Biology Paper 1.1
Microscopes
Light
Electron
Cheap, small, portable, no vacuum required, low magnification.
Expensive, large, vacuum required, high magnification.
Magnification = size of image / real size of image
Practical
Preparing onion cells
Using light microscope
Preparing cheek cells
swab cheek, wipe swap on the slide, put swap in disinfectant, add methyl blue dye, add cover slip (make sure to avoid bubbles)
peel one thick layer, cut into small pieces, put on slide, add iodine, add cover slip.
put slide on stage, put on lowest magnification, use course focusing knob to find cell, increase magnification, use fine focusing knob to observe.
Photosynthesis
Equation
Carbon dioxide + water -> glucose + oxygen
About photosynthesis
Photosynthesis requires energy in the form of light to drive the chemical reaction.
It is an endothermic reaction.
The light energy required is absorbed by a green pigment called chlorophyll.
Chlorophyll is located in chloroplasts in the plant cells, particularly in palisade cells.
Carbon dioxide enters leaves through the stomata, water enters leaves through roots, it is transported to the leaves in the xylem.
Required practical
Method
Set up a boiling tube containing 45cm^3 of sodium hydrocarbonate solution.
Cut a piece of the pondweed.
Use forceps to place the pondweed in the boiling tube.
Position the boiling tube 10 cm away from the light source.
Allow the boiling tube to stand for 5 mins.
Count the number of bubbles, repeat and then calc an average.
Variables
IV - light intensity
DV - the num of bubbles
CV - concentration of sodium hydrocarbonate, temp, same pondweed.
Risks
water near electrical equipment
hands are dry when handling lamp
Factors affecting photosynthesis
oxygen output
carbon dioxide uptake
the rate of carbohydrate production
light intensity
carbon dioxide concentration
Temperature
Plant cells
Plant only organelles
Chloroplast
contain chlorophyll, which absorbs light energy for photosynthesis.
Cell walls
made from cellulose fibres and strengthens the cells and supports the plant.
Vacuole
filled with cell sap to help keep the cell turgid.
Organelles for both
Cytoplasm
a jelly-like material that contains dissolved nutrients and salts and structures called organelles, it is where many chemical reactions occur.
Nucleus
contains genetic material including DNA, controls cells activities.
Cell Membrane
semi-permeable and controls movement of substances in and out of cell.
Mitochondria
contains enzymes for respiration and where most energy is released in respiration.
Ribosomes
Tiny structures where protein synthesis occurs.
Heart
Breathing rate/Heart rate
increases during strenuous exercise.
because muscles need more energy which is released during respiration.
when we need to increase the rate of gas exchange the internal intercostal muscles will pull the ribs down and in to force air out quicker.
there is a greater need to rid the body of carbon dioxide produced.
greater volume of gases exchanged.
natural resting heart rate controlled by group of cells in right atrium.
they form a structure called pacemaker.
the faster the more oxygen for cells to respire.
Circulatory System
the human heart is part of a double circulatory system.
the benefit of this is that blood loses pressure while in capillaries in lungs, by returning blood to the heart from the lungs.
the rate of blood flow = volume of blood / number of minutes.
Biology Paper 1.2
Blood
Red blood cell
disc shaped cell with a dimple in
carries oxygen
no nucleus to fit in more haemoglobin
disease is anaemia
White blood cell
irregular shaped cell with a nucleus
forms the immune response by engulfing pathogens and making antibodies
contains ribosomes
disease is aids
Platelets
disc shaped cell fragments
stick together to clot
in certain conditions they stick together
disease is thromboctopenia
Plasma
straw coloured liquid
carries dissolved nutrients
liquid capable of having proteins and gases dissolved in it
can cause dehyrdration
Osmosis practical and equation
Blood vessels
arteries carry blood away from heart.
veins carry blood towards heart.
capillaries are small and connect arteries to veins.
Use a cork borer to cut 5 potato cylinders of same diameter.
Use a scalpel and ruler to trim each potato cylinder so they are all the same length.
Measure 10 cm^3 of each sugar and salt solution and pour into each boiling tube.
