AQA Categories Archives: GCSE

Helping the heart

Heart attacks:

  • Blood supply is suddenly blocked from getting to the heart
  • Coronary heart disease is the leading cause of heart attacks
  • Blood supply is trapped by fatty substances in the coronary arteries
  • When a plaques ruptures it causes a blood clot
  • Can also block the blood getting to the heart

High and low blood pressure:

  • The exact reasons are unknown
  • High
  • Many factors such as smoking, drinking too much alcohol, being overweight, stress…
  • Low
  • Symptoms are light-headedness, chest pain, blurred vision…


  • Patches of atheroma are like small fatty lumps
  • Develop within the inside lining of blood vessels (arteries)
  • A patch of atheroma can make an artery narrower
  • Can reduce the blood flow through the artery




  • Small mesh tube
  • Used to treat narrow or weak arteries or to improve blood flow and help prevent the arteries from bursting
  • Usually made of metal mesh
  • Some are coated with medicine that is slowly and continuously released into the artery


  • A class of medicines that are used to lower blood cholesterol levels
  • Block the action of an enzyme in the liver that is necessary for making cholesterol
  • Can get many different types


  • Emits electrical impulses through the wires to the heart
  • Rate at which the electrical impulses are sent out is called the pacing rate
  • Almost all modern pacemakers work on demand
  • Means they can be programmed to adjust the discharge rate in response to the body’s needs
  • If the pacemaker senses that the heart has missed a beat or is beating too slowly, it sends signals at a steady rate
  • If it senses that your heart is beating normally by itself, it doesn’t send out any signals

Heart transplants:

  • An operation to replace a damaged or failing heart
  • Use a healthy heart from a donor who has recently died
  • Have to have an in-depth assessment to check whether you’re healthy enough to have one before being placed on a waiting list

Artificial hearts:

  • A device that replaces the heart
  • Typically used to bridge the time to heart transplantation
  • Or to permanently replace the heart in case heart transplantation is impossible
Continue Reading



Actual object size = Image size/magnification I=AxM


  • 1. prepare your slide – add drop of water, specimen, iodine then coverslip
  • 2. clip slide onto stage, select lowest power objective lens, use coarse adjustment knob, adjust focus with fine adjustment knob
  • 3. draw observations (in pencil), write title, magnification, label important features

Electron microscopes have a higher resolution

Iodine is needed to stain the sample to highlight objects in the cell by adding colour

Continue Reading

Plant cell organization



  • Stems
  • Roots
  • Leaves


  • Epidermal
  • Meristem
  • Xylem and phloem
  • Palisade mesophyll
  • Spongy mesophyll

Leaves contain epidermal, mesophyll, xylem and phloem

Phloem: translocation

  • Made of columns of elongated cells with pores in the end walls to let cell sap flow. Transport food (dissolved sugars) made in leaves to rest of plant. transport goes in both directions



  • Made of dead cells joined end to end with no end wall. Strengthened with lining. Carry water and minerals from roots to stem and leaves.

Continue Reading

Transport systems in plants



  • Flowering plants have two separate transport systems
  • Xylem and phloem
  • Xylem tissues transport water and mineral ions from roots to stem, leaves and flowers
  • Phloem cells carry dissolved sugars from the leaves to the rest of the plant (including growing regions and storage organs)
  • The movement of water in plants is called “The transpiration stream”
Continue Reading

Cell differentiation and specialization


Cells differentiate to become specialized – become specialized for the job

  • Develop different subcellular structures to be able to carry out specific functions
  • In most animal cells, the ability to differentiate is lost at an early stage, after they become specialized. lots of plant cells don’t lose this ability
  • Cells that differentiate in mature animals are mainly used for repairing and replacing cells such as skin or blood cells
  • Undifferentiated cells are called stem cells.

