IGCSE BIOLOGY Cellular organization
Appreciate that all living things are made up of cells
All animals, plants, fungi, protists, & bacteria are made of one or more cells.
Know the structure of a typical plant cell & a typical animal cell.
( cell membrane, cytoplasm, nucleus, cell wall, vacuole, chloroplast )
Generalized animal and plant cell
*Make sure you can label diagrams of animal and plant cells.
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Understand the functions of the organelles of plant & animal cells.
Animal cells and plant cells have some organelles in common. organelle function nucleus contains genetic material, which controls the activities of the cell cytoplasm most chemical processes take place here, controlled by enzymes cell membrane controls the movement of substances into and out of the cell mitochondria most energy is released by respiration here ribosomes protein synthesis happens here
Plant cells also have a cell wall, and often have chloroplasts and a permanent vacuole. organelle function cell wall chloroplasts permanent vacuole strengthens the cell contain chlorophyll, which absorbs light energy for photosynthesis filled with cell sap to help keep the cell turgid
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Understand the significance in the structure between plant & animal cells.
PLANT CELLS ANIMAL CELLS
Have a rigid cell wall that helps them keep their shape.
Plants manufacture their own food and use chloroplasts to do that.
Do not have a cell wall and therefore require either external or internal support from some kind of skeleton.
Have a shape related to their function.
Animals must eat their food because they cannot photosynthesize.
Usually have a large central vacuole.
Animal cells may have several small vacuoles, or none at all.
Appreciate that different types of cells perform different functions & that their structure is related to their function.
Specialized cells:
Cells may be specialized for a particular function. Their structure allows them to carry out this function .
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Cell
Leaf cell
Root hair cell
Sperm cell
Red blood cells
Examples of specialized cells
Function
Absorbs light energy for photosynthesis
Adaption
Packed with chloroplasts. Regular shaped, closely packed cells form a continuous layer for efficient absorption of sunlight.
Absorbs water and mineral ions from the soil
Long 'finger-like' process with very thin wall, which gives a large surface area.
Fertilizes an egg cell - female gamete
Contain hemoglobin to carry oxygen to the cells.
The head contains genetic information and an enzyme to help penetrate the egg cell membrane. The middle section is packed with mitochondria for energy. The tail moves the sperm to the egg.
Thin outer membrane to let oxygen diffuse through easily. Shape increases the surface area to allow more oxygen to be absorbed efficiently. No nucleus, so the whole cell is full of hemoglobin.
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Cell
Nerve cells
Function different parts of the body
Adaption


Long
Connections at each end
Can carry electrical signals
Female reproductive cell
(egg cell)
To join with male cell, and then to provide food for the new cell that's been
 formed
Large
Contains lots of cytoplasm
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Be able to interpret light micrographs and simple electron micrographs of plant & animal cells.
Photos produced by microscopes are called micrographs.
Light micrograph Electron micrograph
Root tip cells as seen through Plant cells as seen through an
a light microscope. electron microscope.
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Know that cells are arranged in groups to form tissues. tissue – a structure made from large numbers of one type of cell
Examples of tissues found in the human body
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Examples of tissues found in a leaf
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Diffusion
Dissolved substances have to pass through the cell membrane to get into or out of a cell.
Diffusion is one of the processes that allows this to happen.
Diffusion occurs when particles move.
Particles move from a region where they are in high concentration to a region where they are in low concentration.
Diffusion happens when the particles are free to move.
This is true in gases and for particles dissolved in solutions.
Particles diffuse down a concentration gradient, from an area of high concentration to an area of low concentration.
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Examples of diffusion location particles move from to intestine digested food products intestinal cavity blood in capillary of villus lungs oxygen alveolar air space blood circulating around the lungs
In the intestine, the concentration of molecules used by the body for energy, growth and repair are in higher concentration in the intestinal cavity than in the blood.
In the lungs, the blood will continue to take in oxygen from the alveolar air spaces provided the concentration of oxygen there is greater than in the blood.
Oxygen diffuses across the alveolar walls into the blood, and the circulation takes the oxygen-rich blood away.
Know that osmosis is the diffusion of water molecules through a partially permeable membrane.
Dissolved substances pass into and out of cells by diffusion.
Water passes into and out of cells by osmosis.
Osmosis is the movement of water from a less concentrated solution to a more concentrated solution through a partially permeable membrane.
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Water can move across cell membranes because of osmosis.
For osmosis to happen you need:
 two solutions with different concentrations
 a partially permeable membrane to separate them
A partially permeable membrane will let some substances pass through it, but not others.
In osmosis it is only water that moves in the following direction:
 from a region of high water concentration to a region of low water concentration.
 from a more dilute solution ( with a low solute concentration ) to a more concentrated one ( with a high solute concentration ).
 from a weaker solution to a stronger one.
Relate osmosis to the effect of solutions of different concentrations on animal & plant cells.
Animal cells need a constant supply of food & oxygen.
Food & oxygen dissolved in the blood moves from the capillaries into cells by diffusion.
As cells use food & energy, they produce waste in the form of carbon dioxide.
Carbon dioxide diffuses from cells into the blood.
Osmosis is important to plants.
They gain water by osmosis through their roots.
Water moves into plant cells by osmosis, making them turgid so they that able to hold the plant upright.
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