Section 1 - Chapter 1: Biological Molecules Flashcards
1
Q
What is a monomer? + example
A
- Smaller units from which larger molecules are made.
- e.g amino acid, monosaccharides, nucleotides
2
Q
What is a Polymer?
A
- Molecules made from a large number of monomers
3
Q
What is Polymerisation?
A
The process by which polymers are formed
4
Q
What is the process called when Polymers turn to Monomers? (splits)
A
Hydrolysis -
- Breaks the chemical bond between 2 molecules and involves the use of water
- Disaccharides are split into monosaccharides
5
Q
What is the process called when Monomers turn to Polymers?
A
Condensation
- Monomers join together to form a polymer
- Joins 2 molecules together with the formation of a chemical bond and involves the elimination of a water molecule
- A covalent bond is formed
- e.g 2 monosaccharides forms a disaccharide
6
Q
What is a Monosaccharide? + example
A
- Single Sugar, sweet tasting/soluble
- Contain Carbon, Hydrogen and Oxygen
- Formula (CH2O)n
- Play an important role in cell reactions
- e.g fructose, glucose, galactose
7
Q
What is a Disaccharide? + examples
A
- 2 Monosaccharides joined together
- E.g Maltose, Sucrose, Lactose
- C12H22O11
8
Q
What is a Polysaccharide + examples?
A
- Lots of Monosaccharides joined together in a condensation reaction
- e.g glycogen, starch, cellulose
9
Q
What is a Carbohydrate?
A
- Organic Molecules
- Containing 3 elements: carbon, hydrogen, oxygen
- The general formulae is (CH2O)n
- Ratio: C:H:O= 1:2:1
10
Q
What is the structure of a Alpha glucose?
A
11
Q
What are the reactive groups in a Monosaccharide?
A
- Carboxyl group: C=O
- Hydroxyl group: OH
12
Q
What is the function of carbohydrates?
A
- Great source of energy
- Used commonly as a substrate for respiration
- Forms cell walls
13
Q
What is the Structure of a Beta Glucose?
A
14
Q
What are some examples of Carbohydrates?
A
- Pasta
- Rice
- Bread
- Starch
- Fructose
- Glucose
15
Q
What are the characteristics of lipids?
A
- Contain carbon, hydrogen and oxygen
- Proportion of oxygen to carbon and hydrogen is smaller
- Insoluble in water
- Soluble in organic solvents (e.g alcohol)
16
Q
What are some examples of lipids?
A
- Oils
- Triglycerides
- Waxes
17
Q
What is the function of Nucleic Acids?
A
- To carry the genetic code for the production of proteins
18
Q
What are some examples of Nucleic Acid?
A
- DNA
- RNA
19
Q
What are the functions of protein
A
- Forms the structual components in plasma membranes
- Required for the structure, function, and regulation of tissues and organs
20
Q
What are some examples of proteins
A
- Insulin
- Amylase
- Haemoglobin
- Keratin
21
Q
What are the roles of lipids
A
- Source of energy - oxidised provides more than twice the energy as the same mass of carbohydrate + releases valuable water
- Waterproofing - insoluble in water
- Insulation - fats are slow conductors of heat. Below body surface = retains body heat
- Protection - Fat is often stored around delicate organs
22
Q
What is the structure of triglycerides and what causes variation.
