IGCSE Biology TRIPLE CONTENT

Why does pH affect enzymes?

It will interfere with the bonds holding the enzyme together
This changes the shape of the active site and denatures the enzyme

What does turgid mean?

When a plant is well watered the cells draw in water by osmosis and become plump and swollen

What are the benefits of turgid cells?

The contents of the cell push against the cell wall making tugor pressure which helps support the plant tissues

What happens to a plant if there is no water in the soil?

Plsnts lose tugor pressure and begin to wilt and become flacid
Inelastic cell wall keeps the plant in shape

Why do active people need for energy?

They use more energy

Why do kids/teens need more energy?

They are growing

Why do pregnant women need more energy?

They have to provide energy for their babies to develop

Describe how to find the energy content in a food sample using calorimetry

Weigh + skewer pasta on a mounted needle
Add 25cm of water to a boiling tube help with clamp
Measure temp. of water
Set fire to food using bunsen burner
Hold burning food under boiling tube until it goes out
Relight+repeat until food won't catch fire again
Measure temp. of water
Use the equation

What is the amount of energy in joules equation?

Energy= mass of water x temp. change x 4.2

What is the amount of energy in joules per gram equation?

Amount per gram = energy in food/ mass of food

Why might you insulate the boiling tube with foil in caliometery?

To minimise heat loss and keep more energ in the water to increase accuracy

Describe how to measure CO2 production using an indicator and beans

Soak some dried beans in water for 2 days
They will germinate
Boil similar sized dry beans
These are your control
Put hydrogen-carbonate indicator in 2 test tubes
Place a platform made of gauze into each test tube and place beans on this
Seal with rubber bung
Leave for 1 hour
CO2 produced by germinating beans will have turned hydrogen carbonate indicator yellow

What is the colour change in hydrogen carbonate indicator when CO2 is present?

Yellow to orange

Describe how you measure heat produced by respiration

Prepare 2 sets of beans like the other experiment
Add each set to a vacuum flask with air so they can respire
Place a thermometer into each flask and seal top with cotton wool
The temp. will increase as beans respire and produce heat

What does the net exchange of gases depend on?

Light intensity

What do plants do when light intensity is high?

Release oxygen as they make more than used
Take in CO2 as they use up more than they produce

What do plants do when light intensity is low?

They only respire
Take in oxygen and release carbon dioxide

What colour does hydrogen carbonate indicator go if concentration of CO2 decreases?

Purple

Describe how to show differences in net gas exchange in plants

Add the same volume of hydrogen carbonate indicator to 4 boiling tubes
Put similar sized leaves into 3 of the tubes
Seal with rubber bung
Keep 4th empty as a control
Wrap 1 tube in Al foil and one in gauze
Place in bright light
Leave for 1 hour and check colours

Why did the darkened tube go yellow?

No photosynthesis so CO2 concentration increases

Why does the shaded tube stay a similar colour?

CO2 concentration doesnt change

Why does the well lit tube go purple?

Lowers concentration of CO2 due to lots of photosynthesis

What does phloem do?

Transports sugars like sucrose and amino acids from where they are made in the leaves to other parts of the plant
Translocation

Describe how a vaccination works?

Inject inactive of dead pathogens into the body
These carry antigens so trigger a response
Lymphocytes produce antibodies to attack them
Lymphocytes will remain in blood as memory cells so if live pathogens appear antibodies to kill them will be produced quickly and in large numbers

What are platelets?

Small fragments of cells to help blood clot

What are platelets heald together by?

Mesh of protein called fibrin

Why does blood clot?

To prevent you losing too much blood
To prevent micro organisms from entering the wound

How does the eye look at near objects?

Ciliary muscles contract which slackens suspensory ligaments
The lens becomes fat, more curved

How does the eye look at distance objects?

Ciliary muscles relax which make suspensory ligaments pull tight
The lens becomes thin, less curved

Why are some people long sighted?

Cornea or lens doesn't bend light enough
Eyeball is too short
Near onjects brought into focus behind the retina

Why are some people short sighted?

Cornea or lens bends light too much
Eyeball is too long
Distant objects brought into focus in front of the retina

What does bright light do?

Triggers a reflex that makes pupil smaller allowing less light in

What happens in dim light?

