Topic 1A - Biological molecules ARN * Flashcards
carbohydrates lipids proteins factors affecting enzyme action enzyme-controlled reactions
1
Q
what are polymers?
A
large, complex molecules made of long chains of monomers joined together
2
Q
what are monomers?
A
small, basic molecular units
3
Q
what are some examples of types of monomers?
A
monosaccharides, amino acids and nucleotides
4
Q
what elements do all carbohydrates contain?
A
carbon, hydrogen and oxygen
5
Q
what monomers are carbohydrates made from?
A
glucose, fructose and galactose, they are all monosaccharides
6
Q
how many carbon atoms are in each molecule of glucose?
A
6, its a hexose sugar
7
Q
what are the 2 types of glucose?
A
(α) alpha glucose and (β)beta glucose, they are isomers
8
Q
what are isomers?
A
molecules with the same molecular formula, but their atoms are connected in different ways
9
Q
what is a condensation reaction?
A
when 2 molecules join together with the formation of a new chemical bond and a water molecule is released
10
Q
How do monosaccharides join together?
A
they are joined by a condensation reaction to form a glycosidic bond between the 2 and a disaccharide, a water molecule is also released
11
Q
How is sucrose formed?
A
from a condensation reaction between glucose and fructose
12
Q
How is lactose formed?
A
from a condensation reaction between glucose and galactose
13
Q
How is maltose formed?
A
from a condensation reaction between 2 glucose molecules
14
Q
what are some examples of disaccharides?
A
maltose
sucrose
lactose
15
Q
what is a hydrolysis reaction?
A
a reaction that breaks the chemical bond between monomers in a polymer using a water molecule
16
Q
what is the test for sugars?
A
the benedict’s test
17
Q
what are examples of reducing sugars?
A
all of the monosaccharides, maltose and lactose
18
Q
what are examples of non-reducing sugars?
A
sucrose
19
Q
how to carry out test for reducing sugars:
A
add benedict’s reagent to a sample then heat it in a boiling water bath
look for colour change from blue to red (usually)
if positive coloured precipitate will form
20
Q
How can you tell how much sugar there is from a benedict’s test?
A
blue- no reducing sugar green - very low yellow - low orange - medium red - high or filter and weigh the precipitate produced
21
Q
how to carry out test for non-reducing sugars?
A
if benedict’s is negative
add dilute HCl to a new sample of the solution and heat in boiling water bath to break down into monosaccharides
neutralise with sodium hydrogencarbonate
do benedict’s again if positive it will form precipitate if not it doesn’t contain any sugar
22
Q
how are polysaccharides formed?
A
when more than 2 monosaccharides are joined by a condensation reaction
23
Q
what are examples of polysaccharides?
A
starch
glycogen
cellulose
24
Q
how do cells get energy?
A
from glucose, plants store excess glucose as starch which is hydrolysed when plants need more glucose
25
what 2 polysaccharides is starch a mixture of?
α-glucose amylose and α-glucose amylopectin
26
what is the structure of α-glucose amylose?
long unbranched chain of α-glucose
the angles of the glycosidic bonds make it coiled so it is compact
insoluble in water
large
27
what is the structure of α-glucose amylopectin?
long, branched chain of α-glucose
insoluble in water
large
28
what is starch?
an energy store found in grains in the cytoplasm, or the chloroplasts
29
how does starch's structure aid its function?
compact - good for storage (fit more in small space)
branched - easier for enzymes to get at the glycosidic bonds to hydrolyse the molecule for quick release of glucose
insoluble - osmotically inactive
large - can't diffuse out of the cell
30
what does osmotically inactive mean?
doesn't affect the water potential of the cell, so water doesn't enter the cell by osmosis causing it to swell and damaging it
31
how to test for starch?
add iodine dissolved in potassium iodide solution to sample
| check for colour change from orange/brown to blue/black
32
what kind of bonds are formed in making starch?
α-1,4 bonds and α-1,6 glycosidic bonds
33
what is glycogen?
energy store in animals in the form of granules in the cytoplasm
polysaccharide made from α-glucose via condensation reaction
34
what bonds from in glycogen?
