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B3
...
What osmosis does to keep the right concentration
 Cells use up water in chemical reactions, so the cytoplasm becomes more
concentrated, so water moves in by osmosis
 But if the concentration inside the cell is too dilute (HC), as more water can be
made in chemical reactions, water leaves the cells by osmosis
2
...


Osmosis in plants
1
...
So plants need the fluid surrounding the cell to have a higher concentration of water
to keep the water moving in the right direction
 Into the low concentrated cytoplasm
...




If your body fluids become more concentrated water could move out of the cells,
causing you to be dehydrated
If this water and ions are not replaced the mineral ion/water balance will be
disturbed, causing the cells not to work properly

To keep exercising at your best, and recover quickly, you must replace the mineral ions,
water and glucose

Sport drinks





Mainly water
Contains more glucose, mineral ions than soft drinks
Has colouring and flavourings to make it pleasant
Claims to aid hydration of tissues, and help replace energy, and lost electrolytes
(mineral ions lost in sweat)

Evaluating sports drinks

PROS

CONS

Does more for you than soft drinks

More expensive than soft drinks

Contains water to dilute the body fluids, allows
water to move back into the cells and rehydrate
them by osmosis

Water does the same, and milk is said to be best
at hydrating cells

Contains salt, raising you mineral ion levels, so
Adding a pinch of salt does the same
ions move back into the cells move back into the
cells by osmosis
Raise blood sugar, so sugar moves back into the
cells by diffusion/active transport

Orange squash does the same

The lungs

Why Do We Breath?


The breathing system is used by the body to get the oxygen needed for
respiration
...

These gases are exchanged inside the lungs
...

An exchange surface is a specialised area that is adapted to make it easier for
molecules to cross from one side of the surface to the other

The effectiveness of an exchange surface can be increased by these adaptations:



Large SA- This provides more space for molecules to pass through – it is often
achieved by folding the walls and membrane
Thin- The shorter the distance for diffusion, the less time it takes




Efficient blood supply - This moved the diffusing substances away and maintain a
concentration gradient
...


The lungs are in the thorax





Air breathed in goes through the trachea
Splits into 2 tubes- the bronchi (bronchus)- into
each lung
These split off into smaller tubes- bronchioles
Finally ends at the alveoli for gas exchange

Alveoli






Give the lungs a large SA= for the diffusion of oxygen and CO2
Alveoli have a rich blood supply= maintains a concentration
gradient in both direction
o Blood flow through capillaries takes away oxygenrich and carbon dioxide-poor blood and brings in
blood low in oxygen and high in carbon dioxide
...


Process

 Blood is pumped from the heart to the lungs and passes through the capillaries
surrounding the alveoli

 The blood has come from the respiring tissues of the body, where it has given up
its oxygen to the cells and gained Carbon dioxide

 Because the air in the alveolus has a higher concentration of oxygen than the
blood entering the capillary
...


 The heart then pumps the blood around the body again to supply the respiring
cells
...


 At the same time there is more Carbon dioxide in the blood than there is in the
air in the lung
...


Ventilation
1
...
Expiration






Intercostal muscles relax and the ribs move downwards and inwards
The diaphragm muscle relaxes and becomes dome shaped
The volume of the thorax decreases
Pressure in lungs increases and rises above atmospheric pressure

Artificial breathing aids

Reasons why people may struggle to breathe




Tubes leading to the lungs may be narrow
The structure of the alveoli can break down- the SA for gas exchange is smaller
Some are paralysed by accident or disease (polio)

Iron lung



Air pumped out of the case- pressure drops- lungs expand- air
drawn into lungs
Air pumped into of the case- pressure increases- lungs deflateair drawn out of lungs

Modern ventilator




Forces a breath of air into the lungs
Once the lungs are inflated the air pressure stops- The lungs
deflate; ribs go down, forces air back out of the lungs

Iron lung

Modern ventilator

Lack of freedom
Can talk

Hard to eat/talk
Uncomfortable
More portable

Exchange in the gut

Absorption in the small intestine
The small intestine is lined with villi:





Which increase the SA, increasing the uptake of digested food by
diffusion
Each villus is covered with microvilli, increasing the SA even more
Have a single layer of surface cells
Good blood supply

