Biology: Organisms and Life Processes

Biology, Edexcel: Chapter 1 - Organisms and Life Processes

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  • Created by: Roz
  • Created on: 23-01-12 09:34

The Characteristics of Living Things

Most living things have severn processes in common :

M -Movement

R -Respiration

S -Sensitivity

N -Nutrition

E -Excretion

R -Reproduction

G -Growth\

You can learn these using the acronym: MRS NERG

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Cell Structures

All living organisims are based on unspecilised cells

Unspecilised cells ALL have a Cell Membrane, Cytoplasm, Nucleus and Mitpchondria

PLANT cells also have a Cellulose Cell Wall, Valcole and Chloroplasts which contain Chlorophyll for Photosynthesis.


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They are Biological catalysts; so they speed up reactions without being used up or changed in the reaction. Enzymes are proteins.

The shape of the enzyme makes an active site and the substrate attaches to the active site.

The reaction takes place and products are formed.

This is called the lock and key mechanism.

Anything that changes the shape of the active site stops the enzyme from working this is called denaturing the enzyme. This can be caused by the wrong pH or Temperature.


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Cells break down food to release energy, this happens in the process called cellular respiration or respiration.

The released energy is used for muscel contraction, active transport, building up large molecules and cell division.

Aerobic respiration - oxygen is used to oxidise food. Carbon and water are released as waste products:

Glucose + Oxygen --> Carbon Dioxide + Water (+Energy)


Anaerobic respiration - when no oxygen is available, Glucose is not completely broken down and less energy is released. In yeast the waste products are Ethanol and Carbon Dioxide. In animal cells the waste product is Lactic Acid

Glucose --> Ethanol + Carbon Dioxide (+Some Energy)

Glucose --> Lactic Acid (+Some Energy)

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Movement Into and Out of Cells

Diffusion - the movement of particles from an area of high concentration to an area of low concentration.                                                                                    Diffusion is passive, it goes down the concentration gradient.

Diffusion rate are affected by concentration, Temperature and surface area.

Osmosis - is a special type of diffusion where only water moves across a partially permeable membrane. It moves from an area with a high concentration of water, to an area with a low concentration of water.                                                                It moves down the Concentration gradient.

Osmosis occurs across cell membranes they are partially permeable.

Active Transport - when substances area across a selectively permeable membrane or against the concentration gradient. Active Transport uses the energy produced in respiration.

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Specialised Cells

Specialised Cells -Cells which perform a particular function in the body

Tissue -Specialised cells group together and from a tissue which carries out a particular function 

Organ -Tissues group together and from an Organ which carries out a particular function

Organ System -Organs group together and from an Organ System which carries out a particular function

Body -Organ Systems group together and from a Body

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