B2 Topic1

Revision cards for B2 Topic1 (inside living cells) for the exam board Edexcel. most of my revision notes are from the CGP book and writing them up helps me learn so dont post comments saying ive copied. thanks.

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  • Created by: shamB
  • Created on: 07-11-11 18:34

Respiration.

RESPIRATION

respiration releases the energy that cells need to do just about everything. it is the process of breaking down glucose to release energy -it goes on in every single cell in your body.

glucose contains energy in the form of chemical bonds, this energy is used to do things like;

  • build up larger molecules (like proteins)
  • contract muscles
  • maintain a steady body temperature

remember

RESPIRATION IS THE PROCESS OF BREAKING DOWN GLUCOSE TO RELEASE ENERGY, WHICH GOES ON IN EVERY CELL.

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Aerobic Respiration.

AEROBIC RESPIRATION

aerobic means with air.

aerobic respiration is respiration using oxygen. its the most efficient way to release energy from glucose.

GLUECOSE + OXYGEN --> CARBON DIOXIDE + WATER (+ ENERGY)

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Anaerobic Respiration.

ANAEROBIC RESPIRATION

anaerobic means without air.

this happens when theres not enough oxygen available. this is not the best way to release energy from glucose.

GLUECOSE --> LACTIC ACID (+ ENERGY)

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Anaerobic Respiration.

  • anaerobic respiration isnt great because it produces a buildup of lactic acid in the muscles which gets painful and can give you cramps
  • an advantage is that you can keep using your muscles for a bit longer
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Exercise.

EXERCISE

  • muscles need energy from respiration to contract. when you exercise some of your muscles contract more frequently than normal so you need more energy. this energy comes from increased respiration
  • the increase in respiration means your breathing rate increases to get more oxygen into the blood
  • to get this oxygenated blood around your body faster your heart rate increases. this also removes CO2 more quickly at the same time
  • to deal with the increased demand, the rate of diffusion of carbon dioxide and oxygen at the lung surface and in muscle cells increases
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Raw Materials and Waste Diffusion.

RAW MATERIALS AND WASTE DIFFUSE IN AND OUT OF CELLS

1) the circulatory system carries gluecose, oxygen and CO2 around the body in the blood

2) the glucose needed for respiration comes from breaking down food in the digestive system. the oxygen comes from air breathed into the lungs. CO2 is breathed out

3) the smallest blood vessels in the body are capillaries. all the cells in the body have capillaries nearby to supply them with glucose and oxygen and to take away the waste carbon dioxide

4) these substances move between the cells and capillaries by a process called diffusion

DIFFUSION IS THE MOVEMENT OF PARTICLES FROM AN AREA OF HIGH CONCENTRATION TO AN AREA OF LOW CONCENTRATION

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Raw Materials and Waste Diffusion.

RAW MATERIALS AND WASTE DIFFUSE IN AND OUT OF CELLS CONT.

5) when cells respire they use up oxygen and glucose so the concentration of these inside the cells is low. the concentration of these substances in the blood is higher so they diffuse from the capillaries into the cells

6) when cells respire they produce lots of carbon dioxide, so the concentration of this in the cells is high. this means carbon dioxide diffuses from the cells into the blood where the concentration is lower

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Monitoring.

MONITORING HEART RATES AND BREATHING RATES

you can measure heart rates during exercise by taking the pulse and breathing rate by counting breaths. you can measure body temperature with a thermometer. body temperature goes up during exercise because increased respiration releases more heat energy.

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Electronical Monitoring.

ADVANTAGES OF ELECTRICAL MONITORING

  • the athlete can carry monitoring equipment themselves as they exercise
  • digital recorders dont lose count or miss a beat like humans
  • you can monitor changes continuously instead of having to stop to take a pulse
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Diets.

NOT ALL DIETS ARE SCIENTIFICALLY PROVEN

only a large survey can tell if a weight loss diet plan is more or less effective than just eating less and exercising more. these surveys are not usually done unless its a high profile case (e.g the atkins diet)

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Official Advice.

OFFICIAL ADVICE ON DIETS AND EXERCISE.

DIETS:

the u.k government says that a healthy diet should consist of lots of fruit & veg, starchy foods such as rice and pasta and some protein. they recommend that you eat at least five portions of different fruit & veg in a day and to cut down on staturated fats, alts and refined sugars (e.g sweets)

EXERCISE:

the u.k government recommendation is to exercise at least 30 mins, five times a week in order to stay fit and healthy.

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DNA.

DNA

a DNA molecule has two strands coiled together in the shape of a double helix (two spirals)

the two strands are held together by chemicals called bases. there are 4 different bases: adenine (A), cytosine (C), guanine (G), thymine (T)

 the bases are paired and they are always paired in the same way -

A-T and C-G. this is called base pairing.

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Gene Codes.

GENE CODES FOR A SPECIFIC PROTEIN

a gene is a section of DNA. it contains the instructions to make a specific protein.

cells make proteins by stringing amino acids together in a particular order.

only 20 different amino acids are used to make up thousands of different proteins.

the order of bases in a gene tells cells what order to put the amino acids together.