Exchange in plants

Gas exchange
Leaf adaptations for gas exchange




A flat, broad shape to increase SA for diffusion
Thin- so the distance the CO2/ oxygen has to diffuse in/out of the
photosynthesising cells and the air is short
Have air spaces- allow CO2 to come into contact with lots of cells, and give a large
SA for diffusion

Leaf cells are constantly losing water by evaporation, and if the stomata were open to
collect CO2 all the time then the plant would lose water too fast and die
So when its dark and the plant isn’t photosynthesising it doesn’t need CO2, so the
stomata closes


The leaves are adapted to only allow CO2 in when needed

(A lot of this is in B2
...
Transpiration is caused by the evaporation and diffusion of water from inside the
leaves
2
...
This means more water us drawn up from the roots- so there’s a constant
transpiration stream of water through the plant
4
...

 So more water vapour is released

Controlling water loss:



The stomata are under the leaf away from direct sunlight, and reduces the time
they are open, as it is darker
Wilting- when a plant is losing more water than its taking in it wilts
o Which stops further water loss- a protection mechanism
o SA is reduced for evaporation
o But wilting is prevented by closing the stomata

Xylem



Dead cells
Carry water and minerals to the stem and leaves from the roots

Phloem



Carry food substances (dissolved sugars) made in the leaves to growing regions
(new shoots) and storage organs (root tubers)
Transport goes in both directions

B3
...
Carries deoxygenated blood from the heart to the lungs and back
 Allows oxygen and CO2 to be exchanged with the
air in the lungs
2
...


1
...
The atrium contracts pushing the blood into the right ventricle
3
...
The blood coming into the left atrium from the pulmonary vain= oxygenated from
the lungs
5
...
The ventricle contracts forcing the blood into the aorta and out of the heart
7
...
The atria fill again and the cycle starts again

The 4
chambers of
the heart

Valves



Atrioventricular (AV) valves- prevents the backflow of blood from the ventricles
to the atrium
SEMILUNAR VALVES - responsible for transporting blood away from the heart
and preventing black flow in to ventricles

Thickness of Walls
Thin Right Ventricle

 The right ventricle only has pump deoxygenated blood
to the lungs to pick up oxygen
Thick Left Ventricle



The left ventricle pumps blood further (to all parts of the body)
This needs more muscle to create more force and to create higher pressure
...


They branch off the aorta and deliver oxygenated blood to the muscle of the walls of the
heart
...

o 1
...
Thick inner layer of muscle and elastic fibresstretch with pulse and then return to shape
o 3
...

Do not have a pulse
Often have valves to prevent backflow of blood as it moves back
towards the heart
How are they adapted to carry blood at low pressure?
o Thin outer wall
o Thin inner layer of muscle and elastic fibres
o Wide lumen

Capillaries




Carries blood to and from the body’s cells
Form network of tiny vessels linking arteries and veins
How is it adapted for the exchange of substances
o Thin walls- substances diffuse into the cells from the
blood, and waste produced by the cells can passed
into the walls of capillaries
o Outer wall is 1 cell thick- short diffusion distance for gas exchange
o Narrow lumen- allows the slow movement of cells to give time for
diffusion

Valves (in veins)





If low-pressure blood has to move against gravity, it might
slow down further and even flow in the wrong directionvalves prevent backflow
When blood flows along veins it pushes past the valves, which
can only open in one direction
...


Also many veins are surrounded my muscles, which contract when you move, squeezing
the veins, pushing the blood along the veins back towards the heart

Transport in the blood

Blood- specialised transport medium that is also considered a
special type of tissue


4-6 litres in an adult

Blood has a range of functions such as:





Transport – Hormones, Oxygen, Carbon Dioxide, Nutrients, Urea, Sodium ions
...
RBC
adaptations:







Shape= biconcave discs- increases SA: volume ratio where the
diffusion of oxygen takes place
Small diameter: about the same size as a capillary so slows blood
flow to enable diffusion of oxygen
Packed with haemoglobin, which carries oxygen
Don’t have a nucleus- more space for haemoglobin
In high altitudes- less oxygen- more RBCs are produced
Flexible/Elastic: This allows erythrocytes to fit/squeeze into capillaries

Each haemoglobin molecule can combine with four molecules of oxygen
When haemoglobin takes up oxygen, it becomes oxyhaemoglobin:



Haemoglobin + Oxygen ⇌ Oxyhaemoglobin
Hb + 4O2 ⇌ Oxyhaemoglobin

Increases blood oxygen capacity 70 times compared to oxygen dissolved in blood
...
In the RBC at the lungs, oxygen combines with
haemoglobin to form oxyhaemoglobin
...


