Lecture 1: Intro Cell Membrane Transport Flashcards
Name the parts of a neuron and be able to locate them
Dendrites
Cell body (soma)
Axon
How many neurons are present in the human brain?
86 billion
Put the following in order from highest to lowest amount of neurons
1) Chimpanzee
2) Gorilla
3) Human
4) Elephant
4,3,2,1
What is the order of the neurological system?
Reception
Treatment
transmission
Where is treatment done? Reception? Transmission?
Treatment is done in the soma (intergrate all the signals from the adjacent neurons
Reception: dendrites
Transmission: done at the axon level
What is another name for the cell?
NEURON
Explain the structure of the cell membrane and its size
A thin, elastic structure, 7 to 10 nanometers thick
Composed of:
lipid bilayer
proteins
carbs
What is the purpose of the lipid bilayer and what is it impermeanle/permeable to?
Form a barrier,
Impermeable to water and the usual water-soluble substances (e.g., ions, glucose, urea…)
Permeable to lipid-soluble substances (e.g., oxygen, nitrogen, carbon dioxide, alcohol)
What is the fucntion of membrane proteins?
Membrane proteins transport water-soluble substances across the cell membrane.
Where are integral proteins located and what do they act as
Protrude through membrane
Act as
Pores and channels
Substance carriers
Where are peripheral proteins located and what do they act as?
Attached to only one surface of the membrane (often attached to integral proteins)
Act as
enzymes
Controller of transport through channels
What are the 2 basic processes of transport?
Diffusion (passive)
Active transport
What is the difference between passive and active transport?
PASSIVE= NO ENERGY
What are the 2 subcategories of diffusion?
Simple and faciliated
Give a quick description of diffusion vs active transport
Diffusion: ions and substances can travel freely through the membrane (either straight through the bilayer or by using channel proteins or by binding doing facilitated diffusion)
Active transport: Going against the electric gradient so a pump is needed to redistribute the ions./substances
In simple diffusion, what are the 2 ways molecules move through and what molecules move through them
1) Interstices of lipid bilayer (lipid-soluble substances: oxygen, nitrogen, carbon dioxide, alcohol)
2) Protein channels (water and lipid-insoluble molecules (e.g., ions, urea…)
What are the 2 chracteristics of simple diffusion
1) selective permeability
2) GATES
What are the 4 factors that affect permeability
1) Diameter of channel
2) Diameter of substance
3) Shape of channel
4) Nature of electrical charges along the surface of the channel
How can channels be open?
BY GATES
What are the 2 gates that open channels
Channels can be opened or closed by gates
Voltage gating channels:
Chemical gating (ligand-gated) channels:
Explain voltage gating channels
gate responds to electrical potential
Participate in the generation of action potential
Explain chemical gating (ligand gating) channels
Gate responds to binding of another molecule with the channel (changes conformation)
Participate in synaptic transmission (receptors)
What is the role of facilitated diffusion?
Transporting large molecules (ex gluc)
What are the steps of facilitated diffusion
1) Molecule diffuses by using a specific carrier protein
2) Molecule enters the pore and binds to the binding point of protein
3) A conformational change occurs so that the pore opens to the opposite side
4) At this position:
Molecule is released
True or false: In simple diffusion, the diffusion rate is proportional to the concentration of the transported surface?
true
True or false: Diffusion rate for facilitated diffusion is proportional and explain
FALSE:
Diffusion rate is not proportional to the concentration of the transported substance (i.e. diffusion rate approaches a max as the concentration of the diffusing substance increases)
KNow the graph of the facilitated vs simple diffusion rate
.
Why does faciliated diffusion speed reach a max?
Because speed of diffusion is limited by the speed of change of conformation of the protein
What are the 2 factors that affect net rate of diffusion?
1) concentration difference
2) electrical potential difference
Explain diffusion through concentration difference and what does it create
Net movement of molecules from high conc side to low concentration side
CONCENTRATION GRADIENT
Explain diffusion through electrical potential difference and what does it create?
