9. Cells

10. Objectives Label the different parts of the cell
Describe the functions of the different parts of the cell
Compare a typical animal cell to a typical plant cell
Explain what is meant by ‘tissues’ and ‘organs’

11. Introduction A cell is the basic unit of ALL living things/organisms
It is the smallest part of a living thing that is alive and is only visible under the microscope
As such, they are the building blocks of life

12. They can also carry out specialised functions
Cells can take in nutrients and convert them into energy they need to stay alive
They can also carry out specialised functions
Red blood cells – carry oxygen
Muscle cells – contract to allow movement

13. Living things can be classified as:
Unicellular (only 1 cell) e.g., bacteria
2) Multicellular (many cells) e.g., human, plants

14. There are many kinds of cells with different shapes and sizes
But they may share some common features
Our focus:
Plant cell
Animal cell

15. Animal cells ORGANELLES Basic structure of a typical animal cell:
Cell membrane
Cytoplasm
Nucleus
Vacuole
Mitochondria
Ribosomes
Endoplasmic reticulum
- Smooth and rough
ORGANELLES

16. An organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed

17. Cell membrane A thin layer surrounding the cell
Semi-permeable – it only allows SOME substances to pass through but not others
It functions to control the movement of substances in and out of a cell

18. Cytoplasm Jelly-like substance that fills the cell
Contains water and many other substances
It is where many chemical reactions take place e.g., converting nutrients to energy

19. Nucleus It controls the activities of a cell
Usually found in the centre of an animal cell
Contains hereditary materials called chromosomes
Chromosomes carry genes which are passed from parents to their children

20. Vacuoles
Membrane-enclosed fluid which stores food or nutrients needed by the cells
Animal cells have MANY vacuoles

21. Mitochondria Mitochondria are the cell's power producers
They convert nutrients into energy that is usable by the cell

22. Ribosomes
Can be found in the cytoplasm and on the endoplasmic reticulum
Function in protein production
ribosomes

23. Endoplasmic reticulum
A network tubules and sacs that serves as the cell’s transport system
Can also function in storage and production

24. Rough endoplasmic reticulum Smooth endoplasmic reticulum
Has ribosomes on its outer surface
Mainly involved in protein production
Rough endoplasmic reticulum
No ribosomes on outer surface
Mainly involved in lipid (fat) production
Smooth endoplasmic reticulum

25. Drawing an animal cell

26. Plant cells Basic structure of a typical plant cell: Cell membrane
Cytoplasm
Nucleus
Vacuole
Mitochondria
Chloroplasts
Cell wall
Endoplasmic reticulum
Organelle found only in plant cells

27. Cell membrane
Just like animal cells, plant cells also have a semi-permeable layer around them
Similarly, it controls the movement of substances in and out of the cell

28. Cytoplasm
This is the same kind of jelly-like substance as that found in animal cells
Many chemical reactions would take place here

29. Nucleus
Also like in animal cells, it controls the activities of the cell
Because of a larger vacuole, it is pushed to one side of cell rather than being found in the middle of the cell (e.g., in animal cells)

30. Vacuole
It is often a single, large space containing a liquid called cell sap (large central vacuole)
It contains water and dissolved substance such as sugar and salt

31. Mitochondria Same as in animal cells
These are power sources that fuel cellular activities

32. Ribosomes Play a role in producing proteins Same as in animal cells
Can be found in cytoplasm or surface of endoplasmic reticulum

33. Endoplasmic reticulum
Smooth endoplasmic reticulum
Function in protein synthesis
Rough endoplasmic reticulum
Function in lipid synthesis

34. Cell wall A layer (thicker than cell membrane) surrounding the cell
Made of a tough substance called cellulose
It supports the cell and gives it a regular shape
Prevents the cell from bursting when water enters it excessively

35. Chloroplasts Small disc-like structures found in plant cells
They contain a green substance called chlorophyll which absorbs light energy to make food during photosynthesis

36. Drawing a plant cell

37. Differences between plant cells and animal cells
Cell wall X
Vacuole
Small but many
A single large one
Chloroplast
Shape
Varied
Regular

38. Similarities between plant and animal cells
Plant cell
Cell membrane
Present in both types of cells
Nucleus
Cytoplasm
Ribosomes
Mitochondria
Smooth and rough endoplasmic reticulum

39. Division of labour – cellular level
In multicellular organisms, different cells perform different functions
Division of labour – division of work among cells in an organism
They are specialised in their functions and have special features to allow them to do so
This designation of different functions allows efficient functioning in multicellular organisms

40. Example of specialised cells in animals
RBCs have no nucleus and carry a protein called hemoglobin to transport oxygen

41. Example of specialised cells in plants
Xylem vessels are non-living cells that form tubes for transporting water and mineral salts
Root hair cells have a tubular extension to increase the surface area for water absorption
Palisade cells have many chloroplasts to capture the maximum amount of sunlight for photosynthesis

42. Levels of organisation of cells
From cells to tissues
(When cells of the same type work together to do the same job, they make up a tissue)
Animal
Plant
E.g., muscle tissue – muscle cells work together to allow the body to move
E.g., connective tissue – joins parts of the organism e.g., fats, bone
Vascular tissue – transport water and food throughout the plant
Photosynthetic tissue – capture light energy to make food for the plant

43. From tissues to organ
(When different tissues work together to do a particular job, they make up an organ)
Animal
Plant
E.g., Brain – consists of nerve tissue, connective tissue etc.
E.g., Heart – consists of muscle tissue, connective tissue etc.
E.g., Leaf – consist of photosynthetic , vascular tissues etc.
E.g., Stem – Supporting tissues vascular tissues etc.

44. From tissues to system
(When different organs work together to do a particular job, they make up a system)
Animal
Plant
E.g., Digestive system – mouth, stomach, intestines etc.
E.g., Respiratory system – nose, lungs etc.
Circulatory system - heart, blood vessels
E.g., Transport system – roots, stem etc.