Unit 5Unit 5Anatomy and Anatomy and PhysiologyPhysiology

CellsCells

Aim: To introduce the fundamentals of Aim: To introduce the fundamentals of anatomy and physiology and cell function.anatomy and physiology and cell function.

Learning Intentions:• To secure knowledge by being able to

identify the component parts of a cell. • To further develop our knowledge by

describing the functions of the main cell components.

• To show excellence by creating an annotated display which explains the structure and function of cells.

The human body is made up The human body is made up of:of:

• CellsCells

• TissuesTissues

• Organs Organs

• SystemsSystems

What is a cell?What is a cell?• The “building block” of all living

things.• All living things made up of 1 or more

cells• Organised in groups each of which

have specific functions

Cells - the factsCells - the facts• The human body is made up of millions of The human body is made up of millions of

tiny cellstiny cells• These can only be seen under a These can only be seen under a

microscopemicroscope• They appear in many different shapes and They appear in many different shapes and

sizes and have different functionssizes and have different functions• Each cell has a nucleus which contains the Each cell has a nucleus which contains the

genetic coding called DNAgenetic coding called DNA• Cells cannot function by themselves Cells cannot function by themselves

A Human CellA Human Cell

What is?What is?• DNA (Deoxyribonucleic acid)The chemical containing the genetic code

• CHROMOSOMEA thread shaped body consisting of DNA

http://www.bbc.co.uk/schools/gcsebitesize/science/add_edexcel/cells/dnarev1.shtml

NucleusNucleus• The largest organelle.• Cell survival and reproduction

happens here• Contains DNA, the chromosomes

and proteins and the chromatin

Nuclear EnvelopeNuclear Envelope• a physical barrier (membrane)

separating the contents of the nucleus from the surrounding cytoplasm

Endoplasmic reticulumEndoplasmic reticulum• is concerned with the manufacture

and transportation of materials in the cell.

• Rough ER - are important in the production and transportation of proteins.

• Smooth - creates and stores steroids

RibosomesRibosomes• Produce the protein in a cell.

CytoplasmCytoplasm• This is the fluid that fills the cell. • The cells organelles are suspended in

the cytoplasm.

MitochondriaMitochondria• Mitochondria are know as the

powerhouses of the cell. • They take in nutrients, break them

down and creates energy for the cell• This process is known as cellular

respiration

LysosomeLysosome• Lysosomes hold enzymes that were

created by the cell. • The purpose of the lysosome is to

digest things.

Golgi ComplexGolgi Complex• Is a packaging organelle. • It gathers simple molecules and

combines them to make molecules that are more complex.

• It then takes those big molecules, packages them in vesicles, and either stores them for later use or sends them out of the cell.

The Cell MembraneThe Cell MembraneL.O understand the L.O understand the

organisation of the human organisation of the human bodybody

Cell organelles “2”Cell organelles “2”Learning Intentions:

To secure knowledge by being able to identify the component parts of a cell.

To further develop our knowledge by describing the functions of the main cell components.

To show excellence by building a cell membrane model

Why do cells need Why do cells need membranes?membranes?

• Control entry and exit of substances• Contain the cell contents and

organelles; compartmentalise individual cell processes

• Communication with external environment

• Site of chemical reactions• Allows cell to change shape• Transport and packaging within a cell

What are cell membranes What are cell membranes made of?made of?

• Most of the cell membrane is impenetrable to water soluble substances – it is composed of LIPIDS

• Water-soluble substance and other molecules can pass into the cell through passageways composed of PROTEINS

Fats and WaterFats and Water• These two substances do

not mix• Water is a polar molecule

(the oxygen end is slightly negative and the hydrogen end slightly positive)

• Fats are non-polar and do not form hydrogen bonds with water

• Fats are said to be hydrophobic and lie on the surface of the water to reduce the surface area in contact between the fat and the water

Dietary lipids…Dietary lipids…• The fats that make up the cell membrane are

different in structure to the dietary fats we have come across before

• Dietary fats are composed of one glycerol backbone with three fatty acids attached to it

• The fatty acids are non-polar and do not form hydrogen bonds with water so they are insoluble

Lipids in the cell membraneLipids in the cell membrane• These are

phospholipids• They are composed

of a glycerol backbone, two fatty acid chains and a phosphate group

• The fatty acid chains are non-polar

• The phosphate group is polar

PhospholipidsPhospholipids• They are usually drawn

like this• The head (phosphate

group) is hydrophilic• The tail (fatty acids)

are hydrophobic

And if you shake them

up in water?....

A MICELLE forms!

What happens if you place them in water?....

So how are fats arranged in the So how are fats arranged in the cell membrane?...cell membrane?...

The Fluid Mosaic Model…The Fluid Mosaic Model…• The phospholipid

bilayer is not a fixed structure

• Although the bilayer will always remain arranged in this configuration, the individual phospholipids are able to move, hence why it is also known as the fluid mosaic model

• The phospholipids rotate on their axis

• They can ‘swap' places with the phospholipid next to them

• They can occasionally ‘swap’ places with the phospholipid directly opposite them, though this is rare

All of these movements increase the fluidity of the membrane

What about the proteins in the What about the proteins in the membrane?membrane?

• Some proteins are transmembrane – they span the width of the phospholipid bilayer

• Others are fixed into the bilayer on one side only; these are peripheral proteins

• The proteins have several different functions

Transmembrane ProteinsTransmembrane Proteins• Water soluble substances

pass through proteins channels in the bilayer

• These channels can be permanent or temporary

• Gated channels allow selected molecules through: conditions within the cell determine whether they are open or closed

• Other channels allow substances to pass through freely in both directions

• Some channels are active carrier systems which use energy to transport substances across (e.g. the Sodium-Potassium pump)

Peripheral proteinsPeripheral proteins• Glycoproteins, found on the

cells surface, are protein molecules with a carbohydrate group attached

• These allow cells to communicate with one another

• Individual groups of cells have their own glycoproteins, recognisable by the immune system

• Proteins on the cells surface also act as receivers for incoming messages, such as hormones

• Intracellular cell membranes may also contain enzymes for cell surface reactions

Practical task Practical task

• On A3 paper label a cell leaving space for the model of the cell membrane and label it.