Biology

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AQA GCSE Biology – Unit 2 summary notes

AQA
GCSE Biology
Summary Notes
For Unit B2
Exam Tuesday
th
May 13 2014
Page 1

AQA GCSE Biology – Unit 2 summary notes

B2.1 Cells and Cell Structures
Summary
All living things are made up of cells. The structures of different types of cells are related to
their functions. To get into or out of cells, dissolved substances have to cross the cell
membranes.
Cells
 Cells are the smallest unit of life.
 All living things are made of cells.
 Most human cells, like most other animal cells, have the following parts:
o nucleus
o cytoplasm
o cell membrane
o mitochondria
o ribosomes


Plant and algal cells also have:
o cell wall
o chloroplasts
o permanent vacuole

What do these structures do?
 Nucleus – controls the activities of the cell.
 Cytoplasm – where most of the chemical reactions take place.
 Cell membrane - controls the passage of substances in and out of the cell.
 Mitochondria - where most energy is released in respiration.
Page 2

AQA GCSE Biology – Unit 2 summary notes






Ribosomes - where protein synthesis occurs.
Cell wall – made of cellulose and strengthens plant cells.
Chloroplasts - absorb light energy to make food in plant cells.
Permanent vacuole - filled with cell sap in plant cells.

Yeast
 Yeast is a single-celled organism.
 The cells have a nucleus, cytoplasm and a membrane surrounded by a cell wall.

Bacteria
 Bacterium is a single-celled organism.
 A bacterial cell consists of cytoplasm and a membrane surrounded by a cell wall.
 The genes are not in a distinct nucleus.

Page 3

AQA GCSE Biology – Unit 2 summary notes



Cells may be specialised to carry out a particular function.
Examples:

Movement into and out of cells






To get into or out of cells, dissolved substances have to cross the cell membranes.
Solutes = particles in solution eg glucose, sodium ions, chloride…...

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