b2 - scaling up

the movement of particles from a higher to a lower concentration

occurs when the concentration of particles is higher in one area than another- like a gradient/slope of concentration

moving from an area of low concentration to an area of high concentration ( like going uphill)

moving from and area of high concentration to an area of low concentration (like going downhill)

the bigger the concentration gradient, the faster the rate of diffusion

in liquids and gases

1. diffusion

2. active transport

3. osmosis

movement of particles across a membrane from a lower to a higher concentration - against a concentration gradient (opposite of diffusion)

• active transport requires energy, diffusion dosnt

• active transport is against the concentration gradient whereas diffusion is down a concentration gradient

a membrane with very small holes in it to allow small molecules through but larger molecules cant pass through

the movement of water molecules across a partially permanent membrane from an area of higher water concentration to an area of lower water concentration

• small molecules e.g. glucose, amino acids water and oxygen

• big molecules e.g. starch and proteins cant fit through the membrane

the potential (likelihood) of water molecules to diffuse out or into a solution

you have a high concentration of water molecules

true - water molecules move about randomly all the time

cells full of water by the process of osmosis

when a cell reproduces itself by splitting to form two identical offspring

1. gap phase 1

2. synthesis

3. gap phase 2

4. mitosis

the cell grows and new cell protein and structures are made

the cell replicates its DNA so when it splits during mitosis the two new cells will contain identical DNA

1. molecule of DNA splits

2. bases on free floating nucleotide pair up with matching bases on the DNA

3. cross ties link between the new and old DNA bases and so the new nucleotide join together so two new DNA molecules identical to the original one are formed

1. the cell has 2 copies of its dna all spread out in long strings

2. before the cell divides, the dna forms x shaped chromosomes

3. the chromosomes line up at the centre of the cell and the cell fibres pull them apart. the two arms of each chromosomes got to opposite ends of the cell

4. membranes form around each of the sets of chromosomes. These become the nuclei of these new cells

5. you now have two cells containing the same dna to each other and the parent cell

process by which a cell becomes specialised for its job

perform specific functions / allow organisms to work efficiently

sperms have long tails ans stream lined heads to help them swim. They also have lots of mitichondria to provide them with lots of energy.

• biconcave shape for large surface area to absorb+ release oxygen

• dont have a nucleus so can carry more oxygen

• small and flexible so can pass easily through capillaries

undifferentiated cells which can divide by mitosis to become new cells which can then differentiate

• embryos

• adult animals

• meristems in plants

found in human embryos and have potential to turn into any type of cell

bone marrow and embryos

adult are found in bone marrow and arent as versatile as embyonic as can only develop into a limited number of cell types.

• can grow into any type of cell found in the body

• all tissues and organs can be potentially regrown

• however transplanted tissues and organs may be rejected by the patients immune system

• difficult to obtain and store embryonic stem cells

• Adult stem cells are found only in specific areas of the body and can only develop into a limited number of cell types e.g. bone marrow, breasts and intestines.

• however as from the same body, would not reject their own cells

because they have the potential to develop into different types of cells in the body which can be used for development, growth and repair

only plant cells which divide by mitosis found in the roots and shoots.

once theyre specialised, theyre onlt adapted to carry out 1 job

distance - if diffusion distance is small, it will happen faster

surface area - larger surface area, higher number of particles able to move in given time

1. surface to volume ratio

2. temperature

3. concentration gradient

rate of diffusion,osmosis or active transport is higher in cells with larger surface area to volume ratio

as the temperature increases, particles move in and out of cells faster as they have more energy

• substances move in and out of the cell faster if theres a big difference in concentration between the inside and outside of the cell

• of there are more particles on one side, there are more there to move across

• substances can diffuse straight into and out across the membrane as they only have to travel a short distance

• they have a relativity large surface area to volume ratio which means they are able to exchange enough substance across the cell membrane to supply the volume of the cell

• its too slow as some cells are deep inside the organism meaning its a long way from them to the outer environment

• larger organism have a low surface area to volume ratio meaning you cant supply enough substances through the small outer surface for the large volume organism

they cant do it through their outer membrane so have to use specialised exchange surfaces

an efficient system to transport substances from organs to the cells that use them.

circulatory system and the digestive system

xylem and phloem

• walls are thin so only have short distance to travel

• large surface exchange area

• in animals have lots of blood vessels to get stuff in and out of the blood quickly

• permeable membranes

the alveoli where the gas exchange takes place have a large surface area, thin walls, a good blood supply and a moist lining for dissolving gases

• small intestine contains villi dissolve food molecules are absorbed quicker into the blood

• they have a single layer of surface cells whihc increase surface area

• have a very good blood supply to assist quick absorption

• leaves are broad so have a large surface area for diffusion

• they’re thin which means gases only have to travel a short distance

• air spaces inside the leaf lets gases move easily between the cells and increases the surface area increasing the chance of oxygen to get into cells

• underneath of leaf covered in stomata through which carbon dioxide diffuses into leaf and water vapour diffuses out

• water is drawn into root hair cell by osmosis as there is usually a higher concentration of water in the soil than inside the plant

• mineral ions move into the root hair cell by active transport since the concentration of minerals is usually higher in the root hair cells than the soil (otherwise minerals would diffuse out of the root hair cells)

