Intro Cell And Membrane

Question 1

What is the electrical signal?

Answer 1

It’s called the action potential - a change in the action

Question 2

What composes the nerve cell (neuron)?

Answer 2

Dendrites, cell body and axon

Question 3

What does is the neuron equivalence?

Answer 3

A cell - the neuron goes through the cell membrane

Question 4

What is the structure of a cell membrane?

Answer 4

A thin, elastic structure, 7 to 10 nanometers thicks

Composed almost entirely of lipids and proteins : lipid barrier (2 lipids connected upside down), proteins (open up and let pass de sodium so we can feel the sensation) and carbohydrates (it feeds the cell membrane so it can be well balanced).

Question 5

How many neurone are present un the human brain?

Answer 5

86 billion neurone

Question 6

Place the following species in descending order (highest to lowest number)? 1) Chimpanzee, 2) Gorilla, 3 ) Human and 4) Elephant

Answer 6

4, 3, 2, 1

Question 7

Who’s the #1 animal in the animal kingdom that has the most neurones?

Answer 7

Whales with 500 billion neurone

Question 8

What is the neurological system?

Answer 8

There’s the reception, the treatment and the transmission

Each neuron can be connected up to 10,000 other neurons, passing signals to each other via as many as 1,000 trillion synaptic connections = 1 trillion = 10 à la 12

Question 9

How does the transport if substances go through the membrane?

Answer 9

Through the lipid bilayer of the membrane

Question 10

What can’t go through the barrier?

Answer 10

Impermeable to water and the usual water-soluble substances (ex : ions, glucose, urea

Question 11

What can go through?

Answer 11

Permeable to lipid-soluble substances (ex : oxygen, nitrogen, carbon dioxide and alcohol)

Question 12

What does the membranes protein transport?

Answer 12

Water-soluble substances across the cell membrane

Question 13

What are integral proteins?

Answer 13

Protrude through membrane and the act as pores and channels and substance carriers

Question 13

What are peripheral proteins?

Answer 13

Attached to only one surface of the membrane (often attached to integral proteins) they act as enzymes, controller of transport through channels

Question 14

What is diffusion?

Answer 14

Passive transport (no energy needed)
- It’s simple (lipid bilayer or channel proteins
- It’s facilitated (carrier proteins)

Question 15

What is active transport?

Answer 15

Energy is required (needs ATP)
- Carrier proteins

Question 16

What is simple diffusion?

Answer 16

Molecules move through
1. Intersites of lipid bilayer for lipid-soluble substances : oxygen, nitrogen, carbon dioxide, alcohol

2. Protein channel : water an lipid-soluble molecules (ex: ions, urea)

Question 17

What are the important characteristics for diffusion through protein channels (1) ?

Answer 17

1. Selectively permeable to one or more specific ions or molecules based on the
   - diameter of channel
   - diameter of the substance
   - shape of the channel
   - nature of the electrical charges along the surface of the channel

Question 18

What are the important characteristics for diffusion through protein channels (2) ?

Answer 18

2. Channels can be opened or closed by gates
   - Voltage gating channels such as gate responds to electrical potential and participate in the generation of action potential

• Chemical gating (ligand-gated) channels such as gate responds to binding of another molecule with the channel and participate in synaptic transmission (receptors)

Question 19

What is facilitated diffusion?

Answer 19

Molecule diffuses by using a specific carrier protein

Molécule enters the pore and bonds to the bonding point of protein

A conformational change occurs so that the pore opens to the opposite side

At this position : the molecule is released

Question 20

Role of facilitated diffusion?

Answer 20

Transporting large molecules (ex : glucose and amino acids)

Question 21

What is the difference between simple diffusion and facilitated diffusion?

Answer 21

SD : Diffusion rate (speed) is proportional to the concentration of the transported substance (ex : higher the concentration, the faster the rate fo diffusion)

FD: Diffusion rate is not proportional to the concentration of transported substance (ex : the diffusion rate approaches a max and the concentration of the diffusing substance increases)

Question 22

What are the factors that affect net rate of diffusion?

Answer 22

Concentration difference
- Net movement of molecules from high concentration side to low concentration : concentration gradient

Electrical potential difference
- 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.

Question 23

What does the active transport involve?

Answer 23

Molecules or ions move across the membrane through a carrier protein against their concentration and/or electrical gradient

• An additional source of energy is required to move substances against a gradient
• Substances transported through membrane by active transport are : Na+, K+, Ca2+, Fe2+. H+, Cl-, urate ions, sugars and amino acids. Most of theses substances are also transported by Passive Transport through the process of diffusion

Question 24

What are the types of active transport?

Answer 24

1. Primary active transport : energy is directly drive from adenosine triphosphate
2. Secondary active transport : 2 different substances are transported + energy is driven from concentration gradient of one of the transported substances

Question 25

What happens to the sodium- potassium pump in the primary active transport?

Answer 25

Na + / K + is used to transport Na+ & K+ ions against their concentration gradient

3 Na+ pumped out of cell, 2 K+ pumped into cell )against concentration gradient)

Maintains concentration difference across cell membrane ( ++ Na+ outside & ++ k+ inside)

Establishes negative electrical potential inside celle

Requires one to two thirds of cells energy!

Question 26

Net increases of what?

Answer 26

1 positive charge outside, which is the electrogenic (transfer of one net positive change out of the cell)

Question 27

What is the secondary active transport?

Answer 27

2 substances are transported : principal & co-transported

Energy is from the concentration gradient of the principal transported substance (ex : Na+) : energy radient

Two forms of secondary active transport according to the direction of diffusion of the 2 substances :
- symport : 2 substances move in the same direction
- antiport : 2 substances move in opposite direction

Question 28

What is the main goal of the secondary active transport ?

Answer 28

To maintain homeostasis in the cell

Question 29

Example of symport in secondary active transport

Answer 29

Sodium and glucose
- In this example, the Na+ is the principal substance and the glucose is the co-transported substance

• Carrier protein in the cell membrane = bonding site for both glucose and Na+

Once both are attached a conformational change occurs in the carrier protein

The energy gradient of Na+ causes both Na+ and the glucose to move together to the interior of the cell

Question 30

Example of anti port in secondary active transport

Answer 30

The principal substance and the counter-transported substance are located on opposites sides of the membrane

The principal substance (Na+) binds on the exterior side of the carrier protein and the counter-transported substance (ex : Ca2+, H+) binds on the interior side

A conformational change occurs

With the gradient energy, Na+ is transported from outside to inside and the counter-transported substance is transported from inside to outside

Question 31

What is the fluid concentration difference inside and outside the cell?

Answer 31

Molecules are constantly kept with unequal concentrations inside and outside of celle

Very important for the optimal functioning of the cell

Extracellular fluid
- High in Na+, Ca2+ and Cl- and positively charged

-Intracellular fluid
- High in K+, Mg2+, proteins and negatively charged