Animal & plant cells
Animal cell structure
● The main features of animal cells:
o They contain a nucleus with a distinct membrane
o Cells do not have cellulose cell walls
o Their cells do not contain chloroplasts (so they are unable to carry
out photosynthesis)
o They contain carbohydrates stored as glycogen
Animal cell diagram
A typical animal cell
Plant cell structure
● The main features of plant cells:
o They contain a nucleus with a distinct membrane
o Cells have cell walls made out of cellulose
o They contain chloroplasts (so they can carry out photosynthesis)
o Carbohydrates are stored as starch or sucrose
Plant cell diagram
A typical plant cell
Plant and animal cell structure and function
Structure Function
Nucleus ● Contains the DNA (genetic material) which controls the activities of the cell
● A gel like substance composed of water and dissolved solutes
Cytoplasm ● Supports the internal structures of the cell
● Site of many chemical reactions (including anaerobic respiration)
● Holds the cell together separating the inside of the cell from the outside
Cell membrane
● Controls which substances enter or leave the cell
● Found in the cytoplasm
Ribosomes
● The site of protein synthesis
Mitochondria ● The site of aerobic respiration
Cell structure diagram
An animal and plant cell as seen under a light microscope
Plant cell structure and function
Structure Function
● Made of cellulose (a polymer of glucose)
Cell wall
● Gives the cell extra support, defining its shape
Chloroplast ● Contains the green chlorophyll pigment that absorbs light energy for photosynthesis
● Contains cell sap: a solution of sugar and salt
Permanent vacuole ● Used for storage of certain materials
● Helps to support the shape of the cell
Producing New Cells
● The cells in your body need to be able to divide to help your body grow and repair itself
● Cells grow and divide over and over again
● New cells are produced by the division of existing cells
Specialised Cells
Specialised cells in animals
● Specialised cells are those which have developed certain characteristics in order to perform
particular functions. These differences are controlled by genes in the nucleus
● Cells specialise by undergoing differentiation: this is a process by which cells develop the
structure and characteristics needed to be able to carry out their functions
Specialised Cells in Animals Table
Diagrams of specialised cells in animals:
Ciliated cell
Nerve cell
https://www.youtube.com/watch?v=u87QpOOkdxI
Red blood cells
Sperm cell
Egg cell
Examples of specialised cells in plants:
Diagrams of specialised cells in plants:
Root hair cell
Xylem structure
Palisade mesophyll cell
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Levels of Organisation in an Organism
Levels of organisation
● Your syllabus states that you should be able to identify the different levels of organisation in
drawings, diagrams and images of familiar material
● An example of this is shown in the exam question below:
Typical levels of organisation question
Magnification Formula
Calculating magnification and specimen size using millimetres as units
● Magnification is calculated using the following equation:
Magnification = Image size ÷ Actual size
● A better way to remember the equation is using an equation triangle:
Magnification equation
● Rearranging the equation to find things other than the magnification becomes easy when
you remember the triangle - whatever you are trying to find, place your finger over it and
whatever is left is what you do, so:
o Magnification = image size / actual size
o Actual size = image size / magnification
o Image size = magnification x actual size
Remember magnification does not have any units and is just written as ‘x 10’ or ‘x 5000’
Worked Example
An image of an animal cell is 30 mm in size and it has been magnified by a factor of x 3000. What is
the actual size of the cell?
To find the actual size of the cell:
Using millimetres and micrometres as units
● The table below shows how millimetres are related to two other measures of length
● What this basically means is that 1mm = 1000µm and 1cm = 10,000µm
● This usually comes up in questions where you have two different units and you need to
ensure that you convert them both into the same unit before proceeding with the calculation
● For example:
Example extended magnification question
● Remember 1mm = 1000µm
● 2000 / 1000 = 2 so the actual thickness of the leaf is 2mm and the drawing thickness is
50mm
● Magnification = image size / actual size = 50 / 2 = 25
● So the magnification is x 25 (NO UNITS)
