Cell Membranes Flashcards
What is the purpose of the cell membrane?
To enclose the cell organelles and the content of each cell.
What must be transported in and out of the cell respectively?
Nutrients must be able to be transported into the cell. Examples include: oxygen, water and glucose.
Wastes must be able to be transported out of the cell. Examples include: CO2, water, ammonia.
What is the current accepted model of the cell membrane?
The fluid-mosaic model.
Describe the structure of phospholopids.
They have a polar, hydropholic head and a non-polar, hydrophobic tail
Hydropholic: water loving. Hydrophobic: water hating.
What is the phospholopid bilayer embedded with?
- Transport proteins that act as channels that faccilitate movement of subtances in and out of cell.
- Proteins that act as receptors for hormones and signalling molecules.
- Glycolipids and glycoproteins that act as markers on the cell.
- Cholesterol helps maintain fluidity of the membrane.
The movement of substances across the cell membrane can occur in two ways. What are they?
- Passive transport
- Active transport
What are the 3 types of passive transport?
Osmosis, diffusion + faccilitated diffusion
State what passive transport is used for.
Passive transport is generally used for moving substances down their concentration gradient (high to low).
What does active transportation do?
It moves substances up their concentration gradient (low to high). It requires energy in the form of ATP.
What does ATP stand for?
Adenosine Triphosphate.
What is diffusion?
The random movement of substances from areas of high concentration to areas of low concentration.
The difference in concentration creates a concentration gradient.
Let’s say you pour food colouring into a beaker of water. How do the food colouring molecules diffuse?
When the colour is initially introduced to the water, a concentration gradient is produced. Particles of food colouring will diffuse out into the surrounding water (from high concentration to low) until the concentration is uniform, resulting in an even coloured solution.
Define hypotonic and hypertonic.
Hypotonic: less solute, more water.
Hypertonic: more solute, less water
+ Isotonic: equal amount of solute and water.
What is the difference between diffusion and facilitated diffusion?
Small uncharged particles travel through the membrane by diffusion, large charged particles travelled through the membrane by facilitated diffusion. Because they are large they need to be transported through transport proteins.
What are the two ways to define osmosis?
- The movement of water from an area of high water concentration to an area of low water concentration through a semi-permeable membrane.
- The movement of water from an area of low solute concentration to an area of high solute concentration through a semi-permeable membrane.
