2. Biological Molecules
Water- Reactant in lots of chemical reaction, solvent, transport medium and
temperature control.
Hydrogen Bonds
• Absorb lots of energy gives water high specific heat capacity
• Lots of energy to break, high latent heat of evaporation, good for cooling
• Very cohesive due to polar molecules, helps water transport substances
• Ions dissolve in water due to the atom charges +ve & -ve, water’s
polarity makes it useful as a solvent.
3. Proteins
Primary Structure- the number and sequence of amino acids.
Secondary Structure- hydrogen bonds form between amino acids
to make Beta pleated sheets or alpha helix coils.
Tertiary Structure- further coils or folding to from globular
proteins.
Quaternary Structure- several polypeptides held together by
bonds, these bonds determine the quaternary structure e.g
haemoglobin.
4. Different bonds, different structures
• Primary- Peptide
• Secondary- Hydrogen Bonds
• Tertiary- Ionic interactions, disulphide bridge, hydrophilic/phobic
interactions, hydrogen bonds
• Quaternary- determines by tertiary structure, uses all bonds
Shape related to function
Collagen
- Fibrous, supportive tissues, strong.
- 3 polypeptide chains, triple helix, chains linked by strong covalent bonds
- Minerals bind to helix to increase rigidity.
Haemoglobin
-Globular protein, contains Haem group, binds to oxygen.
- Hydrophillic on outside, hydrophobic on inside.
- Make haemoglobin soluble, good for transport.
6. Starch
• Mixture of amylose & amylopectin
• Amylose – long, unbranched, coils, good for storage
• Amylopectin – long, branched, side branches, allows easy breakdown,
quick energy release
• Insoluble, doesn’t affect water potential, good for storage
Glycogen
• Polysaccharide of alpha glucose
• Similar to amylopectin, more side branches, quick energy release
• Very compact, good for storage
Cellulose
• Long, unbranched Beta glucose
• Bonds between 1-6, chains are straight
• Chains linked by hydrogen bonds, to form microfibrils, provides structural
supports e.g. in plants
7. Lipids
Triglycerides
• Tails
Hyrdophobic
• Makes lipids
insoluble
• Hydrocarbon
tails varies - R
Phospholipids
• Hydrophilic head
• Hydrophobic tails
Cholesterol
• Soluble in water
• Not soluble in blood, so carried by
lipoproteins
8. Lipid structure to function
Triglycerides
• long hydrocarbon tails, lots of chemical energy, when broken
down twice as much energy per gram of carbohydrate
• Insoluble, don’t affect water potential, bundle as insoluble
droplets, tails are hyrophobic, tails face in, heads outwards.
Phospholipids
• Form double layer
• Membrane acts as barrier, water cant pass through
Cholesterol
• Flat rigid shape, bind tails in membrane, increase rigidity,
lower fluidity
9. Biochemical tests for molecules
Reducing sugars – Add Benedict’s to sample & heat, don’t allow
to boil. Colour change Blue-Green-Yellow-Orange-Brick Red. Can
filter & weigh precipitate when comparing, more accurate.
Non-reducing sugar – boil solution with dilute hydrochloric acid
solution & neutralise with sodium hyrdrogencarbonate solution,
then carry out Benedict’s, if test positive do reducing sugar test.
Iodine test – Add iodine disolved in pottasium iodide solution to
test sample. If starch present = browny-orange -> blue-black
Biuret test – add sodium hydroxide then copper (ii) sulphate. If
protein present purple layer forms, if not stays blue.
Emulsion test – shake solution with ethanol, pour solution into
water, goes milky if lipid present, milkier the solution, more lipid.
