Topic 1A- Biological Molecules + RP1 Flashcards
1
Q
What are polymers?
A
Long chains of monomers joined together
2
Q
Name three examples of monomers
A
- monosaccharides
- amino acids
- nucleotides
3
Q
What are carbohydrates made from?
A
monosaccharides
4
Q
What elements are carbohydrates composed of?
A
C, H, O
5
Q
What is a hexose sugar?
A
A monosaccharide with six carbon atoms in each molecule
6
Q
What are the two types of glucose?
A
alpha
beta
7
Q
What is the difference between alpha and beta glucose?
A
They have the -OH group reversed
8
Q
What is a condensation reaction?
A
When two molecules join together with the formation of a new chemical bond, and a water molecule is released when the bond is formed.
9
Q
What type of reaction do monosaccharides join together by?
A
Condensation
10
Q
What type of bond forms between two monosaccharides?
A
Glycosidic
11
Q
What is a disaccharide?
A
Two monosaccharides joined together
12
Q
How is maltose formed?
A
glucose + glucose
13
Q
How is lactose formed?
A
glucose + galactose
14
Q
How is sucrose formed?
A
glucose + fructose
15
Q
What is a hydrolysis reaction?
A
The breakdown of a chemical bond using a water molecule.
16
Q
What is sugar a general term for?
A
monosaccharides and disaccharides
17
Q
How do you test for reducing sugars?
A
Add Benedict’s reagent to a sample, and heat it in a boiling water bath.
If the test is positive, it will form a coloured precipitate. The colour changes from blue, green, yellow, orange, brick red.
The higher the concentration, the more the colour changes.
18
Q
How do you test for non-reducing sugars?
A
Add dilute hydrochloric acid to the sample, and then put it into a boiling water bath. Then, you can neutralise it with sodium hydrogencarbonate. Then just carry out a normal Benedict’s test.
19
Q
What is an example of a non-reducing sugar?
A
Sucrose
20
Q
What are reducing sugars?
A
All monosaccharides and some disaccharides
21
Q
What are polysaccharides?
A
More than two monosaccharides joined together by condensation reactions.
22
Q
What type of molecule is amylose?
A
Polysaccharide- it is lots of alpha glucose molecules joined together by glycosidic bonds.
23
Q
What do plants store excess glucose as?
A
starch
24
Q
What is starch made up of?
A
Two polysaccharides of alpha-glucose: amylose and amylopectin.
25
Describe the structure of amylose
it is a long, unbranched chain of alpha- glucose. The angles of the glycosidic bonds give it a coiled structure, almost like a cylinder. This makes it compact, meaning it is good for storage.
26
Describe how the structure of amylopectin allows glucose to be released quickly
it's side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily. This means glucose can be released quickly.
27
What property of starch makes it good for storage?
Insoluble- it doesn't affect water potential so it means it doesn't cause water to enter the cell by osmosis, which would make them swell.
28
What is the test for starch?
Add iodine dissolved in potassium iodide solution, if starch is present it changes from browny-orange to blue-black colour.
29
What do animals store extra glucose as?
glycogen
30
Describe the structure of glycogen
Similar to amylopectin, except it has lots of side branches, which mean that stored glucose can be released quickly.
Compact molecule, good for storage.
31
What is the main component of cell walls in plants?
Cellulose
32
What is cellulose made up of?
Long, unbranched chains of beta- glucose
33
What links the cellulose chains together?
weak hydrogen bonds, these the form microfibrils (strong fibres that provide structure to the cell wall)
34
What are triglycerides a type of?
lipid
35
Describe the structure of a trigyceride
one molecule of glycerol with three fatty acids attached to it
36
Describe the properties of the fatty acid tail on triglycerides
tails are hydrophobic meaning it makes triglycerides insoluble in water.