A
- Have 3 fatty acids combined to a glycerol molecule. Each fatty acid forms an ester bond with glycerol in a condensation reaction
- Glycerol molecule in triglycerides are the same but properties (variation) depends on the fatty acid tails: chain
- All fatty acid tails have carboxyl group + hydrocarbon chain
- No double bonds = saturated
- 1 double bond = monounsaturated, 2 more polyunsaturated
23
Q
What is the structure of phospholipids
A
- Similar to triglyceride but 1 fatty acid is replaced by a phosphate
- Phospholipid made of 2 parts:
- Hydrophilic head - attracted to water
- Hydrophobic tails - orientates away from water
- When polar phospholipid molecules are placed in water they position so heads face water and tails are away from water
24
Q
How is the structure of triglycerides suited to its function
A
- High ratio of energy storing carbon - hydrogen bonds - excellent source of energy
- Low mass to energy ratio - good storage molecule, energy stored in a smaller volume, animals dont carry much
- Large, Non-polar molecules - insoluble in water, storage is not affected by osmosis (water potential)
- High ratio of hydrogen to oxygen atoms- triglycerides release when oxidised, provides a source of water
25
Q
How is the structure of phospholipids related to their properties
A
- Polar molecules - in aqueous environments form bilayers within cell-surface membranes
- Hydrophilic head helps hold the surface of the cell membrane
- The phospholipid structure helps to form glycolipids combining carbohydrates with the surface - Important in cell recognition
26
Q
What are the 2 types of lipids
A
- Triglycerides and phospholipids
27
Q
Where is Glycogen found
A
- Animals and bacteria (never plants)
- It is stored as small granules in muscles and liver
28
Q
What is the monomer of glycogen and what is its bonds
A
- Alpha glucose
- 1-4, 1-6 glycosidic bonds
29
Q
What is Glycogen’s structure
A
- Like starch it is branched
30
Q
How is the structure of glycogen suited to its function
A
- It is large and insoluble - doesnt draw water into the cell by osmosis and doesnt diffuse out
- Complex/Helical structure - a lot stored in a small space, compact shape
- More highly branched than starch - has more ends that can be acted on simultaneously by enzymes, rapidly broken into glucose monomer and used in respiration
31
Q
Where is starch found
A
- Plants (small grains) - large amounts in seeds and tubers
32
Q
What is the monomer of starch and what is its bonds
A
- Alpha glucose
- 1-4, 1-2 glycosidic bonds
33
Q
What is starchs structure
A
- Chains can be branched or unbranched
- Unbranched wound into a tight coil making it compact
34
Q
How is the structure of starch suited to its function
A
- Large and insoluble - so doesnt affect water potential (no osmotic effect)
- Coiled/helical shape - a lot stored in a small space - compact
- Rapidly hydrolysed to a-glucose- it is easily and readily used in respiration
- Branched form has many ends - which can be acted on by enzymes simultaneously
35
Q
Where is cellulose found
A
- Found in plant cell walls
36
Q
What is the monomer of cellulose and what is its bonds
A
- Beta glucose
- Hydrogen bonds form cross linkages between adjacent chains. The sheer overall number of chains = strength
- Cellulose molecules group together to form microfibrils
- Joined by 1-4 glycosidic bonds
37
Q
How is the structure of cellulose suited to its function
A
Major component of plant cell walls
- Straight unbranched chains
- Made of Beta glucose - so can form long straight unbranched chains
- The cellulose chains run parallel- and are crossed linked by hydrogen = add collective strength
- Cellulose molecules are grouped to form mocrofibrils - provides more strength
38
Q
What is Metabolism
What is Catabolism
What is Anabolism
A
- All the chemical processes that take place in a living organism
- Breakdown of large molecules into smaller ones
- Building of small molecules into large ones
39
Q
What is the test for starch
A
- Place 2cm3 of sample into test tube or 2 drops into a depression on a spotting tile
- Add 2 drops of iodine solution + shake
- Presence of starch is indicated by a blue-black
40
Q
What is a reducing sugar
A
- A sugar that can donate an electron to reduce another chemical (Benedicts reagent)
41
Q
What is the method for testing for a reducing sugar
A
- 2cm3 of sample in a clean test tube
- An equal volume of Benedict’s reagent added
- The solution is heated in a bath for 3-5 mins
- If reducing sugar is present :
- They will reduce Cu2+ in copper sulfate to form an orange- red percipitate copper oxide
- The colour of the mixture can be used to estimate the initial concentration of reducing sugars
42
Q
What is the structure of cellulose
A
- Straight, unbranched chains
- Run parallel
- Overall number of hydrogen bonds adds strength
43
Q
What is the structure of cellulose suited to its function
A
- Made with beta glucose so form long straight unbranched chains
- Cellulose molecules run parallel and cross linked with hydrogen bonds - adds collective strength
- These molecules are grouped to form microfibrils - grouped again to form fibres to provide more strength.
44
Q
What is the test for non-reducing sugars.
(What do you have to do first to make a non-reducing sugar into a reducing sugar)
A
- Add dilute hydrochloric acid to the sample - to break it down into its monosaccharides
- The test tube is heated in a boiling water bath for 3-5 mins
- Sample is neutralised with sodium hydrogencarbonate solution
- Heat sample with benedicts
45
Q
What is the lipid test (emulsion test)
A
- Get a dry/ grease free test tube
- Add 2cm3 of sample add 5cm3 of ethanol
- Shake to dissolve lipid
- Add 5cm3 of water and shake
- A milky white emulsion indicates a positive result.
