biology B2


gcse b2 further biology

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  • Created on: 17-05-11 18:04


nucleus- contains DNA and controls the actions of the cell

cytoplasm- where chemical reactions, controlled by enzymes take place.

cell membrane- controlls what comes in and out of the cell

mitchondria- where respiration takes place

ribosomes- protein sytrhesis takes place here

cell wall- strengthens cells, made of cellulose

chloroplasts - made of chlorophyll, which aborbe light for photosythesis

permanent vacuole- filled with sap, keeps cell turgid

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specialised cells

leaf cell-absorbs light for photosyntheisis, its packed with chloroplasts, the cells are a regular shape and are tightly packed so there is a continuous layer

root hair cell- absorbs water and ions in the soil, thin cell and a project give it a large surface area and make it a good site for transport.

sperm cell-  fertalises an egg cell, gamete, head contains genetic information and an enzyme for fertalisation, the middle bit is packed full of mitchondria for respiration and energy. the flagela is the tail that helps power the cell.

red blood cell contain haemoglobin, to carry oxygen to the body cells, no nucleus so it can carry more haemoglobin.

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this happenbs when cells spread out, its the net moverment of particles from high concentration to low concentration due to the random movement of particles.

the bigger the difference in concentration the faster the rate of diffusion.

a bigger surface area increases the rate too

an increas in temp will also increas rate.

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osmosis is the net movement of water from a high water concentration to a low water concentration through a partiallaly permeable membrane.

the cell membrane is a partially permeable membrane so osmosis can take place in a cell.

equilibrium is reached when both soultions have the same concentration of water. not when there is the same volume of solution there.

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carbon dioxide +water  (+light energy) ---> oxygen +glucose

the chlorophyll absorb the light needed

some of the glucose is used immediately but some is also turned into starch

iodine solution turns blue in the presence of starch.

plants are adapted for photsynthesis

  • they have a broad leave so lots of light falls on it
  • they have lots of chloroplasts
  • they have  air spaces in the leaves, for CO2 and O2 to move about in
  • they have an xylem to take water to the plant
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limiting factors

light intensity increases the rate a  untill another limiting factor takes effect

carbon dioxide  increases the rate a  untill another limiting factor takes effect, in a green house, a tropical forest or dense vegetation there could be a lack of CO2

temperature increases the rate untill optimum, after which is will decrease the rate because enzymes have become dentaured.

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how plants use glucose

plants photosythesise at a much higher rate in the day than they do at night they respire at a constant rate all the time. they respire, to get energy from the glucose

some of the glucose is stored as starch, because it is insoluable

they use some of the energy to combine with nutrients from the soil in order to make amino acids and later on proteins which get built into cells.

the enegry is also used to build up a store of oils and fats for food stores and seeds.

the phloem transports sugars around the plant

the xlyem transports water and mineral ions from the roots upwards

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why do plants need minerals?

the minerals are taken up in the roots by active transport

the root hair cells have a larg surface area

nitrate. is used for making proteins and without it a plant will have stunted growth

magnesium. is used to make chlorophyll and without it it will have pale yellow leaves

a new way of growing plants is through hydrophnics, the plants are grown in water which has plenty of minerals in it.

the crops are also grown in a greenhouse with the other limiting factors controlled

this is an expensive way to farm and is done on a large scale but in the end the crops fetch a high price

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pyramids of biomass

the enrgy for ALL living organisms comes indirectly from the sun.

biomass is the amount of living material in an animal or a living thing.

it is often measured as dry mass in grams

you can represents food chains on pyramids of biomass or pyramids of number

the pyramid of biomass shows us the amount of biological material involved at each trophic level in a way simple numbers do not.

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energy loss

the engergy from one trophic level to the other is always less than the one before it this is because:

not all of the food eaten can be digested so some energy is lost as faeces

some of the enegry is used in respiration for movement and controlling body temperature and only a very small amount is used for growth.

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energy in food production

meat comes from animals which eat plants so because energy is lost by the animal eating plants is more efficient than eating animals.

so in theory if we all became vegaterians there would be more food to go around because less of the energy would be wasted and the energy produced by the plant would go directly to us.

every time we add another trophic level we lose more biomass

factory farming limits the amount of energy lost by controlling temp and movement

this raises moral concerns beacuse the animal welfare is not being considered

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when a plant takes up minerals from the ground, they are passes on the food chain,

when an organism dies and falls to the ground they get recyled and reused. detritus feeders start the deacy process by eating the waste material,

then decomposers, microorganisms including bacteria and fungi, they break down the matter and digest some they also produce watse products including, carbon dioxide water and minerals which plants use

the decomposers work best in warm, moist, oxygenated conditions as they respire.

this process is used in sewage plants and in composte heaps

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the carbon cycle


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farming, intensive or extensive?

