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• What are the basic units of life? • What are the structures within a cell and what are they capable of? • How and why do cells divide? CELL STRUCTURE YEAR 8 BODY SYSTEMS
• What are the basic units of life?
• What are the structures within a cell and what are they capable of?
• How and why do cells divide?
CELL STRUCTURE
YEAR 8 BODY SYSTEMS
Cells alive!
Cells are the smallest units of life
This means that all living things are composed of cells.
They can be either a single cell or multiple cells, each performing a specialised function:
eg:
bacterial cells red blood cells nerve cells skeletal muscle cells
Cells alive!
Cells and their structures were discovered as microscopesbecame more powerful.
When magnified:
o The cells are visible.
o Smaller structureswithin the cells are also visible.
o The cells can be seen dividing to formnew cells.
What’s in a cell?
Our bodies contain organs to carry out specialised functions
o eg. lungs for respiration, stomach for digestion, etc
Likewise, our cells contain organellesthat carry out specialised functions
o eg. mitochondria for respiration, lysosomes for digestion, etc
o The picture on the right is showing a lysosome digesting a broken mitochondria!
Types of cells
Our cells are eukaryotic
This means that:
o they have lots of organelles that surrounded by individual membranes (“wrappers”)
o they have a nucleusthat controls all cell functions
Types of cells
All animal, plant and fungi cells are eukaryotic
But there are stillsome differences between them
Types of cells
Bacterial cells are prokaryotic
This means that:
o they don’t have any organelles!
This saves space because they are 90% smaller than one of our cells!
o they don’t have a nucleus either!
The DNA that controls all cell functions just floats within the cell
Cell functions
All cells are capable of performing the characteristics of life:
I can do this:
Move
Respire (breathe)
Sense stimuli
Grow
Reproduce
Excrete wastes
Need nutrients
So can all of our
cells!!!!
But how ????
We use our organs & organelles!
What’s in anANIMAL CELL?
Nucleus
Nucleus
Nucleus
Nickname: the control centre
Function: controls cell function, division & growth
It contains DNA
It is surrounded by a thin membrane called the nuclear membrane.
Cell membrane
Cell membrane
Cell membrane
Nickname: the “gate keeper”
Function: controls the movement of substances into and out of the cell
It has little channels, gates & pumps within it to allow different substances to cross into & out of the cell eg. water, O2, CO2, glucose
Cytoplasm
Cytoplasm
Cytoplasm
Nickname: the shock-absorber
Function: fills the cell to protect the contents also the site of most chemical reactions
It is the cell fluid (Cyte = cell; plasm = fluid)
It stops damage to the organelles
Mitochondria
Cytoplasm
Mitochondria
Mitochondria
Singular = mitochondrion; Plural = mitochondria
Nickname: the powerhouse
Function: site of cellular respiration, the process used to produce energy for the cell
It has a double-membrane(the inner one is folded like the folds of a curtain)
Ribosomes
Cytoplasm
Ribosomes
Ribosomes
Nickname: the factories
Function: make proteins for use in the cell/body
Located in 2 places within the cell:o floating in the cytoplasm
o attached to the rough endoplasmic reticulum (rER)
It uses instructions from the DNA know what proteins to build and how to build them
Endoplasmic reticulum
Cytoplasm
Rough endoplasmic reticulum
Smoothendoplasmic reticulum
Vesicles
Endoplasmic reticulum
The endoplasmic reticulum is a network of membrane channels in the cytoplasm of the cell.
There are 2 types of ER:
o Smooth ER
o Rough ER
Rough endoplasmic reticulum
Nickname: Rough ER
Function: pieces together and transports the proteins made by the ribosomes
It is covered in ribosomes (hence why it is rough)
It can transport the proteins to other locations in the cell via vesicles (little “bubbles” of membrane)
eg. o 4 proteins are needed to make haemoglobin
o The ribosomes make the 4 proteins
o The rough ER will put the 4 pieces together into one
Smooth endoplasmic reticulum
Nickname: Smooth ER
Function: makes and packages fats & oils
It is smooth because it is slippery from the oils !
It also uses vesicles to transport these fats to other locations in the cell.
Golgi apparatus
Cytoplasm
Golgi apparatus
Golgi apparatus
Nickname: the post office
Function: packages substances into vesicles for transport out of the cell
It is also a network of membrane channels
Often looks like the “wi-fi” symbol in the cell (or a bunch of bananas)
What’s in aPLANT CELL?
Plant cells
Also have:o A nucleus
o Cytoplasm
o A cell membrane
o Mitochondria
o Rough ER
o Smooth ER
o Golgi Apparatus
But they also have some organelles that are found only in plant cells.
Cell wall
Cell wall
Cell wall
Function: supports, strengthens & protects the cell
It surrounds the cell (outside of the membrane)
It is made of cellulose – a complex sugar
It also maintains box-like shape typical of plant cells
Vacuole
Vacuole
Vacuole
Nickname: the “lake”
Function: stores water, nutrients and waste products
It is a large, fluid filled organelle within the cell
A full vacuole means that the cell is more rigid and strong
Chloroplasts
Chloroplasts
Chloroplasts
Function: site of photosynthesis, the process by which the plant uses sunlight to make chemical energy for the cell
Contain chlorophyll (green pigment) that provides the green colour of most plants
They also have a double-membrane