10. Nucleic Acids
DNA- deoxyribose nucleic acid
Bases
Adenine
Thymine
Cytosine
Guanine
Double helix formation
• Hyrdrogen bonding between bases- complementary base
pairing
• A-T & G-C
• Antiparallel polynucleotide strands pair and twist to form the
DNA double helix
11. DNA self replication
1. Hydrogen bonds between strands breaks, helix unzips
2. Each strand acts as a template for free-floating bases to join to the exposed
bases by complementary base pairing
3. Nucleotides on new strand are joined together by DNA polymerase to form
the backbone & hydrogen bonds form between the base
4. Each DNA molecule has one original & one new strand.
DNA copied for protein synthesis
1. All organisms need proteins, instructions for them are in the nucleus
2. Ribosomes make proteins but don’t fir into the nucleus so DNA is copied into
RNA
3. RNA leaves the nucleus via the nuclear pores & joins with the ribosome in
the cytoplasm where it can synthesise a protein
4. DNA & RNA are vital for all organisms to grow & develop
RNA
• Sugar is ribose sugar instead of deoxyribose
• Nucleotides form a single strand
• Uracil replaces thymine, so U-T
• Everything else is the same as DNA
12. Enzymes
• Catalyse metabolic reactions
• Intra or extracellular action
• Globular proteins
• Specific active site for specific substrates
• Specific shape determined by tertiary structure
• For enzyme to work substrate must fit into specific active site
Enzymes reduce activation energy
• Joining of enzyme & molecule reduces repulsion so they bond
easier
• In a catabolic reaction an enzyme is breaking down, it puts strain on
the substrate in the active site, this helps the substrate break more
easily
Lock and key model
Enzymes are picky so substrate must be perfect match for active site or
else they won’t bind.
Induced fit model
Substrate must be right shape & make enzyme change in the right way.
13. Factors affecting enzyme activity
Temperature, pH, Enzyme concentration, Substrate concentration
Cofactors- non-protein substance that binds to the enzyme
Inorganic molecules – help binding, not used up [cofactors]
Organic molecules – needed for reaction & changed [coenzymes]
Enzyme Inhibtion
Competitive- similar shape, block active site, no reaction
Non-competitive- bind away from active sire, alters active site
Irreversible = strong covalent bonds
Reversible = weak hydrogen bonds/ionic bonds
Cyanide irreversibly inhibits cytochrome c oxidase which catalyses respiration. Cells
that can’t respire die.
Some antibiotics inhibit transpeptidase which catalyses protein formation in bacterial
cell walls. This weakens the cell & causes it to burst & die.
14. Diet & Food Production
HDL transport cholesterol from body tissues to the liver. Reduce cholesterol is
too high.
LDL transport cholesterol from liver to blood if levels are too low.
Food production
Animals given antibiotics to kill bacteria & increase food production by
promoting growth.
Microorganisms & food
Advantages
• Rapid Growth
• Inexpensive
• Easy to create
• Artificially controlled
• Longer shelf life
Disadvantages
• High risk of
contamination
• Small environmental
change can kill
bacteria
Food Spoilage
• Salting- prevent micro-
organisms taking in water
• Sugar- same as salting
• Freezing slows growth
• Pickling prevents growth
• Heat treatment kills
• Irradiation kills
15. Health & Disease
Health- a state of physical, mental, & social well being including
the absence of disease & infirmity
Disease- a condition that impairs the normal functioning of an
organism
Pathogen- an organism that infects and can cause damage to it
Parasite- an organism that lives on or in another & cause it
damage
Malaria- cause by Plasmodium, it disrupts liver, RBCs and blood
supply to vital organs.
AIDs- infects WBCs & kills them when it leaves, needs WBCs as
host for reproduction.
TB- caused by Mycobacterium tuberculosis, “droplet infection”
16. Global impact of these diseases
They are common in sub-Saharan Africa as there’s limited
healthcare & equipment, so drugs aren’t always available or
can’t reduce chance of diseasing. Poor health education so
people are unaware how to prevent spread of HIV &
overcrowded conditions, so TB is spread easily.
Studying global distribution of disease can:
• Find where people are most at risk
• Predict where epidemics are most likely to occur
• Provide aid where needed
• Important for research e.g. how it’s spread
17. Immune System
Immune response- body’s reaction to a foreign antigen
4 ways body brings about immune response
1. Phagocytes engulf pathogens- recognise foreign
antigen, engulf, digestive enzymes, present antigens
2. Phagocytes activate T lymphocytes- release
substances to kill B lymphocytes, attach to pathogen
antigens & kill it, some become memory cells
3. T lymphocytes activate B lymphocytes which divide
into plasma cells- antibodies bind to antigens, B
lymphocytes activated by T, divides into plasma &
memory cells.
