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Biology Revision Notes B2 1.1-3.6
Animal and Plant Cells:

Animal Cells - Structure and function:

Nucleus: This controls all of the activities of the cell. It also
contains instructions for making new cells or new organisms.

Cytoplasm: This is a liquid gel in which most of the chemical
reactions needed…

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Plant cells ­ Structure and Function:

Plant cells are very different to animal cells.

All plant cells have the following organelles:



Cell Walls: These are made of cellulose and strengthen the
cell, giving it support.



Many (but not all) plant cells also have these other features:

Chloroplasts: These are found…

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Chemical Reactions within cells:

Cell chemistry works because each reaction is controlled by an
enzyme.
Each enzyme is a protein which controls the rate of a very specific
reaction.
It makes sure that the reaction takes place without becoming
mixed up with any other reaction.
Enzymes are found throughout cells,…

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Sometimes cells become so specialised that they only have one
function within the body.
Good examples of this include sperm cells, eggs, red blood cells
and nerve cells.


Fat cell:

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Organised cells:
Specialised cells are often grouped together to form a tissue.
Connective tissue joins bits of a person's body together.
Nervous tissue carries information around a person's body.

In plants, photosynthetic tissues make food by photosynthesis while storage
tissues store any extra food made as starch.



In larger living…

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Diffusion happens when the particles
of a gas, or any substance in solution,
spread out.

It is the net movement of particles
from an area of high concentration to
an area of lower concentration.



It takes place because of the random movement of the particles of a gas or of…

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Simple sugars, such as glucose and amino acids from the breakdown of
proteins in your gut, can pass through cell membranes by diffusion.
The oxygen you need for respiration passes from the air into your lungs
and into your cells by diffusion.
Individual cells may be adapted to make diffusion…

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In cells, there are chemicals dissolved in water inside a partially permeable bag
of cell membrane.
Cells contain a fairly concentrated solution of salts and sugars.
Water will move from a high concentration of water particles (in a dilute
solution) to a less concentrated area of water particles (in a…

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This swollen/turgid state keeps the leaves and the stems of the plant rigid and firm
meaning that for all plants it is important that the fluid surrounding the cell always
has a higher concentration of water (more water than chemicals/solutes) than the
cytoplasm of the cells. This keeps osmosis working…

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