A1 Biological Molecules Flashcards
(97 cards)
1
Q
Define a Monomer
A
Each individual molecule that makes up a chain e.g. Monosaccharides
2
Q
Define a Polymer
A
Long chain formed by the joining together of monomers
3
Q
Define the monomers for Carbohydrates as singular, in pairs and in multiples?
A
Monomers = Monosaccharides
(x2 Monosaccharides) = Disaccharides
(Large numbers of Monosaccharides) = Polysaccharides
4
Q
Monosaccharides are soluble?
Yes or no?
A
Yes, Monosaccharides are soluble
5
Q
What is the formula for Monosaccharides?
And what number is n?
A
Monosaccharides formula = (CH2O)n’
n = 1-7
E.g. Glucose is a Hexose because of its 6 Carbons. C_6_H12O6
6
Q
Glucose has two isomers. What does this mean? And what are they?
A
Glucose has two different arrangements of Hydrogen and Oxygen.
7
Q
Define reducing sugars.
And how do they relate to Monosaccharides?
A
Reducing sugars = Sugars that donate electrons to other chemicals to reduce them
All Monosaccharides are Reducing sugars.
8
Q
How do we test for reducing sugars?
A
We use the Benedicts test.
9
Q
Analyse the test for Reducing sugars.
A
Benedict’s reagent is an alkine copper sulfate solution.
When heated with a reducing sugar it forms insoluble copper oxide precipitate.
- Grind 2cm3 of food sample in water. And put it into the test tube.
- Add an equal volume (2cm3) of benedict’s reagent.
- Heat mixture in gently boiling water for five minutes.
10
Q
List and arrange the colours of the copper oxide precipitate, in the test for reducing sugars. Through concentration of reducing sugar.
A
Blue = None
Green = Very Low
Yellow = Low
Yellowish Brown = Medium
Red = High
11
Q
Give Three examples of Disaccharides.
And what Monosaccharides form them.
A
Disaccharide Monosaccharides
Maltose = Two Glucose
Sucrose = Glucose and Fructose
Lactose = Glucose and Galactose
12
Q
Describe how to form a disaccharide.
What is it called?
A
A water molecule is removed to join two Monosaccharides together.
This is called a Condensation reaction
13
Q
What bond is formed form creating a disaccharide?
A
A Glycosidic bond.
14
Q
Describe how to break a Disaccharide.
A
You break the glycosidic bond by adding a water molecule.
This is called Hydrolysis.
15
Q
Describe the test for a non-reducing sugar.
And why we test for them?
A
You hydrolyse the non-reducing sugar into its monosaccharides.
We do it because not all disaccharides are reducing sugars.
16
Q
Whats the process for the test for non-reducing sugars?
A
- Grind the sample up in water, into its liquid form.
- Add 2cm3 of food sample and 2cm3 of Benedict’s reagent to test tube. And filter it.
- Put test tube in gently boiling water for five minutes. If the solution stays blue a reducing sugar isnt present.
- To find a non-reducung sugar. Add 2cm3 of food sample and 2cm3 of dilute hydrochloric acid in test tube and gently boil it for five minutes.
- Slowly add Sodium hydrocarbonate solution to test tube to neutralise the acid. This allows Benedict’s reagent to work, as it can’t work in acidic conditions. Test the solution is alkine with PH paper.
- Re-test the solution by heating it with 2cm3 of Benedict’s reagent in gently boiling water for five minutes.
- If a non-reducing sugar is present the Benedict’s reagent will turn orange-brown. This proves non-reducing sugars were present as they produced the reducing sugars during hydrolysis.
17
Q
How are Polysaccharides formed?
A
When many monosaccharides bind together.
18
Q
What are features of Polysaccharides that allow them to be stored effectively?
A
Polysaccharides are Large and Insoluble.
19
Q
Describe the test for Starch.
A
- At room temperature, place 2cm3 of testing sample in a test tube/Or/ Two drops in a depression on a spotted tile.
- Add two drops of iodine solution and shake or stir/Or/ Mix
- Presence of starch indicated by a blue-black coloration.
20
Q
What is starch made of?
Also give two features of starch?
A
Starch is made of chains of a-glucose monosaccharides.
A polysaccharide and a major energy source.
21
Q
Describe starch’s structure.
A
a-monosaccharide chains are branched or unbranched.
