Biological molecules Flashcards
1
Q
What is covalent bonding
A
Bonding between two non metals sharing a pair of electrons
2
Q
What is ionic bonding
A
Bonding between a metal and non metals, it is an electrostatic attraction
3
Q
What is hydrogen bonding
A
A chemical bond that forms between the positive hydrogen atom and the negative charge on another molecule
4
Q
What is a polar molecule
A
A molecule with uneven distribution of charge, the negative and positive regions of these molecules attract each other
5
Q
What is a monomer
A
sub units that join together to form a chain or polymer by the process of polymerisation
6
Q
Give 3 examples of monomers
A
Nucleotides, monosaccharides and amino acids
7
Q
How are polymers joined
A
Durining polymerisation each time a new sub unit is attached a water molecule is formed. This is called a condensation
reaction
8
Q
What type of reactions form polysaccharides from monosaccharides and polypeptides from amino acids
A
Condensation reactions
9
Q
What process can break down polymers
A
Hydrolysis
10
Q
What is hydrolysis
A
The breaking down of a large molecule into smaller ones by the addition of water molecules
11
Q
What is metabolism
A
All the chemical processes and reactions in a living organism
12
Q
What is a molar solution
A
A solution that contains one mole of solute in each litre of water
13
Q
What is a monosaccharide
A
A sweet tasting, soluble substances
14
Q
What is the general formula of a monosaccharide
A
(CH2O)n
15
Q
What are 3 examples of monosaccharides
A
Glucose, fructose and galactose
16
Q
What type of bond does a condensation reaction form
A
Glycosidic
17
Q
What are larger carbohydrates made of
A
Monosaccharide monomers
18
Q
How are disaccharides formed
A
The condensation of two monosaccharides, a water molecule is taken from the monomers (a H from one and OH from the other for H2O
19
Q
What is a reducing sugar
A
A sugar that can donate electrons to another chemical
20
Q
What is the test for reducing sugars
A
Benedict’s test
21
Q
What is Benedict’s solution
A
Alkaline solution of copper (III) sulfate that when heated with a reducing sugar forms an insoluble precipitate of copper (I) oxide
22
Q
How to carry out the benidicts test
A
Add 2cm^3 of food sample to be to a test tube, if it’s not liquid grind it up with water
Add an external volume of Benedict’s
Heat the mixture in a gently boiling water bath for 5 minutes
23
Q
What results mean reducing sugar is present vs not
A
Blue is not present
Red is high concentration
24
Q
What are the 3 disaccharides
A
Maltose lactose and sucrose
25
What monomers make up maltose
Alpha glucose and alpha glucose
26
What monomers make up sucrose
Alpha glucose and fructose
27
What monomers make up lactose
Alpha glucose and galactose
28
What are the two glucose isomers
Beta glucose and alpha glucose
29
Wjat monosaccharide isn’t a reducing sugar
Sucrose
30
How is cellulose formed
The condensation of b glucose
31
How are glycogen and starch formed
The condensation of a glucose
32
How to test for non reducing sugars
First perform the reducing sugars test to determine there is no reducing sugars present
Add another 2cm^3 of food sample to 2cm^3 of dilute hydrochloric acid
Place into gently boiling water for 5 mins
Neutralise the the acid by adding some sodium hydrocarbonate solution
If reducing sugar is present the reagent will turn orange brown
33
What are polysaccharides used for
Storage of monosaccharides and and structural support
34
What are the 3 polysaccharides you need to know
Starch
Cellulose
Glycogen
35
What are the facts of starch
-Storage molecule found in plants
-Made of two smaller polysaccharides called amylose and amylopectin
36
What are the facts of amylose
-Made from alpha glucose
-Inly has 1,4 glycosidic bonds
-Coils into an alpha helix shape
-Held into position by hydrogen bonds
-Single strand unbranched chain
-Helix structure makes it compact suitable for storage
37
What are the facts of amylopectin
-Made from alpha glucose
-Has 1,4 and 1,6 glycosidic bonds
-Branches allows easy access for enzymes, as they break the branches allowing quicker access to more glucose
-Alpha helix shape held together with hydrogen bonds
38
Why is starch so important
-Insoluble so does not affect water potential in the cells
-Large molecule so cannot diffuse out of cells
-Releases alpha glucose needed for respiration
-Branches provide many areas for amylase to act on
39
What are the facts of cellulose
-Made from beta glucose
-Has only 1,4 glycosidic bonds
-Forms unbranched chains
-These chains run parallel to each other cross linked by hydrogen bonds
-Tjese strands form micro fibrils
-Strong fibres make this molecule useful for strength and support of the cell
40
What are the facts of glycogen
-Made from alpha glucose
-Has 1,4 and 1,6 glycosidic bonds
-Forms branched chains
-Glucose store found in bacteria and animals
-Has many side branches compared with amylopectin
41
What elements do lipids contain
Carbon, hydrogen and oxygen
42
What are the two main lipid groups
Triglycerides and phospholipids
43
What are the 5 roles of lipids with explanation
Cell membranes- phospholipids contribute to flexibility of the membrane and transfer of lipid soluble substances
Source of energy- when oxidised lipids provide more than twice the energy as the same mass of carbohydrates and release valuable water
Waterproofing- lipids are insoluble in water some plants and animals have waxy lipid cuticles that conserve water
Insulation- fats are slow conductors of heat and when stored beneath the body surface help to retain body heat
Protection- fat is often stored around delicate organs
44
How do triglycerides form
3 fatty acids form an ester bond with glycerol in a condensation reaction
45
What is the difference in structure between saturated and unsaturated fats
A saturated fat will have no double carbon carbon bonds
46
