2.2 Biological molecules

Question 1

Why is water polar?

Answer 1

Oxygen has more (+ve) protons in nucleus than H

Exerts stronger force for shared electrons making it slightly negative, and hydrogen slightly positive

Question 2

Why is it important that water is a liquid? (4)

Answer 2

habitats for living things
major component of tissues in living organisms
reaction medium for chemical reactions
transport medium e.g. blood

Question 3

Ice only gets denser as it gets colder up until 4 degrees. After that, it gets less dense because its polar.

Why is this important?

Answer 3

stable environment for aquatic organisms

insulation in the cold

Question 4

Because water is polar, the positive and negative parts of the water are attracted to the negative and positive parts of the solute.
Why is it important that water is a good solvent?

Answer 4

molecules can transport whilst dissolved in it.

Question 5

How does water have cohesion and surface tension?

Answer 5

water molecules at surface are all hydrogen bonded to mols beneath so surface of water contracts giving it an ability to resist force applied to it

Question 6

What is specific heat capacity?

Answer 6

the amount of heat energy required to heat one kg of water by 1 degree

Question 7

Why is it good that water has a high specific heat capacity? (2)

Answer 7

stable temp / stable environment for aquatic organisms

stable temp for enzyme controlled reactions in living things

Question 8

Formula for alpha and beta glucose?

Answer 8

C6 H12 O6

Question 9

What is the difference between alpha and beta glucose?

Answer 9

the right h and oh on the beta is the other way around

Question 10

what does a glucose and a glucose make?

Answer 10

maltose

Question 11

what does alpha glucose and fructose make?

Answer 11

sucrose

Question 12

what does beta galactose and alpha glucose make?

Answer 12

lactose

Question 13

what does beta glucose and beta glucose make?

Answer 13

cellobiose

Question 14

What two polysaccharides is starch comprised of?

Answer 14

amylose and amylopectin

Question 15

Which out of glycogen, amylose, and amylopectin are branched?

Answer 15

glycogen and amylopectin (1,6 glycosidic bonds)

Question 16

Why is it good that glycogen are compact in dense granules, and branched? (2)

Answer 16

dont occupy a lot of space

easily snipped off when required for respiration

Question 17

chains of b glucose joined by condensation reaction are straight because every other glucose molecule is rotated by x degrees

Answer 17

180

Question 18

Difference between triglyceride and phospholipid structure?

Answer 18

triclyceride= glycerol+ 3 fatty acid chains
phospholipid= glycerol+2 fatty acids + phosphate group

Question 19

What are proteins? (1)

Answer 19

A large polymer of amino acids

Question 20

What is primary structure?

Answer 20

Primary= order/sequence of amino acids

Question 21

What is the amine group of an amino acid comprised of?

Answer 21

N H H

Question 22

What is the carboyxl group of an amino acid comprised of

Answer 22

C=O

-OH

Question 23

Name 3 fibrous proteins

Answer 23

Collagen
Keratin
Elastin

Question 24

Name 3 globular proteins

Answer 24

Haemoglobin
Insulin
Pepson

Question 25

How do you test for starch/

Answer 25

Iodine solution on white spotting tile

Blue-black colour indicates starch is present

Question 26

How do you test for reducing sugars?

Answer 26

Add benedicts solution then heat in water bath 80oC for 3 minutes
orange red precipitate indicates reducing sugar is present

Question 27

How do you test for non-reducing sugars?

Answer 27

Hydrolyse the bond to free up the reducing groups by boiling with hydrochloric acid
neutralise with sodium hydrogencarbonate
test for reducing sugar as normal

Question 28

How do you test for lipids?

Answer 28

add ethanol
add water
cloudy white emulsion indicates presence of lipids

Question 29

How do you test for proteins?

Answer 29

biuret test

lilac colour indicates protein

Question 30

How is glucose structurally different from fructose?

Answer 30

Fructose has a five membered ring and glucose has a six membered ring

Question 31

State 4 differences between haemoglobin and collagen. (5)

Answer 31

Collagen= triple helix. Haemoglobin=2 helix 2 pleated sheets
C= fibrous H=globular
C=1 type of polypeptide chain H=2 types alpha H betaPS
C=only made of polypeptide chains H= has prosthetic haem group
C=function is fibrous connective tissue H=function transport oxygen

Question 32

Give 2 reasons why water is a good transport medium

Answer 32

Polar- good solvent, can dissolve glucose
Hydrogen bonds allow water to flow as a body
Liquid at room temperature

Question 33

Describe the nature of disulphide bonds (4)

Answer 33

Joins 2 sulphur atoms
covalent bond
Between R groups
Strong

Question 34

What is secondary structure?

Answer 34

Secondary= the way it folds or coils- alpha helix or beta pleated sheet

Question 35

What is tertiary structure?

Answer 35

Tertiary= interaction between r groups when those coils and pleats themselves fold

Question 36

What is quarternary structure?

Answer 36

Quarternary=more than one polypeptide chain

Question 37

State and explaiun 2 ways glucose is suited to its funcction in living organisms.

Answer 37

soluable so easily trasported
small so diffuse across cell membranes
easily broken down/hydrolysed for ATP

Question 38

Why do mammals use glycogen as an energy store? (4)

Answer 38

1 insoluble , so has no effect on ,
water potential / Ψ (of cell) 
2 metabolically inactive 
3 compact / lots can be stored in a small space 
4 able to store , large amounts / lots , of energy 
5 (highly branched so) has lots of ends for ,
adding / removing , glucose (when needed)
or
can be broken down , fast / quickly / rapidly ,
to release glucose

Question 39

What 3 things is ATP made of?

Answer 39

adenine
ribose
phosphate