biology quiz 2 Flashcards
- “Particles are in constant, random motion”
- Helps materials move across the cell membrane.
Brownian Motion
Difference in concentration between two areas.
Concentration Gradient
Molecules move from areas of high concentration to areas of low concentration
This is called…
moving down a concentration gradient
…help move materials across the cell membrane
Concentration Gradients
Occurs when molecules are evenly distributed on either side of the cell membrane.
Equilibrium
The overall (net) flow of molecules..
does not change.
The molecules (?do/do not?) stop moving after reaching equilibrium.
DO NOT
What are the 3 ways in which molecules will be transported across the cell membrane in order to reach equilibrium?
- Passive transport
- Active transport
- Endocytosis/Exocytosis
The movement across cell membranes WITHOUT the input of energy.
Passive transport
Three types of passive transport
- Diffusion
- Facilitated diffusion
- Osmosis
Is the overall (net) movement of particles from an area of high concentration to an area of low concentration
Diffusion
The particles move DOWN their concentration gradient to reach equilibrium
DOES NOT REQUIRE ENERGY
Diffusion
The use of transport proteins to help, or facilitate, the diffusion of particles across the cell membrane.
Facilitated Diffusion
Occurs DOWN a concentration gradient.
This is still passive transport so NO energy is required
Facilitated Diffusion
Facilitated diffusion is used for:
Molecules that are too big.
Charged Ions.
2 Types of transport proteins
- Carrier proteins
- Channel proteins
Used to transport molecules which are TOO BIG (ex. sugar)
They CHANGE SHAPE to allow certain molecules to cross the cell.
Carrier Protein
Used to transport CHARGED IONS.
Forms a TUNNEL-LIKE PORE in the membrane.
When the pores are open, they allow charged ions in and out of the cell.
Channel Proteins
The diffusion of WATER across the membrane.
Water moves from high to low
Water moves down its concentration gradient.
Does not require energy.
Osmosis
Solution with MORE WATER MOLECULES and LESS SOLUTE (PARTICLES)
a cell placed in the solution will SWELL
Hypotonic solution
Solution with LESS WATER MOLECULES and MORE SOLUTE (PARTICLES)
a cell placed in the solution will SHRINK
Hypertonic solution
When the concentration of solute outside the cell is the SAME as the concentration of solute inside the cell.
A cell placed in the solution will REMAIN THE SAME.
Isotonic solution
Allow the passage of some materials but not others.
Cell membranes
membrane properties
membranes can ______ according to each cells needs.
Therefore, membranes are fluid and flexible.
Called…
change, “Fluid-Mosaic Model”.
Composed of a double layer of phospholipids.
Proteins, lipids, and carbohydrates are embedded between the layers.
Membrane structure
each… has a head and a tail.
Phospholipid molecules
Hydrophilic
water loving
Hydrophobic
water fearing
Hydrophilic
Makes up the ____ of the phospholipid.
Dissolve easily in water.
head
Hydrophobic
Makes up the ____ of the phospholipid.
Water molecules repel, or push away the ____ end of the phospholipid.
Tail
Phospholipids arrange themselves into two layers called a…
Bilayer
The hydrophilic head faces…, towards the water.
outside
The hydrophobic tail is sandwiched ______ where it is shielded from water.
inside
2 membrane functions
Biological Barrier
Selective filter
Prevents many substances from entering the cell that may harm the cell in a way.
Biological Barrier
Cell membranes must be able to allow some materials to cross while excluding others.
Called being Semi-Permable
Selective filter
Semi-Permeability depends on..
Particle size
Membrane proteins
Molecules that are small (like water and oxygen) can cross the membrane by slipping in between phospholipids.
Particle size
Proteins embedded in the cell membrane act like… into or out of the cell.
passage ways
They transport certain substances through the membrane.
Transport proteins
The cell membrane is..
semi-permeable
allows water to pass through while excluding all other molecules.
In passive transport, where does the energy that allows the particles to move come from?
Brownian Motion
Factors that affect the rate of diffusion.
Temperature, size, concentration
Why the diffusion rate increases with temperature?
The concentration level depends in the temperature.
In what phase (solid, liquid, gas) does diffusion occur at the highest/lowest rate?
Solid is slowest and Gas is fastest
In facilitated passive transport, why is the size of the channel important?
The amount of ions passing through depends in how wide the channel is.
Wider = more molecules
does the concentration gradient for the ion or molecule determine the net direction and rate of movement?
yes
is atp (a type of energy) required for a cell to do facilitated passive transport (diffusion)?
no energy is needed
The movement of particles from high to low concentration is called..
Diffusion
The order if particle movement from fastest to slowest is..
gas -> liquid -> solid
A channel protein might look like..
a tunnel
A shuttle (carrier) might look like
A lock and key
2 ways in which molecules will be transported across the cell membrane in order to reach equilibrium:
Passive Transport and Active Transport
Uses energy to transport molecules against their concentration gradients.
Moves particles from low to high concentration.
Like riding a bike uphill
Active transport
Cells use active transport for 2 reasons:
plant cells…
animal cells…
plant cells located in the roots take in minerals from the surrounding soil.
animal cells remove waste.
Method of moving molecules into or out of the cell by active transport.
Endocytosis/Exocytosis
Membrane fold in and forms a pocket around the material to be transported.
- requires energy to move particles against their concentration gradient.
Endocytosis
3 types of Endocytosis
Phagocytosis
Pinocytosis
Receptor-Mediated Endocytosis
-Means cells eating
-Used by cells to ingest food or other solid materials.
Phagocytosis
-Means cells drinking
-Used by cells to ingest droplets of water, or fluids.
Pinocytosis
-Receptors protrude from the membrane surface and detect specific compounds or cells in the environment.
-When a receptor identifies an item for transport, the receptor binds to it and triggers endocytosis.
-Used to take in molecules such as cholesterol and some hormones
Receptor-Mediated Endocytosis
-Allows materials stored in vesicles and vacuoles to exit the cell.
-The vacuoles or vesicle fuses with the cell membrane and the stored contents are released.
-Opposite of endocytosis
-Requires energy to move substances against their concentration gradient.
Exocytosis
Semi-permeable membranes extend beyond their role in…
living cells
A variety of technological and medical applications also use types of transport across…
membranes