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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