Biological Molecules Flashcards
1
Q
What is a monomer?
A
A single unit that can be repeated
2
Q
What is a polymer?
A
A long chain of repeating monomers
3
Q
What are reducing sugars?
A
Sugars that can give electrons to other molecules
4
Q
What are monosaccharides?
A
A single monomer of a carbohydrate
5
Q
What are examples of monosaccharides?
A
- glucose
- galactose
- fructose
6
Q
What are examples of reducing sugars?
A
All monosaccharides and the disaccharides maltose and lactose
7
Q
What are isomers?
A
Compounds that have the same chemical formulas but different atom arrangements e.g. alpha and beta glucose
8
Q
How do you test for reducing sugars?
A
- add Benedict’s reagent
- boil in 90º water bath for 5 minutes
- a positive result is a colour change from blue to green/yellow/orange/brick red
9
Q
Is a reducing sugar test quantitative or qualitative?
A
Qualitative
10
Q
What method is used to get a quantitative result for a reducing sugar test?
A
- serial dilution
- create serial dilutions of 2%, 0.2%,0.002% and 0.0002%
- do reducing sugar test
- use a colorimeter to test for absorbance
11
Q
What bonds join monosaccharides?
A
Glycosidic bonds
12
Q
What reaction forms glycosidic bonds?
A
Condensation reaction (removal of water)
13
Q
What reaction breaks glycosidic bonds?
A
Hydrolysis reaction (addition of water)
14
Q
What monomers make maltose?
A
2 alpha glucose molecules
15
Q
What monomers make sucrose?
A
Alpha glucose and fructose
16
Q
What monomers make lactose?
A
Alpha glucose and galactose
17
Q
What are examples of polysaccharides?
A
- cellulose in cell walls
- chitin in fungi and exoskeletons of insects
- glycogen which is the store of sugar in animals
- starch which is the store of sugar in plants
18
Q
What are examples of non reducing sugars?
A
Sucrose
19
Q
How do you test for non reducing sugars?
A
- must receive a negative Benedict’s test
- add acid (HCl)
- leave in a 90º water bath for 5 minutes
- neutralise with an alkali (sodium hydroxide)
- redo Benedict’s test
- positive result is a colour change from blue to green/yellow/orange/brick red
20
Q
How do you test for starch?
A
- add potassium iodide
- positive result is a colour change from orange to blue black
21
Q
What is chitin?
A
- used in fungus cell walls and exoskeletons of insects
- made of beta glucose
- contains NH2
22
Q
What is the structure of starch?
A
- chains of alpha glucose
- insoluble
- branched strands have lots of terminal ends
- unbranded strands are highly coiled into a helix shape
- large molecule
23
Q
What is the function of starch?
A
- main energy storage material in a plant
- doesn’t dissolve in water so no effect on water potential so no movement of water buys osmosis so the cell won’t burst
- unbranched chains are compact for storage
- branched chains allow fast, easy hydrolysis of glycosidic bond so faster rate of respiration
- large molecule so cannot leave the cell
24
Q
What is the structure of glycogen?
A
- alpha glucose molecule chains
- highly branched
- compact
- insoluble
25
What is the function of glycogen?
- main energy storage material in animals
- rapid hydrolysis of glycosidic bonds for respiration
- compact for storage
- doesn’t dissolve in water so no effect on water potential so no effect on osmosis
26
What is the difference between straight glucose chain and a branched chain?
- straight molecule chains have a 1-4 glycosidic bond whereas a branched chain has a 1-6 glycosidic bond
27
What is the structure of cellulose?
- beta glucose molecule chains
- adjacent monomers are inverted to form glycosidic bonds
- long unbranched straight chains
- chains run parallel to eachother and form microfibrils
- form strong fibres
28
What is the function of cellulose?
- major component of a plant cell wall
- structural support
29
Where are lipids found?
- cell membranes
- fat stores
- nerve cells
30
How much more energy does the same mass of lipids produce than carbohydrates?
Twice the amount
31
Why are fats good for waterproofing?
Insoluble in water
32
Why are fats good for insulation?
They are slow conductors of heat and energy
33
Where are fats used for protection?
Often stored around delicate organs to prevent damage
34
What is a triglyceride?
- a glycerol molecule
- 3 fatty acid chains
- joined by an ester bond between each fatty acid and the glycerol
35
What is the bond between the fatty acid and glycerol in a lipid molecule
Ester bond
36
What reaction forms ester bonds?