• cells on plant roots grow into long hairs which stick out into soil

• each branch of root covered in these microscopic hairs

• gives plant big surface area for absorbing water and mineral ions from soil

the sum of all the areas of the faces

you find the surface area and divide it by the volume

Two circuits carrying the blood from the heart to the lungs and back and from the heart to around the body and back

• returning blood to the heart after its picked up oxygen at the lungs means it can be pumped out around the body at a higher pressure

• this increases rate of blood flow at the tissues (blood can be pumped around body faster) so more oxygen is delivered to the cells

• important for mammals ad take up a lot of oxygen maintaining body temp

• blood flows into two atria from vena cava and pulmonary vein

• atria contracts pushing blood into the ventricles

• the ventricles contract forcing blood into pulmonary artery and the aorta and out the heart

• blood then flows into organs through arteries and returns through veins

• the atria fills up again and the cycle starts over

1. arteries

2. capillaries

3. veins

carry blood away from heart

• heart pumps blood out at high pressure so the artery walls are strong and elastic

• walls are thick compared to size of lumen

• contain thick layers of muscle to make them strong and elastic fibres to make them stretch and spring back

are involved with the exchange of materials at the tissues

• carry the blood really close to every cell in the body so can exchange substances with them

• permeable walls so substances can diffuse in and out

• supply food and oxygen and take away waste (co2)

• walls one cell thick - increases rate of diffusion

carry blood to heart

• blood is at low pressure so walls dont need to be as thick

• bigger lumen than arteries to help blood flow

• valves to keep blood flowing in right direction

their volume is large compared to their surface area

has to pump blood further around the body compared to the right side

the right side of the heart

valves stop the blood from flowing backwards

cardiac muscle contains lots of mitochondria to provide the cells with ATP so the cardiac muscle can contract

plasma, platlets, red blood cells, white blood cells

transport oxygen from the lungs to all the cells in the body

liquid that carries everything in blood

1. carbon dioxide ( carried from body cells to the lungs to be breathed out)

2. urea ( carried from liver to the kidneys where its removed in urine)

Plasma is clear and watery. This makes it suitable to transport molecules as many of them are soluble in water.

to transport oxygen from the lungs to all the cells in the body

• small and biconcave disc shape to give large surface area to volume ratio for absorbing + releasing oxygen

• dont have a nucleus - frees up space for more haemoglobin so they can carry more oxygen

• small and flexible so can pass through capillaries

• enables red blood cells to carry oxygen around the body

• in the lungs, haemoglobin binds to oxygen to become oxyhaemoglobin

• in body tissues oxyhaemoglobin splits up to release oxygen to the cells

• magnesium for making chlorophyll

• phospherous to make dna and cell membranes

transport food both up and down the stem to storage tissues.

carry water and minerals from the roots up the shoot to the leaves in the transpiration stream

the movement of sugar to all other parts of the plant

the loss of water from the plant through the evaporation and diffusion of water from a plants surface

the movement of water through the xylem tissue

• evaporation and diffusion of water from the leaves create a shortage of water in the leaves

• means more water is drawn up from the rest of the plant through the xylem vessels to replace it

• causes more water to be drawn up through the roots

1. constant stream of water from ground helps keep plant cool

2. provides plant with constant supply of water for photosynthesis

3. water creates turgor pressure in the plant cells to help support the plant and stop it wilting

4. minerals needed by the plant can be bought in from soil along with the water

• cells are arranged end to end to form phloem tubes with sieve plates inbetween them to allow movement of substances through the plant

thick side walls strengthened by lignin which allows plant to withstand pressure of water moving through the plant

the flow of water through a plant, from the roots to the leaves, via the xylem vessels.

Stomata are tiny holes found in the underside of leaves. They control water loss and gas exchange by opening and closing

1. increase in light intensity

2. increase in temperature

3. increase in air movement

• brighter the light, greater the transpiration rate

• increases the rate of photosynthesis causing stomata to open and let c02 in

• stomata close when dark as photosynthesis cant happen in the dark

• when stomata are closed water cant escape

• the warmer it gets , faster transpiration happens

• when warm, water particles have more energy to evaporate an diffuse out of stomata

• lots if air movement (wind) around leaf transpiration happens faster

• if air around leaf is still water vapour surrounds leaf and dosnt move away

• means high concentration of water particles outside of leaf as well as inside it so diffusion dosnt happen as quickly

• if windy, water vapour is swept away maintaining low concentration of water in the air outside leaf

• waxy cuticle to make it waterproof

• more stomata on lower side of leaf to slow diffusion as its more protected from the wind and cooloer

• having stomata on lower surface of leaf slows diffusion ad its more protected from wind and cooler

• small stomata helps reduce water loss which helps it survive as low availability if water means it needs to conserve as much water as it can

rate of water uptake

1.Cut a shoot at a slant underwater.

2. Assemble the potometer in water and insert the shoot underwater.

3. Remove the apparatus from the water but keep the end of the capillary tube submerged in a beaker of water.

4. Check that the apparatus is water and air tight.

5. Dry the leaves and allow the shoot time to acclimatise and then shut the tap.

6. Remove the end of the capillary tube from the beaker of the water until one air bubble has formed, then put the end back into the water.

7. Record the starting position of the air bubble.

8. Start the stopwatch and record the distance moved by the bubble per unit time, the rate of air bubble movement is an estimate of the transpiration rate.

divide distance the bubble moved by time taken