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Why do cells differentiate?
To become specialised in structure to suit the function that they will carry out
Root hair cells - structure
Large SA to absorb a lot of water
Thin cell wall to allow water to pass through easily
Doesn’t contain any chloroplasts unlike all other plant cells
Root hair cells - function
Absorbs minerals and water from the soil
Xylem vessels cells
Xylem cells die during their development and their top and bottom cell walls disintegrate, forming long, empty vessels
They are very rigid because of hard lignin in their thick side walls, allowing them to withstand high water pressure and support the plant
Phloem vessel cells
Sieve cells that have a large central channel for sugar to flow through. Forms sieve tubes in the phloem tissue
Connected together by holes in the cell wall to allow sugar to flow through to the neighbour sieve cells
Companion cells that are alongside the sieve cells
They actively pump sucrose into/out of the sieve cells. Pumping in increases the pressure and causes the sucrose to flow either up or down to where it is needed
White blood cells - structure
Large nucleus
Can change shape to engulf pathogens
White blood cells - function
Found in our blood
They are attracted to pathogens that enter our body
Some white blood cells engulf any bacteria/disease they encounter so the microbe cannot infect you and make you ill
Other white blood cells produce antibodies that attach to pathogens making it easier for other white blood cells to engulf them
Nerve cells (neurones) - structure
Very long cells
They have axons at one end and dendrons at the other to connect to other nerve cells
The long axis (main branch) is covered in fat to insulate the electrical impulses, speeding up the messages
Nerve cells ( neurones) - function
To carry nerve impulses (messages) around the body
Sperm cells - structure
Long tail (flagellum) so they can swim to find an egg
Lots at mitochondria that create energy for movement
Made in the testes of males
Pointed head to burrow into the egg
Smallest human cell
It has half of the normal number of chromosomes
Sperm cells - function
To carry the father’s genetic information (DNA) and fuse (fertilise) the egg cell
What do epithelial cells in the intestine do?
They absorb nutrients effiiciently
What are the epithelial cells adaptations?
Lots of villi on the walls which increase the surface area for absorption, therefore a faster rate of absorption
Microvilli which increase the SA even more
Lots of mitochondria to provide energy for the transport of digested food molecules into the cell
Ciliated epithelial cells - structure
Cells that line the air passages
Tiny hair called cilia
Ciliated epithelial cells - function
Prevent lung damage
Cilia sweep mucus with trapped dust and bacteria back up the throat to be swallowed and destroyed by acid in the stomach
Tobacco smoke destroys cilia, causing the mucus to build up, leading to smoker’s cough
Egg cells - structure
Many mitochondria and nutrients in the cell to provide energy to the developing embryo
The largest human cell
It has a thick wall, that is broken down by enzymes in sperm, but hardens once a sperm gets in, so no more can enter
It has half the normal number of chromosomes
They cannot divide
Egg cells - function
Fuses with a sperm cell and carries the mother’s DNA
Red blood cells - structure
No nucleus, which increase the surface area
Contain haemoglobin which picks up oxygen and converts it to oxyhaemoglobin for transport
Dimpled shape (biconcave disc), which increases the surface area for oxygen absorption
Red blood cells - function
Carry oxygen from the lungs to the body
What is a tissue?
A group of similar cells with a common origin that perform a specific function
What are the 4 types of tissues?
Connective tissue
Muscular tissue
Epithelial tissue
Nervous tissue
Epithelial tissue
Covering and lining epithelium
Found on all surfaces (e.g. skin, blood vessels)
Consists of sheets of cells
Lines the surface of organs
Protective or secretory function
Many similar types
What is an organ?
A group of tissues that work together to carry out a specific function
Stomach
Connective tissue to hold together the other tissues
Muscle to churn and mix the stomach contents
Epithelium to protect the stomach wall and produce secretion
Leaf
Palisade mesophyll made up of leaf palisade cells
Spongy mesophyll adapted for gaseous diffusion
Epidermis to protect the leaf and allow gaseous diffusion
Phloem to transport organic materials away from the leaf
Xylem to transport water and ions into the leaf
What is an organ system?
A group of organs that work together to carry out a specific function
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