α 1,4 and many α 1,6 glycosidic bonds
35
what is the structure of glycogen?
large
highly branched
α-helix shape so compact
insoluble
36
how does glycogen's structure aid its function?
large- doesn't diffuse out of the cell
branched- rapid glucose release by enzymes
compact - good for storage
insoluble - osmotically inactive
37
what is cellulose?
structural polysaccharide, made from β-glucose joined via condensation reactions
38
what bonds does cellulose contain?
β-1,4 glycosidic bonds
every other β-glucose is inverted
hydrogen bonds form between parallel cellulose chains
39
what is the structure of cellulose?
long, straight, unbranched chains of β-glucose
| chains line up and are linked by hydrogen bond cross-links
40
how does cellulose's structure aid its function?
hydrogen bonds link cellulose chains to form microfibrils which can then form fibres which are very strong so they provide structural support for cell walls
41
what does a reducing sugar do?
it is able to lose electrons to give to other molecules (and reduce them)
42
how does benedict's reagent help test for reducing sugars?
it contains Cu2+ ions as copper (II) sulfate which is blue and reducing sugars reduce them to form Cu+ as copper(I) oxide which is red
43
what are some examples of lipids?
triglycerides
| phospholipids
44
what are triglycerides composed of?
1 molecule of glycerol and 3 fatty acids
| connected via ester bonds
45
what are fatty acids?
molecules with long 'tails' made of hydrocarbons.
these tails are hydrophobic,
this makes lipids insoluble in water
46
what kind of reaction forms a triglyceride?
a condensation reaction between glycerol and 3 fatty acids that connect via ester bonds and 3 water molecules are produced
47
what are the 2 kinds of fatty acids?
saturated
| unsaturated
48
what is a saturated fatty acid like?
it has no double bonds between carbons
| its saturated with hydrogen
49
what is an unsaturated fatty acid like?
it has at least one carbon-carbon double bond
| this causes the chain to kink
50
what lipids are used in cell membranes?
phospholipids
51
what are phospholipids composed of?
1 glycerol molecule
2 fatty acids
a phosphate group
52
what is the purpose of the phosphate group in a phospholipid?
it is hydrophilic
53
what are triglycerides mainly used for?
as energy storage molecules
can be fats (solid at room temp)
or oils (liquid at room temp)
54
what is the structure of triglycerides?
hydrocarbon tails contain lots of chemical energy (high energy to mass ratio)
they're insoluble - form droplets which clump together with hydrophobic tails facing inward
55
how does the structure of a triglyceride aid its function?
high energy : mass - lots of energy is released when its broken down, don't have to carry heavy mass around
insoluble - don't affect water potential of cell and cause water to enter via osmosis and cause it to swell, water proof
56
how much energy do lipids possess in relative to carbohydrates?
lipids contain twice as much energy per gram than carbohydrates
57
what are phospholipids used for?
they make up the bilayer of cell membranes
58
what is the structure of phospholipids?
hydrophilic heads and hydrophobic tails so they are polar, they form a double layer with the heads facing outwards towards water on either side
59
how does the phospholipid bilayer help the cell?
the centre is hydrophobic so water soluble substances can't pass through easily and the bilayer acts as a barrier
60
How to carry out the test for lipids?
add ethanol to substance and shake until it dissolves
pour solution into water
lipid will appear as a white emulsion floating on the water
61
what can lipids be used for?
```
cell membranes
energy store
water proofing
insulation
protection
```
62
what are the monomers of proteins called?
amino acids
63
what are the dimers and polymers of proteins called?
dipeptides
polypeptides
proteins are made up of 1 or more polypeptides
64
what functional groups are amino acids made up of?
a carboxyl group (COOH)
an amine or amino group(NH2)
an R group
65
how are amino acids bonded together?
they are linked by condensation reactions to form polypeptides and a water molecule is released.
the bonds formed are called peptide bonds
66
how many 'levels' make up a proteins structure?
