unit 1

All living things are made up of cells. The structures of different types of cells are related to their functions. Animal cells and plant cells have features in common, such as a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes. Plant and algal cells 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.

Animal and plant cells Function of cells which animal and plant cells have in common Part FunctionNucleus Contains genetic material, which controls the activities of the cellCytoplasm Most chemical processes take place here, controlled by enzymesCell membrane Controls the movement of substances into and out of the cellMitochondria Most energy is released by respiration hereRibosomes Protein synthesis happens here Plant cells also have extra parts: Extra parts of plant cells Part FunctionCell wall Strengthens the cellChloroplasts Contain chlorophyll, which absorbs light energy for photosynthesisPermanent vacuole Filled with cell sap to help keep the cell turgid Make sure you can label diagrams of animal and plant cells, like these: 

Generalised animal and plant cell

Bacterial cells and yeast Bacterial cells Structure of a salmonella bacterium cell 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, but the genetic material in a bacterial cell is not in a distinct nucleus. Yeast Yeast is a single-celled organism. Like bacterial cells, yeast cells have cytoplasm and a membrane surrounded by a cell wall. But unlike bacterial cells, yeast cells have a nucleus.

Diffusion 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 region 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 concentration 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.

Specialised cells Cells may be specialised for a particular function. Their structure will allow them to carry this function out. Here are some examples: Examples of the functions of cells Cell Function Adaption Leaf cell Absorbs light energy for photosynthesis Packed with chloroplasts. Regular shaped, closely packed cells form 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 penetrate 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. You are likely to be given information, perhaps in a diagram, to help you to explain the adaptations of a particular cell type to its function.

intro

Animal and plant cells

Bacterial cells and yeast

Specialised cells

Diffusion