Unbranched chains are wound into tight coils to make the molecule compact.
Hydrogen bonds between the monosaccharides hold the helix in place in condensation reactions.
22
Q
Starch’s main role is energy storage, How does its structure suit it to that?
A
- Insoluble so it doesn’t draw water into cells affecting water potential.
- Large so it doesnt diffuse out of cells.
- Compact so a lot of it can be stored in a small space.
- When hydrolysed it forms a-glucose which is easily transported and readily used in respiration
23
Q
How is specifically branched starch adapted to store energy?
A
Only when it’s branched starch has many ends which are acted upon by enzymes simultaneously. This means a-glucose monomers are released rapidly. ensuring a good energy source.
24
Q
True of false: Starch is never found in Animals cells?
A
True: The animal countermeasure is glycogen.
25
Glycogen is never found in plants, but where is it found?
In animals and bacteria
26
How does the structure of glycogen differ to starch?
It's _more highly branched_ and has _shorter chains_.
27
What is the major carbohydrate storage in animals?
And what is the carbohydrate storage of low ratio to?
_Glycogen_ is the major carbohydrate storage in animals.
Carbohydrate storage is of _low ratio to fat storage._
28
Why is Glycogen suited to storage of carbohydrates?
* _Insoluble_ so doesnt draw ater in affecting water potential of the cell.
* _Insoluble_ so it doesnt diffuse out of cells.
* _Compact_ so a lot can be stored in a small space.
* _More highly branched than starch,_ means animals can respire more efficiently. As its ends can be hydrolysed by enzymes into a-glucose monomers rapidly.
29
Why is Cellulose different in molecular structure to Starch and Glycogen?
Cellulose is made of ß-glucose monomers.
This means unlike the other two it has _straight, unbrached chains_.
30
Describe Cellulose's polymer structure due to its unbranched chains.
The straight chains run _parallel_ to each other , allowing _hydrogen/glycosidic bonds_ to form _cross-linkages_ between them.
31
How is Cellulose able to have it's cross linkages?
Every other ß-glucose monomer is flipped 180°.
This allows potential hydrogen bonding on both sides which are the cross linkages between cellulose chains.
32
Cellulose's function is for strength, how is it suited for this?
Each hydrogen bond is _weak_ but due to their _great numbers_ cellulose becomes _very strong_.
Unbrached chains joined together by many hydrogen bonds are grouped into _microfibrils_ for further strength.
The microfibrils run i parallel groups to form _fibres_ for maximum strengh.
33
Describe cellulose's specific function in plants to benefit the plant.
1. Cellulose is strong for _providing rigidity_ in plant cells.
2. Cellulose also prevents cells form bursting via osmosis by _exerting inwards pressure_ that _stops anymore water entering._
3. This makes plant cells _push against one another_ making the _non-wooden parts semi-rigid._
4. This _turgidity_ can help _provide maximum surface area for photosynthesis._
34
What properties do lipids all share?
* Contain carbon, hydrogen and oxygen.
* Ratio of carbon, hydrogen and oxygen is smaller than in carbohydrates.
* Insoluble in water
* Soluble in organic solvents e.g. alchahol
35
What are the main groups of Lipids?
Triglycerides (Fats and oils)
Phospholipids
36
Give examples of some roles of Lipids.
* Phospholipids contribute to flexibility of memebranes and transfer of lipid soluble substances.
* When oxidised provides twice the amount of energy and water from the same mass of carbohydrate.
* Insoluble so are used as waterproof coverings on plants and insects as well as lipid cuticles.
* Fats retain body heat and insulate electrical impulses of nerve cells.
* Fat stored around organs to protect them.
37
Define a triglyceride.
Three fatty acids and glycerol.
| (hence tri and glycer)
38
When a fatty acid bonds to a glycerol, what reaction occurs? And what bond is formed?
It is a _condensation reaction_ and forms an _ester bond_
39
What is formed when a triglyceride undergoes hydrolysis?
An individual glycerol molecule and three fatty acids.
40
What causes triglyceride's properties to vary?
Varying triglycerides is from different fatty acids between them.
As Glycerol molecules in all triglycerides are the same.
41
Define Saturated, mono-unsaturated and polyunsaturated. In relavence of triglycerides fatty acid hydrocarbon chains.
