Metabolism

Question 1

What are the four classes of carbohydrates?

Answer 1

Monosaccharides

Disaccharides

Oligosaccharides

Polysaccharides

Question 2

How can monosaccharides be classified?

Answer 2

Number of carbon atoms (triose, tetrose, pentose, hexose)

Isomer (D- or L-isomer)

Question 3

In which isomeric form are most important sugars?

Answer 3

D-isomers

Question 4

What is an isomer?

Answer 4

The same atoms but bonded together in a different 3D arrangement

Question 5

What do glucose, fructose and galactose have in common?

Answer 5

They are all hexoses (6 carbons) which different arrangements of the same atoms

Question 6

What do pentoses and hexoses normally form?

Answer 6

Cyclic molecules

Pentose - 5 membered rings
Hexoses - 6 membered rings

Question 7

Name 2 important pentose monosaccharides

Answer 7

Ribose

Deoxyribose

Question 8

Name 3 important hexose monosaccharides

Answer 8

Glucose

Galactose

Fructose

Question 9

Name 4 important polyoligosacchardies

Answer 9

Starch

Cellulose

Glycogen

Dextrin

Question 10

What is starch?

Answer 10

Branched polymer of glucose.

Formed either by a-1,4 (and) a-1,6 glycosidic bonds

Question 11

What is cellulose?

Answer 11

Linear polymer of glucose

Question 12

What is glycogen?

Answer 12

Extensively branched polymer of glucose

Question 13

What is dextrin?

Answer 13

Branched oligomer of glucose

Breakdown product of starch and glycogen

Question 14

What are the four main types of biologically important lipids?

Answer 14

Fatty acids

Triglycerides

Cholesterol

Cholesterol esters

Question 15

What are fatty acids?

Answer 15

Hydrocarbon chains of various lengths

Question 16

Name 2 differences between saturated and unsaturated fatty acids

Answer 16

Saturated
No double bonds between C atoms
Solid at room temperature

Unsaturated
At least one double C bond
Liquid at room temperature

Question 17

What makes a triglyceride?

Answer 17

1 Glycerol

3 Fatty acid chain

Question 18

Describe cis and trans fatty acids

Answer 18

Applies to unsaturated fat

Movement around the double C bond

Question 19

Describe cis fatty acid

Answer 19

Loosely packed together, causes fatty chain to ‘kink’

Remember cis like cissy - floppy wrist, kink, 2 C,s 2 of the same

Question 20

Describe trans fatty acid

Answer 20

Tightly packed together, chain continues on

Question 21

What is a phospholipid?

Answer 21

A phosphate group attached to one or more fatty acid chains

Question 22

How are phosphate groups attached to fatty acid chains?

Answer 22

Via glycerol or sphingosine

Question 23

What is a glycolipid?

Answer 23

Carbohydrate (oligosaccharide) attached to one or more fatty acid chains

Question 24

How are phosphate groups attached to fatty acid chains in modified lipids?

Answer 24

Via glycerol or sphingosine

Question 25

What characteristic of phospholipids makes them essential?

Answer 25

Polar/non-polar nature, integral for membrane structure

Question 26

Why are glycolipids important?

Answer 26

Cell surface recognition e.g. A and B blood groups

Question 27

What are ketone bodies?

Answer 27

Small 4-carbon fatty acids formed by oxidation of fatty acids in the liver, especially during fasting

Question 28

Why are ketone bodies important?

Answer 28

They provide energy substrates for the brain during fasting

Question 29

How are ketone bodies linked to T1DM?

Answer 29

There is an excessive formation of ketone bodies during fasting which can result in dangerously high levels in the blood causing DKA

Question 30

What creates the smell on the breath in DKA?

Answer 30

Acetone formed as a result of the breakdown of ketone bodies and exhaled

Question 31

Give 5 roles of lipids

Answer 31

Fuels (fatty acids, ketone bodies) Energy storage (triglycerides) Transport between tissues (triglycerides) Structural components of cell membranes (phospholipids) Chemical messengers (diglycerides, steroids)

Question 32

What type of process consumes ATP?

