Carbohydrates

Question 1

Name the 3 important hexoses.

Answer 1

Glucose
Galactose
Fructose

Question 2

Name the 3 important Disaccharides in human biochemistry.

Answer 2

Maltose
Sucrose
Lactose

Question 3

Why is Maltose termed a reducing sugar?

Answer 3

Anomeric C-1 can be oxidised.

Question 4

Out of Sucrose and Lactose, which is a reducing sugar and why?

Answer 4

Lactose is reducing, because it has a glucose monomer with an anomeric C whereas Sucrose does not.

Question 5

What monosaccharides make up Lactose?

Answer 5

Galactose

Glucose

Question 6

What are the monomer units of Sucrose?

Answer 6

Fructose

Glucose

Question 7

Describe the difference between a Homopolysaccharide and a Heteropolysaccharide.

Answer 7

Homo = One monomeric species

Hetero = more than one “ “

Question 8

Describe how Amylose differs in structure from Amylopectin.

Answer 8

Amylopectin is branched every 24-30 residues, amylose is straight chained

Question 9

Yay or Nae, including starch in SFM is fucking pointless

Answer 9

Yay

Question 10

90% of body glycogen is found in the liver, and what other part of the body?

Answer 10

Skeletal muscle

Question 11

Why is glycogen’s branched structure beneficial?

Answer 11

More exposed NR ends, so Glucose can be snipped off/added on much more quickly

Highly compact

Insoluble, so is osmotically inactive and is easy to store in the cell

Question 12

Whats the name for a protein with a covalently attached carbohydrate?

Answer 12

Glycoprotein

Question 13

List the ways in which Carbohydrates attached to proteins are used.

Answer 13

Increase solubility

Influence conformation/shape

Protect from degradation

Cell-cell communication

Question 14

Describe what makes Glycosaminoglycans (GAGs) effective lubricants.

Answer 14

Long unbranched polymer chains, so they slide over each other easily

Question 15

Glycosaminoglycans (GAGs) are made of repeating units of an amino sugar and which acid?

Answer 15

Hexuronic Acid

Question 16

Proteoglycans differ from glycoproteins in what way?

Answer 16

Proteoglycans - Carbohydrate&raquo_space; protein

Question 17

Where are proteoglycans found?

Answer 17

On the surface of cells

In between cells in the ECM (connective tissue)

Question 18

What are proteoglycans made up of?

Answer 18

Protein with long carbohydrate chains covalently bonded

At least one GAG present

Question 19

Where are glycoproteins found?

Answer 19

On the outer Plasma membrane
+ ECM (similar to ProtGly)

Blood

Within cells in the secretory system (golgi)

Some cytoplasmic proteins are glycoproteins as well

Question 20

What are Mucopolysaccharidoses?

Answer 20

Genetic disorders causing absence or malfunction of the enzymes that break down Glycosaminoglycans

Question 21

What effect do Mucopolysaccharidoses have?

Answer 21

Build up of GAGs damages cellular architecture + function

Dementia, heart problems and endothelial structures

Question 22

Hurler, Scheie, Hunter, Sanflippo syndromes are examples of what?

Answer 22

Mucopolysaccharidoses

Question 23

List the main effects/symptoms of Hurler syndrome.

Answer 23

Clouding + degradation of cornea

Arterial wall thickening

Dementia (CSF build up + enlarged Ventricular spaces)

Question 24

Describe the structure of Oligosaccharides and how they are digested.

Answer 24

(α1 - 6) linked galactose monomers

not digested

Question 25

What 2 types of amylase are used in digestion?

Answer 25

Salivary | Pancreatic

Question 26

What is the function of Amylase?

Answer 26

Hydrolyses (α1 - 4) bonds of starch

Question 27

What comes first, Jejunum or Duodenum?

Answer 27

Duodenum

Question 28

Mucosal cell-surface enzymes are found where in the digestive tract?

Answer 28

Jejunum

Question 29

Describe the function of Isomaltase.