37
How are triglycerides formed?
condensation reactions
38
Describe how triglycerides are formed
fatty acid joins to a glycerol molecule
when the ester bond is formed a molecule of water is released (condensation reaction)
this process happens twice more to produce a triglyceride
39
What are the two types of fatty acid?
saturated and unsaturated
40
What is the difference between saturated and unsaturated fatty acids?
saturated fatty acids don't have any double bonds
unsaturated fatty acids have at least one double bond between carbon atoms, which cause the chain to kink
41
How is a phospholipid different in structure to a triglyceride?
One of the fatty acid molecules is replaced by a phosphate group
42
Describe one important feature of the phosphate group in a phospholipid
it is hydrophobic
43
What is the main use of triglycerides?
used as energy storage molecules
44
How are triglycerides adapted to be good storage molecules?
1. the long hydrocarbon tails of the fatty acids contain lots of chemical energy, so lots of energy is released when they are broken down
2. they're insoluble, so don't affect the water potential of the cell and cause water to enter by osmosis
45
What part of the cell membrane do phospholipids make up?
bilayer
46
Describe the test for lipids
emulsion test
1. shake the test substance with ethanol for about 1 min so it dissolves, then pour the solution into water
2. any lipid will show up as a milky emulsion
3. the more lipid there is, the more noticeable the milky colour will be
47
What are the monomers of proteins?
amino acids
48
what is formed when two amino acids join together?
dipeptide
49
what is formed when two or more amino acids join together?
polypeptide
50
Describe the structure of amino acid
- carboxyl group (-COOH)
- amine group (-NH2)
- H
- R group
all attached to C
51
What type of reaction are polypeptides formed by?
condensation reactions
52
What are bonds formed between amino acids called?
peptide bonds
53
Describe the primary structure of proteins
a sequence of amino acids in the polypeptide chain
54
Describe the secondary structure of proteins
hydrogen bonds form between amino acids in the chain
this makes it automatically coil into an alpha helix or fold into a beta pleated sheet
55
Describe the tertiary structure of proteins
hydrogen bonds AND ionic bonds form between different parts of the polypeptide chain
disulphide bridges also form whenever two molecules of the amino acid cysteine come close together
for proteins made from a single polypeptide chain, the tertiary structure forms their final 3D structure
56
Describe the quaternary structure of proteins
several different polypeptide chains held together by bonds
57
Name 3 examples of quaternary proteins
haemoglobin
insulin
collagen
58
Name four jobs of proteins
1. Enzymes
2. Antibodies
3. Transport proteins
4. Structural proteins
59
Describe the test for proteins
biuret test
1. the test solution needs to be alkaline so add a few drops of sodium hydroxide solution to it
2. then you add some copper (II) sulphate solution
positive test = purple
nothing present = blue
60
what type of biological molecule are enzymes?
protein
61
How do enzymes speed up the rate of reaction?
they reduce the activation energy needed, often meaning that reactions happen at a lower temperature than they could without an enzyme
62
Why does the enzyme substrate complex lower the activation energy needed for a reaction? (2)
1. If two substrate molecules need to be joined, being attached to the enzyme holds them 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
63
Describe the lock and key model of enzyme action
The substrate fits into the enzyme in the same way that a key fits into a lock
64
Why did the lock and key model need to change?
because new evidence showed that the enzyme-substrate complex changed shape slightly to complete the fit
65
What does the induced fit model show?
As the substrate binds the active site changes slightly
66
What does the induced fit model explain?
it helps to explain why enzymes are so specific and only bond to one particular substrate
67
Why can enzymes only catalyse one reaction?
because only one complementary substrate will fit into the active site
68
What happens if the tertiary structure of the enzyme is altered?
The substrate wont fit into the active site, an enzyme- substrate complex wont be formed and the enzyme will no longer be able to carry out its function
69
How can mutations cause the enzyme to not be able to function?
the primary structure of a protein is determined by a gene, if a mutation occurs, it could change the tertiary structure of the enzyme produced
70
How does temperature effect enzyme activity?
1. increase in temperature means more kinetic energy, so molecules move faster, so enzymes are more likely to collide with the substrate more
2. particles will vibrate more if they are heated, which can break some of the bonds that hold the enzymes structure in shape
3. the active site changes shape and the enzyme and substrate no longer fit together
4. at this point, the enzyme is denatured- it no longer functions as a catalyst
71
What pH do most human enzymes work best at?
