Topic B2 ~ Organisation

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Cell Organisation.

Cells are the basic building blocks that make up all living organisms 

Specialised cells carry out a particular function 

These specialised cells form tissues, which form organs, which forms organ systems.

Large Muliticellular organisms have different systems inside themfor exchanging and transporting materials. 

tissue is a group of similar cells that work together to carry out a function

An organ is a group of different tissues that work together to perform a certain function

An organ system is a group of organs working together to perform a function 

The digestive system is an organ system that breaks down and absorbs food.

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Enzymes

Enzymes are catalysts 

Catalysts are what speed up reactions. Reactions are controlled by enzymes.

A CATALYST is a substance which INCREASES the speed of a reaction, without being CHANGED  or USED UP in the reaction.

Temperature affects the rate of a reaction involving an enzyme ~ a higher temperature increases the rate at first. If it gets too hot, some of the bonds holding the enzyme together break. 

pH can affect the rate of a reaction involving an enzyme. 

If a pH is too high or too low it affects the bonds holding the enzyme together. 

This changes the shape of the active site and denatures the enzyme

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The Lungs

Air moves in and out of the lungs. 

The air that you breathe in goes through the trachea.

Then it passes through the bronchi, then the bronchioles and ends up in the alveoli. 

Alveoli carry out gaseous exchange.

Alveoli in the lungs are surrounded by blood capilleries. 

Blood comes into the lungs through the capilleries.

Oxygen diffuses out of the air in the alveolous into thr blood. 

Co2 diffues out of the blood into the air.

The blood then leaves the lungs and travels around the body. 

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Circulatory System - Blood Vessels

Blood flows around the body in blood vessels. There are three types:

  • arteries 

They carry blood away from the heart, blood from the heart is pumped out at high pressure. Artery walls are strong and elastic. They have thick layers of muscle to make them strong and elastic fibres to allow them to stretch and spring back

  • capilleries

Arteries branch to capilleries. They are really tiny. They carry blood really close to every cell in the body. They have gaps in the walls to allow substances to diffuse in and out. Their walls are only one cell thick which allows diffusion to take place quickly.

  • veins

Capilleries join up to make veins. The blood is at low pressue in the veins. Veins contain valves that keep the blood flowing in the right direction. 

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Circulatory System - Blood

Red Blood cells carry oxygen. 

The job of red blood cells is to carry oxygen from the lungs to the rest of the cells in the body.

They contain a red substance called HAEMOGLOBIN.

Red blood cells don't have a nucleus - leaves moer space for carrying oxygen.

White Blood cells defend against infection 

White blood cells are part of your immune system

Some can change shape to take in unwelcome microorganisms. 

Others produce antibodie and antitoxins to defend against microorganisms 

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Circulatory System - Blood

Platelets help blood clot

These are small fragments of cells 

They help bloof clot at a wound. This stops blood from pouring out of the body. 

It stops microorganisms from getting in the body. 

Plasma is the liquid that carries everything in the blood. 

This is a pale straw coloured liquid. it carries:

  • Red and white blood cells and platelets
  • Food molecules 
  • Waste products 
  • Hormones
  • Proteins 
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Cardiovascular disease

Cardiovascular diseases are diseases of the heart or blood vessels.

Coronary heart disease is a disease of the coronary arteries 

Coronary heart disease is when layers of fatty material build up in  the coronary arteries.

This causes the arteries to become narrow, reducing the blood flow to the heart muscle. 

This means that less oxygen can get to the heart muscle, resulting in a heart attack

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Health and Disease

Communicable diseases

  • These are diseases that can be spread from person to person. 
  • Can be caused by bacteria, viruses parasites or fungi.
  • Measles and malaria are examples of communicable diseases. 

Non-communicable diseases

  • Diseases that cannot spread between people
  • Coronary heart disease is an example

The immune system helps fight off pathogens. some people have weak immune systems which makes them moer likely to suffer from communicable diseases. 

Viruses infect cells in the body ~ can lead to some types of cancer. 

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Cancer

Cancer is caused by uncontrolled cell growth and division.

Tumours can be benign or malignant:

Benign Tumours are masses of abnormal cells 

They stay in one place 

They don't invade other parts of the body the tumour isn't cancerous.

Malignant tumours can spread to other parts of the body

The cells can break off and travel in the blood stream

The cells get into healthy tissues and form secondary tumours

Malignant tumours are dangerous and can be fatal ~ they are cancerous. 

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Risk Factors of Developing Cancer

LIFESTYLE FACTORS

  • SMOKING 
  • OBESITY
  • VIRAL INFECTION 
  • UV EXPOSURE

GENETIC FACTORS

  • GENES AER PASSED ON FROM PARENT TO OFFSPRING
  • SOMETIMES YOU CAN INHERIT FAULTY GENES THAT MAKE YOU MORE LIKELEY TO GET CANCER. 
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Transpiration and Translocation

Phloem Tubes transport food. 

They are made up of elongated living cells.

There are end walls between the cells ~ they have pores to allow cell cap to flow through.

Plants make food substances which the phloem tubes transport around the plant for immediate use or for storage. the transport goes in both directions ~ this is called translocation. 

Xylem Tubes take water up 

They are made up of dead cells 

The cells are joined together with a hole down the middle

Xylem tubes carry water and mineral ions from the roots to the stem and leaves 

The movement of water from the roots, through the xylem and out of the leaves is called the transpiration stream. 

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