Electrical charges of ions cause them to move through the membrane even though no concentration difference exists to cause movement.
A concentration difference of the ions will be developed in the direction opposite to the electrical potential.
=ELECTROCHEMICAL GRADIENT
What is required to move substances across a gradient
An additional source of energy (ATP)
How do molecules move in active transport
move across the membrane through a carrier protein against conc and/or electrical gradient
What are some examples of molecules that use active transport to get across membrane?
Na+, K+, Ca2+, Fe2+, H+, Cl-, urate ions, sugars and amino acids
True or false: the molecules transported by active transport can ONLY be moved by active?
False, they can move through simple diffusion
What are the 2 types of active transport
PRIMARY ACTIVITY TRANSPORT
SECONDARY ACTIVE TRANSPORT
Explain primary active transport
Energy is directly driven from adenosine triphosphate (ATP)
explain secondary active transport
2 different substances are transported
Energy is driven from concentration gradient of one of the transported substances
What is the purpose of the Na+/K+ pump?
to transport Na+ & K+ ions against their concentration gradient
the na/k pump establishes a negative or positive electrical potential inside the cell
negative
Explain the process of the sodium potassium pump
3 Na+ ions transported from inside to outside of the cell,
2 K+ ions transported from outside to inside of the cell,
Enzymatic ATPase activity causes conformational change.
Define electrogenic
ELECTROGENIC: TRANSFER OF ONE NET POSITION CHARGE OUT OF THE CELL
True or false: the sodium/potassium pump is not a electrogenic pump
FALSE (it has a net charge charge of 1 outside)
What are the 2 substances transported in symport secondary active trasport
Principal & co-transported
Where is the energy obtained for secondary active transport?
Energy is from the concentration gradient of the principal transported substance (e.g. Na+):
GRADIENT ENERGY
What are the 2 forms of secondary active transport and what are they dependant on?
Symport (co transport)
Antiport (counter transport)
according to the direction of diffusion of the two substances:
What is the main goal of secondary active transport?
to maintain homeostasis in the cell
What is an example of symport secondary transport?
Glucose & Sodium
What molecule is the principal substance and co transported substance of the glucose and sodium symport pump
Na +: principal substance
glucose: the co-transported substance
Explain the process of the glucose/sodium symport pump?
1) Na+ is principal, glucose is co transported
2) Carrier protein in the cell membrane = binding site for both glucose and Na+
3) Once both are attached a conformational change occurs in the carrier protein.
4) The energy gradient of Na+ causes both Na+ and the glucose to move together to the interior of the cell
Why does Na+ want to diffusion from the cell in symport pump with glucose?
Wants to move down the energy gradient (less Na+ outside)
What are the 2 substances transported in antiport secondary active transport
The principal substance and the counter-transported substance
Are the principal and counter transported substance on the same or opposite sides of the membrane?
OPPOSITE
What are 2 examples of secondary antiport transport>
sodium and hydrogen
sodium and calcium
Explain the process of antiport secondary transport
1) the principal substance (Na+) binds on the exterior side of the carrier protein and the counter-transported substance (e.g. Ca2+, H+) binds on the interior side
2) A conformational change occurs
3) With the gradient energy, Na+ is transported from outside to inside and the counter-transported substance is transported from inside to outside
True or false: molecules are kept in unequal concentrations inside and outside of the cell ?
TRUE
What molecules are found in the extra and intra cellular fluids and the main charge
Extracellular fluid :
High in Na+, Ca2+ and Cl-.
Positively charged
Intracellular fluid :
High in K+, Mg2+, proteins
Negatively charged
Where can you find the Na+ Ca2+ counter transport
occurs through almost all cell membranes
Where can you find the Na+ H+ counter transport pump?
Especially important in the proximal tubules of the kidneys
