Section 1 - Intro cell membrane Flashcards
How many neurons are present in the human brain?
a) 6 billion
b) 16 billion
c) 32 billion
d) 86 billion
e) 36 billion
86 billion
Where is the reception of the signal in the neuron’s structure?
Dendrites
What is the action related to the cell body (soma)?
Treatment
Where is the transmission of the signal in the neuron’s structure?
Axon of the neuron
Cell membrane is almost entirely composed of _____ and _____
Lipids and proteins
- lipid barrier
- proteins
- carbohydrates
How can we describe the lipid bilayer of the membrane?
Impermeable to water and water-soluble substances
Permeable to lipid-soluble substances
With what type of proteins do the water-soluble substances get across the cell membrane? (2)
- Integral proteins (pores and channels)
- Peripheral proteins (enzymes)
What are the two basic processes of transport?
- Diffusion = passive transport (NO energy) + either simple or facilitated
- Active transport = energy required + through carrier proteins
Explain where do lipid-soluble and water-soluble substances move through in the simple diffusion:
Lipid-soluble = interstices of lipid barrier Water-soluble = protein channels
What are the important characteristics of the diffusion through protein channels? (4)
Selectively permeable to one or more specific ions/molecules based on:
- diameter of channel
- diameter of the substance
- shape of channel
- nature of electrical charges along the surface of the channel
During the diffusion through protein channels, channels can be opened or closed by 2 types of gates? Name them
Voltage gating channels and chemical gating (ligand-gated) channels
What do the voltage gating channels respond to? and it participates in ?
- Respond to electrical potential
- Participate in the generation of an action potential
What do the chemical gating (ligand-gated) channels respond to? and it participates in ?
- Respond to binding of another molecule with the channel
- Participate in synaptic transmission (receptors)
T or F : facilitated diffusion uses energy
False
What is the role of the facilitated diffusion?
Transporting large molecules (ex: glucose and amino acids) see image p.22
Explain the difference in the diffusion rate (speed) between simple and facilitated diffusion
Simple = proportional to the concentration of the transported substance ( the higher the concentration, the faster the diffusion)
VS facilitated = not proportional to the concentration of the transported substance ( diffusion rate approaches a max as the concentration of the diffusing substance increases)
What are the two factors that affect net rate of diffusion?
Concentration difference (high concentration to low = concentration gradient) Electrical potential difference (vers le +)
T or F: A concentration difference of the
ions will be developed in the opposite
direction to the electrical
potential.
True
Do molecules/ions move across the membrane through a carrier protein AGAINST or WITH their concentration and/or electrical gradient?
AGAINST
Name the two types of active transport
- Primary active transport
- Secondary active transport
What is the transport used to bring ions against their concentration gradient in the cell membrane in the primary active transport?
Sodium-potassium pump (Na+/K+) see p.27-28
How do we call the two substances transported in the secondary active transport?
Principal and co-transported
What are the two forms of secondary active transport according to the direction of diffusion of the two substances?
- symport (co-transport) = same direction
2. antiport (counter-transport) = opposite direction
What is the main goal?
Homeostasis in the cell
Examples of symport and antiport
symport: Na+ as principal and glucose as co-transported
anti-port: Na+ as principal and Ca 2+ as co-transported
see p.31-32
T or F: Molecules are constantly kept with equal
concentrations inside and outside of cell.
False = unequal concentrations (see p.33)
