Combined science: Biology-B2

  • Created by: Sumaiya
  • Created on: 09-09-18 12:47

Biology-B2: Cell organisation 1

Large multicellular organism are made up of organ systems. Cells are basic building blocks that make up all living organisms.

Similar cells are organised into tissues.

Tissue: Group of similar cells that work together to carry out a function:

  • Muscular tissue - contracts to move together to carry out a function.
  • Glandular tissue - makes and secretes chemicals. E.G. Hormones.
  • Epithelial tissue - covers some parts of the body.

Tissues are organised into organs.

Organs: Group of tissues that work together to perform a function:

  • For example: The stomach is made up of:
    • Muscular tissue - moves the stomach walls.
    • Glandular tissue - makes digestive juice.
    • Epithelial tissue - covers inside + outside of the stomach.
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Biology-B2: Cell organisation 2

Organs are organised into organ systems.

Organ systems: Group of organs working together to carry out a function:

  • Example: The digestive system is made up of the :
    • Liver -  Produces bile.
    • Glands - Produces digestive juice.
    • Stomach + small intestine - Digests food.
    • Small intestines - Absorbs soluble food molecules.
    • Large intestines - Absorbs water.
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Biology-B2: Enzymes

Enzymes are biological catalysts which are produced by living things. Enzymes reduce the need for high tempreture and we only have enzymes to speed up useful chemical reactions.

Catalysts: A substance which increases the speed of reaction, without being changed or used up in the reaction.

Enzymes have an active site with a unique shape that fit onto a substance. Enzymes usually only catalste one specific reaction: The lock and key.

Both tempreture and pH affects enzymes. All enzymes have an optimum tempreture and optimum pH.

Optimum tempreture: The tempreture where the enzymes work best at.

Optimum pH: The pH where the enzymes work best at.

What happens if the tempreture or the pH is too high or too low?

If the tempreture or pH is too high or too low then the enzymes get denatured.

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Biology-B2: Enzymes and digestion 1

Digestive enzymes break down large molecules into smaller, soluble molecules, so they can be absorbed into the bloodstream.

Carbohydrates convert carbohydrates into simple sugars.

Amylase is a carbohydrate but what does it break down?


Where is amylase found?

  • Salivary gland
  • Pancreas
  • Small intestines
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Biology-B2: Enzymes and digestion 2

What does protease convert protein into?

Proteins---protease/enzymes---Amino acids

Where is protease found?

  • Stomach (Pepsin)
  • Pancreas
  • Small intestines
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Biology-B2: Enzymes and digestion 3

What does lipases convert lipids into?

Lipid---lipase/enzymes---Glycerol + Fatty acids

Where is lipase found?

  • Pancreas
  • Small intestines
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Biology-B2: Bile

Bile is produced in the liver.

Where is bile stored?

Bile is stored in the gall bladder before it is released into the small intestines.

The pH of the hydrochloric acid is too acidic for the enzymes to work in. The bile neutralises the acid and makes it more alkaline and the enzymes can work better. 

What else does the bile do?

Bile also emulsifies fatso they can have a big surface area which makes digestion faster.

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Biology-B2: The lungs

The lungs are in the thorax and is seperated by the diaphram.

The lungs are protected by the ribcage.

The air we breathe in goes through the trachea.

Trachea: The trachea splits into two tubes 

What are bronchioles?

Bronchioles: The bronchi the splits into smaller tubes called bronchioles.

At the end of each bronchiole, there is an alveoli.

The alveoli carry out gas exchange but how?

Oxygen diffuses outnof the alveolus (high concentration) and into the blood (low concentration). Carbon dioxide diffuses out of the blood (high concentration) and into the alveolus (low concentration) to be breathed out.

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Biology-B2: Blood vessels

There are three types of blood vessels:

  • Ateries:
    • Carries the blood away from the heart.
    • Pumps blood out at high pressure so the walls are strong and elastic.
    • Thick walls compared to the size of the lumen.
    • Thick layers of muscle to make them strong + elastic fibres for them to strech.
  • Veins:
    • Carries the blood to the heart.
    • Capillaries join to form veins and pump blood at low pressure.
    • Bigger lumen than ateries to help blood flow but have less thick walls.
    • Have valves to prevent backflow.
  • Capillaries:
    • Involved in the exchange of materials at the tissues.
    • Ateries branch into capillaries and are very tiny.
    • Carry blood really close to every cell to exchange substances.
    • Permeable walls so substances can diffuse in and out.
    • Supply food and oxygen but take away waste such as CO2
    • Walls are only one cell thick to increase rate of diffusion.
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Biology-B2: Blood 1

Red blood cells carry oxygen to all the cells in the body.

