UNIT 1: (1.4) Proteins Flashcards
what subunits are proteins made up of?
subunits called amino acids
How many different amino acids are there?
20
How are amino acids held together?
amino acids are held together by peptide bonds to form long polypeptide chains
what do polypeptide chains go onto form?
chains form the protein molecule
what does the structure of a protein depend on?
specific sequence of amino acids
what does the sequence of amino acids determine?
The sequence of amino acids determines the shape and function of the protein
what would happen if the order of bases is incorrect?
The protein shape will be altered and it may not be able to do its job
what is the function, shape and example of a structural protein?
- collagen makes up the body cartilage
keratin makes up hairs and nails - composed of fibres
what is an example, function and shape of an enzyme?
- examples: amylase, pepsin, lipase, phosphorylase
- involved in metabolism, break down or build-up
- globular proteins with a shape that fits snugly with the chemicals they work on
Describe an example, function, shape of a hormone.
- e.g insulin
- act as chemical messengers in the body
- insulin controls blood glucose levels
- small globular proteins
Describe the function and shape of a antibodies
- combine with foreign proteins ( antigens) and mark them to be destroyed by the body’s immune system
- globular proteins, shaped to recognise and bind with the foreign protein
Describe the function and shape of receptors
- found on the surface of particular cells which allow hormones to target these cells
- the shape of a receptor protein on a cell allows the cell to respond to a specific hormone
what are enzymes known as?
biological catalysts which are present in all living cells. They speed up chemical reactions but remain unchanged by these reactions
what effect do enzymes have on activation energy?
lower the activation energy needed for metabolic reactions to proceed in cells
name which are the catalyst, reactant and products
manganese dioxide
water + oxygen
hydrogen peroxide
manganese dioxide= catalyst
water + oxygen= products
hydrogen peroxide= reactant
what is the function of the enzyme catalase?
breakdown hydrogen peroxide which is produced in living cells into harmless oxygen and water
why does dead tissue show no reaction when boiled?
as boiling denatured the enzyme
what does denatured mean?
The change in the shape of a protein such as an enzyme that results in them no longer fitting their substrate
what are different variables?
- volume
- mass/substrate
- concentration
- temprature
what is a degradation reaction?
A breakdown reaction - when a chemical compound splits into smaller parts.
what is a synthesis reaction?
A build-up reaction - when two or more substances join together to form one product.
how are enzymes different from other catalysts?
- enzymes are made inside living cells
- all enzymes are proteins but all catalysts are not
why are enzymes vital to living organisms?
speed up chemical reactions inside cells to sustain life
what temperature do enzymes work best in the human body?
37°C
why do you use different syringes for different liquids?
to prevent cross-contamination of the solutions
what is the function of phosphorylase?
builds up glucose-1-phosphate into starch
what is meant by a control?
control acts as a comparison to show that it is the factor being investigated that is having an effect
what is meant by optimum?
the conditions under which an enzyme is most active (eg temperature and pH)
what happens during digestion?
large insoluble molecules are degraded with the help of enzyme action into smaller soluble ones
what are the 3 main groups of digestive enzymes?
- carbohydrases
- proteases
- lipases
what is the function of carbohydrates?
break down carbohydrates into sugars such as maltose and glucose
what is the function of proteases?
break down proteins into polypeptides then into amino acids
what is the function of lipases?
break down fats into fatty acids and glycerol
what happens during an enzyme controlled reaction?
where the substrate joins temporarily at the active site on the surface of the enzyme
why is the shape of the active site of an enzyme important?
the shape of the active site of an enzyme molecule is complementary to its specific substrate
what is the function of a substrate molecule?
substrate molecules fit into the active site creating the enzyme-substrate complex
what can the structure and shape of all proteins be affected by?
- temperature
- pH
what are enzymes made of?
proteins
in general what pH are most enzymes most active?
neutral pH ( pH 7 )
draw a conclusion about the working range of different enzymes
Each enzyme has a different working range
what will happen when pepsin on egg albumen cylinders is investigated?
- pepsin will digest the insoluble egg protein
- decrease in length of cylinders ( indicates the amount of digestion)
- the greater the decrease in length of the cylinders, the more active the enzyme pepsin
how do you work out percentage change?
difference ÷ original number x 100
how does the change of pH in solutions relate to the activity of the enzyme used?
- As the pH of the solution decreases enzyme activity increases.
- can be observed as a greater percentage change in length
what are the names of the substrate, enzyme and product(s) in the egg albumen investigation
substrate - egg albumen
enzyme - pepsin
product(s) - solid white albumen
what happens to enzymes at higher pHs ( 6.7)?
the enzymes active site changes shape and is no longer complementary to its substrate so is not active
what happens to enzymes at high temperatures?
enzymes can be denatured resulting in a change to their shape
in the investigation of the effect of temperature on the activity of invertase, why was the sucrose and invertase adjusted to the correct temperature before being mixed?
so they would not start to react with each other before reaching the required temperature
what can be done to make results more reliable?
class results can be compared and averages calculated to make it more reliable
if the temperature denatured the enzyme but was brought back to a normal temperature.
what would happen to enzyme activity?
the rate would stay at 0% as the enzyme has denatured and the shape change is permanent
what are the 2 types of enzyme reactions?
- degradation reaction
- synthesis reaction
what are examples of a degradation reaction?
hydrogen peroxide + catalyase = oxygen + water
surcrose + invertase = glucose + frucose
starch + amylase = maltose
what is an example of a synthesis reaction?
glucose-1-phosphate + phosphorylase = starch
what is a test for starch?
benedicts reagent orange= sugar present brick red ( once heated) = maltose
where does sugar come from?
broken down starch
what are examples of proteins?
- hormones
- enzymes
- antibodies
- receptors
- structural proteins ( HEARS )
what is the active site?
location on the surface of the enzyme which matches the shape of the substance that it works on ( its substrate)
around what temperature will it denature the enzyme?
45 or above