2
...


 Oxygen diffuses from the RBC across the lining of the
capillary and into body’s cells
...
RBCs that have released oxygen to the body’s cells have to get back to the lungs
...


 At the lungs, RBCs pick up more oxygen and start another journey around the
body
...

Help the blood clot a wound:


Produce a network of protein threads that capture lots of
RBC and more platelets to form a clot



It then dries and hardens to form a scab that protects the new growing skin, and
stops bacteria getting in and blood pouring out

o 1- Platelets help to make tiny fibres that form a net at the site of a cut
...

o 3- The clot dries and forms a scab which protects the cut while new skin
grows
...

They also get narrower when fatty deposits form on
the lining of the vessel

What’s the harmful result of this?




Supply of oxygen to the heart can become
interrupted
Leading to anaerobic respiration occurring during
exercise
Lactic acid builds up – causing pain/death of muscle

Treating this (both are expensive)
1
...
Perform a bypass surgery
 Sometimes a coronary artery is so badly blocked
that a stent cannot be used
...


Leaky valves
Heart valves- keep blood flowing in the right direction






Have to withstand lots of pressure
So can weaken and start to leak
Then the heart doesn’t work so well, and causes death if not solved
If valves weaken and leak, person can be breathless and eventually die
...


Mechanical
Made of titanium/polymers

Biological
From animals

Last a long time

Only last 15 years

But you have to take drugs for the
rest of your life to stop blood clots

Don’t have to take drugs

Artificial Hearts




People die while waiting for a heart transplant
...

Usually only used in hospital while waiting for a transplant
...
Plasma/saline
 The simplest way to replace blood is with plasma or saline (salt water)
 Plasma carries dissolved oxygen, but saline doesn’t
 Doctors do this is to replace the volume of blood lost to keep a person’s BP
normal, to buy time of their body to make more blood, or for a donor to be found

2
...
Haemoglobin based products
 Doesn’t contain any RBC
 Take from animal/human blood, or can be made synthetically or by genetically
engineered bacteria
PROS
Doesn’t needed to be kept in a fridge
Carries more O2 than normal blood

Transport systems in plants

Phloem:

CONS
Doesn’t clot or fight disease
Broken down quickly




Transport glucose made by photosynthesising cells in the leaves to the rest of the
plant where photosynthesis cannot happen
Plant pests feed on the sugary liquid in the phloem- if too many attack the plant
can die

Xylem:



Carries water to the leaves for photosynthesis from the rots
Xylem cells are dead

Trees:



Xylem is in the middle of the bark, and the phloem is around it
So you can kill a tree by stripping away the first layer of the bark, as it cannot
sent the glucose to other part of the plant

Why is transport important?




Glucose is needed for respiration, and to grow
Mineral ions are needed for the production of proteins and other molecules
Water is needed for photosynthesis to make sugar, to keep the plant rigid (if a
cell has plenty of water the vacuole presses against the cell wall) and provides
support

B3
...
Waste:



Urea
CO2

CO2



Produced in respiration by every cell in the body
Vital that you remove this as dissolved CO2 is acidic, and will affect how enzymes
work



CO2 moves out of the cells into the blood, which carries it back to the lungs to be
breathed out

Urea





If you eat more protein that you need, or body tissues are worn out extra protein
has to be broken down into amino acids
The liver then removes the amino group and converts it into urea, which passes
into the blood from the liver cells
Urea is filtered out of the blood by the kidneys, and is passed out of the body as
urine, along with excess water and salt
Urea= made in the liver
...

