0226 - Cell Biology 1 - EG Flashcards
Describe the structure of the cell membrane.
Essentially a phospholipid bi-layer, with hydrophobic tails orientated on the inside and hydrophilic heads on the outside, however on electron microscope (e/m) shows as three layers (tri-laminar structure), with an internal space between the phospholipid heads representing 2x hydrophobic tails. It is a fluid membrane.The external cell membrane is also known as the plasmalemma.
What are the functions of the cell membrane?
To act as an interface between the intracellular and extracellular, for the compartmentalisation of organelles, and provides large surface area.
List the various types of integral proteins of cell membranes and what they allow.
- Channels - passive diffusion of small molecules.2. Pumps - require energy to transport ions, amino acids, sugars.3. Receptors - for recognition and binding of ligands, hormones.4. Linker proteins - anchor cells to the extracellular matrix.5. Structural proteins - attach to neighbouring cells.6. Enzymes.6.
Describe the nucleus of the cell.
The largest organelle within the cell, visible on light microscopy. Has a double membrane with nuclear pores. Contains DNA.
Describe ribosomes.
Small round dense particles of 3nm diameter, found on the outer edge of the nuclear envelope or bound to the endoplasmic reticulum. Involved in the synthesis of proteins from mRNA.
Describe endoplasmic reticulum.
A network of interconnected tubules that runs from the nuclear envelope to the Golgi apparatus. rER (rough ER) contains ribosomes and is involved in the synthesis of proteins. sER (smooth ER) is involved in the synthesis of lipids and metabolic functions.
Describe the Golgi apparatus.
Structure similar to stacked pancakes with bulbous edges. Functions to modify and pack proteins into granules for secretion, to synthesis sialic acid and galactose and polymerisation of proteoglycans to create more complex structures, such as hyaluronic acid, and to assemble membranes for internal use.
Describe lysosomes.
Cytoplasmic vesicles, 250-750mn in size, containing hydrolytic enzymes (proteases, lipases, nucleases at low pH), bounded by a membrane. Function as “digestion system of a cell”.
Describe peroxisomes.
Similar to lysosomes, but enclose oxidase enzymes and use alkaline conditions. The end product of their reactions is hydrogen peroxide.
Describe mitochondria.
Double membrane organelles where the inner membrane is folded into cristae. Function in oxidative phosphorylation with the end product of ATP. The higher the energy requirements of the cell, the more mitochondria present. Contain specific DNA (mDNA)not replicated in the nucleus obtained by maternal inheritance.
