Cell Membrane (PPT 5-7) (U1) Flashcards
About how thick is the plasma membrane?
- Around only 8nm thick
nm= nanometers
The function of the cell membrane is too…
- Isolate the cytoplasm from the external environment.
- Control what moves in and out of the cell.
- Cell to cell recognition.
What cells have a cell wall?
- Bacteria
- Fungi
- Plant
What is the membranes structure?
Hint= Fluid mosaic model
A double layer of phospholipids which are arranged with the hydrophobic tails facing inwards.
The double layer is fluid, with proteins floating within it.
Glycoproteins, glycolipids and cholesterol are an integral part of the membrane structure.
Define Hydrophobic and Hydrophilic?
Hydrophobic= Water hating end
Hydrophilic= Water loving end.
Why is it fluid mosaic?
Fluid because the components can move
Mosaic because the proteins embedded create a mosaic tile look.
Phospholipids create a —– to —— soluble ——-. (Fill in the blanks).
1- barrier
2- water
3- molecules
What type of molecules will Phospholipids let through the membrane?
- Lipids (as they are soluble in lipids)
- Hydrophobic molecules. (Water hating)
—— molecules like —– cannot cross. (fill in the blank)
1- Large
2- Proteins.
Are phospholipids stationary?
No, they can move and do so frequently.
It is the phospholipids ability to —- that makes the membrane fluid. This is crucial because ————? (Finish the sentence)
1- move
2- it allows the embedded proteins to move where they are required.
What does semi-permeable mean?
Semi-permeable means they allow some things through, but not all.
What are the two types of membrane proteins?
1- Integral proteins (transverse the membrane)
2- Peripheral proteins (stuck on the inside or outside of the membrane)
What is the structure and function of Integral proteins?
S= Generally span both phospholipid layers.
F= Transport of molecules. Signal transduction Cell to cell communication Joining of cells Anchorage (attachment to cytoskeleton).
Glycoproteins and glycolipids are a… (finish the sentence)
Short chain of carbohydrates attached to proteins and lipids on extracellular side of the membrane.
What is the structure and function of Cholesterol molecules?
S= Within the phospholipid layers, providing stability without affecting its fluidity.
F= Increase strength. Increase flexibility, Increase the rigidity of the membrane.
Assist with changing temperatures.
Membranes are also found ——- ———– cells as part of the ——- of membranous ———. (Fill in the blank)
1- within
2- eukaryotic
3- structure
4- organelles
What are the two ways substances are moved across the plasma membrane?
- Passive (not requiring energy)
- Active (energy requiring)
Give examples of passive transport.
- Diffusion
- Facilitated diffusion
- Osmosis
Give examples of active transport.
- Ion pumps
- Cytosis
What is diffusion?
- Diffusion is a passive transport process, does not require energy.
- The movement of molecules from high concentration to low concentration. (Across the concentration gradient).
Each type of diffusing molecule moves across….
Its own concentration gradient. The bigger this concentration, the faster the diffusion.
What is facilitated diffusion?
- When a substance is aided across a membrane by selective protein channels.
What is the upside to facilitated diffusion?`
- Transport is quicker than diffusion.
- The channels are specific for particular molecules.
- Does not require energy.
What is the downside to facilitated diffusion?
- The channels can become saturated as the concentrations of the transported substances increase
- Transport of one substance is stopped by another as they compete for a channel.
What is Osmosis?
- The net movement of water molecules across a partially permeable membrane from high to low concentration.
What does Isotonic mean? (hint, Osmosis)
- No net movement of water between the cell and environment because the water concentrations are equal.
What does Hypertonic mean? (hint, Osmosis)
- The solution has a higher concentration, water will leave the cell and enter the solution.
What does Hypotonic mean? (hint, Osmosis)
- The solution has a lower concentration, water will leave the solution and enter the cell.
What factors affect the diffusion and osmosis?
- Concentration gradient
- The diffusion distance
- Surface area
- Physical barriers
If animal cells are placed in a hypotonic solution, what is their ultimate fate?
How is this different to plant cells
Animal cells do not have a cell wall. Meaning if they take in too much water the cell membrane will rupture.
- Plant cells have a cell wall to stop the cell from rupturing.
What are implications?
Implications are anything that come into or out of the cell across the cell membrane.
A small organism has a —— surface are.
As the organism becomes —–, its ——– —– decreases. (Fill in the blanks)
1- Large
2- larger
3- surface area
So the —- size is limited by the ——– capability. (Fill in the blanks)
1- Cell
2- Diffusion
Which method of transport do cells prefer to use and why?
Passive because it does not cost them energy (ATP)
If a substance is going to be brought in against the concentration gradient, what transport type must be used?
Active
What is active transport?
-Active transport is when materials are moved against their concentration gradient, this is why it requires energy (ATP).
What is cytosis and what does it involve?
Cytosis is a form of active transport that involves the formation of membrane-bound vesicles.
What does Endocytosis mean?
The incorporation of substances from outside the cell to inside the cell as membrane bound vesicles. (Coming in)
What does Exocytotosis mean?
The release of substances from inside the cell to outside the cell. (Going out)
How does Endocytosis take place?
The membrane folds in around the molecules to be transported into the cell.
What are the two types of Endocytosis? And what are their roles?
1- Phagocytosis (the engulfment of soils particles).
2- Plnocytosis (the engulfment of liquid particles).
The plasma membrane —– the ——- of ——— into and out of the cell
1- regulates
2- movement
3- molecules
What factors effect the transport of molecules to and from cells?
- Size of molecule
- Type of molecule
- Effected by surface area of membrane
- Membrane thickness
- Concentration gradient
- Available protein carrier molecules.
