Animal and plant cells have features in common, such as nucleus, cytoplasm, cell membrance, mitochondria and ribosomes.
Plant and algal celss also have a cell wall, and often have chloroplasts and a permanent vacuole.
Bacterial and yeast cells have different structures to animal and plant cells.
Dissolved substances pass into and out of cells by diffusion.
Function of cells which animal and plant cells hav
Nucleus - contains genetic material, which controls the activities of the cell
Cytoplasm - most chemical processes take place here, controlled by enzymes
Cell membrane - Controls the movement of substances into and out of the cell
Mitochondria - Most energy is released by respiration here
Ribosomes - protein synthesis happens here
However plant cells have extra parts
Extra parts of plant cells
Cell wall - strengthens the cell
Chloroplasts - contain chlorophyll, which absorbs light energy for photosynthesis
Permanent vacuole - filled with cell sap to help keep the cell turgid (swollen and distended or congested)
A bacterium is a single-celled organism.
A bacterial cell has a different structure to an animal or plant cell.
It has cytoplasm, a membrane and a surrounding cell wall.
Genetic material in a bacterial cell is not in the distinct nuclues
Yeast is a single-celled organism.
Like bacterial cells, yeast cells have cytoplasm and a membrane surrounded by a cell wall.
Unlike bacterial cells, yeast cells have a nucleus.
Cells may be specialised for a particular function.
The structure will allow them to carry this function out.
Leaf cell - Absorbs light energy for photosynthesis, packed with chloroplasts. Regular shaped, closely packed cells from a continuous layer for efficient absorption of sunlight.
Root hair cell - Absorbs water and mineral ions from the soil, long 'finger-like' process with very thin wall, which gives a large surface area
Sperm cell - Fertilises an egg cell - female gamete, the head contains genetic information and an enzyme to help pentrate the egg cell membrane. The middle section is packed with mitochondria for energy. The tail moves the sperm to the egg.
Red blood cells - Contains haemoglobin to carry oxygen to the cells, thin outer membrane to let oxygen diffuse through easily. Shape increases the surface area to allow more oxygen to be absorbed efficiently. No nucleus, so the whole cell is full of haemoglobin.
Dissolved substances have to pass through the cell membrane to get into or out of a cell.
Diffusion is one of the processes that allows this to happen.
Diffusion occurs when particles spread. They move from a reigion where they are in high concentration to a region where they are in low concentration.
Diffusion happens when the particles are free to move.
This is true in gases and for particles dissolved in solutions.
Particles diffuse down a concetration gradient, from an area of high concentration to an area of low concentration.
This is how the smell of cooking travels around the house from the kitchen for example.
Examples of diffusion
Location, particles move, from, to
Gut, digested food products, gut cavity, blood in capillary of villus
Lungs, oxygen, alveolar air space, blood circulating around the lungs
- Particles continue to move from a high to a low concetration while there is a concetration gradient
- In the lungs, blood will continue to take in oxygen from the alveolar air spaces provided the concentration of oxygen there is greater than in the blood
- Oxygen diffuses across the alveolar walls into the blood, and the circulation takes the oxygen - rich blood away.