Cells

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’

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

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

Living things can be classified as: 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: Plant cell Animal cell

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

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 Rough endoplasmic reticulum No ribosomes on outer surface Mainly involved in lipid (fat) production Smooth endoplasmic reticulum

Drawing an animal cell

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

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 Smooth endoplasmic reticulum Function in protein synthesis Rough endoplasmic reticulum 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 Cell wall X Vacuole Small but many A single large one Chloroplast Shape Varied Regular

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

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

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

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

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.

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.