(1) biological molecules

Question 1

what is a monosaccharide and what are some examples?

Answer 1

the monomers from which lather carbohydrates are made
glucose(C6H12O6) ( alpha, beta), fructose, galactose

Question 2

what is the test for reducing sugars?

Answer 2

only reacts with sugars with an aldehyde group, makes it a reducing sugar

add Benedict’s reagent (alkaline solution of copper II sulfate to food, heat mixture for 5 mins

will turn red if reducing sugar is present (forms an insoluble precipitate of copper I oxide)

Question 3

how is a disaccharide formed?
how does the hydrolysis of a disaccharide work?

Answer 3

when monosaccharides join together in a condensation reaction forming a glycosidic bond

water is added to a disaccharide and it breaks the glycosidic bond releasing the monosaccharides

Question 4

What is the test for non-reducing sugars?

Answer 4

test w Benedict’s reagent in a water bath for 5 minutes, still blue = no reducing sugar present
add food sample with a dilute acid (HCL)in a test tube and in the water bath to hydrolyse the disaccharide into its monosaccharides
then add NAOH to neutralise the HCL and test with pH paper
then add BR and heat again and if turns orange brown reducing sugar is present (hydrolysis of non reducing sugar proved reducing sugars)

Question 5

how is
a) lactose
b) maltose
c) sucrose
made

Answer 5

a) galactose n glucose
b) glucose and glucose
c) fructose and glucose

Question 6

what is a polysaccharide?

Answer 6

polymers formed by combining many monosaccharide molecules
large molecules that are insoluble and useful for storage and when hydrolysed they break down into mono and disaccharides

Question 7

what are some examples of polysaccharides?

Answer 7

starch, glycogen and cellulose

Question 8

what are the properties of a starch molecule?

Answer 8

forms an important component of food and is the main energy source in most diets
found in many parts of a plant in the form of small grains

made up of chain of alpha glucose monosaccharides linked by glycosidic bonds formed by condensation reactions

can be un/branched: unbranded chains are wound into a tight coil that makes the molecule compact

Question 9

what is the role of starch and how is its structure suited for its role?

Answer 9

main role: energy storage

• insoluble and therefore doesn’t affect water potential so water is not drawn into the cell by osmosis
• large and insoluble: does not diffuse out of cells
• compact: it can be stored in a small space
• when hydrolysed it forms alpha glucose which is easily transported and can be used for respiration
• the branched form has many ends which can be acted on by enzymes to release glucose monomers rapidly

Question 10

what glycosidic bonds do amylose and amylopectin have?

Answer 10

amylose: 1-4 g bond
amylopectin: 1-6 1-4g bond

Question 11

what are the properties of glycogen?

Answer 11

found in animals and bacteria but not plants
made of alpha glucose and has shorter and more highly branched chains that starch

main carbohydrates storage in animals
stored as small molecules in the liver and muscles

mass is small because fat is the main storage molecule in animals g

Question 12

how does glycogen’s structure suit for storage?

Answer 12

insoluble: does not draw water into cell by osmosis
insoluble: does not diffuse out of cell
compact: can be stored in a small space

more Highly branched with more ends than starch which can be acted on by enzymes. More rapidly broken down to form glucose monomers used in respiration
important to animals as they have a higher metabolic rate and respiratory rate as they are more active

Question 13

how does the structure of cellulose suit its function?

Answer 13

made of monomers of beta glucose
has straight unbranched chain, run parallel to one another allowing hydrogen bonds to form cross-linkages between adjacent chain which add collective strength

cellulose molecules group together to form microfibrils which make up fibres to provide more strength

Question 14

what are the characteristics of lipids?
what are the main groups?

Answer 14

contain carbon hydrogen and oxygen (proportion of oxygen to carbon and hydrogen is smaller than carbohydrates)
Insoluble in water
soluble in organic solvents such as alcohols and acetone

triglycerides and phospholipids

Question 15

what are the roles of lipids?

Answer 15

source of energy: when oxidised lipids provide more than twice the energy as the same mass of carbohydrate and release valuable water

waterproofing: lipids are insoluble in water and are useful as waterproofing
(plants and insects have waxy lipid cuticles that conserve water, while mammals produce an oily secretion from sebaceous glands in the skin)

insulation: fats are slow conductors of heat and when stored beneath the body surface heal to retain body heat

protection: fat is stored around delicate organs

Question 16

what is the formation of triglyceride?