  • Advantages
    • Large amount produced very quickly and products cheaper than free range
    • Not much land required
    • Less people employed
    • Chickens get really big quickly
    • Heats itself as animals keep each other warm
    • Restricted movement ensures more energy more energy goes into growth
  • Disadvantages
    • Stressed animals = poor quality meat
    • Disease spreads quickly
    • Increased food costs as no supplement with grubs and seeds
    • Lighting costs and some heating costs
    • Risk to all products if problem occurs in a barn
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enzyme structure

lost of reactions take place in your body and they all need to be controlled

they are controlles by biological catalysts, enzymes.

enzymes are made of proteins, each enzymes has its own shape because its active site is different so different substrates can be controlled with it.

they work by lowering the activation energy, or by providing a site for a reaction to take place on.

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factors effecting enzymes

a rise in temperature can speed up the rate of reaction but too high and the enzymes shape will be deformed and it will become denatured.

the higher the concentration of enzymes the faster the rate of reaction untill there is a higher concentration of enzymes than substrate.

different enzymes work in different pH ranges but too acidic/alkaline and it will be denatured

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aerobic respiration

oxygen + glucose --> carbon dioxide + water

C6H12 +O2 --> 6CO2 + 6H2O + energy

respiration takes place in the mitchondria

respiration has four main functions:

  • breaking down the glucose from our food
  • making new cell material
  • to contract and relax muscles
  • energy for homeostasis
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enzymes in digestion

amylase- is produced in the salivary glands, pancreas and small intestine

starch---> sugars

protease-  is produced in the pancreas stomach and small intestine

proteins---> amino acids

lipase is produced in the pancreas and the small intestine

lipids--> fatty acids and glycerol

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speeding up digestion

the stomach is acidic

but the enzymes in the small intestine work best in slightly alkaline conditions

so we have bile which nuetralises the stomach acid and it emulsifies fats.

it is made in the liver

and it is stored in the gall bladder

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making use of enzymes


protease- used to manafacture baby food, so the proteins are already pre-digested

lipase- used in biological detergents to break down (digest) the the substances in stanis into small soluble molecules.

carbohydrase- used to convert starch into sugar syrups which has more worth and is used in sports drinks

isomerase- used to convert glucose into fructose which is sweeter so lees needs to be used so it is often found in slimming foods.

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controlling internal conditions

for your body to work the conditions around your body must stay constant.

excretion- carbon dioxide and water

amino acids are a form of urea and taken out the blood by the kidney

too much water can damage a cell.

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controlling body temp

  • heat from muscles in exersice
  • fever from disease
  • the external temp falling or rising

when your too hot

  • you sweat
  • vasodilation
  • metabolism slows down

when your too cold

  • you shiver - this is contracting and relaxing of your muscles with creates heat from respiration
  • vasocontriction
  • hairs stand on end
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controlling blood sugar levels

blood sugar levels are controlled by the pancreas

too high- the pancreas excretes insulin which tells the liver to convert glucose into glycogen

too high - pancreas excretes glucagon which tells the liver to convert glycogen into glucose which goes back into the blood.

diabetes is where your body cant control your blood sugar levels.

type 1- dont produce insulin so they have to inject, they have to check to make sure they inject the right amount

type 2- their cells dont respond to insulin so they have to controll blood sugar levels with diet and exercise

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cell division and growth

mitosis occurs in all cells

it results in two cells identical to each other

when early enbryos are formed they are made of stem cells, these are un differentiated cells to can become anything.

by the time a human has been born the cells are specialised except some partially specialised cells in the bone marrow.

plants can be cloned so easily because the cells can become unspecialised and move around the plant to perform other jobs, because they never stop growing.

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stem cells

stem cells are not specialised and can become differntiated into many different types of cell when when required.

there are ethical issues surrounding the use of stem cells

stem cell research is slow and expensive but ultimately could save millions of lives

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cell division in sexual reproduction

cells in reproductive organs divide to form gametes

the cell divides twice, to form four gametes

each gamete only contains one chromosome of the original pair

this process is known as meiosis

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from mendel to DNA

gregor mendel was a sceintist that first thought about DNA by crossing pea plants..

DNA - deoxyribose nucleic acid

your genes are small strings of DNA

genes are codes for making proteins out of amino acids

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inheritance in action

phenotype - physical appearance

genotype- genetics

homozygeous- same alleles

hetrozygeous- different alleles

recessive- the effect can be masked by a dominant allele, and can only take effect if the person has inherited both from both parents

dominant- this one can mask the effect of another allele and be the one that takes effect

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inherited deseases

cystcis fibrosis-

it affects the cell membranes and is inherited from a recessive allele

huntingtons disease-

it affects the nervous system and is a dominant allele, so only one parent need to have it for there to be a chance that the child inherits the condition.

embryo screening is doctors test the embryos for genetic disorders

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Amazing so far... :D


Amazing so far... :D


Really Good :))

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