CELL STRUCTURE 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? 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 microscopes became more powerful. When magnified: o The cells are visible. o Smaller structures within the cells are also visible. o The cells can be seen dividing to form new 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 organelles that 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 nucleus that controls all cell functions
Types of cells All animal, plant and fungi cells are eukaryotic But there are still some 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 We use our organs & organelles! But how???? So can all of our cells!!!!
What s in an ANIMAL 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, O 2, CO 2, 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 Vesicles Smooth endoplasmic reticulum Rough endoplasmic reticulum
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 Golgi apparatus Cytoplasm
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 a PLANT 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