Year 10 Biology mocks

Cells are either PROKARYOTIC or EUKARYOTIC;

Prokaryotic cells  are smaller and simpler, e.g. bacteria

Eukaryotic cells are complex and include all animal and plant cells

Most animal cells have:

• Nucleus - contains genetic material that controls the activities of the cell
• Cytoplasm - where most of the chemical reactions happen. Contains enzymes
• Cell Membrane - holds the cell together and controls what goes in and out
• Mitochondria - most reactions for aerobic respiration take place here. Respiration transfers energy that the cell needs to work
• Ribosomes - where the proteins are made in the cell

Plant cells usually have all the parts animal cells have, plus a few extra;

• Rigid cell wall - Made of cellulose. Supports and strengthens the cell
• Permanent vacuole - contains cell sap
• Chloroplasts - Where photosynthesis occurs. Contains a green substance called chlorophyll which absorbs the light needed for photosynthesis

Microscopy - MAGNIFICATION = IMAGE SIZE/ REAL SIZE

Photosynthesis = CARBON DIOXIDE + WATER -> GLUCOSE + OXYGEN

Prokaryotic cells can reproduce using binary fission.

In binary fission, the cell splits in two:

• The circular DNA and plasmids replicate
• The cell gets bigger and the circular DNA strands move to the opposite 'poles' of the cell
• The cytoplasm begins to divide and new cell walls begin to form
• The cytoplasm divides and two daughter cells are produced. Each daughter cell has only one copy of the circular DNA but can have a variable number of of copies of the plasmids

• Sperm cells: It has a long tail and a streamlined head to help it swim to the egg. Lots of mitochondria in the cell to provide the energy needed. It also has enzymes to digest through the egg membrane.
• Nerve cells: Their function is to carry electrical signals from one area of the body to another. These cells are long and have branched connections at their ends to connect to other nerve cells and form a network throught the body
• Muscle cells: Muscles cells are specialised to contract quickly. These cells are long (so they have to contract) and contain lots of mitochondria to generate the energy needed for contraction
• Root hair cells: They are cells on the surface of plants roots, which grow into long 'hairs' that stick out into the soil. This creates a bigger surface area for absorbing water and mineral ions from the soil
• Phloem and Xylem cells: The create phloem and xylem tubes, which transport substances such as food and water around the plant. To form the tubes the cells are long and joined end to end. Xylem cells are hollow in the centre and phloem cells have very few subcellular structures so that things can flow through them

Differentiation is the process by which a cell changes to become specialised for its job.

As cells change, the develop different subcellular structures and turn into different types of cell. This allows them to carry out specific functions. 

In most animal cells, the ability to differentiate is lost at an early stage, after the've become specialised. However, lots of plant cells don't ever lose this ability.

The cells that differentiate in mature animals are mainly used for repairing and replacing cells, such as skin or blood cells. 

Some cells are undifferentiated cells - they're stem cells.