Cells

Objectives1. Label the different parts of the cell

2. Describe the functions of the different parts of the cell

3. Compare a typical animal cell to a typical plant cell

4. Explain what is meant by ‘tissues’ and

‘organs’

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

• Cells can take in nutrients and convert them into energy they need to stay alive

• They can also carry out specialised functionsRed blood cells – carry oxygen Muscle cells – contract to allow movement

• Living things can be classified as:1) Unicellular (only 1

cell) e.g., bacteria

2) Multicellular (many cells) e.g., human, plants

• There are many kinds of cells with different shapes and sizes

• But they may share some common features

• Our focus:1. Plant cell2. Animal cell

Animal cells• Basic structure of a

typical animal cell:1. Cell membrane2. Cytoplasm3. Nucleus4. Vacuole5. Mitochondria6. Ribosomes7. Endoplasmic

reticulum- Smooth and rough

ORG

ANEL

LES

An organelle is a specialized subunit within a cell that has a specific function, and is usually

separately enclosed

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

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

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

Vacuoles• Membrane-

enclosed fluid which stores food or nutrients needed by the cells

• Animal cells have MANY vacuoles

Mitochondria• Mitochondria

are the cell's power producers

• They convert nutrients into energy that is usable by the cell

Ribosomes• Can be found in

the cytoplasm and on the endoplasmic reticulum

• Function in protein production

ribosomes

Endoplasmic reticulum• A network

tubules and sacs that serves as the cell’s transport system

• Can also function in storage and production

Rough endoplasmic

reticulum

Smooth endoplasmic

reticulum

• Has ribosomes on its outer surface

• Mainly involved in protein production

• No ribosomes on outer surface

• Mainly involved in lipid (fat) production

Drawing an animal cell

Plant cells• Basic structure of a typical

plant cell:1. Cell membrane2. Cytoplasm3. Nucleus 4. Vacuole 5. Mitochondria 6. Chloroplasts 7. Cell wall8. Endoplasmic reticulum

Organelle found only in plant cells

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

Cytoplasm• This is the same

kind of jelly-like substance as that found in animal cells

• Many chemical reactions would take place here

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)

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

Mitochondria

• Same as in animal cells

• These are power sources that fuel cellular activities

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

Endoplasmic reticulum

Rough endoplasmic

reticulum

Smooth endoplasmic

reticulum

Function in protein

synthesis

Function in lipid

synthesis

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

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

Drawing a plant cell

Differences between plant cells and animal cells

Animal cell Plant cell

Cell wall X Vacuole Small but

manyA single large

one

Chloroplast X Shape Varied Regular

Similarities between plant and animal cells

Animal cell Plant cell

Cell membrane

Present in both types of cells

Nucleus

Cytoplasm

Ribosomes

Mitochondria

Smooth and rough endoplasmic reticulum

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

Example of specialised cells in animals

RBCs have no nucleus and carry a protein called hemoglobin to transport oxygen

1. Xylem vessels are non-living cells that form tubes for transporting water and mineral salts

2. Root hair cells have a tubular extension to increase the surface area for water absorption

3. Palisade cells have many chloroplasts to capture the maximum amount of sunlight for photosynthesis

Example of specialised cells in plants

Levels of organisation of cellsFrom cells to tissues

(When cells of the same type work together to do the same job, they make up a tissue)

Animal PlantE.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

From tissues to organ(When different tissues work together to do a particular

job, they make up an organ)

Animal PlantE.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.

From tissues to system(When different organs work together to do a particular

job, they make up a system)

Animal PlantE.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.