Triggers a reflex that makes pupil bigger letting more light in

What happens when you are too hot?

Lots of sweat produced + evaporates to transfer heat
Blood vessels close to surface widen (vasodilation)
Hairs lie flat

Describe vasodilation

More blood can flow near the surface so it can radiate more heat to the surroundings

What happens when you are too cold?

Very little sweat is produced
Blood vessels near the surface constrict (vasoconstriction)
Shiver to generate heat in the muscles
Hairs stand on end

What is vasoconstriction?

Less heat can be transferred from the blood to the surroundings

What are the conditions needed for seed germination?

Water
Oxygen
A suitable temperature

Why is water needed in seed germination?

To activate the enzymes that break down food reserves in the seed

Why is oxygen needed in seed germination?

For respiration which provides energy for growth

Why is a suitable temperature needed in seed germination?

For the enzymes in the seed to work

Describe the steps in germination?

Seed takes in water and starts to grow using its store of energy
First root starts to grow down into the soil
Shoot grows up
Finally extra roots grow and the first green leaves appear

How does a germinating seed get energy?

It gets glucose for respiration from it's own food store
This gives it energy it needs to grow

What is the role of the placenta?

Placenta develops when embryo have been implanted
This lets blood of embryo and mother get very close to allow exchange of food, oxygen and waste

What is the role of amniotic fluid?

The amnion membrame forms
This surrounds embryo and is full of amniotic fluid
This acts as a shock absorber to protect the baby

What increases mutations?

Ionising radiation EG x-rays, gamma rays
Chemicals called mutagens EG chemicals in tobacco

Describe the stages in the water cycle?

Heat from sun makes water evaporate from land and sea turning it into water vapor (and from plants as transpiration)
Warm water vapour is carried upwards and cools and condenses to form clouds
Water falls from clouds as precipitation
Returned to land and sea

What is nitrogen fixation?

The process of turning N2 from the air into nitrogen compounds in the soil which plants can use

What are the two main ways nitrogen fixation can happen?

Lightening
Nitrogen fixing bacteria

How does lightening work in the nitrogen cycle?

Energy in a bolt of lightening makes nitrogen react with O2 in the air which gives nitrates

What do decomposers do in the nitrogen cycle?

Break down proteins in rotting plants and animals and urea in animal waste and turn them into ammonia

What does nitrifying bacteria do in the nitrogen cycle?

Turn ammonia in decaying matter into nitrates

What does nitrogen fixing bacteria do in the nitrogen cycle?

Turn atmospheric N2 into nitrogen compounds that plants can use

What does denitrifying bacteria do?

Turn nitrates into N2 gas which is of no benefit to living organisms

Where do the nitrogen cycle bacteria live?

In the soil or on nodules on plant roots

What are the effects of sewage?

Sewage contains phosphates from detergents EG washing powder and nitrates from urine and faeces
These extra nutrients cause eutrophication the same way fertilisers do

Describe the stages in producing yogurt?

Equipment is steralised
Milk is pasteurised (72 degrees for 15s) to kill harmful microbes and then is cooled
Lactobacillus bacteria is added and the mixture is incubated (heated to 40 degrees) in a fermenter
Bacteria ferment the lactose sugar in milk to form lactic acid
Lactic acid causes milk to clot and solidify into yogurt
Flavours and fruit and sweetners are added and packaging occurs

What is fermentation?

When micro organisms break sugars down to release energy

What is the liquid in a fermenter called?

Culture medium

What is the jobs of paddles?

Microorganisms are kept in contact with eachother by paddles to increase product yield as microorganisms can always access nutrients needed for growth

How do microbes get oxygen in a fermenter?

Pumping in sterile air so microbes can require to get energy for growth

What is the job of the cooling jacket?

So temp. is kept at an optimum level so enzymes don't denature

How is pH kept constant?

Monitered closely

How are vessels steralised?

Superheated steam to kill unwanted icrobes so that they don't compete with eachother and the product doesn't get contaminated

What does transgenic mean?

Transfer of genetic material from one species to a different species

What are the advantages to cloning?

Useful proteins used for arthiritis therapy
Pig organs used to save human lives
Useful genetic charecteristics always passed on

What are the negatives of cloning?

Cloned animals may not be as healthy as normal ones
Difficult
Time consuming
Expensive