And everything it doesn’t is passed out in the urine



Glucose, amino acids, mineral ions, water move out of the blood into the kidney
tubules
They move by diffusion along as concentration gradient



The blood, and large molecule (protein) are left behind- they cannot pass though
the membrane of the tubule

All glucose is reabsorbed back into the blood by
active transport, but the amount of water and
mineral ions the body needs depends on what the
body needs, so varies:



This is selective reabsorbing
The amount reabsorbed into the blood is
controlled by a very sensitive feedback
mechanism

Urea is lost in the urine


But some of it leaves the kidney tubules and moves back into the blood by
diffusion along a concentration gradient

What does urine contain?
Urea, excess mineral ions and water not needed by the body
The exact quantities of these depend on what has been taken in and out



Hot day, drink little, exercise a lot- produce little and concentrated urine
Cool day, drink a lot, do little- - produce a lot of dilute urine

Urine is yellow, everything else is colourless, as a result of urobilins= yellow pigments
from the breakdown of haemoglobin in the liver

Dialysis- an artificial kidney

Kidneys can be damaged/ destroyed by infection, genetic problem, accident
Untreated failure of both kidneys= death
But we have 2 ways of treating it:



Carrying out the functions of the kidneys artificially using dialysis
Kidney transplant

Dialysis
The dialysis machine relies on the process of dialysis to clean the blood



In the process a person’s blood leaves their body and flows between partially
permeable membranes
On the other side is the dialysis fluid that contains the same concentration of
useful substance as the blood

If the kidneys don’t work the concentrations of urea and mineral ions build up in the
blood



Dialysis restores the concentration to normal
Dialysis has to be repeated, as the substances build up again, and patient has to
keep a stable diet to keep their blood chemistry stable

Dialysis fluid carrying
waste products and
urea is removed

Blood thinnerprevents clotting

Gets rid of any
bubbles

During dialysis patients loss excess mineral ions and urea they have built up
But it is important that they don’t lose useful substance like glucose and useful mineral
ions




This is prevented using dialysis fluid, which contains the same concentration of
mineral glucose and mineral ions as blood
This makes sure that glucose and useful mineral ions are not lost
As dialysis fluid contains normal plasma levels of mineral levels, any excess ions
are removed from the blood by diffusion

Dialysis fluid contains no urea, so there is a steep concentration gradient between the
blood and the fluid; so much of the urea leaves the blood
The process of dialysis depends on diffusion long concentration gradients, which have
to be maintained

Kidney transplants

Clean and balance the blood chemistry
The donor kidney is place in the groin and attached to the blood vessels in the bladder

Rejection
As the kidney come from a different person there is a risk of rejection



As the antigens will be different, the antibodies of the immune system of the
recipient could attack the antigens of the donor organ
Results in rejection and the destruction of the kidney

To reduce rejection



Match the antigens as much as possible-you a kidney with a tissue type very
similar to recipients, and with the same blood group
The recipient is given immunosuppressant drugs to supress their immune
system, to prevent rejection

Finding donors
Never enough, so many don’t get the chance of getting another kidney



Not enough are on the donor register
Car are safer now, so less are in accidents

Xenotransplantation


Producing genetically engineered pigs with organs that could be used for human
transplants

Stem cells could also be a way to grow new kidneys

Dialysis VS transplant
Dialysis
CONS

PROS

PROS
Free form the
restrictions of
dialysis

Transplant
CONS

Readily
available

Have to follow a
carful diet

Don’t last long, so a person
has to go back on dialysis
and wait for another
donor

Can lead a
relatively
normal life

Have to spend regular Eat what you
long sessions
want
connected to the
machine

Immunosuppressant dugsprevents patents from
dealing with infectious
diseases well, which is bad
as they have to take them
from the rest of their lives

Over the years the
balance of substances
can become harder to
control

Risk of rejection

Long term dialysis is
more expensive than
a transplant

Issues linked with the treatment of kidney failure




In developing countries many cell their kidneys for money
Some people can be so desperate for themselves or a loved one for a kidney
transplant may result to buying one illegally
Transplants and dialysis both cost the UK a lot of money

Controlling body temp

Needs to stay as 37- enzymes work best
The core body temp is the most important to keep stable
This can affect this though:




Energy produced by the muscles in exercise
Fever caused by disease
External temp changing