Saturated: All carbon atoms are linked to the maximum number possible of hydrogen atoms, so no carbon-carbon double bonds.
Mono-unsaturated: One Carbon-carbon double bond
Polyunsaturated: More than one Carbon-carbon double bond is present.
42
Describe why triglycerides have certain structures relating to their properties.
* _High ratio of carbon-hydrogen bonds_ so are an excellent source of energy
* _Low mass to energy ratio,_ so lots of energy can be stored in a small volume. Helps animals carry less mass.
* _Large and non-polar so insoluble,_ so doesnt affect water potential of cells.
* _Good source of water,_ as they release it during oxidation as they have a high ratio of hydrogen to oxygen atoms. More possibility for H2O.
43
How are phospholipids different to Triglycerides?
Phospholipids are _polar_ and _can attract water._
_No Glycerol_ and one fatty acid is _replaced by a Phosphate molecule_
44
Describe and explain the to parts of Phospholipids.
Hydrophillic phosphate head that attracts water but not fat
Hydrophobic fatty acid molecules that repel water but mixes with fat.
45
How do phospholipids behave in water?
Phospholipid molecules position themselves so phosphate head is close to water and fatty acid tail is far away.
46
True or false: Phospholipids are Polar? Explain your answer.
Yes, as phospholipids have two ends with molecules that behave in water differently.
47
Describe the structure of phospholipids relating to their properties.
_Due to being polar they form a bi-layer._ This works in the cell membrane and lets it control how much water it takes in as the bi-layer is hydrophobic inside.
_Hydrophillic heads_ help hold at the surface of the cell membrane.
_Can combine with carbohydrates in the cell membrane_ to form glycolipids which are important in cell recognition.
48
Describe and define the test for Lipids.
_Called Emulsion test_
1. Put _2cm3 of testing sample_ in a test tube and add _5cm3 of ethanol._
2. Shake tube to _dissolve_ any _lipid in sample._
3. Add _5cm of water_ and _shake gently._
4. If it goes _cloudy white_ a _lipid is present._
5. As a control, _repeat using water as a sample_ if valid the _solution should remain clear._
49
In the test for Lipids why does the solution go cloudy?
The solution goes cloudy because, _light passing through the emulsion is refracted_ as it _passes from oil droplets to water droplets._ Making it appear cloudy.
50
Define Amino acid.
Amono acid: Monomers that combine to make polymers, that combine to make proteins.
51
How do Amino acids provide indirect evidence for evolution?
20 amino acids occur in all living organisms.
52
What's the structure of an Amino acid?
* _Central carbon atom_ to which four chemical groups are attached to.
* Amino group
* Carboxyl group
* Hydrogen atom
* R(side) group
53
Whats unique about amino acid's R(side) groups?
The R group is a variety of different chemical groups.
Each naturally occuring amino acid only differs in their R(side) group. And every amino acid has a different R(side) group.
54
Describe the formation of a peptide bond.
Amino acid _monomers combine to form dipeptides_. This is a _peptide bond_ from a _condensation reaction._
Water is taken out by, combining _-OH_ from _one carboxyl group_ and _-H_ from _one amino group_ of another amino acid. This makes H2O!
As a result, _peptide bond forms between_ the _carbon atom in the carboxyl group_ and the _nitrogen atom in the amino group_ of two amino acids.
55
Describe the breaking of a peptide bond.
A water molecule is added via hydrolysis to the carbon atom of one amino acids carboxyl group and a nitrogen atom of anothers amino group.
This encourages them to revert back to their original structure as amino acid monopeptides.
56
Define Polypeptide.
Polypeptide: Chain of many hundreds of amino acids and the primary structure of a protein.
57
What is the primary structure of a Protein? And it's function?
It is the polypeptides that make the protein themselves.
The polypeptide determines the protein's ultimate shape and therefore function.
E.g. Change in one amino acid = change in shape = change in function.
58
What is the Secondary structure of a protein? How does it work?
The polypeptide coiling into a helix.
This works as, _amino acids_ in polypeptides have _amino and carboxyl groups on each side_ of _every peptide bond._
_Hydrogen_ in amino acid group is _posotively charged_
_Oxygen_ in carboxyl group is _negatively charged._
Due to this when they _bond with other dipeptides_ they _form weak hydrogen bonds_ causing the _sides of the polypeptide chain to attach to each other_
This makes it coil into an _a-helix_
59
What is the tertiary structure of a protein? And describe how it works?
a-helix is _folded more_ and _compacts together_ to form a _long collumn._
Maintained by,
* _Disulfide bridges_ which are strong and not easily broken.
