Cell Biology

All living organisms consists of cells. All cells have the following structure:

• Cell membrane - lets through water (most important) and other substances in solution. Larger molecules are unable to pass through it, so its partially permeable.
• Cytoplasm - consists of the nucleus and where all the metabolic reactions take place.
• Nucleus - contains a number of chromosomes, large made of the chemical, DNA. Chromosomes consists of genes - responsible for programming the cytoplasm to produce certain proteins.

When cells undergo mitosis, chromosomes form exact replica (copy) of itself.

Plant cells have the following structure:

• Vacuole - containing cell sap. Separated from the cytoplasm by the vacuolar membrane.
• Cell Wall
• Chloroplasts - contains chlorophyll (magnesium is an important component of it)
• May store starch

Animal cells structure do not consists of any of the above components.

Unicellular organisms have one cell to carry out all the functions of the organism (eg.bacteria). Multicellular organisms have cells that are modified to carry out one main function.

Thus, there is a relationship between structure and the particular function of a cell.

Root Hair Cell: The outer part of its cell warm forms a long, turbulent extension to absorb and water and salts from the ions.

• Able to form a close contact with the water film surrounding the soil particles.
• Gently increases the surface area of the cell; available for the uptake of water, ions & oxygen (for respiration).

Xylem Vessels: Long narrow tubes, streching from the roots, via the stem to the leaves.

• Conducts water & ions from roots to other parts of the flower - the walls of xylem vessels have been strengthened by the addition of chemical, lignin. Kills xylem vessels. No layer of cytoplasm to restrict the flow of water & ions.
• Are parts of the vascular bundles. Runs through the stem of plants - restricts the bending strains caused by the wind.

Red Blood Cells: Carries oxygen around the body

• Contains the pigment haemoglobin - combines with oxygen to form oxyhaemoglobin
• Small - provides a large surface area for the absorption of oxygen
• Bi - concave shape - increases the surface area
• Flexible - allows it to be easily pushed through blood capillaries

• Cells
  
• Tissues
• Organs
• Organ Systems
• Organisms