preview

The Cells And The Cell Membrane

Good Essays
T1.

All species of fungi, plants and animals are formed from eukaryotic cells. The Eukaryote have a true nucleus; their DNA is confined to a definite area within the cell enclosed by a Nuclear envelope. Prokaryotes evolved before eukaryotic cells and their cells do not have a true nucleus. Prokaryote DNA is not enclosed by a membrane.

ORGANELLE STRUCTURE FUNCTION PLANT OR ANIMAL
Nucleus Within the cell membrane Site of the nuclear material-the DNA both
Nucleolus Inside nucleus Manufacture of ribosomes both
Mitochondrion Numerous in cytoplasm. Up to 1000 per cell. Aerobic respiration both
Rough endoplasmic reticulum Continuous throughout cytoplasm Isolation and transport of newly synthesised proteins Both both Smooth endoplasmic
…show more content…
These compartments allow the chemicals involved in a particular process in the cell, such as photosynthesis or respiration to be kept separate from the rest of the cytoplasm. This cell structure and high degree of internal organisation optimizes essential chemical reactions, and allows the processes within the cell to function. The fluid that occupies the space between the organelles is called the cytosol, a solution containing a complex mixture of enzymes, amino acids and waste materials.

T2. The cell surface plasma membrane covers the outside of a cell, and this is a double-layered sheet of phospholipid molecules interspersed with proteins. It separates the cell from the outside environment; this protects the cell, and allows the import and export of selected chemicals.

1Phospholipds are the main component of cell membranes. They naturally form membranes in water because they automatically arrange themselves into a bilayer that is almost impermeable to water and to water soluble substances. The membrane keeps the cell contents in and other substances out. There is however a need for selective transport into and out of a cell and the cell does this through membrane proteins.
2 Membrane proteins act as hydrophilic pores, water filled channels that allow water soluble substances to pass through. These pores are small and
Get Access