?
fructose-1,6-biphosphate converted into two 3-carbon triose phosphates
= 2 interconvertible 3-carbon molecules, triose phosphates, are formed
what happens in stage 3 of glycolysis?
triose phosphate then used 2 NAD →2 NADH + 2H+ and 4ADP →4 ATP to make 2 pyruvate
(both triose phosphate undergo reaction so reaction happens twice →2 pyruvate)
pyruvate kinase catalyses last step to pyruvate making final bit of ATP