Add one potato cylinder to each boiling tube and leave for a specified amount of time.
Remove the potatoes, blot dry and record the final mass and length of each.
change in mass = (mass at end - mass at start) / mass at start then x 100
Pathogens
Measles is caused by a virus
red skin rash and fever
treated by vaccination
Malaria
caused by mosquitos
fever
mosquito bites
It is a microorganism that causes a disease.
Antibiotics - only for bacteria
Medicines to treat the symptoms of the diseases, caused by toxins release.
Antibiotics cure bacterial disease by killing infective bacteria inside body.
Antibiotic resistance reduces the number of bacteria that are becoming resistant to antibiotics, shouldn't be overused.
Mitosis
The cell cycle
Cell growth
Dna synthesis - the chromosomes are now double stranded
Further growth occurs, DNA checked for errors
Mitosis
The cytoplasm separates - two cells are formed
Temporary cell resting period
The cell begins to divided
The DNA replicates to form two copies of each chromosome
The nuclear membrane breaks down, the chromosomes line up across centre of cell
one set of chromosomes pulled to each end of cell, nucleus divides
The cytoplasm and cell membranes divide to form two identical cells
length of time in phase = observed number of cells at that stage / total number of cells observed x total length of time of cell cycle
Biology Paper 1.3
Digestion
stages
food is digested in the mouth, stomach and small intestine.
digested food is absorbed into the bloodstream in the small intestine.
excess water is absorbed back into the body in the large intestine.
any undigested food passes out of the anus and faeces.
Structures and functions
Mouth/Salivary Gland
Oesophagus
Stomach
Small intestine
Large intestine
Pancreas
Liver
Gall Bladder
where you chew food, your salivary glands make saliva, which breaks down starches.
transport food entering the mouth through the throat and into the stomach
holds the food while it is being mixed with stomach enzymes.
breaks down food, absorbs nutrients and gets rid of unneccessary components.
absorbing water, produces and absorbs vitamins as well as propelling faeces toward the rectum.
produces enzymes that help to digest food, particularly protein.
to make and secrete and bile, to purify blood.
stores and concentrates bile from liver.
Enzymes
biological catalysts that speed up chemical reactions, they are made of proteins, they have an active site that is complementary for a substrate.
they are responsible for reactions which occur in living things.
Amylase breaks down starch to sugar, Protease breaks down proteins into amino acids, Lipase breaks down fats to fatty acids and glycerol.
Enzymes denature if far away from their optimum.
Fermentation
Equation
glucose -> ethanol + carbon dioxide
yeast, a type of single-celled fungus, provides the enzymes needed for fermentation.
it is an anaerobic process.
it is the chemical breakdown of substance by bacteria, yeasts or other microorganisms.
Anaerobic and Aerobic Respiration
Aerobic - oxygen is needed, glucose breakdown is complete, products are carbon dioxide and water and a lot of energy is released.
Anaerobic - oxygen is not needed, glucose breakdown is incomplete, products are lactic acid, yeast, carbon dioxide and ethanol and a little energy is released.
Alveoli
Large surface area to enable more diffusion of oxygen into the blood and more carbon dioxide out.
One cell thick walls so there is a short distance for gases to diffuse through.
Permeable walls to allow gas to pass through.
Moist walls helps them pass across the gas exchange.
Extensive blood supply ensures that blood rich in oxygen is carried away from the lungs and blood rich in carbon dioxide is carried to the lungs.
Large diffusion gradient.
Cancer occurs when cell diffusion goes wrong, this causes cells to grow out of control and form a tumour, it is caused when cells divide uncontrollably and spread into surrounding tissues.
Drug trials
Preclinical testing is testing on cells.
Whole organism testing is testing on animals, they have to be tested on two different animals by law.
Clinical trials where the drug is tested on healthy volunteers at low doses.
double blind trials, neither the doctor nor patient know what they are giving / getting in order to avoid the placebo effect and biased results
Bacteria are able to reproduce rapidly once inside the body, on the other hand viruses can only reproduce once inside of a "host cell"
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