To control temp
The control of the core body temp relies on the thermoregulatory
centre/hypothalamus in the brain:




Contains receptors sensitive to temp changes
They monitor the temp of the blood flowing to the brain
Extra info comes from the temp receptors in the skin that’s send impulses to the
thermoregulatory centre about skin temp

Cooling the body down- VASOCONSTRICTION (lower than 37)
Too hot= enzymes denature, and can no longer catalyse the reactions in the cells
When the core body temp begins to rise impulses are sent from the thermoregulatory
centre to the body for more energy to be released



Blood vessels dilate, so more blood can flow through and release energy by
radiation (why your skin goes red)
Sweat= cools the body as it evaporates
...
What happens?




Eventually glucose is excreted through urine
Glucose cannot get into cells- so you lack in energy
You break down fat and protein for fuel, so you lose weight

Treating diabetes
Inject insulin




Allows glucose to be taken into the body cells and converted into glucose in the
liver
This stops BSL from getting too high, and keeps them stable

What to do if you have type 1 diabetes




Keep a stable diet- carful of the levels of carbohydrates eaten
Regular meals
Exercise to keep heat and vessels healthy

These are all keep you BSL steady and you cells supplied with glucose
The disadvantage with the treatment of injecting insulin is that you have to take it every
day

Glucagon and the control of BSL
The control of BSL doesn’t just control insulin
...
4- How Humans Can Affect the Environment
The effects on the population explosion

Population growth
The population has grown into a huge human population (HHP)


If the population of another species grew suddenly that nature would restore
balance with predators, lack of food, build-up of waste, disease to reduce the
population

Why has the population increased?






No natural predators
Better living conditions- electricity, heat
Less infectious disease- Medicine- can cure/prevent killer diseases
Growing lots of food
This rapid growth can be described as population explosion
...

The HHP drains the resources of earth




Raw materials are rapidly being used up
Including non-renewable oil and gas
Metal ores- once processed cannot be replaced

Managing waste
Because of the HHP there are increasing amounts of waste




Bodily waste
Rubbish
Industrial waste (increase in manufacturing and industry for want of consumer
goods)

Can cause serious pollution
...

 Air - smoke and poisonous gases such as sulphur dioxide
...

Dumping this reduces the amount of land for habitats

Land and water pollution

Land
If human waste is not treated properly the soil becomes polluted with chemicals and gut
parasites
Household waste goes straight into landfill sites which take up land and destroyed
habitats



Toxic chemicals can also spread into the soil
Along with the toxic chemical from industrial waste

Farming’s effect on the land



Weeds compete with crops for light water and ions
...

Causes of deforestation

 Make more land available for housing and industry
 Timber
 Make land available for large scale crop growth (soy and palm oil) + for cattle
ranching
Effects of deforestation
Increases the amount of CO2







When forest are destroyed for farming it isn’t used, it is burnt
o land is only fertile for a short time- more land is destroyed- No trees to
replace
Burning the trees= CO2
The dead vegetation decays= CO2
This would be absorbed by photo, but dead trees don’t do this- so CO2 levels
increase
Machinery to clear away plants give off CO2

Soil erosion

 Without tree roots to anchor soil + increased exposure to sun, the soil can dry
out

o Leading to problems like increased flooding and inability to farm
...
g
...
Change in the earth’s climate
 Unpredictable weather conditions
 High winds, floods
2
...
Reduces biodiversity
 Climate change= many animals will be unable to survive
 Eg: no ice caps, no polar bears
4
...
Changes in distribution
 Some may extend their range as conditions become more favourable
 Some may shrink
 Some may disappear entirely from an area
Biofuels

= fuel that is produced form biological material which is renewable and sustainable



Made from natural products by fermentation using yeast or bacteria
There are 2 biofuels- ethanol, biogas

Ethanol
Bioethanol is an alcohol produced by the natural fermentation of starch in sugar cane or
wheat crops
...


