2.3 | Cell Requirements | Year 11 HBIO Flashcards
What’s another name for the cell membrane?
The plasma membrane.
What does the cell membrane do?
It encloses the contents of the cell and controls what is able to enter and leave.
Why is the cell membrane thin?
It allows for diffusion to readily occur.
What is the cell membrane made of?
A phospholipid bilayer.
Define selective permeability.
Where some substances can go through a membrane easier than others.
What are phospolipid molecules made of?
Lipid molecules containing a phosphate group.
Which substances can’t diffuse through the cell membrane and why?
Most water-soluble substances.
(excl. Oxygen and Carbon Dioxide)
List 3 functions of the cell membrane.
- It acts as a physical barrier.
- It regulates the passage of substances.
- It supports the cell.
Define macromolecule.
A very large molecule important to biological processes.
Give an example of a macromolecule.
Protein.
What do transport proteins do?
Regulate the movement of water-soluble substances in and out of the cell.
What are the two types of transport proteins?
- Channel proteins (aka ion channels)
- Carrier proteins
What is the function of a channel protein?
To provide a channel for water-soluble substances to cross the cell membrane.
What is the function of a carrier protein?
To allow certain specific substances to cross the cell membrane.
(Carrier-mediated transport)
What’s the difference between channel proteins and carrier proteins?
One creates open channels that allow for facilitated diffusion
The other binds to molecules and changes shape to deliver it across the membrane.
What is passive transport?
The transport of substances in and out of the cell without the use of energy.
Give an example of passive transport.
Diffusion.
What is active transport?
The movement of substances in and out of a cell with energy.
What is facilitated diffusion?
The process where proteins allow diffusion of molecules, bypassing the membrane.
What is facilitated transport?
Where proteins (channel and carrier) allow molecules to be transported across the membrane.
What are the types of active transport?
- Facilitated transport
- Vesicular transport
What is diffusion?
The tendency for particles to move from an area of higher contentration to an area of lower concentration.
Occurs in gases and liquids
(Diffusion is passive, meaning it does not use energy.)
Define permeable.
(of a membrane) allowing substances to pass through
Define Osmosis.
The diffusion of water across a selectively permeable membrane.
(Like diffusion, osmosis is passive, meaning it does not use energy.)
Define hypotonic.
having a lower solute concentration
Define hypertonic.
Having a higher solute concentration.
Define isotonic.
An area of water with an even distibution of water molecules.
(e.g. after diffusion has finished)
Give an example of a non-permeable substance.
Sucrose.
What happens if a cell is inside a hypotonic solution?
The cell will become lysed and expand due to osmosis.
Which molecules can’t fit into protein channels?
Large (macro)molecules.
(e.g. Glucose)
What is a diffusion/concentration gradient?
The difference in concentration between the area of high concentration and the area of lower concentration.
What is an example of active transport?
The Na/K (sodium-potassium) pump.
(extra information)
Define vesicular transport.
The movement of substances in vesicles into, out of, or within the cell.
(VT is active, meaning it uses energy.)
What are the types of vesicular transport?
Endocytosis and exocytosis
What is endocytosis?
The process of taking liquids into the cell by vesicular transport
What are the two different types of endocytosis?
- Phagocytosis
- Pinocytosis
Explain endocytosis.
- The cell membrane folds around a droplet of external substance
- It then pinches off and forms a vesicle within the cell.
Define Phagocytosis.
When endocytosis brings a solid into the cell.
Define Pinocytosis.
When endocytosis brings a liquid into the cell.
What is exocytosis?
When the contents of a vesicle within the cell is passed back outside the cell.
Explain the process of exocytosis.
- A vesicle inside the cell contacts the cell membrane and fuses with it.
- The contents of the vesicle are then blown back out into the extracellular fluid.