4
| primary, secondary, tertiary and quaternary
67
what is the primary structure of a protein?
the sequence of amino acids in the polypeptide chain
68
what is the secondary structure of a protein?
hydrogen bonds form between the amino acids in the chain. This makes it automatically coil into an alpha helix or fold into a beta pleated sheet
69
what is the tertiary structure of a protein?
coiled or folded chain is coiled or folded further. more bonds form between different parts of the polypeptide chain, including hydrogen and ionic bonds. disulfide bridges also form whenever 2 molecules of cysteine come closer together. for proteins made from a single polypeptide chain, this forms their final 3D structure
70
how do disulfide bridges form between cysteine molecules?
when the sulfur atom in one cysteine bonds to the sulfur atom in the other
71
what is the quaternary structure of a protein?
proteins made of several different polypeptide chains held together by bonds are assembled here. this is the final 3D structure for these proteins
72
what are some examples of proteins found in living organisms?
enzymes
antibodies
transport proteins
structural proteins
73
what are enzymes?
roughly spherical in shape due to tight folding of the polypeptide chains. they're soluble and often have roles in metabolism
74
what are some examples of what enzymes do?
some break down large food molecules (digestive enzymes) and other enzymes help to synthesise large molecules
75
what are antibodies?
involved in the immune response. they're made up of 2 light (short) polypeptide chains and 2 heavy (long) polypeptide chains bonded together. antibodies have variable regions - the amino acid sequences in these regions vary greatly
76
what's an example of a transport protein?
e. g. channel proteins are present in cell membranes
| e. g. haemoglobin
77
what do channel proteins do?
contain hydrophobic and hydrophilic amino acids which cause the protein to fold up and form a channel. these proteins transport molecules and ions across membranes
78
what are structural proteins?
physically strong, they consist of long polypeptide chains lying parallel to each other with cross-links between them.
79
what are examples of structural proteins?
keratin - found in hair and nails
| collagen - found in connective tissue
80
What's the test for proteins?
biuret test
81
how to carry out the biuret test?
solution must be alkaline so a few drops of NaOH solution is added
copper(II) sulfate solution added
positive - purple
negative - blue
82
how much of the body is made up of proteins?
they make up 20% of the body
83
how many different amino acids are there?
20, they all have the same general structure, only the R group changes
84
what is the prosthetic group of a protein?
a non-amino acid part of a protein
85
what is a catalyst?
a substance that speeds up a chemical reaction without being used up in the reaction itself
86
what do enzymes do?
catalyse metabolic reactions - both at a cellular level and for the organism as a whole
87
what things can enzymes affect in an organism?
structures- e.g. enzymes involved in the production of collagen
functions - e.g. respiration
88
enzyme action can be:
intercellular - within cells
| extracellular - outside cells
89
what features does an enzyme have?
they have an active site, which has a specific shape. enzymes are highly specific due to their tertiary structure
90
what is an enzymes active site?
the part of the enzyme where the substrate molecules bind to
91
what is the activation energy?
a certain amount of energy that needs to be supplied to the chemicals before the reaction will start. it's often provided as heat
92
what do enzymes do to the activation energy?
they lower the amount of activation energy needed, so the reactions can happen at a lower temperature, this speeds up the rate of reaction
93
what is an enzyme-substrate complex?
when a substrate fits into the enzyme's active site this is formed. it lowers the activation energy
94
why do enzyme-substrate complexes lower the activation energy?
1. being attached to the enzyme holds the 2 substrate molecules close together, reducing any repulsion between the molecules so they can bond more easily
2. if the enzyme is catalysing a breakdown reaction, fitting into the active site puts a strain on bonds in the substrate, so the substrate molecule breaks up more easily
95
what is the 'lock and key' model?
enzymes only work with substrates that it their active site, in this model the substrate fits into the enzyme in the same way a key fits into a lock
96
what is the 'induced fit' model?
active site changes shape slightly to complete the fit and form an enzyme substrate complex. this locks the substrate even more tightly to the enzyme
97
why is the induced fit model so good?
it helps explain why enzymes are so specific and only bond to 1 particular substrate. the substrate has to be the right shape to fit and make the active site change shape in the right way.
