Cell Membranes Flashcards
Intracellular
Inside the cell
Extracellular
Everything outside the cell
Intersitial
Is another term for outside the cell.
-Especially used when many cells are together
What makes up the membrane of a cell?
Phospholipids are the basic structure of a membrane.
Phospholipid Bylayer
Two layers of phospholipids with the lipid tails facing each other.
Why is Cholesterol a necessary component of the Cell Membrane?
- It helps loosen the membrane
- Maintains membrane fluidity and strength
How do proteins help the membrane?
They make the membrane functional.
Transport Proteins
Transports stuff across the cell membrane
- Inside to outside and outside to inside
- very specific, they will only let one thing through
Receptor Proteins
A signaling molecule binds to the receptor outside the cell membrane and on the other side the signal is taken and does something within the cell membrane.
-Very specific
Membrane Bound Enzyme
Help carry out chemical reactions within or without the cell membrane.
Recognition Proteins
It is often a Glycoprotein
- they tag on cells like a finger print saying I am this kind of cell.
- So cells know what kind of cell it is.
Cell Adhesion Molecules
Hold cells together
Tight Junctions
Holding the cell membranes together, so tight that no extracellular fluid can get through.
Desmosomes (Spot or Adhering Junctions)
Proteins hold the cell together with rivets, so extracellular fluid can slip between the membranes.
Gap Junctions
Form a channel between membranes.
- Specialized form of cell communication.
- The extracellular fluid passed through
- -All the cells of the heart are linked this way.
Membrane Transport
Moving things across the membrane.
- Membranes are semi-permeable
- -Membranes will let somethings through easily, some with difficulty, and some not at all.
Factors Effecting Membrane Permeability
Solubility- (fat solubility) if it is fat soluble it can slip across (oxygen)
Size- If it is to big it can’t go through. It needs to be smaller.
–If it is unsaturated phopholipids it can have more pass through them than saturated.
Membrane transport based on passive forces mean
No energy needed to move it across the membrane.
- Diffusion
- Osmosis
- Electrical
Diffusion
Random movement of particles
- Movement of a solute from an area of high concentration to an area of lower concentration
- Until they reach equilibrium
- The concentration difference/gradient is what drives diffusion.
Simple Diffusion
Going through the membrane
Facilitated Diffusion
Going through proteins, so they can slip through. No energy needed.
What is the diffusion rate driven by?
The gradient
Factors affecting net rate of diffusion
- Concentration Gradient
- Temperature
- Area
- Size
- Distance
Concentration Gradient on diffusion rate
Bigger concentration gradient faster it goes through. Lower concentration gradient slower it goes through.
Temperature on diffusion rate
Higher temperature, higher diffusion rate. Lower temperature lower diffusion rate.
Area on diffusion rate
The space they have to diffuse. Bigger area faster rate of diffusion, smaller area slower rate of diffusion.
Size on diffusion rate
The bigger something is the slower the diffusion rate will be.
Distance on diffusion rate
How far something has to travel. The greater the distance the slower the rate of diffusion.
Osmosis
The Movement of Water
- Water molecules move from areas of low solute concentration to areas of high solute concentration.
- The solute is to big to move, so the water moves through instead to equalize the solution.
Osmotic Pressure/Potential
To move water molecules.
-The water is moving over to the high concentration to dilute the solution bringing them to equilibrium.
Aquaporins
Protein channel to let water through.
Tonicity
The concentration of a solution compares to what is inside your cell.
Isotonic Solution
This solution is the same tonicity as your cells.
-No osmotic pressure created
Hypertonic Solution
The solution has a higher concentration than the cell.
- Through osmosis the water will move out of the cell to create equilibrium.
- Causing the cell to crenate (shrink)
Hypotonic Solution
The solution has a lower concentration than the cell.
- Water will be drawn into the cell. Making the cell swell.
- If the difference is big enough it will cause the cell to burst. (Lyse/Lysis)
Electrical (membrane transport)
Passive movement requiring no energy.
- the movement of ions.
- difference in charges between 2 areas produces an electrical gradient that passively causes movement.
- the forces of same charges trying to spread out will make it pass through the cell membrane.
- -more powerful than something without a charge in diffusion.
Electrochemical Gradient
- All cells have one
- They all have different amounts of ions on the outside and inside.
- Some cells use this to do what they do.
Membrane Transport based on Active Processes
- Molecules which are impermeable because the are large, poorly lipid soluble.
- Going against a concentration gradient
- Active Transport–Pumps
- Bulk Transport
Active Transport– Pumps
- Proteins that pump/push something through using energy to do it.
- Moving something across/against the concentration gradient.
- Very helpful in moving against the concentration gradient.
What is a common protein pump?
Na+/K+ pump
Na+/K+ Pump
Always pumps 3 Na+ out of the cell and pumps 2 K+ into the cell.
What are the 3 Kinds of Bulk Transport?
Phagocytosis
Pinocytosis
Receptor-Mediated Endocytosis
Phagocytosis
The Membrane reaches out and grabs what it needs and closes around it pulling the vesicle into the cell.
-Big items normally
Pinocytosis
The Membrane dimples in around what it needs and comes together and brings it into the cell.
Receptor-Mediate Endocytosis
Receptors tell the cell to bring something in.
Endocytosis
To bring into the cell.
Exocytosis
Sending something out of the cell.
-Vesicles fuse to the membrane and the membrane opens and dumps what is in it outside the cell.
