Chapter 1.4-1.5 Biological Molecules

Question 1

how are glycogen and starch formed

Answer 1

via the condensation of alpha glucose

Question 2

how is cellulose formed

Answer 2

via condensation of beta glucose

Question 3

starch func + structure

Answer 3

1. The α-helical structure of starch makes it good for storage as its compact
2. large + insoluble so dosent affect water potential, wont diffuse out of cells
3. when hydrolysed it forms a-glucose which can be transported easily and readily used in resp.
4. enzymes can simult. act on the ends of the branches therefore they can be released rapidly

Question 4

Glycogen structure and func

Answer 4

1. Insoluble - dosent draw in water into the cell via osmosis, and also cannot diffuse out of cell

2. compact - a lot stored in small space
3. highly bracnhed (more than starch) = more exposed ends for enz to simultaneously act on= therefore more rapildy broken down to form glucose monomers which are used in respiration

This is benefical for animals bc we have a high metabollic rate, therefore higher resp. rate, as we’re more active than plants.

Question 5

Cellulose struc + func

Answer 5

provides support and rigidity:

1. made of B-glucose and so form long straight, unbranched chains that run parallel to eachother and are cross linked by hydrogen bonds, which add collective strength
2. these molecules are grouped to form microfibrils which in turn are grouped to form fibres all of which provides yet more strength

Question 6

what monomers and polysacc are found in plants

Answer 6

poly= starch, cellulose
mono= a-gluc, b=gluc

Question 7

which of the polys. has a structural function

Answer 7

cellulose

Question 8

which polysacc. can be hydrolysed

Answer 8

starch, cellulose and glyc

Question 9

what can move in/out of cells easily via facilitated diffusion

Answer 9

alpha gluc, beta gluc

Question 10

what forms an esther bond

Answer 10

a condensation reaction between glycerol and a fatty acid (RCOOH)

Question 11

how are triglycerides formed

Answer 11

via the condensation of one molecule of glycerol and three molecules of fatty acids = forming triglyceride and (3) waters

Question 12

saturated

Answer 12

when fatty acid dosen’t contain carbon-carbon double bonds

Question 13

mono-unsaturated

Answer 13

one double bond between carbon atoms

Question 14

polyunsaturated

and why this makes oils liquid at room temp

Answer 14

more than one double bond between carbon atoms

the double bonds cause the molecule to bend, so it cannot pack together so closely making them liquid at room temp e.g oil

Question 15

structure and properties of triglycerides

Answer 15

1. energy storage= they have high ratio of Carbon-Hydrogen bonds: Carbon atoms
2. storage molecules= have low mass: energy ratio so they can store lots of energy in a small volume. This is beneficial for animals as it reduces the mass they’ve to carry as they move around
3. insoluble due to being large and non-polar; therefore their stroage dosent umpact osomsis in cell OR their water poitential
4. source of water= have high ratio of H:O atoms = they relase water when oxidised, beneficial for dessert animals as they act as a source of water

Question 16

whats the difference between tri. and phospho.

Answer 16

in phospholipids; 2 fatty acids and 1 phosphate group- have hydrophilic head and hydrophobic tails

triglycerides; 3 fatty acids, no phosphate, non-polar

Question 17

what two parts are phospholipids made of, and how do they differ?

Answer 17

a hydrophillic head = interacts with water but dosent interact with fat (phosphate group has neg charge)
a hydrophobic tail= orients itself away from water but readily mixes with fat (no charge)

THEREFORE: when placed in water, the hydrophillic heads are as close to the water as possible, and the hydrophoic tails are as far away from the water as possible

Question 18

structure of phospholipids relayted to their property

Answer 18

1. Polar molecules therefore in an aq enviornment, they form a phospholipid bilayer within the cell mem. As a result a hydrophobic barrier is formed between inside and outside of cell
2. hydrophillic heads (-ve charge) hekp to hold at the surface of nthe cell-surface memebrane
3. Phosphilipid structure enables them to form glycolipids by combining with carbohydrates witihin the cell (s) mem. These are important in cell recogintion

Question 19

describe the test for lipids and the name of the test

Answer 19

EMULSION TEST

1. completely dry and grease free test tube
2. add 2cm3 food sample and 5cm3 of ethanol
3. shake throughly to enusure ther lipids have dissolved
4. then add 5cm3 of water and shake gently
5. a milky-white emulsion = lipids present
6. control varible= repeat producedure with water insetad of sample and final sol should remain clear

Question 20

if the lipids are present in the sample why does it turn cloudy

Answer 20

due to any lipid in the sample being finely dispersed in watee to form an emulsion

the light passing through this emulsion is refracted as it passes from oil droplets to water droplets, making it appear cloudy

Question 21

suggest why mobile organisms use lipids as an energy store rather than carbs

Answer 21

lipids provide more than x2 as much energy as carbohydrate when oxidised. if fat is stored, the same amount of energy can be provided for less than half the mass. Therefore, its a lighter sotrage molecule - a benefit if the organisem is motile.