Unit 2 Exchange and Transport Flashcards
What are plasma membranes?
Plasma membranes are the combination of all membrane within the cell and the within organelles that have the same basic structure
Describe the cell-surface membrane?
The specific name given to the membrane that surrounds all the cells and its cell membrane as well as creating a barrier between the cytoplasm and the environment outside the cell
Describe the function of the cell-surface membrane?
It established different conditions inside and outside the cell as well as controlling the movement of substances inside and outside the cell
What are the component of the cell-surface membrane?
Phospholipids, proteins, cholesterol, glycolipids and glycoproteins
Give 2 reasons why phospholipids are important for the cell-surface membrane?
1) The hydrophilic heads of the phospholipids point outwards towards the cell-surface membrane attracted by water on both sides
2) The hydrophobic tails of the phospholipids point into the cell-surface membrane repelled by water on both sides
Through which portion do lipid-soluble substances enter the cell-surface membrane?
Lipid-soluble substances enter the cell-surface membrane via the phospholipid portion
What are the 3 functions of the phospholipids in the cell-surface membrane?
1) Allow the entry/exit of of lipid-soluble substances
2) Prevention of water-soluble substances entering or leaving the cell
3) Making the cell membrane flexible and self-healing
Where are proteins found within the cell-surface membrane?
They are interspersed throughout the whole cell-surface membrane
What is the 1st way proteins are interspersed throughout the cell-surface membrane?
Some proteins occur in the surface of the phospholipid bilayer and never extend across so they give mechanical support to the membrane, conjunctions with glycolipids and acts as cell receptors for hormones
What is the 2nd way proteins are interspersed throughout the cell-surface membrane? (1)
Other proteins completely span across the phospholipid bilayer. 1 type is called protein channels - water filled tubes to allow water-soluble ions to diffuse across the membrane
What is the 2nd way proteins are interspersed throughout the cell-surface membrane? (2)
2nd type is carrier proteins - bind to other molecules such as glucose and amino acids and these carrier proteins change in shape in order to move the molecules along the membrane
What are first 3 roles of the proteins along the membrane?
cp - carrier proteins
1) Provide structural support
2) Act as channels to transport water-soluble substances along the membrane
3) Allow active transport across membrane - cp
What are last 3 roles of the proteins along the membrane?
cp - carrier proteins
4) To form cell surface receptors for identifying cells
5) To help cells adhere together
6) Act as receptors for hormones
Where are the cholesterol molecules in the membrane?
Cholesterol molecules within the phospholipid bilayer of the cell-surface membrane
What does cholesterol add to the membrane?
Cholesterol adds strength to the membrane by pulling the hydrophobic tails of phospholipids together
What is the relation between cholesterol and water?
Cholesterol is a very hydrophobic molecule and so they help prevent loss of water and dissolved ions from the cell
What is an additional function of cholesterol in relation to structure?
Cholesterol also pulls together fatty acids tails of the phospholipid molecules which limits their movement as well as other molecules’ movement as well but at the same time allows the membrane not to be too rigid
What are the 3 main roles of cholesterol?
1) Reduces lateral movement of other molecules including the phospholipids
2) Makes the membrane less fluid-like at high temperatures
3) Prevent leakage of water and other dissolved ions
What is the definition of a Glycolipid?
Glycolipids are a carbohydrate covalently bonded with a lipid
Describe where the glycolipid is around the phospholipid bilayer?
Glycolipids portion extends from the phospholipid bilayer into the watery environment outside the cell in which acts as a cell-surface receptor for specific chemicals.
Give an example of a system that relies on the glycolipids on the cell-surface membrane as a receptor?
The human ABO system operates as a result of glycolipids on the cell-surface membrane
What are the 3 main roles of Glycolipids?
1) To act as a recognition sites
2) To help maintain the stability of the membrane
3) Help cells to attach to one another and form tissues
What are Glycoproteins?
Glycoproteins are Carbohydrate chains attached attached to many extrinsic proteins on the outer-surface of the cell membrane
What is a function of the Glycoproteins?
Glycoproteins act as cell-surface receptors mainly for hormones and neurotransmitters