* _Ionic bonds,_ bonds between any carboxyl and amino group not contributing to peptide bond.
* _Hydrogen bonds_ which are numerous and weak so easily broken.
60
What is the Quaternary structure of Protein? And how does it work?
Any non-protein (prosthetic) groups associated with the molecules.
E.g. Iron containing haem group in haemoglobon.
61
Identify and describe the test for proteins.
_Buiret test_ it detects peptide bonds.
1. Put _sampling solution_ in _test tube_. Add _equal volume_ of _Soduim hydroxide solution_ at _room temperature._
2. Add _few drops_ of _very dilute (0.05%) copper(II) Sulfate solution_ and _mix gently._
3. _Purple coloration_ means _peptide bonds_ so _protein_. If it stays _blue, no peptides_ so _no protein._
62
Define an Enzyme.
Biological catalysts that speed up reactions by lowering activation energy.
63
Define a catalyst.
Alter rate of chemical reactions without undergoing permanent changes themselves.
64
Define Activation energy
Activation energy: Minimum amount of energy needed to trigger a reaction.
65
What do enzymes do to activation energy? And why?
Enzymes _lower_ the level of _activation energy_ allowing _reactions_ to _take place_ at _lower_ _temperatures._
This allows many critical reactions to take place at 37°c, human body temperature.
66
Describe an Enzyme's structure and how it works during a reaction.
Active site made up of a small number of amino acids.
The substrate fits into the active site to form the enzyme-substrate-complex.
Substrate held in active site by bonds formed between amino acids on active site and substrate molecule.
67
How does the induced fit model of an enzyme work?
Suggests, enzyme has a general shape that changes to form an active site that fits the substrate.
However, this strains the substrate molecule and can distort some of it's bonds. This lowers the activation energy needed to break the bond.
Sometimes colliding with the substrate can change the enzyme's environment and shape it. This is called _induced fit._
68
How do you? And what do you measure? To measure enzyme-catalysed reactions.
To measure an enzyme catalysed reaction we measure how long it takes so its time course.
Mostly measure two changes,
_Formation of the products of a reaction._ (e.g. how much oxygen is produced when enzymes catalyse hydrogen peroxide)
_The disappearence of the substrate._(e.g. reduced concentration of starch when catalysed by amylase)
69
Whats the process of an enzyme catalysed reaction?
1. Lots of substrate, no product
2. Very easy for substrate molecules to come into contact with empty active sites.
3. All active sites are occupied at any moment and substrate is rapidly broken down into it's products.
4. As substrates break down they decrease and products increase more and more as the reaction progresses.
5. More difficult for substrates to react with enzyme molecules as there are fewer substrate molecules so a lower probability of succesful collision. Also products can obstruct active sites.
6. As a result it takes longer for remaining substrate molecules to be broken down due to lower probability. So it's rate of dissapearence slows and so does the formation of the product.
7. Rate of reaction continues to slow until the concentration of substrate becomes so little it's unmeasurable.
8. On a graph the line plateaus as all measurable substrate has been used up so no products can be produced anymore either.
70
How do you measure rate of change on a graph?
You measure the gradient at any point on the graph curve.
The gradient is the line drawn over your point in the curve then draw two lines off of the line to make a triangle. (Equal to the gradient of the tangent to the curve at that point).
This doesn't just just apply to enzyme reaction rate. It can be applied to any reaction rate on a graph.
71
What should you do when investigating the effects of a variable on enzyme action?
Make sure all other factors are kept constant, they must be complimentary to your experiment.
72
Recite the process of how temperature effects enzyme action.
Due to higher kinetic energy of molecules they move around more rapidly and collide more often. So enzymes and substrates collide more often.
This creates more enzyme-substrate-complexes so reaction rate increases.
Eventually, the temperature becomes too great and causes the enzyme's bonds e.g. hydrogen bonds to break. This changes the shape and chemical structure of the enzyme and its active site.
As a result the substrate fits less easily into the active site slowing the rate of reaction.
