Module 2:Biological molecules

Question 1

Why is water a polar molecule?

Answer 1

due to an uneven distribution of charge within the molecule
the H atoms are more + charged than the O atoms so one end of the molecule is more positive

Question 2

Which metabolic reactions is water a metabolite for?

Answer 2

condensation and hydrolysis

Question 3

Is water a solvent?

Answer 3

yes

Question 4

Does water have a high SHC?
If so , what benefits does this have?

Answer 4

yes

-it helps to minimise temp fluctuations in living things as lot of energy is required to warm it up

Question 5

Does water have a high latent heat of vapourisation?
If so what benefits does this have?

Answer 5

yes
it means that evaporation has a cooling effect on the body with minimal water loss

Question 6

Is water compressible ?
What does this provide?

Answer 6

no
this means it provides good support

Question 7

What does strong cohesion between water molecules enable?

Answer 7

the effective transport of water in tube like transport cells as the strong cohesion supports the columns of water

Question 8

Is ice less or more dense than water?
If less , what does this enable?

Answer 8

Its less dense than water meaning it floats above water which creates an insulating layer which prevents organisms in large bodies of water from freezing

Question 9

What is a monomer?
Give 3 examples

What is a polymer?

Answer 9

the small units that are the components of larger molecules
( glucose , amino acids and nucleotides)

large molecules made from repeating monomer units joined together

Question 10

What molecule is eliminated during a condensation reaction and what is a condensation reaction?

What is a hydrolysis reaction ?

Answer 10

a water molecule
a reaction that joins monomers by chemical bonds

a reaction that adds a water molecule to break a chemical bond between 2 molecules

Question 11

What elements do carbohydrates contain?

Answer 11

carbon
hydrogen
oxygen

Question 12

What is the structure of a carbohydrate?

Answer 12

a long chain of sugar units called saccharides

Question 13

What are the three different types of saccharide?

Answer 13

monosaccharides-small simple sugars
disaccharides-made of two monosaccharides
polysaccharide-long chain of monosaccharides

Question 14

Name three important functions of carbohydrates

Answer 14

-as a usable energy source for cells
-an energy storage molecule
-formation of cell wall in plants/fungi/bacteria

Question 15

What do monosaccharides provide and how?

Give an example of a monosaccharide and describe its structure and function

Answer 15

a rapid source of energy
as they are small and simple they are readily absorbed and require little/no change before use in cell activity

Glucose-a hexose monosaccharide
its the main substrate for respiration
its breakdown releases ATP which is required by cells for every chemical reaction they undergo

Question 16

Monosaccharides/disaccharides can’t be used to store energy , but why not?

Answer 16

they are chemically active and soluble in water so would affect the water potential of the cell

Question 17

What are the two isomers of glucose and how do their molecular structures differ?

Answer 17

alpha and beta glucose
alpha-on the 1st carbon the H atom is at the top
beta-on the 1st carbon the OH group is at the top

Question 18

What is the name of the covalent bond that links monosaccharides together?

Answer 18

glycosidic bonds

Question 19

What are the 3 main disaccharides and what monosaccharides do they consist of?

Answer 19

maltose-2 glucose molecules
sucrose-glucose and fructose
lactose-glucose and galactose

Question 20

Name the three main polysaccharides and which glucose isomer they consist of

Answer 20

starch(alpha) , cellulose
(beta) and glycogen(alpha)

Question 21

What is the role of glycogen?
Describe its structure… (4)

Answer 21

it is the main energy storage in animals
-made of many alpha glucose monomers joined by glycosidic bonds in condensation reactions
-contains 1-4 and 1-6 glycosidic bonds
-has a highly branched structure which allows glucose and therfore energy to be released easily
-its a large molecule but is compact which maximises the amount of energy it can store

Question 22

What is the role of starch?
How is it produced?
Which 2 polysaccharides does it consist of?
Is it soluble/insoluble and is it compact?

Answer 22

it is a major carb storage molecule in plants
from glucose made in photosynthesis
amylose and amylopectin
its insoluble and compact but it is easily broken down

Question 23

Describe the structure of amylose…

Answer 23

unbranched structure consisting of alpha glucose monomers joined by 1-4 glycosidic bonds
-therefore it has a coiled(helix) structure making it very compact

Question 24

Describe the structure of amylopectin…

Answer 24

a branched chain(every 20 monomers) made up of alpha glucose monomers joined by 1-4 and 1-6 glycosidic bonds
-its branched structure results in it being rapidly digested by enzymes which releases energy quickly

Question 25

What is the role of cellulose?
Describe its structure…

What are microfibrils and what is their function?

Answer 25

it is the main component of plant cell walls
it has an unbranched structure consisting of beta glucose monomers joined by 1-4 glycosidic bonds
H bonds are present between monomers on the same/adjacent chains to prevent the structure spiralling and losing strength

-strong threads made of long cellulose chains joined by H bonds
-they provide structural support to plant cells

Question 26

What is a lipid?
What elements do they contain
Are they polar/non polar
State the 2 types of lipids and what they mean , what is their state at room temp?

Answer 26

a biological molecule that is only soluble in organic solvents such as alcohols

-contain C , H and O , they are non polar

saturated-(solid)don’t contain any carbon-carbon double bonds
unsaturated-(liquid)contain 1 or more carbon-carbon double bonds

Question 27

What does the presence of double bonds cause to happen in molecules?

Answer 27

causes them to kink so they are unable to pack closely together
the greater the number of double bonds , the weaker the intermolecular bonds resulting in lower melting point

Question 28

What do triglycerides consist of?

Answer 28

1 glycerol molecule and 3 fatty acid chains joined by ester bonds in condensation reactions

Question 29

What molecules are triglycerides and phospholipids examples of?

Answer 29

macromolecules

Question 30

What is the role of triglycerides in plants and animal cells?
What molecule group does glycerol belong to?
What molecule group do the fatty acid chains belong to?
What group do both molecules contain?

Answer 30

to act as energy reserves

glycerol-alcohols group
fatty acids-carboxylic acids

an OH group

Question 31

What elements do phospholipids contain?

How is a phospholipid different to a triglyceride.

Which part of phospholipids are hydrophilic / hydrophobic

Answer 31

C , H , O and phosphorus

one fatty acid chain is replaced by a phosphate group

the CHARGED phosphate heads are hydrophilic so they interact with and are attracted to water

the NON POLAR tails are repelled by water so they are hydrophobic

Question 32

Name all the reducing and non reducing sugars

Answer 32

REDUCING-all monosaccharides and some disaccharides(lactose and maltose)

NON-REDUCING-disaccharides(sucrose) excluding lactose and maltose and simple polysaccharides