46
Q
What is the monomer of protein
A
Amino acid
47
Q
How is a dipeptide formed. How is a polypeptide formed
A
- Formed when 2 amino acids join together in a condensation reaction
- Formed when more than 2 amino acids are joined together in a condensation reaction
48
Q
What is the structure of an amino acid
A
- A carboxyl group (-COOH)
- An amine group/amino group (-NH2)
- An R-group: a variable side group) a variety of different chemical groups. Each amino acid has a different R-group. There are 20 amino acids found in living organisms.
- Hydrogen atom - H
49
Q
How are amino acids combined and what do they form
A
- Amino acids are linked together in condensation reactions to form dipeptides and polypeptides
- A water molecule is released (combined from -OH from carboxyl group and -H from amino group)
- The bonds formed between amino acids is a peptide bond (between C and N atoms)
- These bonds can be broken by the addition of water (hydrolysis) into amino acids
50
Q
What is the Primary Structure of an amino acid
A
- The sequence, number and type of amino acids in the polypeptide chain
- It is the primary structure that determines its ultimate shape and function - a change to a single amino acid can lead to a change in the shape and function.
51
Q
What is the Secondary Structure of proteins
A
- The hydrogen of the -NH group has an overall positive charge
- Whilst O of -C=O has a negative charge
- These 2 groups form weak bonds called hydrogen bonds between amino acids in the chain.
- This causes the polypeptide chain to be coiled into alpha helix or folded into beta-pleated sheets
52
Q
What is the Tertiary Structure of proteins
A
- The coiled or folded chain of amino acids can be coiled or folded further to give the complex and specific 3D structure of each protein
- This structure is maintained by bonds:
- Disulfide bridges - fairly strong
- Ionic bonds - formed between carboxyl and amine groups that aren’t involved in formation of peptide bond. Weaker/broken by changes in pH
- Hydrogen bonds - numerous but easily boken.
53
Q
How are proteins folded
A
- The folding ensures the R-groups that are polar and hydrophilic are on the outside of the molecule
- The non-polar/hydrophobic groups are on the inside
- This allows arrangement to be more stable
54
Q
What is the Quaternary Structure
A
- Large proteins often form complex molecules containing a number of individual polypeptide chains.
- The quaternary structure is the way the polypetide chains are assembled together.
- The quaternary structure is the protein’s final 3D structure
55
Q
- What does a proteins shape determine
- Put examples of proteins
A
- Determines its functions
- Globular (e.g enzymes and haemoglobin) - soluble, carry out metabolic functions, transport proteins
- Fibrous (e.g keratin - hair/nails and collagen - found in connective tissue) - consist of long polypeptide chains lying parallel to eachother with cross links. Very stable.
- Antibodies are enxamples of proteins.
56
Q
What is the test for proteins
A
- The biuret test - detects peptide bonds
- Place a sample of solution in a test tube and add an equal volume of sodium hydroxide solution (make alkaline)
- Add a few drops of very dilute copper sulfate solution and mix gently
- A purple colouration indicates presence of peptide bonds. Stays blue if no protein is present.
57
Q
- What part of an enzyme is functional
- What is the molecule called that an enzyme acts on
A
-
The active site
- Made of relatively small number of amino acids.
-
Substrate
- This fits into depression to form an enzyme-substrate complex
- The substrate is held within the site by bonds formed between amino acids on the active site and the substrate.
58
Q
What is the model called for enzyme action
A
The induced fit model. - helps to explain why enzymes are so specific an bond to a particular substrate.
- When an enzyme and substrate interact - the proximity of the substrate ( a change in the environment of the enzyme) leads to a change in the enzyme that forms the active site.
- As it changes shape, the enzyme puts a strain on the substrate molecule. The strain distorts bonds in the substrate which lowers the activation energy
59
Q
Explain why the induced fit model is a better explanation of enzyme action than lock and key
A
- Key operates on a lock which is specific - a substrate will fit in only 1 particular active site
- A limitation - the enzyme like a lock is considered as a rigid structure. Scientists observed that other molecules could bind to the enzyme at sites other than the active site.