Answer 32

Anabolic process

Question 33

What type of process produces ATP?

Answer 33

Catabolic process

Question 34

Name the 3 parts of ATP

Answer 34

Adenosine Ribose 3 phosphate chain

Question 35

Describe the role water has in making ATP from ADP

Answer 35

ADP --> ATP = water is lost ATP --> ADP = water is added

Question 36

How is energy released from ATP?

Answer 36

By breaking up the high energy bonds between phosphate groups

Question 37

Where is the only place ketones can not be used as an energy source?

Answer 37

The liver (synthesised there) They are importantly used by the brain as substitute for glucose when it is not available

Question 38

How is glucose stored in the liver?

Answer 38

As glycogen (a polymer of glucose)

Question 39

Describe the relationship between fatty acids and glucose, and explain why this is important

Answer 39

Fatty acids can be formed from glucose, but not vice versa. Glucose can be stored as lipids, but then can only be metabolised as lipids. This is to save energy so fatty acids and glucose are not being used at the same time, and provides an energy storage solution

Question 40

Name the 2 types of glucose transporters and state whether they are active or passive transporters

Answer 40

GLUT - passive SGLT - active

Question 41

What is the main difference between GLUT and SGLT transporters?

Answer 41

SGLT can transport Na+ as well as glucose

Question 42

Which GLUT transporter has the highest affinity and where is it found?

Answer 42

GLUT-1 RBCs Brain

Question 43

Which GLUT transporter has the lowest affinity and where is it found?

Answer 43

GLUT-2 Pancreatic B-cell Liver

Question 44

Why is it beneficial to have a low affinity GLUT-2 transporter on a pancreatic B-cell and in the liver?

Answer 44

Because it will only uptake glucose if there is an excess of it in the blood. This means that insulin will not be released prematurely into the blood stream by pancreatic B-cells, and the liver will only start to store glucose as glycogen if there is an excess of it in the blood, meaning more is readily available.

Question 45

Which GLUT transporter is insulin sensitive?

Answer 45

GLUT-4

Question 46

What is a lipid and what is it made from?

Answer 46

Glycerol Fatty acids Insoluble in water

Question 47

What is the difference between mono- and poly-unsaturated fats?

Answer 47

Monounsaturated fatty acids have one C=C bond Polyunsaturated have more than one C=C bond

Question 48

What are the bonds in a triglyceride called? How are they formed?

Answer 48

Covalent bonds Condensation reactions

Question 49

What is the difference between a triglyceride and a phospholipid?

Answer 49

Phospholipids only have 2 fatty acid tails, and have replaced the 3rd fatty acid with a phosphate group

Question 50

Sucrose is made of:

Answer 50

Glucose and fructose

Question 51

Lactose if made of:

Answer 51

Glucose and galactose

Question 52

Maltose is made of:

Answer 52

Glucose and glucose

Question 53

What 2 substances make up ketone bodies?

Answer 53

Acetoacetic acid B-hydroxybutyric acid

Question 54

What is the role of carbohydrates?

Answer 54

Energy source

Question 55

What is the role of lipids

Answer 55

Energy source Membrane components Hormonal signalling

Question 56

What is the role of proteins?

Answer 56

Enzymatic catalysis Antibodies Hormonal signalling Structural proteins Contractile proteins Gas transport

Question 57

What is the role of nucleic acids?

Answer 57

Information storage/transmission

Question 58

Where can glucose be used as an energy source?

Answer 58

Most tissues - obligatory for brain and RBCs

Question 59

Where can fatty acids be used as an energy source?

Answer 59

Most tissues - minimal in neurons as energy source

Question 60

Where can amino acids be used as an energy source?

Answer 60

Not used by many fuel types - but are used by fast dividing cells e.g. enterocytes and cancer cells