18. 4. Plasma cells make more antibiotics to a
specific antigen-
Antibodies help clear infection by:
• Agglutinating pathogens- clump pathogens
• Neutralising toxins- antibodies bind to toxins
• Prevent pathogen binding to
human cells- block cells surface
receptor , pathogen can’t bind
or infect target host cell
19. Immunity & Vaccination
Active- Long term immunity, memory cells produced
Passive- Short term immunity, no memory cells
produced
Vaccination contains antigens that cause your body to
produce memory cells against a pathogen without
causing disease. Results in immunity without symptoms
Natural Artificial
Active Immune after catching a disease Immune after vaccination
Passive Baby recieves mother’s antibodies
via the placenta & breast milk
Immune after injection of someone
else’s antibodies
20. Herd Immunity- most people in a community vaccinated so disease
becomes rare, people not vaccinated are unlikely to get the disease.
New flu vaccines required each year as new strains are formed
regularly.
Possible medical sources needing to be protected:
1. Many drugs are made from natural compound; animals, plants,
fungi etc.
2. Small proportion of organisms have been discovered, chances are
some undiscovered could hold a cure for ‘incurable’ diseases.
3. Possible sources of drugs may not have been studied for medicinal
properties.
4. New techniques are developing which may mean already
discovered, known sources of medicine may have more than one
use/application than previously known.
21. Smoking & Disease
Atherosclerosis- lining of artery damages, plaque builds up,
forms atheroma, restricts blood flow, high blood pressure.
Nicotine cause high blood pressure.
CHD- coronary arteries have atheromas, causing angina or heart
attack.
Stroke- rapid loss of brain function due to disruption of blood to
brain. Can be caused by clot in artery leading to the brain.
Nicotine- increase BP, makes platelets clot.
Carbon Monoxide- reduces oxygen available as it binds to
haemoglobin.
Chronic Bronchitis- Inflammation of lungs, cilia damages, goblet
cells produce more mucus. Increased coughing, decreased gas
exchange.
22. Lung cancer- carcinogens cause mutation of lung cells which
leads to formation of a malignant tumour, which causes reduced
gaseous exchange & blocks air flow. Tumour cause weight loss as
it requires nutrients.
Emphysema- Foreign particles trapped in alveoli. Phagocytes
enter area & break down elastin. Alveolar walls destroyed, lungs
elasticity lost. Alveoli SA decrease so rate of gas exchange does
too. Shortness of breath, wheezing, increased breathing rate.
Linking smoking to disease or death- how to improve
• Larger sample size- more reliable
• Lies told may reduce reliability
• Who study is done on can affect results e.g. doctors may be
bias, so they seem healthy
• Control as many variables as possible
23. Biodiversity
Biodiversity- the variety of living organisms in an area
Species- a group of similar organisms able to reproduce to give fertile
offspring.
Habitat- the area inhabited by a species, including physical & living factors.
Habitat diversity- no of different habitats in an area
Species Diversity- no of different species & abundance of each species in an
area.
Genetic diversity- variation of alleles within a species
Species richness- no of different species in an area, higher the number,
greater the richness.
Species evenness- measure of relevant abundance of each species in an area.
The more similar the population size of each species, the greater the species
evenness.
24. Sampling
• Choose sampling area
• Count number of species, plants=quadrat, flying insects=net,
ground=pitfall trap, aquatic = net
• Repeat, better indication of habitat
• Use results, estimates total number of individual or of species
in habitat.
• Use same sampling technique when comparing different
habitats.
• Sampling MUST be random.
Simpson’s index of diversity:
n= total no of individuals in a species
N= total no of organisms of all species
25. What affects biodiversity:
Climate- temperature, CO₂ levels, rainfall could cause species to migrate
or to become extinct if they can’t migrate.
Disease- insects carrying disease become greater, and can move with
climate change, e.g. area becomes warmer, mosquitoes move in.
Agricultural Problems- land previously is available after climate change,
can affect crops, food chains. Crop failure affect food chains.
Importance of biodiversity
Economy- Food, drink, clothing, drugs, fuels, paper, oils, rubber, pesticide.
Ecological- disruption of food chains & nutrients cycles, loss of habitats,
habitat destruction.
Ethical- organism has right to exist, moral responsibility, religion.