DNA also determines which genes are switched on or off, and so which proteins the cell produces e.g haemoglobin, that then determines what type of cell it is e.g red blood cell, skin cell

some proteins help to make al the other things that arent made of protein (cell membrane) from substance that come from your diet (fats and minerals)

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Proteins.

PROTEINS ARE MADE BY RIBOSOMES

proteins are made in the cell by organelles called ribosomes. DNA is found in the cell nucleus and cant move out. the cell needs to get information from the DNA to the ribosome in the cell cytoplasm. this is done using a molecule called mRNA (mRNA is very similar to DNA but its much shorter and only a single strand)

mRNA is like a messenger between the DNA in the nucleus and the ribosome. this is how its done:

1- the two DNA strands unzip and a molecule of mRNA is made using the DNA as a template. base pairing makes sure its an exact match. this is called transcription

2- the mRNA molecule moves out of the nucleus and joins with a ribosome

3- the job of the ribosomes is to stick amino acids together in a chain to make a polypeptude (protein), following the order of bases in the mRNA. this is called translation.

(molecules called tRNA molecules carry amino acids to the ribosome)

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Using Microorganisms.

MICROORGANISMS PRODUCE USEFUL BY-PRODUCTS

like all other living things, microorganisms respire. they use an external food source (usually a sugar) to get their energy. the breakdown of sugars into simpler molecules is often called fermentation. microorganisms can respire aerobically or anaerobically.

1- aerobic respiration produces carbon dioxide as a by-product. yeast, used in making bread, respire aerobically - the CO2 produced makes the bread rise.

2- lots of bacteria can respire anaerobically to make lactic acid. bacteria are added to milk to make cheese - they convert the lactose sugar in the milk into lactic acid, which acidifies the milk. the milk then curdles to form cheese

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Medicines.

SOME MEDICINES COME FROM MICROORGANISMS

ANTIBIOTICS:

antibiotics are used to destroy/stop growing bacteria which cause diseases. antibiotics are the producs of microorgansims. e.g penicilin is an antibiotic made by growing mould in a fermenter

HUMAN PROTEINS:

microorganisms can be genetically engineered to make medicines. some human diseases are caused by lack of working protein e.g people with type1 diabetes cant produce the protein insulin. the gene coding for the working protein can be taken from a healthy human and put into a microorganism. the microorganisms are then grown in fermenters and they produce large amounts of the protein which can be taken by the person suffering to treat the disease.

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Insulin.

MICROORGANISMS ARE USED TO MAKE HUMAN INSULIN TO TREAT DIABETES

  • a loop of DNA called plasmid is removed from the bacteria
  • the human insulin is 'cut' from human DNA using enzymes. enzymes are also used to cut the plasmid from the bacteria and then to insert the useful gene. the plasmid containing the useful gene is then put back into the bacteria.
  • the bacteria are then grown and soon there are millions of identical bacteria all producing human insulin, this is then purified and used to treat sufferers
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Mycoprotein.

MYCOPROTEIN - FOOD FROM FUNGI

1- mycoprotein is used to make meat substitutes for vegetarian meals e.g Quorn

2- the fungus is grown in fermenters, using glucose syrup as food

3- the fungus respires aerobically, so it needs to be supplied with oxygen

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Advantages.

ADVANTAGES OF USING MICROORGANISMS FOR FOOD PRODUCTION

  • microorganisms (like bacteria and fungi) can grow very quickly
  • theyre easy to look after, all you need is something to grow them in, food, oxygen and the right temperature
  • food can be produced whether the climate is hot or cold
  • they can be used to produce food anywhere if you have the right equipment
  • its a lot cheaper than other methods
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Fermenters.

A FERMENTER IS A BIG CONTAINER FULL OF LIQUID 'CULTURE MEDIUM' WHICH MICROORGANISMS CAN GROW AND REPRODUCE IN. THE FERMENTER NEEDS TO HAVE THE RIGHT CONDITIONS FOR THE MICROORGANISMS TO GROW AND PRODUCE THEIR USEFUL PRODUCT.

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The Way Microorganisms Are Grown.

THE WAY MICROORGANISMS ARE GROWN IN FERMENTERS ON A LARGE SCALE

  • food is provided in the liquid culture medium, microorganisms ned carbohydrates (sugars) as an energy source, plu mineral ions and sometimes nitrates (to make protein) and vitamins. more nutrients can be pumped if needed
  • air is piped in to supply oxygen to the microorganisms (if they respire aerobically)
  • the microorgansims need to be kept at the right temperature for optimum growth. if its too cold the growth rate will slow down and if its too hot the enzymes in the microorganisms will be destroyed and growth will stop. the fermenters must be cooled as the microorganisms produce heat by respiration. (usually done with a water jacket)
  • the right PH is needed for the microorganisms to thrive. instruments measure this
  • sterile/aseptic conditions are needed to prevent contamination from other microorganisms
  • the microorganisms need to be kept from sinking to the bottom. a motorised stirrer keeps them moving around and maintains an even temperature
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