Lecture 10: Cell transport (Part 2) Flashcards
What is active transport?
process in cells of transporting molecules or ions across the membrane against their concentration gradient to concentrate them to one side
Is active transport a spontaneous process?
no
What are pumps?
membrane transport proteins that carry out active transport
Does active transport require energy?
Yes
What form of energy does active transport require?
ATP
How do you call a transport protein that pumps ions specifically across a membrane?
electrogenic pump
What type of gradient do electrogenic pumps create?
electrochemical gradient
How do electrogenic pumps work?
they convert chemical energy from ATP to electrical energy which can be used for cellular work.
What is the main electrogenic pump for animal cells?
the sodium/potassium (Na+/K+) pump
What is the main electrogenic pump for plant, fungi and bacteria cells?
proton (H+) pumps
What are the two combined forces that drive the diffusion of ions across a membrane?
- chemical force
2.electrical force
What does chemical force result from? (that drives diffusion of ions across a membrane)
from the ion’s concentration gradient
What does electrical force result from? (that drives diffusion of ions across a membrane)
from the membrane potential
What is the membrane potential?
voltage in cells created by unequal distribution of ions generated by pumps
What are electrochemical gradients used for?
- Neuron cell stimulation and propagation of impulse
- Muscle cell stimulation
- Powering of bacteria’s flagella to swim
- Secondary active transport: organisms transport substances against their concentration gradients using electrochemical gradients
Where does the potential energy for electrochemical gradient come from?
During primary active transport, the chemical energy in ATP is transformed into the potential energy of an electrochemical gradient.
What is secondary active transport?
Using the energy stored from primary active transport to drive the active transport of another chemical
the ATP indirectly drives the transport of a chemical
What is another name for secondary active transport?
cotransport
What is an example of how plants use secondary active transport?
Plants and other organisms commonly use the gradient of hydrogen ions generated by proton pumps to drive the active transport of substances into the cell.
What is an example of how animals use secondary active transport?
Animal use the gradient of sodium ions generated by Na+/K+ pumps to drive active transport of substances in digestive and urinary systems.
What are the three different types of carriers/transporters?
- uniporter
- symporter
- antiporter
What type of carrier/transporter is this?
What type of carrier/transporter is this?
What type of carrier/transporter is this?
What type of transporter are H+/sucrose cotransporters in plants?
symporter
What type of transporter are Na+/K+ transporters in plants?
antiporter
Which transport protein is faster: Channel or Carrier? Why?
channel since its a like an “open gate” and things can just flow out
whereas carriers need a process of changing shape
What type of membrane transport is this?
diffusion
What type of membrane transport is this?
facilitated diffusion
What type of membrane transport is this?
active transport
What does cystic fibrosis result from?
from abnormal functioning of the CFTR chloride channel in cells.
CFTR=Cystic Fibrosis Conductance Regulator
What is cystic fibrosis?
autosomal recessive genetic disease
In cystic fibrosis, what alters the production, structure, or stability of the chloride channel? What is the outcome of the malfunction of the channels?
Over a thousand different mutations
it impairs the transport of chloride ions and the movement of water into and out of cells
In cystic fibrosis which body parts are the most affected and are the cause of the characteristic signs and symptoms of cystic fibrosis?
cells that line the passageways of the lungs and other organs
The thick mucus obstructs these passageways, leading to the symptoms
Which type of molecules cross the membrane in bulk?
polymers such as polysaccharides and proteins
Through what do molecules get through the membrane in bulk transport?
vesicles
Do bulk transport require energy?
yes
What are the two major types of bulk transport?
- Exocytosis
- Endocytosis
What is exocytosis?
bulk transport where cells export their products outside of the cell.
How do cells export their products outside of cells during exocytosis?
Transport vesicles migrate to the membrane, fuse with it, and release their cargo into the extracellular fluid.
What is the general function of exocytosis
it allows the efficient release of large quantities of large molecules.
What are the two types of exocytosis?
- constitutive e.g. making membranes.
*regulated e.g. secretion of hormones or neurotransmitters or digestive enzymes.
What are the large molecules released by exocytosis?
Which one(s) are released by constitutive and which by regulated exocytosis?
A. Chemical messengers e.g., hormones, neurotransmitters
B. Enzymes e.g., digestive enzymes
C. Extracellular matrix components
D. Waste products
regulated: A,B,D
constitutive: C
What is endocytosis?
Cells use endocytosis to import substances from the extracellular fluid.
How does endocytosis work?
The membrane folds inwards and forms a transport vesicles containing cargo.
What are the three types of endocytosis?
A. Receptor-mediated endocytosis.
B. Pinocytosis (“cellular drinking”). C. Phagocytosis (“cellular eating”).
How do receptor mediated endocytosis work?
its is a specific uptake where binding of ligands to receptors triggers vesicle formation bringing cargo in the cell.
What is Familial Hypercholesterolemia?
Genetic disorder that results in a defect in the system that allows cells to uptake LDL particles.
What does this image represent?
Receptor-Mediated Endocytosis:
Top: A coated pit.
Bottom: A coated vesicle forming during receptor-mediated endocytosis (TEMs).
What is a problem with receptor-mediated endocytosis?
Some intracellular parasites such as viruses trick the cell and use this mechanism to take them in.
What does this image represent?
Pinocytosis vesicles forming in a cell lining a small blood vessel (TEM).
What is pinocytosis?
a type of endocytosis that is a non-specific uptake
Molecules extracellular fluid (water and solutes) is gulped into tiny vesicles.
What does this image represent?
What is phagocytosis?
type of endocytosis that is a specific uptake via receptors (not shown in figure).
- A cell engulfs a particle in a phagocytic (food) vacuole (large vesicle).
- The vacuole fuses with a lysosome which will digest the particle.
Give two examples of the use of phagocytosis.
- Unicellular protists eat organic material using this type of transport.
- Certain white blood cells in our immune system are phagocytes.
Why would the altered chloride ion movement affect water’s movement in cystic fibrosis?
because the chloride ions are transported by channels, which means that water also flows simultaneously
since there is no more chloride ions that flow out of the cells in cystic fibrosis, there is also limited water that is able to flow out
