topic 1 & 2

eukaryotic cells include plant and animal cells. Prokaryotic cells are smaller and more complex than eukasryotic cells. All prokaryotes are single-celled organisms 

chloroplast - contains chlorophyll which absorbs light used for photosynthesis 

 cell wall - provides struture and protecting for the cell. 

chromosomal dna - the chromosomal dna carries the genes of the cells 

proteins are synthesised within cells, this is done when information from genes is used to join together a sequence of amino acids 

mrna is the subcellular structure involved in the translatioon of genetic material in protein synthesis 

the egg cells of an animal tend to have half the amount of chromosomes as the amount of chromosomes there are in the body cells

the sperm acrosome - the acrosome penetrates the egg cell, the enzymes break down the outer membraneof the ovum allowing the haploid nucleus in the sperm to be able to join the haploid nucleus in the ovum 

the membrane of the egg cell changes in order to ensure that no other sperm cell can penetrate the egg

the cytoplasm in the cell contains nutrients for the growth of the early embryo

the epithelial cell - the epithelial cell creates a barrier between the inside and outside of your body and protects it from viruses 

when using a light microsope its important to start with the low power objective lensas it increases the field of view which increases the number of cells in which you will be able to see

drawing cell structures:

• drawn in pencil
• large with proportional aspects to the cell
• labelled using straight lines spread out throughout the diagram 
• a title using the magnification or size

magnification = size of image / actual size of the object

electron microscopes:

electron microscopes pass beams of electrons through a specimen and have a much greater resolution than light microscopes

the resolution of the electron microscopes can show up to 0.0001µm allowing scientists to see the clear detials inside a chloroplast or mitochondriun

enzymes are biological catalysts

a catalyst - a catalyst increases the speed of the rate of reaction

the active site is the section of the enzyme in which the substrate molecules bind to

enzymes have a 'high specificity' for their substrate, this means that the enzymes substrates only bind to the single active site

increasing the substrate concentration fails to affect the rate of an enzyme-controlled reaction after a certain point, this is beavuse the reaction can not take place in certain conditions meaning the rate of reaction stops from increasing

if the temperature reaches above a certain level the active site may change due to the extreme temperatures which can cause the substrate to no longer fit 

the optimum level - the level in which the rate of reaction is at its peak and where the rate of reaction is taking place the best 

biuret test: 

the biuret test is the test for proteins

• place one / two spatulas of the food sample into the test tube with 1cm³  of water and mix well
• add an equal volume of potassium hydroxide solution to the test tube and stir
• add two drops of the copper sulfate solution and stir for two minutes
• record the colour of the solution

if the solution turns a purple / mauve coliur then there are proteins present

iodine test:

the iodine test is the test for starch

• place one spatula of the food sample in a dish
• place a few drops of the iodine sloution into the dish
• record any change in the colour of the food

if the food turns blue-black then starch is present in the sample

benedicts test: 

the benedicts test is the test for reducing sugars

• place two spatulas of the food sample into a test tube, add 1cm³ of water to the test tube and stir to mix
• add an equal volume of benedicts solution and mix
• place the test tube into a water bath at around 95^oc for a few minutes
• record the colour of the solution

emulsion test: 

the emulsion test is the test for lipids

• place two spatulas of food into a test tube
• add 2cm³ of ethanol tyo the tube, cover the end and shake vigorously
• allow the contents to settle
• pour the liquid from the top of the ixture into a test tube half-fill with water 
• record the level of food and weather the water is clear or cloudy 

a milky-white emulsion forms if the test substance contains lipids

diffusion: 

diffusion is the movement of particles from a higher concentration into a lower concentration

• the particles will move in both directions but there will be a net movement from a high to low concentration
• the particles will end up evenly spreading througout the liquid or gas, but will continue to move 

mitosis: 

mitosis is a type of cell division in which a diploid body cell copies itself and divides into two identical diploid daughter cells

• interphase - the dna in chromosomes copies itself ready for mitosis
• prophase - the dna condenses to beome more visible, the membrane disappears
• metaphase - chromosomes and their copies line up in the middle of the cell
• anaphase - the chromosomes and their copies are pulled apart to the ends of the cell
• telophase - the new membranes form around the chromosomes at each end of the cell
• cytokenisis - the cell membrane pinches in and eventually divides into two daughter cell

stem cells are undifferentiated, meaning that they are not yet specialised, embryonic stem cells are removed from the embryo they will differentiate into any cell type 

some adult stem cells remain in the bodies of adults, these are found in limited numbers in certain locations throughout the body, these include:

• nose 
• brain 
• eyes 
• blood
• heart 
• liver 
• bone marrow 
• skin 
• muscle

in plants: 

cell division in plants occurs in regions called meristems, these can be used to produce any type of plant cell throighout the whole of the plants lifetime

these are mainly found close to the tip of the shoot and the tip of the root

the body has lots of sensory receptors, which detect environmentsl stimuli. when this jappens, nervous impluses are snet along sensroy neurones to the central nervous system

from the central nervous system, impulses are sent along motor neurones to effectors, which produce a response

motor neurones:     

• there are several short dentrites 
• one long axon which carries the impulses

stimulus > receptor > sensory neurone > relay neurone > motor neurone > effector > response

the receptor identifies the stimulus of danger and sends the message to the sensory neurone, the impulse is sent to the relay neurone, located in the spine, and followed through to the motor neurone the impulse is then sent to the effector which contracts the muscle causing the body to pull away from danger

communicable - which can be transferred from one perosn to another, or from one organism to another, eg in humans, these include measles, food poisoning and malaria

non-communicable -  which are not transferred between people or other organisms

different types of disease may interact which can mean that the presence of one disease can lead to a higher possibility of someone or something developing another disease

pathogen - a pathogen is an organism that causes a disease, there are four main types of pathogen these include: 

• viruses (example - HIV/AIDS)
• bacteria (example - salmonella)
• fungi (example - athletes foot)
• protists (example - malaria)