AS biology - Molecules, Biodiversity and Health

HideShow resource information
  • Created by: Elena
  • Created on: 02-05-14 10:08
Four main types of bond
Covalent bonds, double bond, ionic bond and hydrogen bond
1 of 88
Covalent bonds
It involves sharing electron pairs between atoms. e.g Carbon can form four covalent bonds with other carbon atoms or other atom types
2 of 88
Double bonds
Exists where atoms share multiple electrons in order to stabilise (a double bond is just two covalent bonds)
3 of 88
Ionic bonds
Always between 1 anion (non-metal) & 1 cation (metal). Don't share electrons but metal ion donates electron/s to non-metal ion to complete the outer energy level and stabilise the atom
4 of 88
Hydrogen bonds
One of most important bonds-used to hold together individual monomers into larger groups (polymers)-Form where slightly +ve parts of a molecule meet slightly -ve parts of another-very weak but when there are loads, they are pretty strong together.
5 of 88
What is a Carbohydrate made up of?
A carbohydrate is a biological molecule made of carbon, hydrogen and oxygen atoms
6 of 88
What are carbohydrates used for in the body?
Energy source, energy storage or it has structural properties
7 of 88
What is the formula for a carbohydrate?
8 of 88
Simplest sugar - monosaccharide, monomer - C6H12O6 - first product of photosynthesis
9 of 88
2 forms of Glucose?
alpha-glucose (hydrogen on top and hydroxyl on bottom) & beta-glucose(hydroxyl on top and hydrogen on bottom)
10 of 88
Condensation reaction
2 monosaccharides polymerise (join together) and release water in the process - 2 alpha-glucose join to make maltose, held together by a glycosidic bond (C-O-C)
11 of 88
Hydrolysis reaction
A disaccharide splits by adding water to break or split the bond - produces 2 alpha-glucose.
12 of 88
The energy store used in plants - made from 2 different molecules: 20% amylose (straight chain joined by glycosidic 1,4 bonds) and 80% amylopectin (branched chain - glycosidic 1,6 bonds and 1,4 bonds). Starch -broken down to be used in respiration
13 of 88
Energy stpre in animals-glycosidic 1,4 chains are shorter and more 1,6 bonds per chain = molecules more compacted and complex.
14 of 88
H on top, OH on bottom - forms starch (plants) and glycogen (animals) -used for storage.
15 of 88
OH on top, H on bottom - forms cellulose (plants) - 1 long, straight chain - structural form. Every other beta-glucose flips 180 degrees to allow bonding of OH groups.
16 of 88
Variable group that contains carbon, hydrogen and oxygen. Most common are fats, oils, waxes, steroids and phospholipids
17 of 88
Lipid that covers fats and oils group - contain 6 oxygen atoms. One triglyceride molecule contains 3 fatty acids and 1 glycerol molecule
18 of 88
Fatty acid molecule
2 parts: acid group (COOH) at one end & hydrocarbon chain at other end.
19 of 88
Glycerol molecule
contains 3 OH groups & is always the same in any triglyceride.
20 of 88
3 fatty acid + 1 glycerol
3 fatty acids and 1 glycerol join in a condensation reaction - 3 water molecules released - bond between them is a O-C=O bond (ester bond) - This attaches 1 fatty acid to each carbon atom of glycerol molecule
21 of 88
Form the basis of all biological membranes - structurally similar to triglycerides (glycerol & fatty acids (only 2)) - formed in condensation reaction. Head - hydrophilic & tail - hydrophobic
22 of 88
Water-loving (phospholipid head)
23 of 88
Water-hating (phospholipid tail)
24 of 88
Type of lipid formed from 4 carbon-based rings. Small & hydrophobic - in all biological membranes (between fatty acid tails) - vital to living organisms so a lot of cells can make it (liver)
25 of 88
Excess cholesterol
Can cause health problems - hypercholesterolemia - genetic disorder where cells make and secrete cholesterol even though they have enough in the blood already
26 of 88
Polymer - Made up of amino acids (individual monomers). Amino acids contain the elements carbon, hydrogen, oxygen and nitrogen, and some also contain sulphur
27 of 88
Amino acid
Consists of an amine group, is basic and has the formula NH2
28 of 88
vital to living organisms - reactant in loads of chemical reactions like photosynthesis and hydrolysis. Solvent so substances dissolve in it. Transports substances helps with temp control
29 of 88
What do the hydrogen bonds in water do?
gives water a specific heat capacity (stops rapid temp changes in living organisms) and gives water a high latent heat of evaporation (A lot of energy used up when water evaporates - cools organisms)
30 of 88
Water's polarity
Makes it very cohesive (helps water to flow so it's good for transporting substances) and makes it a good solvent (because it's polar - positive end will be attracted to negative ion and vice versa
31 of 88
What are proteins (polymers) made up of?
One of more polypeptides. Polypeptides = when more than 2 amino acids join together
32 of 88
When 2 amino acids join together
33 of 88
When more than 2 amino acids join together
34 of 88