Some of the deforested land it used for crops that are used to produce biofuels



Sugar can is fermented anaerobically with yeast, producing ethanol and CO2
The ethanol is them extract by distillation

Used in cars as fuel

Pros and cons of ethanol:
PROS

CONS

Efficient- renewable

Takes a lot of plant material

Does not produce toxic gases
And produces less carbon monoxide, SO2,
nitrogen oxides than other fuels

Reduced the space that would be used for
food, but is instead used as fuel
Adding to world hunger

It can also be mixed with petrol to make
gasohol, reducing pollution levels

Although biofuels themselves produce
relatively little when combusted, their
production needs energy from fossil fuels
...


 Also built underground- Less visual impact- Less heat loss - Easier to maintain
optimum temp- Withstand pressure build-up

Pros and cons of biogas
PROS

CONS

Continuous= efficient- continuously fed in,
waste is pumped in and out mechanically

Batch= less convenient as it has to be
loaded, emptied and cleaned, and has to be
positioned away from home as it smells

Raw material is cheap and readily
available

Continuous= more expensive

Acts as a waste disposal system, that, if
left, could cause disease and pollute the
water
Methane that would be given off from
waste, is instead burnt
Making food production efficient

Food chain
By the time the food reaches us much of the energy in the plants had been used up


Efficiency of food production is improved by reducing the stages in the food
chain

There is a limited amount of room on the earth for food




The most efficient way to use this for food is to grow plants
But if we use it to farm animal, less food is produced- animal takes up more
space
Every extra stage we put in results in less energy at the end of the food chain

The arrows show the transfer of energy from one organism to the next
...


 Measuring the biomass at each trophic level can give a more accurate picture
...

Shows the total weight of organisms at each level of a food chain
Always pyramid shaped
...
To do this:



Limit movements- don’t use as much energy moving - more biomass from food to
grow
Control temp of surroundings- not use energy to control temp- more biomass for
growth

 Controlled feeding – e
...
growth hormones/modified food
Factory farming
PROS

CONS

Used to combat the increase in demand for Disease can spread quickly, so they need
cheap meat and animal produce
constant monitoring which costs
But they can be sold for meat very quickly

The animals live unnatural and restricted,
stressed lives

Outside- takes more space and weather
can be a problem and grow more slowly

Outside- there is no heating or lighting to
pay for
Outside- have a better quality of live

Food miles



How far the food travels
Uses fuel which increases the amount of CO2

Sustainable food production

Sustainable food production means:



Producing food in ways that can continue for many years
...


 It also involves taking care of the fish stocks in our oceans so that they do not run
out
...

It has less fat – so less chance of heart disease
...

It has more fibre – less chance of colon cancer/prevents cons5pa5on
...

Fermenters have

 The growing conditions inside it can be manipulated and controlled in order to






ensure the best possible yield of the product
...
As the water is heated it is replaced with more cold water
Measuring instruments that measure pH and temp, so changes can be made if
needed

The fungal biomass is them harvested and purified

Then it is dried and purified to make Mycoprotein



On its own has little flavour, but a range of flavours and textures can be given to
make it similar to other foods
It is a meat substitute

Mycoproteins are versatile, high in protein and fibre, low in fat and calories and very
sustainable, so is used a lot in the developing world

Asepsis
= absence of unwanted microorganisms
Aspesis is vital in biotechnological processes involving microorganisms as the nutrient
medium may also support the growth of many unwanted microorganisms
(contaminant)
...

Reduce the yield of useful products from the culture microbes
...

May produce toxic chemicals
...

At laboratory and starter culture level:
 Fume cupboard – air circulation
carries any airborne contaminants
away from the bench space
 Sterile equipment – sterilise all
equipment before use (e
...
flame
loop, or by UV light)
...




Closed cultures – keep closed
where possible

At large-scale culture levels
 Sterile fermenters – washing,
disinfecting and steam cleaning the
fermenter- Fermenters made of
polished stainless steel to prevent
microbes and medium sticking
 Sterile nutrient media – sterilise all
media before adding to the
fermenter
...


The oceans
It is important to maintain fish stocks at a level where breeding continues successfully,
otherwise certain species such as cod and Bluefin tuna might disappear completely
...

With these we can conserve the fish stocks and will be able to fish sustainably for years
to come

Environmental issues

Issues with the growing demand for water
The way we get water can affect the environment
Water is needed for us, animals and plants

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