cell membrane structure
A fine, semi-permeable membrane made of protein threads and lipids (fats),
cell membrane function
To keep the nucleus and the cytoplasm in the cell but to let other substances, like fats and proteins, out.
It works as a filter between the fluid inside the cell and the tissue fluid outside it.
DIFFUSION
The membrane has tiny holes, or pores, between its proteins and lipids through which small molecules, like oxygen and carbon dioxide, can pass.
Osmosis
Osmosis: the process of transferring water across the membrane by osmotic pressure — when the concentration or pressure of a solution is greater on one side of the membrane, water passes through to that side until the concentration is equal on both sides.
isotonic pressure
When both sides of the membrane have solutions of the same pressure, it is called isotonic pressure
DISSOLUTION
Dissolution (or dissolving): fatty substances are too big to diffuse through the membrane’s tiny pores, so they dissolve into the fatty or lipid part of the membrane.
ACTIVE TRANSPORT
Active transport: when substances are too large to pass directly through the membrane, or are not soluble in fat, a carrier substance in the cell membrane takes them from the outside to the inside.
Glucose and amino acids are both transferred by active transport. It is active because energy is used.
FILTRATION
filtration: the movement of water and soluble substances across a membrane caused by the difference in pressure either side of the membrane.
The force of a fluid’s weight pushes against a surface and the fluid is thus moved through the membrane. This is called hydrostatic pressure which is the process responsible for the formation of urine in the kidneys.
Example of filtration
Waste products are filtered out of the blood into the kidney tubules because of a difference in hydrostatic pressure.
Example of osmosis
The kidneys are a major site of osmosis. Water moves in and out of the kidney structures, called nephrons, in order to help balance out your salt and pH levels. The more water you have in your blood, the more will leave via osmosis in the kidneys. Osmosis also happens in your capillary beds.
Example of dissolution
The structure of the lipid bilayer allows small, uncharged substances such as oxygen and carbon dioxide, and hydrophobic molecules such as lipids, to pass through the cell membrane, down their concentration gradient, by simple diffusion.
NUCLEAR MEMBRANE
Double layered membrane around nucleus
NUCLEUS
Largest cell structure containing chromosomes, DNA and protein. The “control centre” of all cellular activity
Nucleolus
A small body within the nucleus that controls the formation of the ribosomes which then move into the cytoplasm of the cell Golgi apparatus
Mitochondria
Contain enzymes which convert raw materials into energy, power house of the cell
Lysosome
These contain digestive enzymes which digest worn out parts of the cell and bacteria. Break down parts of food to allow them to be used as energy within the cell
Cytoplasm
liquid substance surrounding nucleus within the cell membrane
Centrosome
Dense area of cytoplasm containing the centrioles
Centromere
The centromere is the part of a chromosome that links sister chromatids
Chromosome
This comprises of the cells DNA molecule
Ribosomes
The protein factories of the cell. They product enzymes and other protein compounds used for growth and repair
Vacuoles
Spaces within the cytoplasm. They contain waste material or secretion formed by the cytoplasm and are used for storage or digestive purposes in some cells
Endoplasmic Reticulum
Forms the circulatory system of the cell. They transport the protein made by the ribosomes throughout the cell
Centrioles
These play an important roll in mitosis
