Chapter 6 - Interactions between Cells and The Extracellular Environment Flashcards
Materials are transported in and out of a cell through the _____ _______
cell membrane
What is vital for all cells to maintain?
constant/stable intracellular environment (homeostasis)
The cell membrane is _____ _________.
Explain what this means
selectively permeable
only allows substances of certain sizes/charge in/out
Explain why the cell membrane is selectively permeable
It is selectively permeable because it brings in molecules it needs and exclude molecules it does not need.
What are the different ways substances can move across the cell membrane?
- passive transport
- active transport
- bulk transport
What is another term for passive transport?
diffusion
What are two examples of passive transport?
- simple diffusion
- facilitated diffusion
What are two examples of active transport?
- primary active transport
- secondary active transport
In passive transport, substances move from a ______ to _________ concentration.
higher
lower
In which transport system across the cell membrane do NOT use energy?
passive transport
In which transport system across the cell membrane USES energy?
active transport
In active transport, substances move from a ______ to _________ concentration.
lower
higher
Passive transport is ________ movement of substances from an area of high concentration to low concentration
spontaneous (natural)
Define the concentration gradient
the concentration difference across a cell membrane
Compare simple diffusion vs facilitated diffusion. Include examples
simple diffusion is for movement of small, non-polar and/or uncharges substances and move in/out the cell directly through the cell membrane (ex. o2, co2 (gases), steroids (fats)).
facilitated diffusion is for movement of large, polar, and/or charged substances and are repelled by the phospholipid bilayer (ex. Na+, Cl- (ions), glucose (large)). It requires facilitators to move substanecs in/out of the cell membrane (protein channels+carriers)
Why are steroids allowed to travel straight through the cell membrane but not Na+
steroids are uncharged and nonpolar, meaning they use simple diffusion
Na+ is an ion with a positive charge, needing facilitated diffusion.
What is a facilitator? Why are they important?
it helps move substances through the cell membrane (protein channels and protein carriers)
it helps move large, polar, and charged particles down the concentration gradient (high -> low)
Compare the different facilitators in facilitated diffusion
protein channels
- embedded in cell membrane
- closed/open state (gate)
- move substances high -> low
- ex: Na+ channel, K+ channel, water channel
protein carriers
- embedded in cell membrane
- carrier physically attaches to substance being transported -> changes shape of protein carrier -> opens at opposite end -> releases substance
- ex: glucose carrier protein
ion channels and protein carriers are mostly ______
specific (show specificity)
In facilitated diffusion, which type of facilitator shows specificity?
protein carriers are more specific than ion channels because they have to bind to a substance
ion channels and protein carriers can show ______ and _________
saturation and competition
What does it mean when we say channels and carriers can show “competition”
some proteins (ion channels and protein carriers) can transport more than one molecule, which causes competition
What is saturation and what happens to the rate of particle transport when saturation has been met?
when a molecules transport rate reaches its plateau
Describe saturation and competition
The transport rate increases with increasing molecule concentration until all the carriers are in use -> transportation rates plateau -> saturation has been met
Some proteins are able to transport more than one molecule, which can cause a competition effect
The maximum transport rate is known as the transport maximum (Tm)
If saturation is met after reaching a certain molecule concentration, what can you say about the number of channels and/or carriers present in the cell membrane?
there is a limited number of channels/carriers
T or F: The number of channels and carriers embedded in the cell membrane is constant throughout the life of the cell
False, they can be inserted or removed when needed
The amount of carriers are determined by the need of the cell
What type of carrier proteins transport glucose?
GLUT (1,2,3,4)
Active transport requires some form of energy. List the 2 types of energy used in active transport.
direct ATP and indirect ATP (another form of E involving ATP; the energy needed to move molecules against their concentration gradient in secondary active transport is acquired by moving Na+ back into the cell)
What words indicate a molecule is moving from a high to low concentration?
- moving down the concentration gradient
- moving with the concentration gradient
- moving with diffusion
What words indicate a molecule is moving from a low to high concentration?
- moving up the concentration gradient
- moving against the concentration gradient
- moving against diffusion
Compare passive and active transport (which way do substances move)
passive transport: high -> low
active transport: low -> high
There are 2 types of active transport: _________ active transport and ___________ active transport
primary active transport
secondary active transport
Primary active transport uses _______ ________ embedded in the cell membrane
protein pumps
Describe how protein pumps work
protein pumps are used in PRIMARY active transport and require direct ATP to change the shape of a pump and open to the other side to release the substance (works kinda like a protein carrier, but needs ATP)
What types of pumps are involved in primary active transport? Be specific
- Na+/K+ pump
- Ca2+ pump
The Na+/K+ pump is described as an ________ pump
exchange pump
Summarize in words what is happening when a Na+/K+ is operating in the cell membrane and draw it out
The Na+/K+ pump using ATP to move 3Na+ out the cell and 2K+ into the cell and they both move against the concentration gradient (low -> high). ATP becomes converted into ADP + Pi
Where is the Na+/K+ pump found?
in all body cells (ex. neurons, cardiac cells)
Why is the Na+/K+ pump described as an exchange pump?
3Na+ are moving out of the cell in exchange for 2K+ moving in the cell
Why does the cell become more negative inside as a result of the Na+/k+ pump operating?
There are more Na+ moving out of the cell, than there is K+ moving back in.
What can cause the Na+/K+ pump to stop working?
- ATP production is altered
- Presence of Na+/K+ pump inhibitors
Describe secondary active transport
- movement of 2 substances simultaneously across cell membrane; 1 with diffusion (Na+) and 1 against diffusion (a different substance)
- movement relies on primary active transport (the Na+/K+ pump); indirect use of ATP
How does secondary active transport facilitate movement?
the energy needed to move molecules against their concentration gradient is acquired by moving Na+ back into the cell (Na+ was originally pumped out of the cell using ATP in primary active transport, the secondary active transport is also considered to be active transport)
What are the different types of secondary active transport?
- co-transport/symport
- counter-transport/antiport
Compare co-transport/symport to counter-transport/antiport
co-transport/symport: both substances move in the SAME direction (both in or both out)
ex: Na+/Glucose symporter
K+/Cl- symporter
counter-transport/antiport: both substances move simultaneously in the OPPOSITE direction
ex: Na/Ca2+ Exchanger
Na+/H+ Exchanger
Cl-/HCO3- Exchanger
How is ATP involved in secondary active transport?
1) high [Na+] outside
2) movement of Na+ by diffusion is the driving force for moving the second particle
Bulk transport is the movement of relatively _______ macromolecules
large
What are the different types of bulk transport?
Describe them and give examples
endocytosis: movement into the cell; pinching to form a vesicle
ex: protein, hormones, neurotransmitters
exocytosis: movement out of the cell; intracellular vesicle fuses with plasma membrane
ex: cholesterol