Sperm cells: reproduction

  • Male DNA to the female DNA
  • Long tail and streamlined head to help swim to the egg
  • Lots of mitochondria to provide energy
  • Enzymes to digest through egg cell membrane

Nerve cells: rapid signalling

  • Long and have branched connections

Muscle cells: contraction

  • Long (space to contract)
  • Lots of mitochondria to generate the energy

Root hair cells: absorbing water and minerals

  • Long hairs stick into the soil (large surface area)

Phloem and xylem cells: transporting substances

  • Long tubes joined end to end
  • Xylem cells are hollow
  • Phloem have very few subcellular structures so stuff can flow through them
Continue Reading

The Digestive System




  • How food enters the body
  • Chewing breaks up food and mixes it with enzymes to start digestion



  • Carries food from mouth to stomach by peristalsis
  • Peristalsis is the contraction and relaxation of muscles which pushes the food down



  • Acid and enzymes added
  • Stomach contents mixed by churning of muscular wall



  • Produces bile, which helps in the digestion of fats in small intestine
  • Converts food molecules absorbed from small intestine into other molecules


Gall bladder:

  • Where bile from the liver is stored until needed in the small intestine



  • Produces enzymes that are released into the small intestine


Small intestine:

  • Digestion of food molecules completed
  • Food molecules are absorbed into the blood by villi containing capillaries
  • Water absorbed from digested food


Large intestine:

  • Some water is absorbed
  • Undigested food forms faeces that pass out of the body through the anus


The roles of enzymes:

  • Carbohydrase digest carbohydrates, e.g. Amylase digests starch to simple sugars
  • Proteases digest proteins to amino acids
  • Lipases digest fats to fatty acids and glycerol


Bile is added in the small intestine to neutralise stomach acid. This means that the enzymes in the stomach can work at their optimum pH. Bile also emulsifies (break up large drops of fat into smaller droplets that remain mixed in a watery liquid) fats so that there is a greater surface area for lipases to work on.


Alimentary canal – a muscular tube running from the mouth to the anus.

Continue Reading

The Circulatory System

Veins carry deoxygenated blood from the body to the heart. They have wide passages because the blood flows slowly under low pressure.


Arteries carry oxygenated blood from heart to the body. The blood has to be under high pressure, so they have strong, thick walls.


Capillaries exchange materials such as oxygen, glucose and carbon dioxide. They have very thin walls so that substances can diffuse easier.


The key function of the blood is to deliver oxygen and glucose to cells for respiration and to remove the carbon dioxide produced by respiration.

Continue Reading

The Heart

Cells are grouped into tissues and tissues are grouped into organs.

  • Pulmonary artery – carries deoxygenated blood from heart to lungs
  • Vena cava – brings deoxygenated blood from body to heart
  • Aorta – carries oxygenated blood from heart to body
  • Pulmonary vein – carries oxygenated blood from lungs to heart


The left ventricle is thicker than the right ventricle as it pushes blood all around the body.


Continue Reading





  • Liquid part of the blood
  • Carries the blood cells through the blood vessels
  • Contains many dissolved substances such as carbon dioxide and glucose


White blood cells:

  • Larger than red blood cells
  • Have a nucleus
  • Some surround and destroy pathogens
  • Some produce antibodies that destroy pathogens



  • Are fragments of larger cells
  • Have no nucleus
  • Causes blood to clot when a blood vessel has been damaged


Red blood cell:

  • Contains haemoglobin which carries oxygen
  • Has a biconcave shape which gives it a larger surface area
  • Oxygen diffuses in and out of the cell
  • Has no nucleus to give the cell more room for more haemoglobin to carry more oxygen
Continue Reading

Growth in Plants and Animals



Growth in plants:

·  Grow through all their lives

·  Meristems are a place where cells keep dividing

·  Once cells have divided, they get longer (elongate)

·  Meristem can specialise/differentiate


Growth in animals:

·  Stop growing when they become adults

·  Have stem cells that can differentiate

·  Most animals cannot regrow damaged limbs


All the cells in an embryo are stem cells. This means they can produce any kind of cell. Only a few cells in an adults body are stem cells, and these are used to help repair damaged tissue.


Continue Reading