Bond joining amino acids together
Peptide bond forms when a molecule of water is released. C-N bond.
35 of 88
Four structural levels of protein
Primary, secondary, tertiary, quaternary
36 of 88
What is the primary structure?
The sequence of amino acids in the polypeptide chain
37 of 88
What is the secondary structure?
Shows the Hydrogen bonds that form between the amino acids in the chain - Makes it automatically coil into an alpha helix or fold into a beta pleated sheet
38 of 88
What is the tertiary structure?
When more bonds form between different parts of the polypeptide chain. If protein is made from only one polypeptide chain, this forms final 3D structure
39 of 88
What is the quaternary structure?
Some proteins made from several different polypeptide chains held together by bonds - this structure is the way these polypeptides are assembles together - e.g haemoglobin made up of 4 polypeptide chains. - final 3D structure for most proteins
40 of 88
Bonds in primary structure
Peptide bonds between amino acids
41 of 88
Bond in secondary struture
Hydrogen bonds form between nearby amino acids - these bonds create alpha-helix chains or beta-pleated sheets
42 of 88
Bonds in tertiary structure
Ionic interactions -weak attractions between -ve & +ve charges. Disulfide bonds, Hydrophobic & Hydrophilic interactions - hydrophobic groups clump together so get pushed to the outside. Hydrogen bonds
43 of 88
Bonds in quaternary structure
Determined by tertiary structure - can be influenced by all bonds in tertiary structure which are?...
44 of 88
2 examples of protein shapes
Collagen (fibrous protein) and Haemoglobin (globular protein)
45 of 88
Fibrous protein, forms supportive tissue in animals so it needs to be strong - made of 3 polypeptide chains, tightly coiled together into a strong triple helix - chains interlinked by strong covalent bonds and minerals can bind to triple helix
46 of 88
Globular protein - iron-containing haem group (binds to oxygen and carries round body) - Structure is curled so hydrophobic chains on outside - makes it soluble in water so good fro transport in blood
47 of 88
Fibrous proteins
Tough and rope-shaped. Tend to be found in connective tissue like tendons. E.g collagen (supportive tissue in animals)
48 of 88
Globular proteins
Round and compact, soluble and easily transported in fluids. E.g Haemoglobin (carries oxygen around the body)
49 of 88
Biochemical tests for molecules
Benedict's test (sugars), iodine test (starch), biuret test (proteins), emulsion test (lipids) and colorimetry ( determine conc of a glucose solution
50 of 88
Benedict's test
For sugars - blue - Add to a sample & heat it (not boil) - if +ve, it will form a coloured precipitate (blue-green-yellow-orange-brick red)
51 of 88
Iodine test
For starch - Add iodine dissolved in potassium iodide solution - if starch present, sample changes from browny-orange to dark blue-black colour.
52 of 88
Biuret test
For proteins - needs to be alkaline (add few drops of sodium hydroxide solution), then add copper (II) sulfate and if protein present, purple layer forms. If no protein - solution stays blue
53 of 88
Emulsion test
For lipids - shake with ethanol then pour into water - if lipid present, solution will turn milky.
54 of 88
What is DNA used for?
To store genetic information (instructions needed to grow and develop from a fertillised egg to a fully grown adult
55 of 88
What is DNA made from?
It's a polynucleotide made from lots of nucleotides joined together
56 of 88
What are nucleotides made up of?
A deoxyribose sugar, a phosphate group and a nitrogen-containing base - same sugar and phosphate but bases can vary.
57 of 88
What are the four possible bases?
Adenine (A), thymine (T), cytosine (C) and Guanine (G)
58 of 88
What are the purine bases?
Adenine and Guanine
59 of 88
What are the pyrimidine bases?
Thymine and Cytosine
60 of 88
What base joins to Adenine and how many hydrogen bonds are between them?
Thymine and there are 2 hydrogen bonds between them
61 of 88
What base joins to Cytosine and how many hydrogen bonds are between them?
Guanine and there are 3 hydrogen bonds between them
62 of 88
Complementary base pairing
Each base can only join one particular partner - G and C, A and T
63 of 88
Similarities between RNA and DNA
Both contain sugar, nitrogen-containing base and phosphate, contains 4 diff bases and form a polynucleotide strand that is joined up between the sugar of 1 nucleotide & phosphate of the other
64 of 88
Differences between RNA and DNA
Sugar in RNA nucleotides is ribose sugar (not deoxyribose), nucleotides form a single polynucleotide strand (not a double) and Uracil (pyrimidine) replaces Thymine as a base -pairs with Adenine in RNA
65 of 88
Why is Self-replication important?
It's before cell division so each new cell has the full amount of DNA
66 of 88
Stages of self-replication
Hydrogen bonds break (heliz unzips). Original strands act as templates for new strand and free-floating DNA nucelotides join to exposed bases. DNA polymerase joins nucelotides together. H bonds form between bases on original and new strand
