Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
32 Cards in this Set
- Front
- Back
- 3rd side (hint)
|
What are cell membranes also known as? |
Plasma membranes |
|
|
|
Give 3 ways that substances can get through the membrane |
1) Some very small molecules simply diffuse through the cell membrane in between the structural molecules 2) Some substances dissolve in the lipid layer and pass through 3) Other substances pass through special protein channels or are carried by carrier proteins |
|
|
|
Name 7 roles of the membrane |
1) Separates the cell components from its external environment 2) Regulates transport of materials into and out of the cell 3) May contain enzymes involved in specific metabolic pathways 4) Has Antigens so that the organisms immune system can recognise the cell as being 'self' and not attack 5) May release chemicals that signal to other cells 6) Contains receptors so it is the site for cell communication or signalling 7) May be the site of chemical reactions |
|
|
|
Mitochondria have folded inner membranes what is it called and why do they have it? |
It is called cristae and it gives a large surface area for some of the reactions of aerobic respiration. |
|
|
|
Chloroplasts have inner membranes what is it called and why do they have it? |
It is called thylakoid. On these membranes some of the reactions of photosynthesis occur |
|
|
|
Why is it called 'the fluid mosaic model'? |
It is because it makes up a mosaic pattern and the lipid molecules can change places with each other and some of the proteins may move giving fluidity |
|
|
|
Draw the structure of the fluid mosaic model |
|
|
|
|
Give me two properties of phospholipids |
1) The main part of the membrane forming a barrier to dissolved substances 2) The centre of the bilayer where is hydrophobic so water soluble substances like ions can't pass through it |
|
|
|
Give me three properties of cholesterol |
1) Gives the membrane stability as without it the cell will burst 2) Present in all membranes except bacteria 3) They bind to the hydrophobic tails causing them to pack more closely together this makes the membrane less fluid and more rigid |
|
|
|
Give me four properties of proteins |
1) Most are involved in transport across the membrane others act as enzymes (a biological catalyst) 2) Some form channels these allow small or charged particles through 3) Carrier proteins transport molecules and ions by active transport or facilitated diffusion 4) The act as receptors for molecules. |
|
|
|
Give me three properties of glycoproteins and glycolipids |
1) These are formed when carbohydrate chains attached to a phospholipid or protein. 2) Act as sites for cell recognition also form weak hydrogen bonds with surrounding water to help stabilise the cell. 3) They're also antigens cell surface molecules involved in the immune response. |
|
|
|
What is a size of a cell membrane |
7 - 10nm |
|
|
|
Explain what is meant by the term cell signalling |
A way for cells to communicate with one another to bring about a response |
|
|
|
Outline the 3 steps of cell communication |
1) One cell releases a molecule EG hormone 2) The hormone travels through the blood to get to the other cell 3) The cell detects the hormone which then binds to a receptor on its cell membrane |
|
|
|
What is a membrane bound receptor? |
It is a protein in the cell membrane which acts as a receptor for messenger molecules |
|
|
|
What is a target cell? |
A cell that response to a particular messenger molecule |
|
|
|
Why would a receptor protein have a specific shape? |
It is so that only messenger molecules of a complementary shape can bind to them |
|
|
|
How are drugs involved in cell signalling? |
Drugs can also bind to receptors so that they could trigger a response or block the receptor to prevent it from working. |
|
|
|
How does the temperature below zero degrees affect the membrane permeability |
Phospholipids have very little energy to don't move very much Channel proteins and carrier proteins deform increasing permeability Phospholipids are closely packed together and the membrane is rigid An ice crystal may form and pierce the membrane so it leaks |
|
|
|
How does the temperature between 0 and 45 degrees affect the membranes permeability? |
Phospholipids can move around so they're not packed as tightly making the membrane partially permeable Therefore the more energy phospholipids have the more they move and the more permeable they are |
|
|
|
How does the temperature above 45 degrees affect the membranes permeability? |
The phospholipid bilayer breaks down becoming more permeable. Water inside the cell expands putting pressure on the membrane. Channel proteins and carrier proteins deform so they can't control what enters or leave the cell. |
|
|
|
How can changing the solvent affect the membranes permeability? |
Surrounding cells in a solvent eg. Ethanol increases permeability this is because the solvent dissolves the lipids in the cell membrane so it loses its structure. Some solvents increase cell permeability more than others increasing the concentration of the solvent will also increase the membrane's permeability |
|
|
|
What is diffusion? |
Diffusion is the net movement of particles from an area of high concentration to an area of lower concentration |
|
|
|
How does small, non polar molecules transport across the cell membrane? Name 2 examples and the exception |
They are able to diffuse easily free spaces between the phospholipids Examples include oxygen and carbon dioxide Water is also small enough to fit between phospholipids even though it is polar |
|
|
|
What is facilitated diffusion? |
It is diffusion that moves particles down a concentration gradient using carrier proteins and channel proteins being a passive process so it doesn't use energy |
|
|
|
How does large molecules pass through the cell membrane? |
These use carrier proteins going down a concentration gradient A large molecule attaches to the carrier protein, the protein changes shape releasing the large Molecule on the opposite side |
|
|
|
How do ions pass through the membrane |
Uses channel proteins going down a concentration gradient |
|
|
|
What is active transport? |
Uses energy in the form of ATP to move molecules and ions against the gradient, this process involves carrier proteins |
What does it involve? |
|
|
What is bulk transport and name the two types? |
Where large quantities of materials enter and exit a cell being n active process Two types: Endocytosis (enter), Exocytosis (exit) |
|
|
|
Explain why endocytosis is used and Name the steps of endocytosis? |
Some molecules are way too large to diffuse through the Channel or carrier proteins so energy is used to pass them through 1) Surrounds the substance with a section of the its plasma membrane 2) The membrane then pinches off to form a vesicle inside the cell |
Is energy used? |
|
|
Explain why exocytosis is used and name the steps |
Substances produced by cell eg. Digestive enzymes, hormones and lipids needs to be released 1) Vesicles containing substances pinch off from the sacs of the Golgi apparatus to move towards the cell membrane 2) Vesicles fuse with the plasma membrane and release the contents Some substances are inserted straight into the plasma membrane |
Where can some of the substances go straight into? |
|
|
Describe the whole process of bulk transport |
1) The membrane folds inwards it can then fuse at the top pinching of a vesicle 2) The vesicle moves through the cell where lysosomes fuse to them 3) They release enzymes into the vesicle to break down the contents. 4) The 'good stuff' diffuses into the cell 5) The vesicle fuses with the cell membrane and the 'bad stuff' is ejected |
|