They have a biconcave shape to increase surface area absorb blood better.

It does not have a nucleus so it can carry more oxygen.

Contains a red pigment called haemoglobin.

Haemoglobin: Binds to oxygen to become oxyhaemoglobin in the lungs. In the body tissues, the oxyhaemoglobin split up to release oxygen into the cells.

White blood cells defend against infection.

Phagocytosis: Some white blood cells change shape to eat unwelcomed microorganism.

Some white blood cells produce antibodies to fight off microorganisms and antitoxins to neutralise toxins.

White blood cells do have a nucleus.

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Biology-B2: Blood 2

Platelets are small fragments of cells and have no nucleus. 

Platelets help the blood to clot to stop blood from falling out and to stop microorganism from getting in.

Lack of platelets can cause excessive bleeding and bruises.

Plasma is a liquid that carried everything in the blood.

Plasma carries:

  • Red + White blood cells
  • Platelets
  • Carbon dioxide
  • Hormones
  • Proteins
  • Antibodies + Antitoxins
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Biology-B2: Health and disease

Health is the state of physical and mental well being. Disease is often responsible for causing ill health.

Disease can either be communicable or non-communicable.

Communicable: Spread from people to people and animals. It can be caused by bacteria, viruses, parasites and fungi. Eg. Measles and malaria.

Non-communicable: Cannot be spread. Generally lasts for a long time. Eg. Asthma and cancer.

People with immune system problem have an increased chance of suffering from communicable diseases. Cancer can be triggered by certain viruses.


  • Hepititis virus can increase the chance of liver cancer
  • HPV can cause cervical cancer.

Other factors that cn effect your health:

  • Your diet
  • Stress
  • Life situation
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Biology-B2: Risk factors for non-communicable dise

Risk factors can increase your chance of getting a disease. Risk factors are often aspects of a person's lifestyle.

Risk factors: Things that are linked to an increase of likelihood that a person will develop a certain disease. It is not a guarantee.

Risk factors that can directly cause a disease:

  • Smoking: Can cause cardiovacular disease, lung disease and lung cancer. Damages walls of arteries and cells in lining of the lungs.
  • Obesiety: Can cause type 2 diabetes by making the body more sensitive/resistant to insulin.
  • Alcohol consumption: Too muh alcohol can cause liver disease. Can also affect brain functions as it damages nerve cells.
  • Exposure to certain substances or radiation: Cancer can be caused due to exposure. Things that cause cancer are called carcinogens. Eg. Ionising radiation (e.g. X-Rays)
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Biology-B2: Cancer

Cancer is caused by uncontrolled cell growth and division which can cause tumours.

Two types of tumours:

  • Benign: Stays in one place and is not cancerous.
  • Malignant: Grows to spread to healthy tissues. Malignant tumours are fatal and cancerous.

Risk factors for cancer:

  • Smoking: Mostly linked with lung cancer. Also linked with other types of cancer such as mouth, bowel and cervical cancer.
  • Obesity: Linked woith many different cancers such as liver, bowel and kidney cancer.
  • UV exposure: People who are often exposed to UV rays from the sun and tanning beds have a high risk of skin cancer.
  • Viral infection: infection with some viruses have been shown to incease chances of certain cancers. Eg. Hepititus B can increase the risk of liver cancer.
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Biology-B2: Plant cell organisation

Plants are made up of organs such as stems and leaves. The plant organs are made up of plant tissues.

Examples of plant tissues:

  • Epidermal tissue: Covers the whole plant.
  • Palisade mesophyll tissue: Where photosynthesis happens.
  • Spongy mesophyll tissue: Contains big air sacs to allow gases to diffuse in and out of cells.
  • Xylem and Phloem: Transport things like water, mineral ins and food around the plant.
  • Meristem: Able to differentiate into lots of different types of plant cells, allowing the plant to grow.
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Biology-B2: Transpiration and stomata

Transpiration rate is affected by four things:

  • Light intensity: Brighter the light, the greater the transpiration rate. The stomata closes during the dark as photosynthesis cannot happen in the night.
  • Tempreture: The warmer it is, the faster the transpiration rate. When it is warm, water has more energy to evaporate and diffuse out.
  • Air flow: Better the air flow, the greater the transpiration rate. If the air flow is poor, then the water vapour just surrounds the leaf and does not move away.
  • Humidity: The drier the leaf, the faster the transpiration rate. If the air is humid, then there is already a lot of water in the plant.

The guard cells open and close the stomata to control water loss. They have thin outer walls and thickened inner walls to make the opening and closing work.

The guard cells are also sensitive to light and close at night to save water from falling out.

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