Aesthetic- rich biodiversity=attractive, more biodiversity=more visitors
(£’s)
Agriculture- pollinators, source of food for livestock, pest control (natural
predators), new varieties (selective breeding), protection against disease,
more variety more chance of resistant individual.
26. CITES- Convention on international trade of endangered species
Regulates trade in wild species, makes it illegal to kill endangered
species, trade only through licensing, no trade in endangered
animals/materials, raise awareness of threat via education.
Rio convention on biodiversity
Aims to develop international strategies on conservation, how to
use plant/animal resources sustainably, international law that
biodiversity conservation is a global responsibility, provide
guidance guidance to governments on conservation.
EIA- Environmental impact assessment
• Estimate biodiversity on site, evaluate affect of development
on biodiversity
• Identify how to conserve biodiversity
• Identify endangered species & laws regulating them
• Decide on planning stipulations
27. Conservation
In situ-
• National parks, protected areas, restrict urban development
• Control/prevent introduction of threatening species
• Protect habitats
• Restore damaged areas
• Promote particular species e.g. adjust food source
• Legal protection on endangered species
Ex situ-
• Relocate organism to a safer area
• Breed organisms in captivity & release them into the wild
• Botanic gardens preserve rare plants
• Seed banks- freeze & store seeds with out fertility loss.
28. Classification
Do you wanna King Prawn Curry Fat Greasy Sausage?
Kingdoms- Prokaryotae(bacteria), protoctista (algae), fungi,
plantae & animalia
Phylogeny- Study of evolutionary history of organisms
Classification based on molecular evidence, behavioural
embryological & anatomical evidence.
Dichotomous Key- a way to identify organisms using observable
features.
29. Evolution
Variation- the differences that exist between individuals
Within species= intraspecific variation
Between species= interspecific variation
Continuous variation; animal mass, no of leaves, length of flagellum
Discontinuous variation; animal sex, plant colour, antibiotic
resistance
Factors that affect variation:
Genes
• Different species different genes
• Same species, same genes, different alleles
• Different genotype = variation in phenotype
• Genetic variation is inherited
30. Environmental
• Differences in environment
• Characteristics controlled/change by environment
Both
• Height-genes determine height possible, diet affects actual height
• Flagellum- genes determine height possible, environment affects actual
length.
Adaptions
• Being adapted means an organism’s features increase its chance of
survival & reproduction
• Adaptions develop because of evolution by natural selection
Behavioural Physiological Anatomical
Possums ‘play dead’ Brown bear hibernation Otters have streamline
shape
Scorpions dance for mating Bacteria produces
antibiotics
Whales have thick blubber
layer
31. Darwin
Observations
1. Organisms produce more offspring that survive
2. Variation of characteristics in same species
3. Some characteristic passed on
4. Best adapted individuals more likely to survive
Theory
• Individuals show variation in phenotype
• Predation, disease, competition = struggle for survival
• Better adapted individuals more likely to survive & reproduce
• Over time, individuals with advantageous adaption increases
• Over generations leads to evolution
32. Evolution can lead to speciation
Speciation- formation of a new species
1. A species is defined as a group of similar organisms that can
reproduce fertile offspring
2. Species can exist as one or more populations
3. Speciation occurs when population of the same species
evolve so different that they can’t produce fertile offspring
e.g. Darwin’s finches
Evidence supporting Evolution
• Fossil record evidence
• DNA evidence
• Molecular evidence
33. Populations of Bacteria can evolve resistance to Antibiotics
1. Variation in population of bacteria. Mutations makes some bacteria naturally
resistant
2. If population of bacteria exposed, onty mutated bacteria survive to reproduce
3. Alleles causing resistance passed on, so population become resistant to
antibiotics
Implications for humans:
• Infections caused by antibiotic resistant bacteria are harder to treat
• Bacterium could develop resistance to all known antibiotics
Populations of insects can evolve resistance to pesticides
1. Variation in population, mutations causes some insects to be naturally resistant
2. If population exposed only mutated individuals would survive & reproduce
3. Alleles that cause resistance passed on so population becomes resistant
Implications for humans:
• Crop infestation with pesticide resistant insects harder to control
• If disease carrying insects become resistant the of disease would increase
• A population of insects could evolve resistance to all pesticides in use