- This suggested the enzyme’s shape was being altered by the binding molecule - structure is flexible not rigid.
60
Q
What are catalysts
A
- Catalysts lower the activation energy/ alter the rate of a reaction but are chemically unchanged at the end, They can be reused repatedly and are effective in small amounts.
- Enzymes are globular proteins and acts as catalysts.
61
Q
What are the conditions for reactions to take place
A
- Molecules must collide with sufficient energy to alter the arrangement of their atoms to produce product
- The free energy of the products must be less than that of the substrates
- Many reactions require an initial amount of energy to start. The minumum energy needed to activate the reaction - activation energy
62
Q
How do enzymes work to catalyse the reaction. How does it lower the activation energy
A
- Enzymes work by lowering the actibvation energy :
- If 2 substrate molecules need to be joined, being attached to the enzyme holds them together. Reducing repulsion so they can bond easily
- Fitting into the active site puts strains on the bonds of the substrate. So it breaks more easily.
63
Q
For an enzyme to work it must
A
- Come into physical contact with its substrate
- Have an active site which fits the substrate.
64
Q
How do you measure the progress of an enzyme-catalysed reaction
A
- Usually measure its time course - how long it takes for a particular event to run its time course
- Changes most frequently measure are
- The formation of products
- The disappearance of substrate
65
Q
Give an explanation about an enzyme catalysed reaction using graphs
A
- At first there ia a lot of substrate and no product.
- It is very easy for substrate to come into contact with the empty active sites on the enzymes
- All active sites are filled at any moment and the substrate is rapidly broken down into its products.
- The amount of substrate decreases - resulting in an increase of product formed
- It becomes difficult for the substrate to come into contact with the enzyme because there are fewer substrate and product ‘gets in the way’ - prevents from reaching
- It therefore takes longer for substrate to be broken down - rate of disappearance slows
- The graph flattens because all substrate is used up and no new product can be produced
66
Q
How do you measure the rate of change at a point on a graph
A
- Measure gradient at a chosen point
- Draw a tangent on the curve and finding the gradient.
67
Q
What is the effect of temperature on the rate of enzyme action
A
- A rise in temperature increases kinetic energy of molecules.
- In an enzyme-catalysed reaction - this means more enzyme and substrate molecules come together to form enzyme-substrate complexes more often
- On a graph - this gives a rising curve
- The temperature rise also begins to cause the hydrogen bonds to break - active site changes
- The enzyme becomes disrupted (denatured - permanent change)
68
Q
What is the effect of pH on enzyme action
A
- A change in pH away from the optimum reduces enzyme action.
- If the change is more extreme = denatured
- A change in pH alters ionic and hydrogen bonds of the active site that hold the tertiary structure - as a result no enzyme substrate complexes can be formed
69
Q
What is the effect of enzyme concentration on the rate of reaction
A
- The more enzyme molecules there are, the more likely a substrate molecule will collide with one to form enzyme substrate complex
- As long as there is an excess of substrate - increasing enzymes leads to a proportionate increase in rate
70
Q
What is the affect of substrate concentration on the rate of enzyme action
A
- If concentration of enzyme is fixed, then the rate of reaction is propotionate to the concentration of substrate.
- At low concentrations, enzyme has limited number of substrates to bind to - active sites arent at full capacity
- They are gradually filled as substrate conc is increased.
- After that substrate wont have any effect - levels off
71
Q
What are the enzyme inhibitors and what are the 2 types
A
- Are substances that directly or indirectly interfere with the functioning of the active site of an enzyme and reduce its activity.
- Competitive inhibitors: bind to active site
- Non-competitive: bind to position other than active site
72
Q
What are Competitive inhibitors
A
- Have a molecular shape similar to substrate
- Allows them to occupy active site of enzyme and compete with substrate.
- It is the difference between concentration of inhibitor to concentration of substrate that determines effect on enzyme activity
- Substrate conc increased - inhibitor effecr reduced.
73
Q
What is a Non-Competitive inhibitor
A
- They attach themselves to an enzyme at a binding site which isnt the active site.
- Upon attaching to the enzyme, the inhibitor alters the shape of the enzyme’s active site so substrate can’t occupy it (enzyme can’t function)
- Increase in substrate = doesnt decrease effect of inhibitor (not competing for same site)
