a level biology enzymes and digestion

?
what are enzymes?
globular proteins that act as biological catalysts by lowering activation energy.
1 of 50
what are the conditions needed for a reaction to take place?
reactants must collide with energy energy to alter the arrangement of their atoms to form products, free energy of products must be less than substrates, require activation energy
2 of 50
describe the structure of an enzyme
specific 3D shape that is a result of their primary structure, functional area called the active site made up of amino acids, acts upon a substrate
3 of 50
what is a substrate?
the molecule on which the enzyme acts, forms an e/s complex, substrate held to active site by temporary bonds which form between amino acids of the active site and groups on the substrate molecule.
4 of 50
which bonds maintain an enyme's shape?
hydrogen bonds
5 of 50
what is the induced fit model of enzyme action?
the enzyme is flexible and can mould itself around the substrate in the way that a glove moulds itself to the shape of the hand, has a certain general shape but changes in the presence of the substrate, this puts strain on the molecule and so lowers the a
6 of 50
what is the lock and key model of enzyme action?
each key (substrate) has a specific shape that fits the lock (shape of enzyme's active site), shape of substrate exactly fits the active site of the enzyme.
7 of 50
limitations of the lock and key model of enzyme action
scientists have observed that other molecules can bind to enzymes at other sites and alter the activity of the enzymes so shape of enzyme is altered by the binding molecule. t/f enzymes structure is flexible not rigid.
8 of 50
what is the effect of temperature on enzyme action?
rise in temp, increases ke of molecules so they move around more rapidly and collide more often so substrate and enzyme molecules come together more often, more effective collisions so more e/s complexes formed and so rate increases. eventually temperatur
9 of 50
what is denaturation?
permanent change which stops the enzyme from functioning again. Happens at around 60 degrees.
10 of 50
how can enzyme-catalysed reactions be measured?
from the formation of products of the reaction or the disappearance of the substrate.
11 of 50
describe the rate of reaction in the formation of oxygen due to the action of catalase on hydrogen peroxide
at first lots of substrate no product so easy for substrate molecules to come into contact with empty active sites, all are filled at any given time and substrate is quickly broken down, amount of substrate decreases and product increases, fewer substrate
12 of 50
why have our body temperatures evolved to be 37 degrees?
at higher temps any further rise in temp (e.g. due to illness) may denature the enzymes), more energy needed to maintain a higher temperature.
13 of 50
what is the effect of pH on enzyme action?
a change in the ph alters the charges on the amino acids that make up the active site of the enzyme so substrate can no longer attach to active site and e/s complexes can't form. can cause bonds maintaining tertiary structure to break so active site chang
14 of 50
what is the pH of a solution?
a measure of its hydrogen ion concentration
15 of 50
how is pH of a solution calculated?
-log10(H+)
16 of 50
why does a pH change cause the active site of the enzyme to change shape?
change in H+ ions affects the ionic and hydrogen bonds between amine and carboxyl groups of the polypeptides that make up the enzymes.
17 of 50
does an increase or decrease in pH affect enzyme action?
both because it depends on the optimum pH of the enzyme - a change away from this reduces rate. can become denatured if beyond a certain pH.
18 of 50
why are enzymes not used up in reactions?
once an active site on an enzyme has acted on its substrate it is free to repeat the procedure on another substrate molecule.
19 of 50
how does low enzyme concentration affect rate of reaction?
too few enzyme molecules to allow all substrate molecules to find an active site at one time. rate is only half of the maximum possible for n.o. of substrate molecules available.
20 of 50
how does intermediate enzyme concentration affect rate of reaction?
twice as many enzyme molecules available, all substrate molecules can occupy an active site at the same time. rate has doubled to its max because all active sites are filled.
21 of 50
how does high enzyme concentration affect rate of reaction?
addition of further enzyme molecules has no affect on rate as there are already enough active sites for the available substrate molecules. no increase in rate.
22 of 50
how does low substrate concentration affect enzyme action?
too few substrate molecules to occupy all available active sites so rofr is only half the max possible for n.o. of enzyme molecules available.
23 of 50
how does intermediate substrate concentration affect enzyme action?
twice as many substrate molecules available, all active sites occupied at any one time. rate has doubled to its maximum as all active sites are filled.
24 of 50
how does high substrate concentration affect enzyme action?
addition of more substrate molecules has no effect as all active sites are already occupied at one given time. no increase in rate.
25 of 50
what is a competitive inhibitor?
similar shape to substrate, binds to active site of enzyme, not permanently bound (when it leaves another molecules can take its place), its effect is reduced if substrate concentration is increased as more likely a substrate molecule will take its place