98
why do enzymes only usually catalyse 1 reaction?
only 1 complementary substrate will fit into the active site
99
what is the shape of the active site determined by?
the enzyme's tertiary structure, (which is determined by the primary structure)
each different enzyme has a different tertiary structure and so different shaped active site
100
what happens to the active site when the tertiary structure of an enzyme is altered?
the shape will change, the substrate won't fit into the active site, an enzyme-substrate won't be formed and the enzyme will no longer be able to carry out its function
101
what can alter the tertiary structure of an enzyme?
changes in pH or temperature
102
how can the primary structure effect the secondary structure?
a gene determines the primary structure of a protein, if a mutation occurs in that gene it could change the tertiary structure of the enzyme produced
103
what factors affect enzyme activity?
temperature
pH
enzyme concentration
substrate concentration
104
how does temperature affect enzyme activity?
as temperature increases rate increases
more kinetic energy so molecules move faster and are more likely to collide with the substrate molecules
higher energy = more likely successful collision
too high = reaction stops
105
why does a reaction stop when the temperature gets too high?
enzyme molecules vibrate more
vibration breaks some bonds
active site changes shape, so substrate doesn't fit
enzyme = denatured
106
how does pH affect enzyme activity?
every enzyme has an optimum pH
above and below optimum pH - H+ and OH ions can mess up ionic bonds and hydrogen bonds that hold tertiary structure in place
active site changes shape
enzyme = denatured
107
how does enzyme concentration affect enzyme activity?
more enzymes, more likely to collide and form enzyme-substrate complex
so increase in enzymes = increase in rate
only limited by amount of substrate
108
how does substrate concentration affect enzyme activity?
higher concentration = faster reaction
| more substrate = more likely to collide with enzymes and form enzyme - substrate complex
109
what stops a rate of reaction increasing when substrate increases?
saturation point - too many substrates for enzymes to process
substrate is used up in a reaction so if no more is added the rate will begin to decrease
110
how do enzymes work?
it works by forming an enzyme-substrate complex which strains bonds, lowering the activation energy, some lower Ea by bringing substrates closer together
111
how can enzyme activity be prevented?
by enzyme inhibitors
112
what are the different enzyme inhibitors?
competitive inhibitors
| non-competitive inhibitors
113
what do competitive inhibitors do?
similar shape to the substrate
they bind to the enzymes active site but no reaction takes place
prevents enzyme-substrate complex forming
114
what affects how much an enzyme is inhibited by competitive inhibitors?
the relative concentrations of the inhibitor and the substrate
high conc. of inhibitors means hardly any substrate will get to the enzyme
but increasing substrate increases rate of reaction
115
what do non-competitive inhibitors do?
they bind to an enzyme away from the active site
changes tertiary structure of active site permanently
no longer complementary
no more enzyme-substrate active sites
116
how to combat non-competitive inhibitors?
increasing substrate won't make any difference, enzyme activity is still inhibited
more enzymes must be added
117
how can the rate of an enzyme-controlled reaction be measured?
measuring how fast the product is made
| measuring how fast the substrate is broken down
118
what's an example of how the rate of an enzyme-controlled reaction be measured by measuring how fast the product is made?
catalase catalysing the breakdown of hydrogen peroxide into water and oxygen
119
what happens in the breakdown of hydrogen peroxide experiment?
set up boiling tubes with the same volume and concentration of hydrogen peroxide and a suitable buffer
put each boiling tube in a water bath set at different temperatures along with a tube containing catalase and wait
add the same volume and concentration of catalase to each tube then quickly attach bung and delivery tube
record how much oxygen is produced in the 1st minute
repeat 3 times for each temperature
120
how should the experiment for the breakdown of hydrogen peroxide be set up?
a boiling tube with a delivery tube pointing into an upside down measuring cylinder filled with water in a trough of water.
as oxygen is produced water is pushed out of the cylinder
121
what's an example of how the rate of an enzyme-controlled reaction be measured by measuring how fast the substrate is broken down?
put a drop of iodine in potassium iodide into each well on a spotting tile
mix a known concentration of amylase and starch in a test tube
a pipette should be used to put a drop of the mixture into each well at regular intervals until the indicator stops changing colour, this means no more starch is present
repeat times for each different concentrations of amylase
122
what is the initial rate of reaction?
the rate at the start of the reaction, this is when its fastest
