Carbohydrates

Question 1

What are 4 main features of carbohydrates?

Answer 1

Highly oxidisable, store potential energy, structural and protective functions, cell-cell communication

Question 2

What are three important hexose monosaccharides?

Answer 2

Glucose, Fructose, Galactose

Question 3

What are three important disaccharides?

Answer 3

Maltose, Lactose, Sucrose

Question 4

What links a disaccharide and on which groups?

Answer 4

Hydroxyl group binds to Anomeric carbon (1) by glycosidic bond

Question 5

Where is maltose found/ how is it made?

Answer 5

In beer and baby food as sweetener. We don’t have much from our diets. Made from the breakdown of starch

Question 6

Which disaccharides are reducing sugars and why?

Answer 6

Maltose and lactose. Anomeric C1 is available for oxidising, so they’re reducing sugars.

Question 7

Where is sucrose found + what are its monomers?

Answer 7

Made by plants, found in sugar and processed foods. Glc + Fru

Question 8

What are 4 ways to distinguish polysaccharides?

Answer 8

Monosaccharide units, length of chain, types of bonding, amount of branching

Question 9

What are 2 subcategories of polysaccharides?

Answer 9

Homopolysaccharide (1 monomer only) and Heteropolysaccharide (2+ monomers)

Question 10

What is starch and what glucose polymers does it contain?

Answer 10

Glucose polymer. Includes Amylose and Amylopectin

Question 11

How often is there branching in amylopectin?

Answer 11

Every 24-30 glc monomers

Question 12

Is starch reducing?

Answer 12

It has many non-reducing ends but few reducing ends

Question 13

What is the structure of glycogen?

Answer 13

a-Glucose with 1-6 links every 8-12 monomers, so very branched

Question 14

Where is glycogen mostly found in our bodies? (2)

Answer 14

In our liver to replenish blood glucose levels when we aren’t eating. In our skeletal muscle catabolising to ATP to allow our muscles to contract

Question 15

Why are polymers a great form of storage for glucose? (2)

Answer 15

Many non-reducing ends to breaks down/forms very quickly. Very compact due to branching.

Question 16

Glycoproteins structure

Answer 16

Protein with carbohydrates attached/associated with it

Question 17

Features carbs bring to proteins (4)

Answer 17

Increase solubility, protect it from degradation, induce folds/conformation in protein, involved in cell-cell communication

Question 18

Where are glycoproteins usually found? (6)

Answer 18

Plasma membrane, ECM, Cytoplasm and nucleus proteins, in the blood and in the Golgi apparatus

Question 19

What is a glycosoaminoglycan (GAG) formed of?

Answer 19

A hexuronic acid and amino sugar alternating in an unbranched chain

Question 20

Where are GAG’s found?

Answer 20

In the mucus and in synovial fluid around joints

Question 21

What is a proteoglycan?

Answer 21

A GAG attached to proteins (e.g. cytokines). Mostly carb with attached protein

Question 22

Where do we find proteoglycans on the body? (3)

Answer 22

On cell membranes attached to proteins, in the ECM and in the ground substance of connective tissue

Question 23

What is mucosopolysaccharidosis?

Answer 23

Genetic disorder where enzymes cant break down GAG’s so they build up in cells, blood and ECM of connective tissue

Question 24

What are some of the effects of mucosopolysaccharidosis? (5)

Answer 24

Heart and epithelial tissue damage, Stunted bone growth, Inflammad and damaged joints and sever dementia

Question 25

Where does digestion of carbs occur in our body?

Answer 25

In the mouth and small intestine (duodunum and jejunum)

Question 26

What 2 enzymes phosphorylise glucose and where are the found?

Answer 26

Glucokinase in the liver and hexokinase in other tissues

Question 27

What benefit do Cellulose and Hemicellulose bring us?

Answer 27

Increase faecal bulk and decrease transit time

Question 28

What are oligosaccharides and some examples in food?

Answer 28

Short monomer chain (with a1-6 ), not as large as polysaccharides. Peas, beans, lentils

Question 29

How are carbs digested in the mouth and duodenum?

Answer 29

Amylase in saliva hydrolysed 1-4 bonds of starch

Question 30

What are the 4 digestive processes in the jejunum and the name of the reaction?

Answer 30

Lactase, Glucoamylase (removes Glc), Sucrase, Isomaltase (1-6 bonds) - All Hydrolysis

Question 31

What are the names of the first and middle part of the small intestine?

Answer 31

Duodenum and Jejunum

Question 32

What are the products of carb digestion and where do they go?

Answer 32

Glc, Gal, Fru. They’re absorbed by the gut into the blood stream

Question 33

What allows glucose to be absorbed by the gut and moved into the blood stream?

Answer 33

Low Na+ conc. in epithelial drives Na+ and glucose to enter the epithelial cell. Then glucose transports into blood through GLUT2.

Question 34

What are some causes of disaccharidase deficiencies? (5)

Answer 34

Genetic inability to produce enzymes, Inflammation in gut, Damage to gut wall, removal of intestine, Intestinal infection

Question 35

What are the symptoms of a disaccharidase deficiency?

Answer 35

Cramps or Abdominal distension

Question 36

What is the cause and effect of lactose intolerance (2)?

Answer 36

Inability to produce lactase. Undigested lactase broken down in gut causing gas. Lactose also drags water from gut into lumen, causing diarrhoea

Question 37

What are the enzymes that phosphorylase glucose and where can they be found?

Answer 37

Glucokinase in the liver and Hexokinase in all other tissues

Question 38

What do terms Km and Vmax refer to?

Answer 38

Km refers to an enzymes affinity to a substrate. Low Km means an enzyme has a high affinity for a substrate (grabs on).
Vmax refers to the efficiency of an enzyme to catalyse a substrate. High Vmax = very efficient enzyme

Question 39

What is the difference between Glucokinase and Hexokinase?

Answer 39

G in liver, H in other tissues.
G has high Km and high Vmax, so doesn’t grab many substrates but phosphorylises Glc quickly
H has low Km and low Vmax, so grabs a lot of substrate (good for low blood glucose level) but phosphorylises Glc slowly

Question 40

What is the main fate of glucose/G6P?

Answer 40

To be converted to energy during respiration/oxidative phosphorylation in the liver, tissues or skeletal muscle

Question 41

How is glycogen distributed around the body?

Answer 41

90% is in the liver and skeletal muscle for energy storage, 10% in the blood

Question 42

What is the livers role in glucose storage?

Answer 42

Glucose is converted to G6P and stored as glycogen. When blood Glc levels are low, glycogen is broken down and converted from G6P back to glucose, to be released into the blood

Question 43

What is skeletal muscle’s role in glucose storage?

Answer 43

Glucose phosphorylises into G6P and then glycogen forms. When required, glycogen breaks down to G6P, but can’t return to Glc, so converts through glycolysis to lactate to make ATP

Question 44

How is Glycogen degraded?

Answer 44

Glycogen phosphorylase removes Glc from non reducing ends, producing G1P monomers. Debranching enzyme removes 1-6 bonds

Question 45

How is Glycogen synthesised? (3 steps)

Answer 45

(1) Glycogenin forms short glucose chain. (2) Then Glycogen synthase adds further glucose molecules. (3) Branching enzyme breaks chain and reforms it as a 1-6 bond.