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Fifth Form
Revision Guide

Unit Title
12.1 Animal and Plant Cells
12.2 Diffusion and Osmosis
12.3 Plant Requirements
12.4 Food Chains and Energy Flow
12.5 Decay and the Carbon Cycle
12.6 Enzymes
12.7 Homeostasis
12.8 Genetics and Inheritance

12.1 Animal and Plant Cells

Common Features

- Nucleus ­ `brain' of…

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- Mitochondria ­ where energy is released in respiration, `power
stations' of the cell (see enzymes in respiration (12.6)
- Ribosomes ­ where protein synthesis occurs
- Chemical reactions inside cells are controlled by proteins
known as enzymes

Plant Cells
Plant cells also have:
- Cell wall ­ cellulose cell…

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Specialised Cells
For each of the following cells, briefly describe how their
structure is related to their function (job):
Sperm Long tails with muscle like
Cell proteins for swimming
High numbers of mitochodria to
provide energy
Acrosome ­ containing digestive
enzymes to break through jelly…

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organs are grouped together into:
Organ Systems

Whole Body

12.2 Diffusion and Osmosis

Cells need to take in substances as well as getting rid of waste
Substances move in and out of cells across the cell membrane
This can occur by diffusion, osmosis or active transport

Diffusion is:…

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Some cells make diffusion more rapid by increasing surface
area where diffusion can occur. Folds of the cell membrane
(villi) greatly increase the s.a.

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- Cell membranes are partially permeable and allow water to
move across them
Osmosis is the movement of water across a partially
permeable membrane
- Water will move from a high water concentration (ie dilute
solution) to a low water concentration (concentrated solution).
- The amount of solutes (salts…

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12.3 Plant Requirements

- Animals = heterotrophs ­ get their energy from eating other
living things
Plants = autotrophs - make their own food
They do this through Photosynthesis (p/s)
Carbon Dioxide + Water Glucose + Oxygen
6CO2 + 6H2O C6H12O6 + 6O2

- Light energy absorbed by chlorophyll…

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- 0.4% surrounding concentration decreases throughout the
day ­ so in sunny weather CO2 normally the limiting factor
* Can control all these factors by growing in glasshouses

Using Glucose
- Respiration ­ all living cells respire, break down glucose to get
energy (waste products ­ CO2 and water…

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- Disadv ­ expensive way to farm, uses lots of resources

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12.4 Food Chains and Biomass

- Energy of all living things comes from the sun
- Some of the sun's radiated energy is trapped by p/s
- But a lot of the sun's energy doesn't hit plants or is reflected
back off the Earth's surface
The energy that is absorbed…


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