Animal and Plant Cells

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: 

• nucleus 
• cytoplasm 
• cell membrane 
• mitochondria 
• ribosomes

Plant cells also have: 

-cell wall 

-chloroplasts 

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

There are many similarities and differences between animal and plant cells. 
Make sure you know these.

Similarities	Differences
1. Have a nucleus	1.  Plant cells have a cellulose cell wall
2. Have a cytoplasm	2.  Plant cells have a vacuole containing cell sap
3. Have a cell membrane	3.  Plant cells have chloroplast
4. Contain mitochondria	4.  Many plant cells have a box-like shape whilst animal cell shape varies
5. Contain ribosomes	5.  Plant cells have the nucleus to the side of the cell, animal cells have a nucleus in the middle

Other facts: 

The chemical reactions inside cells are controlled by enzymes. 

Examples:

• Enzymes for respiration are in the mitochondria. 
• Enzymes for photosynthesis are in the chloroplasts. 
• Enzymes for protein synthesis are on the ribosomes. 

Cells may be specialized to carry out a particular function. 

Cell Specialization

Now we have established the general features of both animal and plant cells we must also remember that many cells do look different and this is because they have their own special jobs to do. These cells display specialized features that make them suited to carry out their specific function.

Cell Specialization – Animals

Cell Type	Specific Function	Specialised Feature
Red Blood Cell
	Contain haemoglobin which transports oxygen to other cells and around the body.	Have biconcave shape for maximum surface area to allow more oxygen to be absorbed efficiently. Biconcave shape also allows for a flexible framework which means cells can squeeze through the thinnest of capillaries. Cells have a thin outer membrane allowing oxygen to diffuse through easily. Have no nucleus so there is more room for oxygen to be carried in the cell and hence around the body.
Sperm Cell
	To fertilise the ovum (female egg cell).	The tail of the sperm cell enables it to swim to the ovum and fertilise it. The head is streamlined also to aid swimming The head contains genetic information and a nucleus and has an enzyme to help penetrate the egg cell membrane to allow fertilisation. The middle section immediately behind the head is packed with mitochondria to provide energy.
Nerve Cell
[Motor Nerve Cell]	Transmit electrical nerve impulses and so carry information from one part of the body to another ie from receptor to an effector.	Dendrites extend from the cell body to make connections with other neurones. Have a long axon (nerve fibre) to carry the impulse to the target organ. End plate forms a synapse with an effector (a muscle or a gland).

Cell Specialisation – Plants

Cell Type	Specific Function	Specialised Feature
Xylem Cell
	Small tubes that carry water from the roots to the leaves.	Long and tube-like hollow vessels to carry the water. Cells have no end walls between them so they form a 'pipeline' to carry the water. Spirals and rings of lignin in the cell walls strengthen them to withstand pressure of water.
Root Hair Cell
	Absorb water and mineral ions from the soil.	Located in the root epidermis and in direct contact with the soil Thin walls make up-take of water easier. Wall nearest the soil has a long 'finger-like' projection with very thin walls into the soil. This projection increases the surface area for more efficient uptake of water and ions.
Leaf Palisade Cell
	Carries out photosynthesis.	Packed with chloroplasts which contain the light absorbing pigment chlorophyll. Regular shaped closely packed cells forming a continuous layer for efficient and maximum absorption of sunlight.

Tissues, organs and systems 

• A tissue is a group of similar cells carrying out a particular function. 
• An organ is a group of different tissues carrying out a particular function. 
• A system is a group of different organs carrying out a particular function.