2.3

Question 1

What are the 3 types of carbohydrates, and list 3 examples for each:

Answer 1

Monosaccharides: alpha-glucose, beta-glucose, ribose

Disaccharides: maltose, sucrose, lactose

Polysaccharides: cellulose, starch, glycogen

Question 2

What is the structure and function of cellulose (in plants)?

Answer 2

• straight unbranched chain of β-glucose residues
• linked by β-1, 4 glycosidic bonds
• every other glucose residues is flipped over
• the chains form bundles linked by H-bonds & they have very high tensile strength
• used to make plant cell walls
• –> provides plant cell walls w/ shape & structure
• –>prevents plant cell from bursting

Question 3

What is the structure and function of starch (in plants)?

Answer 3

Amylose:

• unbranched chain of α-glucose residues
• linked by α-1, 4 glycosidic bonds
• forms a helix—> compact
• insoluble
• only has 2 ends–> more resistant to digestion

Amylopectin:

• branched chain of α-glucose residues
• has α-1,4 glycosidic bonds in chains, but α-1,6 glycosidic bonds @ branch points
• insoluble, less compact
• many end points=quickly digested
• stores energy in plant cells
• has specialised organs for storage

Question 4

What is the structure and function of glycogen (in animals)?

Answer 4

• similar to amylopectin but more highly branched
• has α-1, 6 glycosidic bonds @ branch points & in chains
• insoluble & quite compact
• many ends=digested quickly

-Is energy storage found in animal cells (liver & luscle cells)

Question 5

How are triglycerides formed?

Answer 5

By condensation from 3 fatty acids & one glycerol

Question 6

What can fatty acids be?

Answer 6

Saturated (only C-C bonds) or Unsaturated (has some C=C bonds)

Unsaturated fatty acids can be cis or trans isomers

cis: have H atoms attached on the same side = bend chain
trans: H atoms attaches on opposite sides = straight chain

Question 7

Compare how carbohydrates & lipids can be used for energy storage:

Answer 7

Carbs:
short term energy store
can be broken down easily to release energy quick
release less energy per gram compared to lipids
soluble & easily transported
stored as glycogen
can be used in anaerobic & aerobic respiration

Lipids:
long term energy store
take longer to break down & release energy slowly
release twice as much energy
insoluble & less easily transported
stored as fat
can only be used in anaerobic respiration

Question 8

How do you calculate BMI?

Answer 8

BMI=mass in kg / (height in m)^2

Question 9

What is the evidence for health risks of trans fats & saturated fatty acids?

Answer 9

Coronary Heart Disease:
arteries become blocked by fatty deposits—>leads to blot clots & heart attacks
saturated fatty acid intake increase CHD risk
cis-monounsaturated fatty acid intake lowers CHD risk
dead people from CHD found to have more concentrations of trans fats