Answer 29

Hydrolyses (α1-6) bonds

Question 30

Which enzyme snips of glucose from the end of starch?

Answer 30

Glucoamylase

Question 31

What are the main products of carbohydrate digestion?

Answer 31

Glucose Fructose Galactose

Question 32

How is glucose absorbed through 'indirect' ATP power?

Answer 32

ATP is used to maintain Na+ concentration gradient

Question 33

Why is Fructose absorption different from the other hexose sugars?

Answer 33

It binds to a channel protein and simply moves down a concentration gradient

Question 34

Why are cellulose and hemicellulose important?

Answer 34

Increase faecal bulk and decrease transit time

Question 35

What is transported alongside glucose into the epithelial cells in the gut?

Answer 35

Na+

Question 36

How is Glc 'trapped' in the liver?

Answer 36

Glucokinase phosporylates it - not recognised by transporters

Question 37

What significance does the portal blood have in Glc transport?

Answer 37

Transport to liver

Question 38

What role do hepatocytes have in Glc usage?

Answer 38

Site of phosphorylation by glucokinase in the liver

Question 39

What is glycogen?

Answer 39

Branched polysaccharide of Glc

Question 40

Describe the structure of a glycogen molecule.

Answer 40

Glycogenin protein attached to primer Glycogen chains branch out from primer in 'tiers'

Question 41

What enzyme is involved in extending glycogen chains?

Answer 41

Glycogen synthase

Question 42

Describe how glycogen becomes branched.

Answer 42

Glycogen-branching enzyme breaks α1-4 bonds and reattaches α1-6

Question 43

Which end is broken down during glycogen degradation?

Answer 43

Non-reducing

Question 44

What is glycolysis?

Answer 44

Sequential breakdown of glucose, glycogen or other carbohydrates To pyruvate Not requiring oxygen

Question 45

How much ATP is gained from each Glycolysis cycle?

Answer 45

2 ATP

Question 46

Why is the Payoff phase carried out twice?

Answer 46

1 Glc produces 2 G-3-P in preparatory phase

Question 47

True/False NADH used to convert pyruvate to lactate must be replaced using stores of NADH.

Answer 47

False NADH is regenerated in Glycolysis so is not used up

Question 48

What is gluconeogenesis?

Answer 48

Process that converts lactate (+ other carbohydrates) to glucose

Question 49

Why is gluconeogenesis not the opposite of glycolysis?

Answer 49

GNG pathway has 4 reactions the bypass the irreversible reactions in glycolysis

Question 50

Why does the gluconeogenisis process not end with pure Glucose?

Answer 50

G-6-P is trapped in cell Glc would escape

Question 51

Why are glycolysis and gluconeogenesis not reverse processes?

Answer 51

Some reactions in glycolysis pathway are irreversible Bypass reactions take place

Question 52

Where do the bypass reactions take place in glconeogenesis?

Answer 52

Mitochondria | then Cytosol

Question 53

In gluconeogenesis, G-6-P is converted to Glc where in the cell?

Answer 53

ER Enzyme embedded in the membrane

Question 54

How are Galactose and fructose catabolised?

Answer 54

They do not have their own pathway They feed into the glycolysis pathway at different points

Question 55

What does the pentose phosphate pathway do?

Answer 55

Takes G-6-P Makes NADPH and/or Pentose sugars Varies depending on cells requirements - energy or replication

Question 56

Excessive alcohol intake will inhibit gluconeogenesis. How?

Answer 56

Ethanol => Acetate => Acetyle CoA => CAC or stored Processing ethanol requires NAD+ Uses up NAD+ which is needed for gluconeogenesis

Question 57

Black water fever arises from a deficiency in what enzyme?

Answer 57

G-6-P dehydrogenase deficiency

Question 58

Why is a deficiency in G-6-P dehydrogenase a problem?

Answer 58

PPP Less enzyme - less NADPH produced in RBC Free radical build up Damage to membrane Vulnerable