Intro to Cell Membrane Transport Flashcards
How many neurons are present in the human brain?
86 billion neurons
which animals have the highest to lowest number of neurons?
elephant, humans, gorilla, chimpanzee
What is a cell membrane?
A thin elastic structure, 7 to 10 nanometers thick
What are the 3 components of the cell membrane?
lipid barrier, proteins, carbohydrates
what is the neuron membrane composed of?
A lipid-bilayer
What is the lipid bilayer impermeable and permeable to?
it is IMpermeable to water/ water-soluble substances (glucose, ions, urea)
it is permeable to lipid-soluble substances (oxygen, nitrogen, carbon dioxide, alcohol)
What do membrane proteins transport across the cell membrane?
water-soluble substances
What do integral proteins act as?
Pores, channels and substance carriers
What do peripheral proteins act as?
Enzymes, controller of transport through channels
What are peripheral proteins often attached to?
Integral proteins
Define the two basic processes of transport
Diffusion: Passive transport, simple (lipid bilayer or channel proteins), facilitated (carrier proteins)
Active Transport: Energy required, carrier proteins
What do molecules move through in simple diffusion?
interstices of lipid bilayer, proteins channels
What characteristics do proteins channels have for molecules passing through?
Diameter of channel, shape of channel, diameter of the substance, nature of electrical charges along the SURFACE of the channel
Which gates can open or close protein channels and how?
Voltage gating channels: responds to electrical potential and participates in the generation of action potentials
Chemical (ligand-gated) gating channels: responds to binding of another molecule with the channel, participates in synaptic transmission
What are the steps of facilitated-diffusion?
Molecules diffuses by using a specific carrier protein; molecule enters the pore and binds to the binding point of protein; a conformational change occurs so that the pore opens to the opposite side; the molecule is released
what are two examples of large molecules?
Glucose and amino acids
What is the diffusion rate proportional to in simple diffusion?
To the concentration of the transported substance
What is the diffusion rate NOT proportional to in facilitated diffusion?
To the concentration of the transported substance
What factors affect the Net Rate of Diffusion?
Concentration difference (high concentration to low concentration; concentration gradient), Electrical potential difference
How do molecules or ions move across the membrane in active transport and what do they move through?
against their concentration gradient/ electrical gradient and they move through a carrier protein
What is required to move substances against their concentration gradient?
An additional source of energy
Name the substances that are transported though the membrane via active transport
Na+, K+, Ca2+, H+, Cl-, urate ions, sugars and amino acids
Name the two types of active transport and what differentiates them
Primary Active Transport: Energy is directly driven from ATP
Secondary active transport: 2 substances are transported, energy is driven from concentration gradient of ONE of the two substances
what is the sodium potassium pump used for?
To transport Na+ and K+ against their concentration gradients
After an action potential, where is there more sodium and where does it move?
More sodium inside the cell, it gets pumped out o the cell for the cell to return to its negative charge
What is the ratio of Na+ an K+ that is pumped in/out of the cell?
3 Na+ pumped OUT of the cell and 2 K+ pumped INTO the cell
At resting state, what charge does the cell have?
Always negative
What causes a conformational change in primary active transport for the sodium-potassium pump?
Enzymatic ATPase
Where does the additional source of energy come from in secondary active transport?
From the concentration gradient of the principal transported substance
Define symport and antiport
Symport: The two substances move in the SAME direction
Antiport: the two substances move in OPPOSITE directions
What is the main goal of secondary active transport?
To maintain homeostasis in the cell
Between sodium and glucose in a symport, which is the principal substance and which is the co-transported substance?
Sodium is the principal substance and glucose is the co-transported substance
Where are the principal an co-transported substances located on the membrane?
On opposite sides of the membrane
What type of changes occurs in a symport secondary active transport situation?
A conformational change
Where is the Na+ H+ counter-transport especially important?
In the proximal tubules of the kidneys
