Cell Membrane
What is the cell membrane?
What is it's role?
Cell/ Plasma Membrane: a selectively permeable barrier surrounding all cells.
It protects the cell, selectively controls what enters and exits (leaves) the cell, and serves in cell recognition/communication.
What is the cell membrane made out of? How is it arranged?
The cell membrane is mostly made out of phospholipids. They are arranged in what is called a phospholipid bilayer. It is also called a fluid mosaic model.
The hydrophilic head faces the water filled sea outside the cell and also the watery inside of the cell; the hydrophobic fatty acid tail form the inner core.
What materials pass across the semi-permeable cell membrane - Name materials the cell needs and materials the cll gets ride of.
Materials the cell needs : nutrients, water (H2O), oxygen (O2)
Materials the cell gets rid of: waste (ex. Co2, carbon dioxide)
What is passive transport?Give examples
Passive transport: substances move down the concentration gradient from high to low; it does not use energy. Ex: 1) simple diffusion (oxygen, carbon dioxide): oxygen moves from oxygen into blood, Co2 moves from cell into blood;2) facilitated diffusion (some glucose, larger molecules); uses protein carriers/channels; 3) osmosis - specific diffusion of water
Osmosis and Diffusion - what kind of transport?
Does it need energy (ATP)?
What is the difference?
Passive transport; does not need energy
Diffusion is substances going from high to low concentration.
Osmosis is movement of water from his to low.
Purpose of the cell membrane
The cell membrane's purpose is to assist the cell in maintaining homeostasis (stable internal environment) by controlling what enters and leaves (exits) the cell.
What is the structure of a phospholipid?
The phospholipid has 1) the hydrophilic "head" which is comprised of a phosphate group and glycerol
2) Hydrophobic "Tail" which is comprised of two fatty acid chains
How do molecules move across the cell membrane?
1. Molecules from from high concentration to low concentration
2. Molecules try to reach a balance called equilibrium
3. Once equilibrium is reached, these is balance (homeostasis)
What is active transport? Give examples
Active transport: transport against the concentration gradient - low to high that requires the use of cellular energy (ATP);uses carrier proteins (pumps)
Examples: Phagocytosis (macrophages engulf bacteria); pinocytosis (cell "drinks" or takes in fluids); glucose in the intestines
Why might it not be good to drink salt water?
If you drink salt water, the concentration i
of water is less than in your cell,, so cells will lose water (high to low concentration) and you will be dehydrated ( still thirsty). Water is pulled mOUT of your body cells.
What does hydrophilic mean?
What does hydrophobic mean?
Hydrophilic: Liking water - "head" of the phospholipid
Hydrophobic: fear of water - the "tail" of the phospholipid
What are the four molecules that can be found in the cell membrane and their function
Phospholipids: main component, forms the phospholipid bilayer (semi-permeable) Proteins: embedded in the cell membrane and used for transport into and out of the cell (like a tunnel). Carbohydrates: attached to phospholipids or proteins and used for cell identification - unique markers (like immune cells / bacteria) Cholesterol: found in hydrophobic part of the membrane, it regulated the fluidity, organization and permeability.
what is equilibrium?
Equilibrium is a state where there is a balance between the movement of molecules into the cell and out of the cell
What happens in the egg experiment?
What happens when the egg is placed in water? Why?
What happens when the egg is placed in corn syrup? Why?
Testing the permeability and transport across the membrane.
In water, the concentration outside the egg is greater than inside - water goes into cell trying to balance: egg enlarges/swells
In corn syrup: water concentration grater inside the cell, water goes out of cell - cell shrinks
What requires energy to pass through the cell membrane? What kind?
Active transport (glucose inn the intestines, Phagocytosis, Pinocyosis) ; ATP
Cell membrane is selectively permeable - what does that mean?
Selective permeability: cell membrane allows some materials, but not all to cross it or permeate it. Also called semi-permeable.
In a cell: small non polar molecules (oxygen, carbon dioxide/ uncharged, hydrophobic) lipid soluble -pass through simple diffusion; small polar molecules (charged, hydrophilic)-like water, diffuse slowly using channels; facilitated diffusion
large/ polar molecules (some sugars/ions) need protein facilitated diffusion
Active transport - uses cellular energy (ATP) Ex. glucose in the intestines
What is a gradient? Explain
The gradient is the change or difference in the concentration of a substance
In diffusion (passive), substances move across the cell membrane from an area of high concentration to an area of low concentration ; moving "down' the gradient
In active transport, substances move against the gradient from low to high concentration ("up" the gradient).
What is osmosis?
How can this be illustrated?
Osmosis is the process of the transport of water-
molecules move from high to low concentration
We can illustrate this using models to show the movement of molecules.
What type of transport occurred in this experiment?
Be specific
Passive - Osmosis
1. Gummy bear is water?
2. Gummy bear in salt water?
1. It will cell since higher concentration in pure water goes into gummy bear.
2. Gummy bear will shrink - higher concentration of water inside gummy bear will pass out into salt water
When you spray air freshener in a room and the smell changes in intensity, what is happening>
When you spray air freshener in a room, you smell it for a couple of minutes, then the molecules spread out (diffuse) or float away to different areas and you do not smell it anymore. This is an example of diffusion because it is the movement of particles from high concentration to low concentration.
what is concentration ?
Concentration is the amount of a substance
All animals start out as a single ________.
What are living things are made of?__________.
What happens when you place a cell in vinegar?
cell
cells
Vinegar eats away at (dissolves) the shell of the egg.
Ddid the movement of molecules in this experiment require energy?
NO
What happens if salt on a sluG?
slug loses water and dehydrates (shrinks)