67 of 88
After self-replication, what does each new DNA molecule contain?
One strand from original DNA molecule and one new strand
68 of 88
Semi-conservative replication
self-replication because half of the new strands of DNA are from original piece of DNA
69 of 88
What does DNA contain?
Genes (instructions for proteins) - Diff proteins have diff no. and order of amino acids which determines order of amino acids in particular protein. Diff sequences of bases code for diff amino acids
70 of 88
Protein synthesis
DNA is copied into RNA - Instructions (in DNA) are in nucleus and ribosomes (make proteins) are in cytoplasm but DNA is too large to get out of nucleus so sections of DNA are copied into RNA. RNA leaves nucleus & joins ribosome - makes proteins.
71 of 88
Why is DNA and RNA vital for living organisms?
DNA contains all the genes which are instructions for proteins & RNA is used to get the information out of the nucleus to bind to ribosomes in the cytoplasm to make proteins
72 of 88
What are enzymes?
Enzymes are biological catalysts which speed up chemical reactions - globular proteins & it's specific shape of active site is determined by tertiary structure.
73 of 88
How does an enzyme work as a catalyst?
It reduces activation energy, often making reactions happen at a lower temp which speeds up the rate of reaction
74 of 88
Lock and Key model
Enzymes only work with substrates that fit their active site - scientists realised it wasn't fully correct - evidence showed enzyme-substrate complex changed shape slightly to complete the fit.
75 of 88
Induced fit model
Better theory than lock and key - helps to explain why enzymes are so specific and only bond to one particular substrate. Substrate doesn't have to be the right shape to fit, it has to make active site change shape
76 of 88
Effect of temperature on enzyme activity
Rise in temp makes molecules vibrate more = more kinetic energy so faster the reaction. If temp gets too high - bonds break due to vibrations, active site changes shape and substrate no longer fits = denatured.
77 of 88
Effect of pH on enzyme activity
Have an optimum pH - Pepsin works best at pH 2 as it's found in the stomach. Above & below optimum pH, H and OH ions found in acids and alkalis can mess up ionic and hydrogen bonds that hold tertiary structure in place = denatured.
78 of 88
Effect of enzyme concentration on the rate of reaction
more enzymes = more chance of collisions = increases R.O.R. If amount of substrate is limited, there's a point when there's more than enough enzyme molecules to deal with all available substrate - no further effect
79 of 88
Effect of substrate concentration on rate of reaction
higher substrate conc = faster the reaction = more collisions. Saturation point = there are so many substrate molecules that the enzymes have about as much as they can cope with (active sites are full) - makes no difference
80 of 88
How to measure rate of an enzyme-controlled reaction
Measure how fast product of reaction appears or how fast the substrate disappears
81 of 88
Cofactors & Coenzymes
a non-protein substance that binds to the enzyme to make it work.
82 of 88
What are cofactors?
inorganic molecules - help enzyme and substrate bind together - don't directly participate in reaction so they aren't used up or changed.
83 of 88
What are coenzymes?
Cofactors - organic molecules - participate in the reaction and are changed by it (second substrate basically) - often act as carriers, moving chemical groups between diff enzymes. Continually recycled during process.
84 of 88
Competitive inhibitors
Similar shape to substrate & compete with it for active site but no reaction takes place - block active site so no substrate molecules can fit into it.
85 of 88
Non-competitive inhibitors
Bind to enzyme away from it's active site - causes active site to change shape to substrate no longer fits. Don't 'compete' with substrate molecules because they're a diff shape.
86 of 88
Metabolic poisons
Enzyme inhibitors- causes damage, illness or death - Cyanide (irreversible-inhibits cytochrome c oxidase-stops cells respiring), Malonate (stops cell respiration) and Arsenic (inhibits pyruvate dehydrogenase-stops cells respiring) are examples
87 of 88
Medicinal drugs that are enzyme inhibitors
Some antiviral drugs (inhibits enzyme which catalyses replication of viral DNA) & some antibiotics (penecillin inhibits an enzyme which catalyses formation of proteins in bacterial cell walls)
88 of 88

Other cards in this set

Card 2


Covalent bonds


It involves sharing electron pairs between atoms. e.g Carbon can form four covalent bonds with other carbon atoms or other atom types

Card 3


Double bonds


Preview of the front of card 3

Card 4


Ionic bonds


Preview of the front of card 4

Card 5


Hydrogen bonds


Preview of the front of card 5
View more cards


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Biological molecules resources »