Biology Unit 3

Controlling Blood Glucose

The pancreas monitors and controls the level of glucose in our blood.

If there is too much glucose in the blood the hormone INSULIN is added. Insulin causes the glucose to move from the blood into the body cells.

The liver converts the excess glucose to glycogen for storage. If the blood gulcose levels are too low then glucagon makes the liver turn glycogen back into glucose which is then released back into the blood.

Blood glucose level TOO HIGH = INSULIN is ADDED 

Blood glucose levels TOO LOW = GLUCAGON is ADDED

Someone with Type 1 diabetes cannot produce any or too little Insulin. As a result the blood glucose levels rise to dangerous levels.

Methods of Transport

OSMOSIS - the movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration.

DIFFUSION - where particles move from an area of high concentration to low concentration.

ACTIVE TRANSPORT - sometimes substances need to go AGAINST the concentration gradient. This is when active transport is required, which needs ENERGY. 

ACTIVE TRANSPORT NEEDS ENERGY FROM RESPIRATION FOR IT TO WORK

Exchange surfaces are:

• VERY THIN SO ONLY A SHORT DISTANCE TO DIFFUSE 
• LARGE SURFACE AREA SO A LOT CAN DIFFUSE AT ONCE
• IN ANIMALS LOTS OF BLOOD VESSELS
• IN ANIMALS GAS EXCHANGE SURFACES ARE VENTILATED  

Structure of Leaves 

Stomata are underneath the leaf - this is where the CO2 diffuses through.

After photosynthesis stomata allow oxygen and water vapour to diffuse out.

GUARD CELLS control the stomata - so if more water is being lost than replaced the stomata will close. Without the GUARD CELLS the plant would wilt.

The shape of the leaf INCREASES the surface area.

Gas Exchange in the Lungs 

The job of the lungs is to remove waste CO2 and transfer oxygen into the blood. To do this the lungs contain a lot of air sacs called alveoli - where gas exchange takes place.

To maximise the diffusion alveoli have:

• ENORMOUS SURFACE AREA
• MOIST LINING FOR DISSOLVING GASES
• VERY THIN WALLS 
• GOOD BLOOD SUPPLY

Villi 

Inside the small intestine it is covered with villi. They have a large surface area so food is absorbed much more quickly into the blood. To do this quickly they have:

• SINGLE LAYER OF SURFACE CELLS 
• VERY GOOD BLOOD SUPPLY 

Water flow through Plants 

PHloem transports Food in both directions 

Xylem carry water and minerals from the roots to the stem and leaves

Blood Vessels 

ARTIERIES - these carry the blood away from the heart. They are very strong and elastic because the blood is pumped out at a high blood presssure.

CAPILLARIES - these are involved in the exchange of materials at the tissue. Here are the main features:

• Carry blood very close to every cell in the body to exchange substances with them.
• They have permeable walls, so substances can diffuse in and out. ONE CELL THICK.
• Supply food and oxygen and take away waste like CO2.

VEINS - carry blood to the heart.

The Blood 

The blood is a massive transport system for:

RED BLOOD CELLS:

Red Blood Cells carry oxygen from the lungs to all the cells in the body. They have a concave doughnut shape to create a larger surface area for absorbing oxygen. They also don't have a nucleus to create more space.

Contains HAEMOGLOBIN, which combines with oxygen to become OXYHAEMOGLOBIN. In the cells OXYHAEMOGLOBIN splits to release oxygen into the cells.

WHITE BLOOD CELLS:

They can change shape to destroy unwelcome microorganisms. Produce antibodies and antitoxins.

PLATELETS:

They help the blood to clot at a wound - to stop blood pouring out and to stop microorganisms getting in. Lack of platelets can cause excessive bleeding and bruising.

PLASMA: PLASMA CARRIES EVERYTHING IN THE BLOOD 

Kidneys 

Kidneys do three main things:

• REMOVE UREA from the blood 
• Adjustment of IONS in the blood 
• Adjustment of WATER CONTENT of the blood 

This the process:

1) WATER, UREA, IONS, SUGARS are squeezed out of the blood and into the BOWMANS CAPSULE. This is where everything is filtered. Molecules such as PROTEINS CANNOT BE FILTERED OUT BECAUSE THEY ARE TOO BIG.

2) As the liquid flows along the nephron useful substances such as sugars are REABSORBED.

THIS NEEDS ACTIVE TRANSPORT 

3) Released wastes exit down the bladder as urine.