Condensation reaction (removal of water)
37
What reaction breaks an ester bond?
Hydrolysis reaction (addition of water)
38
Is a triglyceride a polymer?
No
39
What do fatty acid chains all have in common?
A carboxylate group (COOH)
40
What causes the different properties of lipid molecules?
Variations in the fatty acid chain
41
What is a saturated fatty acid chain?
a hydrocarbon chain that has no double carbon bonds
42
What is an unsaturated fatty acid chain?
- monounsaturated means that the hydrocarbon chain has 1 double carbon bond
- polyunsaturated means the hydrocarbon chain has multiple double carbon bonds
43
What is the structure of phospholipids?
- glycerol molecule
- 2 fatty acids
- phosphate group
- 3 ester bonds
44
Is the phosphate head attracted to water?
Yes, it is hydrophilic
45
Is the fatty acid tail attracted to water?
No it is hydrophobic
46
What is the function of phospholipids?
- form a phospholipid bilayer
- in the cell membrane
47
How do you test for lipids?
- dissolve the sample in ethanol and shake it
- add distilled water and shake it
- a positive result is a cloudy white emulsion
48
What is the structure of amino acids?
- an amine group (NH2)
- a carboxyl group (COOH)
- an R group (the variation between amino acids)
- a carbon atom
49
What are amino acids a monomer of?
Polypeptides
50
What bond forms between amino acids in a polypeptide?
Peptide bond
51
What reaction forms a peptide bond?
Condensation reaction (removal of water)
52
What reaction breaks a peptide bond?
Hydrolysis reaction (addition of water)
53
What is the primary structure of proteins?
The specific sequence of amino acids
54
What is the secondary structure of proteins?
Folding/twisting of the amino acid chain into an alpha helix or a beta pleat
55
What is the tertiary structure of proteins?
- further twisting and folding
- held together by disulphide bridges (strongest), ionic bonds (weaker), and hydrogen bonds (strong in numbers)
56
What is the quaternary structure of proteins?
- the addition of multiple polypeptide chains into one molecule
- MAY have a prosthetic group
57
What is the test for proteins?
- add biuret solution
- positive result is a colour change from blue to purple
58
What is the structure of enzymes?
- tertiary globular proteins
- has a specific active site which is complimentary to a specific substrate
59
What is an enzyme-substrate complex?
The combination ad binding of an enzyme and substrate
60
What is the lock and key theory of enzymes?
The enzyme has an active site which is exactly complimentary to the substrate and breaks it down
61
What is the induced fit theory of enzymes?
The enzyme is complimentary to the substrate but changes shape once E-S complex is formed and puts more strain on the on and distorts the bonds in the substrate to break it down
62
How does temperature affect the rate of enzyme action?
- when temperature is low, particles have less kinetic energy so there is less E-S complexes
- at optimum temperature, enzymes have lots of kinetic energy so lots of E-S complexes formed
- when temperature is high, particles have too much kinetic energy to H bonds in tertiary structure are broken, active site denatures, less E-S complexes formed
63
How does pH affect the rate of enzyme action?
- at low pH, there are lots of hydrogen ions which affect the ionic bonds so active sites denature so less E-S complexes formed
- at optimum pH, lots of collisions between enzymes and substrates so there is the maximum amount of E-S complexes
- lots of hydroxide ions which affect ionic bonds so active site denatures and less E-S complexes formed
64
How does substrate concentration affect rate of enzyme
action?
- few substrate molecules limit chance of successful collisions, many active sites empty, few E-S complexes
- more substrate molecules increases chance of successful collisions so there is more E-S complexes
- excess substrate molecules but active sites are full so there is no increase in rate
65
How does enzyme concentration affect rate of enzyme action?
- new enzymes, limits rate of successful collisions, not enough active sites available so fewer E-S complexes
- lots of enzymes, increased chance of successful collisions, max amount of E-S complexes
- excess enzymes so there is empty active sites so there is no increase in rate
66
How do competitive inhibitors work?
- they are a similar shape to the substrate
- bind to the active site
- compete with the substrate
- rate of reaction decreases but will still happen
67
How do non-competitive inhibitors work?
- different shape to substrate
- attach to allosteric site
- alters shape or enzymes active site
- can get stuck and permanently change active site shape