Eventually, at about 60°C the enzyme has changed to a point where it no longer works, this loss of function is called _denaturing_
73
Why has the human body evolved to be 37°C for enzymes?
* We would have to eat more for energy to compensate for the higher temperature
* Other proteins may be denatured at higher temperatures than 37°C
* Any further rise in temperature to roughly 40°C may denature essential enzymes
74
True or false: Animals that move more, will have higher body temperatures, for higher metabollic rates?
True!
75
What is the PH of a solution?
Ph of a solution = Its hydrogen ion concentration
76
True or false: Every enzyme has an optimum PH
True!
77
Ask sir what PH = -log10-9 is and how it works XD
78
True or false: PH can't change to a scale where enzymes denature.
False!
Ph **can** change to a scale where enzymes denature
79
Recite the process of how PH effects enzyme action.
* PH alters the charges of amino acids that make up the active site. Meaning the substrate and active site cant attach.
* When large enough PH change can cause the enzyme's tertiary structure to break. This causes the active site to change shape.
* The active site is partly determined by hydrogen and ionic bonds between amino and carboxyl groups of the enzyme's polypeptides. The change in PH and therefore hydrogen bonds affects bonding causing active site to change shape.
80
True or False: Most of the time PH changes enzyme's activity rather than denatures them.
True!
Only in extreme cases can PH denature an enzyme.
81
Why do enzymes work well at low concentrations?
Active sites can repeatedly attach to substrates, meaning enzymes arent used up and work well at low concentrations.
As long as substrates avaliable, increasing the enzyme amount, increases rate of reaction.
They are proportionate.
82
What would the rate of reaction be like at low enzyme concentration?
Too few enzyme molecules to join to all substrate molecules at one time.
So rate of reaction is slow, maximum half possible.
83
What would rate of reaction be like at medium enzyme concentration?
All enzymes can join to substrate molecules at one time. Rate of reaction is therefore at its maximum.
84
What would rate of reaction be like at high enzyme concentration?
No change in rate of reaction, still maximum as all substrates are already accomadated.
85
What would rate of reaction be like at low substrate concentration?
Too few substrates to fit all active sites at one time. So rate of reaction is slow maximum half possible.
86
What would rate of reaction be like at medium substrate concentration?
All substrates are occupying all active sites at one time. This maximises eaction rate.
87
What would rate of reaction be like at high substrate concentration?
No change in rate of reaction as all active sites are already occupied. So still maximum
88
Define Enzyme inhibitors.
Enzyme inhibitors: Substances that directly or indirectly interfere with enzyme's active site to reduce its activity.
89
Where do competetive inhibitors bind?
The active site of enzymes.
90
Why is the competetive inhibitor a similiar shape to the substrate?
So it can compete to fit in the active site and stop the enzyme-substrate-complex from forming.
91
True or False: The concentration of the substrate determines the competetive inhibitors effectiveness.
True!
More substrate = less effective
92
Competetive inhibitors dont permanently bind to active sites. So what do they do?
They prolong the proccess of all substrates joining the active sites.
The more the inhibitor the longer it will take.
e.g. Malonate that inhibits a repiratory enzyme instead of Succinate the substrate.
93
Where do Non-competetive inhibitors bind to?
Enzyme binding sites that arent the active site.
94
What do Non-competetive inhibitors do after attachment?
They alter the enzyme's shape so substrates can't join to newly shapen active site to form the enzyme-substrate-complex.
95
True or False: An increase in substrate concentration decreases the effects of the non-competetive inhibitor. Explain your answer.
False!
An increase in substrate concentration does not decrease the effects of the non-competetive inhibitor. As the non-competetive inhibitor and the substrate aren't competing for the same site on the enzyme.
96
Give an example of a use of inhibitors? In this case Non-competetive.
Non-competetive inhibitors are used to control the metabollic pathway in cells. This helps maintain concentrations of crucial chemicals in cells.
97
Give me an example of a use of enzyme inhibitors? In this case competetive.
Some Enzyme Inhibitors can be used as Medicines in the treatment of conditions.
1. For example, infection by viruses can be treated by Inhibitors to the viral enzyme Protease, often competitive Inhibitors. This means that viruses cannot build new protein coats and therefore cannot replicate.
2. Penicillin works by Inhibiting a bacterial enzyme that is responsible for forming cross-links in bacteria cell walls. This therefore halts reproduction.