Homeostasis 

HOMEOSTASIS IS THE MAINTENANCE OF A CONSTANT INTERNAL ENVIRONMENT

Six things need to be controlled:

• Body Temperature cannot get too hot or cold 
• Water Content cannot get too high or low 
• Ion Content 
• Blood Sugar Level
• CO2 needs to be disposed 
• Urea needs to be disposed 

Controlling Temperature 

There is a thermoregulatory centre in your brain which acts as your own thermostat. There are sensors that are sensitive of the temperature of the blood flowing through your brain. 

WHEN YOU'RE TOO HOT:

• Hairs lay flat 
• Sweat is produced which evaporates on the skin
• The blood vessels dilate, so blood flows closer to the surface of the skin, so heat can transfer more easily.

WHEN YOUR TOO COLD:

• Hairs stand up trapping an insulating layer of air
• No sweat is produced 
• The blood vessels constric to close off the skins blood supply
• You shiver, this makes the muscles contract. This needs respiration which needs energy. This releases some heat to keep you warm.

Human Impact

There are four main things humans do which reduce the amount of land and resources for animals and plants:

• BUILDING 
• FARMING
• DUMPING WASTE
• QUARRYING  

Greenhouse Effect

Gases such as Methane and CO2 naturally form an insulating layer absorbing and releasing the heat back to earth. If this did not happen then the planet would not keep any heat in and it would be very cold.

The levels of CO2 and Methane in the atmosphere are rising dramatically KEEPING TOO MUCH HEAT IN. Therefore the temperature of the planet is rising.

CO2 can be locked up in natural sources such as:

• OCEANS/LAKE/PONDS
• GREEN PLANTS
• PEAT BOGS  

Destroying the Peat Bogs releases all of the CO2 which has been locked up for hundreds of years. This will ultimatly add to the greenhouse effect.

Biofuels 

Fuels can be made by fermentation of natural products - such as waste. Fermentation is when bacteria or yeast is broken down BY ANAEROBIC RESPIRATION.

Biogas is made by the ANAEROBIC FERMENTATION OF WASTE MATERIAL. Biogas is usually 70% methane 30% CO2.

Lots of different microorganisms are used to produce biogas. Biogenerators need to be kept at a constant temperatureto stop them respiring away.

Four factors have to be considered when building a Biogas Generator:

• COST
• CONVINIENCE - batch generators are less convinient than continuous generators because they have to be continually loaded and cleaned.
• EFFICIENCY 
• POSITION - they smell so would need to be away from the home but close to the waste source.

Managing Food Production 

1) Reducing the number of stages in the food chain. There is less energy and less biomass every time you move up the food chain.

2) Restricting the energy lost by animals. You can do this by keeping animals close together indoors. This means animals are NOT wasting energy on keeping warm and movement.

3) Developing new food sources such as MYCOPROTEIN. A FUNGUS CALLED FUSARIUM IS THE MAIN SOURCE OF MYCOPROTEIN. The fungus is grown using fermenters and glucose syrup as food. The fungus respires aerobically. The advantages of mycoprotein is that it is a massive source of protein which doesn't need a lot of space to grow - like meat does. It grows quickly and can feed off waste.

Overfishing 

To stop overfishing fish stocks can be conserved by:

INTRODUCING FISHING QUOTAS - there are limits on the number of fish that can be caught in a certain area. This prevents a certain species from being overfished.

NET SIZE - this reduces the number of unwanted and discarded fish. Using a bigger mesh will allow different species to swim through. Young fish will also get through so they can then breed.

The Breathing System 

The lungs work essentially like this:

1) Diaphragm contract

2) This decreases the pressure

3) AIR IS DRAWN IN 

4) Diaphragm relaxes 

5) Increases the pressure 

6) AIR IS FORCED OUT 

VENTILATION IS THE MOVEMENT OF AIR IN AND OUT OF THE LUNGS 

Artificial Ventilators 

Artificial ventilators are machines which move air in and out of a persons lungs. These help people who cannot breath by theirselves.

A person used to have to go in a giant case/iron lung with only the head visible. The pressure is changed inside the case so the lungs work like explained on the previous card.

THE PRESSURE IS DROPPED 

THEN

PRESSURE IS INCREASED 

The Heart 

Humans have a double circulatory system - two circuits joined together:

1) The first side pumps deoxygenated blood to the lungs to TAKE IN OXYGEN. This blood then returns to the heart.

2) The second  pumps oxygenated blood around all of the over organs in the body. The blood gives up its oxygen when it arrives at the body cells. This deoxygenated blood then returns to the heart to be pumped to the heart.

VALVES STOP BLOOD FROM GOING IN THE WRONG DIRECTION