Carbohydrates

Question 1

Carbohydrates are highly oxidisable or not l

Answer 1

Yes they are

Question 2

Carbohydrate functions

Answer 2

Structure in cell walls and ECM of animal cells. Store energy as starch in plants and glycogen in animals. Cell to cell communication eg ABO blood groups

Question 3

Types of monosaccharides

Answer 3

Glucose fructose galactose

Question 4

Disaccharide

Answer 4

Formed from monomers that are linked by glycosidic bonds

Question 5

Glycosidic bonds

Answer 5

Covalent bond formed between hydroxyl group and anomeric carbon of different monosaccharide

Question 6

Anomeric carbon

Answer 6

Anomers are mirror images of each other( left and right handed forms ). Stabilises the structure of glucose. Only residue that can be oxidised

Question 7

Types of disaccharide

Answer 7

Maltose lactose sucrose

Question 8

Sucrose is a reducing sugar true or false and why

Answer 8

False because no free anomeric carbon

Question 9

Polysaccharides

Answer 9

Polymers of medium to high molecular weight

Question 10

Types of polysaccharides

Answer 10

Homopolysaccharides - single monomer species

Heteropolysaccharides- have two or more monomer species

Question 11

Starch contains

Answer 11

Amylose mainly straight and amylopectin (75% of it) (got alpha 1-4 chains and 1-6 chains). Non reducing ends

Question 12

What is more extensively branched glycogen or starch

Answer 12

Glycogen

Question 13

Glycogen is in what part of the body

Answer 13

Liver (replenish blood) and skeletal muscle (produces atp for contraction)

Question 14

Why store glucose in polymers

Answer 14

Compactness, have lots of non reducing ends so can be readily synthesised and degraded, form hydrated gels and not rlly in solution - omsotically inactive

Question 15

What do carbohydrates attached to proteins do

Answer 15

Communication between cells, protect it from degradation, influence folding, increase solubility

Question 16

Glycosaminoglycans

Answer 16

Found in mucus, un branched polymers made from units of hexuronic acid and amino sugar which alternates through the chains

Question 17

Proteoglycans

Answer 17

Carbohydrate part muchhh more than protein. Formed from GAGs. They are macromolecules found on surface of cells or in between cells in the ECM. Form part of connective tissue

Question 18

Glycoproteins

Answer 18

V similar to proteoglycans but protein part more than glucose. Found in blood and in cells in secretory system

Question 19

Carbohydrate digestion order

Answer 19

Mouth- salivary amylase
Duodenum- pancreatic amylase
Jejunum (small intestine)- mucosal cell surface enzymes

Question 20

Glucose is absorbed how

Answer 20

Using glucose symport and sodium potassium pump in epithelial cells of the small intestine

Question 21

Fructose is absorbed how

Answer 21

Uses GLUT5 transporter. Then goes down the conc gradient high in gut lumen low in blood

Question 22

Cellulose and hemicellulose break down

Answer 22

Don’t get digested but they get broken down. Increase faecal bulk and decrease transit time. Break down yields CH4 and H2 (farts)

Question 23

Disaccharide deficiencies

Answer 23

Genetic, cramps because struggle to break down. Enzyme tests to see if they are working. Lactose intolerance

Question 24

Fate of absorbed glucose

Answer 24

Goes from epithelial cells into blood then to liver. Converted into glucose-6-phosphate which cannot diffuse out of cell because GLUT transporters won’t take it so it is trapped. Enzymes work on it. Then go through blood as glucose to other tissues

Question 25

What enzyme is better for glucose- glucokinase or hexokinase

Answer 25

Hexokinase (low Km but low Vmax)

Question 26

In skeletal muscle what does glycogen get broken down into

Answer 26

Lactate because of glycolysis

Question 27

Synthesis of glycogen

Answer 27

1- glycogenin binds glucose to form short chains then glycogen synthase extends the chains 2- chains broken by glycogen branching enzyme and react hard via alpha1-6 bonds to give branch points

Question 28

Degradation of glycogen

Answer 28

Glucose monomers are removed by glycogen phosphoylase one at a time from non reducing ends as G1P. Then glucose is removed then reattached at the nearest non reducing end. Glucosidase then removes the final glucose by breaking a alpha1-6 link to release free glucose

Question 29

What happens to pyruvate at the end of glycolysis

Answer 29

Converted into ethanol and carbon dioxide, lactate or carbon dioxide and water

Question 30

What coenzyme is needed in glycolysis

Answer 30

NAD and NADH

Question 31

What is glycolysis

Answer 31

Catabolic pathway that saves some potential energy from glucose by forming ATP through substrate level phosphorylation.only way energy can be made when oxygen is in short supply

Question 32

Process of glycolysis

Answer 32

Glucose to F-1,6-BP (Used 2ATP) then to G3P to PEP to pyruvate or to DHAP. Produces 4 ATP

Question 33

When is cori cycle used

Answer 33

When the muscles don’t receive oxygen fast enough to make ATP so ATP is made via substrate level phosphorylation which produces lactate. Lactate converted and then the liver repaid oxygen debt to molecules

Question 34

Gluconeogenesis is

Answer 34

Process that transforms non carbohydrate substances such as glycerol, amino acids, lactate into glucose

Question 35

What is cori cycle

Answer 35

Interaction between muscle and liver with glucose

Question 36

How can glycolysis and gluconogenesis be independently controlled

Answer 36

Bypass reactions that sidestep the irreversible ones of glycolysis. Prevents them cancelling each other out

Question 37

What other sugars can be added to glycolysis

Answer 37

Galactose at beginning (converted into glucose 6P) and then fructose at second stages (converted into fructose 6P) or from liver converted into GAP or DHAP