Answer 16

glycerol + 3 fatty acids -> triglyceride and 3 water molecules

In the condensation reaction each fatty acid forms an ester bond with glycerol

Question 17

what is the characteristic of an
a) saturated glycerol molecule
b) mono unsaturated
c) polyunsaturated

Answer 17

a) single bonds between carbon atoms only
b) one double bond between carbon atoms
c) more than one double bond between carbon atoms

Question 18

how are triglycerides a good source of energy, good storage molecules, an important source of water?

Answer 18

good source of energy: high ratio of energy-storing carbon hydrogen bonds to carbon

good storage molecules: much energy can be stored in a small volume

source of water: when oxidised they release water as they have a high ratio of hydrogen to oxygen atoms

Question 19

what is the formation of a phospholipid?
what 2 parts is a phospholipid made of ?

Answer 19

glycerol + 2 fatty acids and a phosphate ion

hydrophilic head and hydrophobic tail

Question 20

what is the emulsion test?

Answer 20

add sample of food to a test tube and add ethanol and add water (Ethanol extracts the liquid from the crushed solid sample and the lipid comes out of the solution when water is added)

cloudy white colour indicates the presence of a lipid (A layer is formed at the top as lipids are less dense than water, droplets diffract water turning cloud white)

Question 21

what is the general structure of an amino acid?

Answer 21

central carbon atom surrounded by:

amino group (NH2) (L)
carboxyl group (COOH) (R)
H atom (T)
R group (B) each amino acid has a different R group

Question 22

what are the biological roles of proteins?

Answer 22

structural: main component of body tissues
catalytic: all enzymes are proteins catalysing biochemical reactions
signalling: many hormones and receptors are proteins
immunological: all antibodies are proteins

Question 23

how is a dipeptide formed?

Answer 23

when 2 amino acids join together in a condensation reaction to produce a dipeptide and water
the 2 amino acid monomers are linked together by a peptide bond
can be broken in hydrolysis

Question 24

what is the primary structure of proteins?

Answer 24

many amino acids monomers can be joined in polymerisation
the sequence of amino acids in a polypeptide chain that form the protein

Question 25

what is the secondary structure of proteins?

Answer 25

form when the polypeptide chains coil (because of the hydrogen bonds) and form an alpha helix or beta pleated sheet

Question 26

what is the tertiary structure of proteins?

Answer 26

the 3D shape is held together by different bonds (disulphide, hydrogen, ionic and hydrophobic and hydrophilic interactions

Question 27

what is the quaternary structure of proteins?
examples?

Answer 27

some proteins formed by more than one polypeptide chain, (produced when different polypeptides interact)
haemoglobin, collagen

Question 28

what is an enzyme?

Answer 28

large globular proteins that catalyse the biochemical reactions that cells need to survive and carry out its function

Question 29

how does the formation of an enzyme sub rate comp,ex increase the rate of reaction?

Answer 29

when the active site and substrate bind to create the enzyme substrate complex, bonds are created and bent which allows the activation energy to be lowered and speed up the reaction

Question 30

what does the lock and key model state?

Answer 30

the substrate fits into the active of an enzyme like a lock and key, the shapes are complementary and the same remain the same throughout

Question 31

what does the induced fit model state:

Answer 31

the enzyme changes shape slightly to allow the substrate to enter the active site
this can happen because the hydrogen bonding holding much of the protein together is quite weak, so bonds can be reformed and broken easily

Question 32

what are the 4 factors that affect enzyme activity?

Answer 32

temperature
pH
enzyme concentration
substrate concentration

Question 33

how does temp affect enzyme activity?

Answer 33

high temp: molecules gain kinetic energy and collide with eachother more often and more e-s complexes are formed
too high temp affects the hydrogen binding, causes bonds to break and alters shape of active site
substrate will not fit into the active site, causes denaturation of enzyme
low temp, molecules will move slowly and meet less often therefore fewer reaction will happen and less product is made

Question 34

how does pH affect enzyme activity?

Answer 34

in highly acidic or alkaline environments, H+ or OH- ions interact with amino acids in the enzyme, breaking bonds and altering the shape of the active site causing the enzyme to denature

Question 35

how does enzyme and substrate concentration affect enzyme activity?

Answer 35

high concentration, higher rate of reaction as more molecules meet and more ES complexes are formed and more product is made

Question 36

what are inhibitors?

Answer 36

substances that interfere with enzyme activity

Question 37

what is a competitive inhibitor?

Answer 37

the inhibitor molecule binds to the active site and prevents the substrate from enetering

Question 38

what is non competitive inhibitor?

Answer 38

inhibitor molecule bonds to the enzyme away from the active site and alters the shape of the active site, preventing an ES complex from forming