26 of 50
what is a non-competitive inhibitor?
attach to the enzyme at another binding site that isn't the active site, alters shape of enzyme and its active site so substrate molecules can't occupy it, increase in substrate concentration doesn't decrease effect of the inhibitor because the substrate
27 of 50
what is a metabolic pathway?
a series of reactions in which each step is catalysed by an enzyme.
28 of 50
what is the function of the oesophagus?
carries food from the mouth to the stomach.
29 of 50
what is the function of the stomach?
a muscular sac with an inner layer that produces enzymes. stores and digests foods, especially proteins. has glands that produce enzymes which digest proteins.
30 of 50
what is the function of the ileum?
long muscular tube, enzymes produced in its walls to further digest food, glands pour their secretions into it.
31 of 50
what are the adaptations of the ileum?
inner walls are folded into villi, gives a large sa whch is increased by millions of tiny projections called microvilli o the epithelial cells of each villus. adapts ileum for absorbing products of digestion into the bloodstream.
32 of 50
what is the function of large intestine?
absorbs water, most of which is from the secretions of many digestive glands.
33 of 50
what is the function of the rectum?
the final section of the intestines, stores faeces before periodically being removed via the anus during egestion.
34 of 50
what is the function of the salivary glands?
situated near the mouth, pass their secretions via a duct in the mouth. secretions contain amylase which hydrolyses starch into maltose.
35 of 50
what is the function of the pancreas?
a large gland located below the stomach, produces pancreatic juice.
36 of 50
what is pancreatic juice?
a secretion which contains proteases to hydrolyse proteins, lipase to hydrolyse lipids and amylase to hydrolyse starch.
37 of 50
what is physical breakdown?
teeth break down larger food into smaller pieces which allows us to ingest food and provides a large surface area for chemical digestion. muscles in the stomach wall churn and break up food.
38 of 50
what is chemical digestion?
large insoluble molecules are hydrolysed into smaller, soluble ones by enzymes, more than one needed to hydrolyse a large molecule, usually done in sections, three types: carbohydrases, lipases and proteases.
39 of 50
what are carbohydrases, lipases and proteases?
carbohydrases hydrolyse carbohydrates into monosaccharides
lipases hydrolyse lipids into glycerol and fatty acids
proteases hydrolyse proteins into amino acids
40 of 50
what is sucrase?
hydrolyses the single glyosidic bond in the sucrose molecule, producing two monosaccharides - glucose and fructose.
41 of 50
what is lactase?
hydrolyses the single glyosidic bond in the lactose molecule, producing two monosaccharides - glucose and galactose.
42 of 50
what happens in lipid digestion?
lipids hydrolysed by lipases produced in pancreas which hydrolyse the ester bond found in triglycerides to form fatty acids and monoglycerides. lipids firstly split up into droplets called micelles by bile salts produced in liver. this is called emulsific
43 of 50
what happens in protein digestion?
proteins hydrolysed by peptidases (proteases). there are 3 different peptidases: endopeptidases, exopeptidases and dipeptidases.
44 of 50
what are endopeptidases?
hydrolyse peptide bonds between amino acids in the centre of a protein molecule forming a series of peptide molecules.
45 of 50
what are exopeptidases?
hydrolyse peptide bonds on the terminal amino acids of the peptide molecules formed by endopeptidases. progressively release dipeptides and single amino acids.
46 of 50
what are dipeptidases?
hydrolyse bond between two amino acids of a dipeptide. membrane-bound as they are part of cell-surface membrane of the epithelial cells lining the ileum.
47 of 50
how is the ileum adapted to absorb he products of digestion?
folded so increase sa for diffusion, thin walled which reduces diffusion pathways, epithelial cells lining the villi have microvilli, finger like projections which further increase SA, rich network of blood capillaries so blood can carry away absorbed mol
48 of 50
how are amino acids and monosaccharides absorbed?
digestion of proteins produces amino acids and that of carbohydrates produces monosaccharides and these are all absorbed by diffusion and co-transport.
49 of 50
how are triglycerides absorbed?
through the movement of material within the lumen of the ileum, micelles come in contact with epithelial cells lining villi where they break down and release monosaccharides and fatty acids, non-polar so can easily diffuse across cell surface membrane int
50 of 50

Other cards in this set

Card 2

Front

what are the conditions needed for a reaction to take place?

Back

reactants must collide with energy energy to alter the arrangement of their atoms to form products, free energy of products must be less than substrates, require activation energy

Card 3

Front

describe the structure of an enzyme

Back

Preview of the front of card 3

Card 4

Front

what is a substrate?

Back

Preview of the front of card 4

Card 5

Front

which bonds maintain an enyme's shape?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

Biology
Biology
Teacher recommended
See all Biology resources »See all Biological molecules resources »