Carbohydrates

Question 1

Carbs

Answer 1

Monomers joined by glycosidic bonds
Highly Oxidisable
Store potential energy (starch, glycogen)
Structural and Protective functions (cellular matrices)
Cell-cell Communication

Question 2

*Anomeric Carbon

Answer 2

Its the only oxidisable residue
Stabilises the glucose structure
Lactose and Maltose are named reducing sugars since an anomeric carbon is present in glucose??

Question 3

Homopolysaccharides

Heteropolysaccharides

Answer 3

Single monomeric species

2 or more monomer species

Question 4

Starch

Answer 4

Glucose polymer
Amylose + Amylopectin which form A-Helices
Many non reducing ends and few reducing ends

Question 5

Amylose

Answer 5

20-25% of Starch

D-Glucose residues (a1-4 linkage)

Question 6

Amylopectin

Answer 6

75-80% Starch
Branched
Glycosidic (a1-4) bonds join glucose in chains but branches at (a1-6) every 24-30 residues

Question 7

Glycogen

Answer 7

Polymer of glucose (a1-4) linked subunit with (a1-6) branches every 8-12 residues
More Extensively branched than Starch
Many reducing ends which speed up degradation
90% in liver and skeletal muscles

Question 8

Polymers exist bc?

Answer 8

Polymers form hydrated gels which are

Osmotically inactive

Question 9

Glycosaminoglycans GAGs

Answer 9

Function: Mucus and synovial fluid
Un-branched polymers made from
Repeating units of hexurinic acid and amino sugar

Question 10

Proteoglycans

Answer 10

GAGs covalently attaching to proteins
Macromolecules found in cell surface / bw cells in extracellular matrix
Part of the connective tissue
Carbs&raquo_space; Protein

Question 11

Glycoproteins

Answer 11

Protein&raquo_space; Carbs
Outer Plasma Membrane
ECM
Blood

Question 12

Mucopolysaccharidoses

Answer 12

Malfunction or Absence of enzymes required for Glycosaminoglycans breakdown
GAGs build up in connective tissue, blood and cells
Damages cellular architecture and function
Dementia, Heart, Endothelial function, Inflamed joints

Question 13

Hurler Syndrome

Answer 13

Clouding and degradation of cornea
Arterial Wall Thickening
CSF buildup, Ventricular space enlargement - Dementia
Developmental Abnormalities

Question 14

Carbohydrate Digestion

Answer 14

Mouth: Salivary amylase hydrolyses a1-4 bonds
Duodenum: Pancreatic Amylase a1-4 bonds
Jejunum -
Isomaltase: Hydrolyses a1-6 bonds
Glucoamylase: removes Glc sequentially from non-reducing ends
Sucrase Hydrolyses Sucrose
Lactase: Hydrolyses Lactose

Question 15

Cellulose and Hemicellulose

Answer 15

Oligosaccharides

Cannot be digested - Increase faecal bulk

Question 16

Lactose Intolerant

Answer 16

Lactose is osmotically active draining water in small intestine - diarrhoea
Bacteria in gut break down undigested lactose causing gas to build up

Question 17

Absorbed Glucose

Answer 17

Glc diffuses through intestinal epithelium to blood and liver where is phosphorylated into G6P by hepatocytes
G6P cannot diffuse out of cells since GLUT cannot recognise it

Question 18

Glucokinase

Hexokinase

Answer 18

High Km and Vmax (When Glc is high in concentration it quickly phosphorylates to G6P in *liver)
Low Km and Vmax (When Glc is low in concentration it quickly phosphorylates to G6P in tissues, it is easily satisfied-efficient)

Question 19

Where is G-6-P (GLYCOGEN) found?

Answer 19

Liver

Skeletal muscles form lactate from G-6-P in Glycolysis

Question 20

Glycogen Synthase

Answer 20

Glycogenin covalently binds Glc from Uracil Diphosphate (UDP)-Glc to form chains of 8Glc Recidues
Glucose Synthase extends the Glc chains
Glycogen Branching Enzyme breaks chains

Question 21

Glycogen Degradation

Answer 21

1) Glc monomers are removed one at a time from the non-reducing ends as G1P by Glycogen Phosphorylase
2) Transferase activity of de-branching enzyme removes a set of 3Glc Residues and attaches them to the nearest non-reducing end via (a1-4) bond
3) Glycosidase removes final Glc by breaking (a1-6) linkage to release free Glc

Question 22

McArdles’s Disease

Answer 22

Skeletal Muscle Phosphorylase Deficiency

Cramps, High muscle Glycogen