(B4) Cell Transport Mechanisms Flashcards
Purpose of the cell surface membrane
To maintain the osmotic balance of the internal environmentand control what goes in and out of the cell
Types of Passive Movement
- Diffusion
- Osmosis
- Facilitated Diffusion
Types of Active Movement
Active Transport
Properties of cell membranes
- Partially Permeable
- Flexible
- Fluid
Chemical structure of the cell membrane
- Lipids (phospholipids and cholesterols)
- Proteins
- Carbohydrates (Glycoproteins and glycolipids)
Regions of the phospholipids
- Polar head
- Two non-polar tails
What does polar mean
Hydrophilic, is soluble in water
What does non-polar mean?
Hydrophobic, is non-soluble in water
What are the tails of the phospholipids?
Fatty acid chains
What is the head of the phospholipids?
Phosphate groups
In the fluid mosaic model cell membranes are “fluid” because…
The phospholipids and proteins move around via diffusion
How do the phospholipids move?
Mainly sideways within their own layer
What is facilitated diffusion?
Where certain substances that cannot diffuse through the phospholipid bilayer use proteins to diffuse pass the bilayer
What substances cannot diffuse pass the phospholipid bilayer?
- Large polar molecules such as glucose or amino acids
- Ions such as sodium ions (Na+) or Chloride Ions (Cl-)
What are the types of proteins needed for facilitated diffusion?
- Channel Proteins
- Carrier Proteins
Each individual protein only allows for one type of molecule or ion to pass through
What are channel proteins?
Water-filled pores which allow ions to diffuse pass the cell membranes
How do channel proteins control diffusion?
The channel protein can open and close the pore allowing the protein to control the exchange of ions
What are carrier proteins?
Carrier protein have no fixed shape and can switch between two shapes
What is the benefits of the carrier protein being able to change shapes
Carrier protein can open one side of the membrane to let a molecule in and then change shapes to open up the other other side
What is active transport?
The movement of molecules and ions through a cell membrane from a region of low concentration to a region of high concentration using energy from respiration
What does active transport need?
Energy and carrier proteins
Active transport is important because …
It is used in the reabsorption of useful molecules and ions into the blood after filtration
Forms of Active Transport
- Endocytosis
- Exocytosis
What is endocytosis?
Bulk transport into cells
What is exocytosis?
Bulk transport out of cells
What substances need endocytosis/exocytosis?
- Whole Cells (Bacteria)
- Parts of Cells
- Large Molecules (Proteins or Polysaccharides)
What is phagocytosis?
A type of endocytosis where a molecule is engulfed in a vesicle which moves into the cell
What is pinocytosis?
If the molecule in phagocytosis is a liquid it is pinocytosis
What is osmosis?
The diffusion of water from a area of high concentration to a area of low concentration through a partial permeable membrane
What is diffusion?
The movement of particles from a area of high concentration to a area of low concentration
What is needed for diffusion?
The particle needs to be soluble, not charged and the membrane needs to be permeable
What is equilibrium?
Where the concentration in all regions is the same and net movement is zero