What is a unsaturated fat with more than 1 double carbon carbon bond
Polyunsaturated
47
What are the structure of lipids in relations to their properties
-High ratio of energy storing carbon hydrogen bonds so excellent source of energy
-Low mass to energy ratio making them good storage molecules
-Large non polar molecules so are insoluble in water so storage doesn’t affects water potential
-High ratio of hydrogen to oxygen atoms so they release water when oxidised
48
What part of a phospholipid is hydrophobic and hydrophilic
Hydrophilic ‘head’ or phosphate
Hydrophobic ‘tail’ or 2 fatty acids
49
What is a phospholipid bilayer
The two ends behave differently, when places in water the heads are as close to the water as possible and the tail are as far away from the water as possible
50
What is the structure of phospholipids relating to their properties
-Polar molecules so form a bilayer within cell surface membranes in an aqueous environment
-Hydrophilic phosphate help to hood at the surface of the cell surface membrane
-Phospholipid structure allows them to form glycolipids by combining with carbohydrates
51
what are amino acids
basic monomer units of a polypeptide
52
what are the 4 different groups the central carbon is attached to in an amino acid
amino group NH2, carboxyl group COOH, hydrogen atom H and R group
53
what bond if formed between an amino acid
peptide bond
54
how is a peptide bond formed
condensation reaction- removal of a water molecule (OH from carboxyl group and H from amino group)
55
explain the primary structure of proteins
polypeptide chain of many amino acids formed from many condensation reactions, this determines the proteins shape and therefore its function
56
explain the secondary structure of proteins
the amino and carboxyl groups form hydrogen bonds causing the chain to form an alpha helix
57
explain the tertiary structure of proteins
the alpha helix can be twisted into an even more complex and specific 3D structure, these are held together by disulphide bridges, ionic bonds and hydrogen bonds. This again is important to its function
58
explain the quaternary structure of proteins
large proteins are often comprised of many different polypeptide chains, linked in various ways, non protein groups can also be associated with the molecules
59
What is the difference between globular and fibrous proteins
Fibrous are long strands used for structural purposes and generally more organised
Globular protein is roughly circular and has irregular R groups
60
What are transport proteins
Protein that forms a channel which allows specific molecules to be transported across membranes, these are present in cell membrane
61
What are structural proteins
Consist of long polypeptide chains lying parallel for increased cross links for example collagen
62
What makes enzymes highly specific to one substrate shape and effects their properties
Their tertiary structure
63
What are the two ways enzymes lower activation energy
By the active site putting a strain on the bonds or holding two substrates together reducing repulsion
64
Describe lock and key
Enzymes active site and substrate have a complementary shape
65
Describe induced fit
Active site shape will change in presence of the substrate
66
What are the 4 factors affecting enzyme action
Temperature
pH
Substrate concentration
Enzyme concentration
67
Explain how temperature affects enzyme action
An increase in temperature increases kinetic energy causing more successful collisions however beyond optimum temperature the enzyme denature so it’s active site changes shape meaning its no longer complimentary to the substrate
68
Explain how pH affects enzyme action
Enzymes have different optimum pH values, and variations in pH will change the concentration of H+ OH- ions which will disrupt ionic and hydrogen bonds of the active site
69
Explain how substrate concentration affects enzyme action
Increase substate concentration causes increased frequency of collisions resulting in more enzyme substrate complexes however this will only increase up to a saturation point (when all active sides are occupied by substrates)
70
Explain how enzyme concentration affects enzyme action
Higher enzyme concentrations will result in faster rate of reaction as frequency of collisions increases causing more enzyme substrate complexes
71
What is the allosteric site of an enzyme?
A different area of the enzyme that’s not the active site
72
What are inhibitors
Molecules that will slow down or stop an enzymes activity
73
Explain competitive inhibitors
They have similar shape to the substrate so bind to the active site. They can be affected by the concentration of a substrate.
74
Explain non-competitive inhibitors
Binds to the allosteric site which causes the active side of the enzyme to change shape the substrate will no longer be complimentary, not affected by concentration of substrate
75
Explain reversible inhibitors
These are competitive inhibitors which form weak hydrogen or ionic bonds with the enzymes that can be easily broken
76
Explain the steps to test for lipids
1) add 2 cm³ of the sample being tested to a test tube
2) to the sample add 5 cm³ of ethanol and shake the tube thoroughly to dissolve any lipid in the sample
3) Add 5 cm³ of water and shake gently
A cloudy white colour indicates the presence of a lipid
77
Explain the steps to test for starch
1)Place 2cm3 of sample into test tube or sporting tile
2)Add two drops off iodine solution and shake or stir
3)Presence of starch is indicated by blue-black colour
78
Explain the step to test for proteins
1) Place a sample of the solution to be tested in a test tube and add an equal volume of sodium hydroxide solution at room temperature
2) Add a few drops are very dilute 0.05% copper(II) sulphate solution (biuret) and mix gently
A purple collation indicates the presence of peptide bonds and hence a protein if no protein is present the solution remains blue