7
72
What pH does pepsin work best at?
2, which is useful as it is found in the stomach
73
Explain how pH can affect enzyme activity
acids (H+) and alkalis (OH-) can mess up the pH, and therefor mess up the ionic bonds and hydrogen bonds that hold the enzymes tertiary structure in place. this makes the active site change shape, so the enzyme is denatured
74
How can enzyme concentration affect rate of reaction?
Increasing the concentration means that there is more chance that the substrate molecule will collide with an enzyme and form an enzyme-substrate complex.
So, increasing the concentration of the enzyme increases the rate of reaction.
However, if the amount of substrate is limited, there comes a point where there will be no more available substrate to react, so adding more enzyme has no further effect.
75
Explain how increasing substrate concentration affect rate of reaction
The higher the substrate concentration, the faster the reaction, as more substrate molecules are likely to collide with an enzyme.
However, this is only true up to a 'saturation point' , after that adding more substrate makes no difference as all the active sites are full
76
What is the relationship between substrate concentration and time?
substrate concentration decreases with time during a reaction, (if no more is added during the reaction) so if no other variables are changed, the rate of reaction will decrease over time too. This makes the initial rate of reaction, the highest rate of reaction
77
Name four things that effect enzyme activity
- temperature
- pH
- substrate concentration
- enzyme concentration
78
What are the two types of enzyme inhibitors?
competitive
non competitive
79
Explain how competitive inhibitors work
1. competitive inhibitors have a similar shape to that of the substrate
2. they compete with the substrate molecules to bind to the active site, but no reaction takes place
3. instead they block the active site, so no substrate molecules can fit in it
80
When using competitive inhibitors, what can effect how much the enzyme is inhibited?
concentrations of the substrate and the inhibitor
81
What will the effect on rate of reaction be when using a competitive inhibitor in high concentrations?
If there's a high conc of inhibitor, it will take up nearly all the active sites, and hardly any of the substrate will be able to react with the enzyme. This leads to a slow rate of reaction
82
What will the effect on rate of reaction be when using a competitive inhibitor with high concentrations of substrate?
if there's high conc of substrate, then the substrates chances of getting to an active site before the inhibitor increase
so, increasing the conc of substrate will increase the rate of reaction (up to a point)
83
Where do non competitive inhibitors bind?
bind to the enzyme away from its active site
84
What does a non competitive inhibitor do to an enzyme?
it causes the active site to change shape so substrate molecules can no longer bind to it
85
When using non competitive inhibitors, what will happen to the rate of reaction when you increase the concentration of substrate?
Increasing the concentration of substrates wont make any difference to the reaction rate- enzyme activity will still be inhibited
86
RP1- What are the four factors that effect enzyme activity?
pH
temperature
substrate concentration
enzyme concentration
87
RP1- How is a control set up in a practical measuring enzyme activity?
replace the enzyme solution with distilled water or boiled enzyme solution
88
RP1- How can the results of a practical measuring enzyme activity be used to find the initial rate of reaction?
Plot your results on a graph of rate of reaction against time
Draw a tangent at time=0 to find initial rate
89
RP1- Outline the practical procedure used to measure the effect of temperature on enzyme activity, using trypsin and milk
Immerse equal volumes of trypsin and milk, stored in different test tubes, in a water bath for 5 minutes for the temperature to equilibrate
Mix together and immediately start timing, record the time taken for the milk to be completely hydrolysed/ colourless.
Test at least 5 temperatures, with 3 repeats of each.
90
RP1- How is the rate of reaction calculated with time?
rate = 1/time
91
RP1- What is the effect of temperature on enzyme activity?
As temperature increases, kinetic energy increases, so more ES complexes form. The rate of reaction increases up to the optimum temperature
beyond that, bonds in the enzyme tertiary structure break, which changes the shape of the active site. The substrate and enzyme are no longer complementary, so rate of reaction decreases.
92
RP1- What is the risk with handling enzymes?
students may have allergic reactions to them
