Epithelia

Question 1

What is a tight junction?

Answer 1

connect two adjacent plasma membranes of two cells NOT the cytosols
Separates apical side to basolateral side

Question 2

What is a gap junction?

Answer 2

Connects cytoplasm of cells - little tunnels between cells allowing small solutes to move between cells
Important for conductive cells like cardiomyocytes

Question 3

What is a desmosome?

Answer 3

Strengthening connection of cells and epithelia
Connects cells by adherence by intracellular filaments via cadherines
Stabilise to withstand pressure and provide structure to cells like velcro

Question 4

Why do we have epithelia?

- Functions (PASSF)

Answer 4

To separate and control homeostasis of the inside and outside environment

Protection (skin)
Absorption (kidney, GIT)
Secretion (glands)
Sensation (skin, eye)
Filtration (kidney)

Question 5

What is the main goal of controlling water and solutes?

Answer 5

Maintaining blood pressure

Question 6

Epithelia definition

Answer 6

Cells must be connected to create a barrier
Have a cell polarity to create an electrochemical gradient to facilitate a function
Different protein expression
Different behaviours and regulations

Question 7

What is the basolateral membrane and what happens there?

Answer 7

Serosal interstitial meaning inside or facing the blood side
High water and K+ permeability
Contains Na+/K+ ATPase

Question 8

What is the apical side of the cell and what does it do?

Answer 8

Mucosal lumenal facing lumen/ outside
Brush border membrane - extends surface area of membrane for absorption
Variable water permeability
DOES NOT contain Na+/K+ ATPase

Question 9

Leaky junction

Answer 9

Allows water and sodium to go throuigh

Question 10

Leaky junction

Answer 10

Allows water and sodium to go through

Highly water permeability

Question 11

PCT type of tight junction

Answer 11

leaky oh no lets paracellular flow of water and solutes

Question 12

CCT type of tight junction

Answer 12

tight tight doesnt let that water through

Question 13

PCT type of tight junction

Answer 13

leaky oh no
high water permeability
lets paracellular flow of water and solutes
Transcellularly AQP1

Question 14

CCT type of tight junction

Answer 14

tight tight barely lets that water through
ONLY transcellularly AQP2
Hormonally controlled by ADH, aquaporins are present depending on hydration levels

Question 15

Tight junctions connect cytoplasmic compartments of cells

Answer 15

False

Question 16

The exchange of ions between cells can facilitate the propagation of action potentials (T/F)

Answer 16

True

Question 17

Tight junctions connect cytoplasmic compartments of cells (T/F)

Answer 17

False

Question 18

Absorption is driven by ….. transport

Answer 18

Na+ transport

Question 19

Secretion is driven by ….. transport

Answer 19

Cl- transport

Question 20

Simple diffusion definition

Answer 20

If the membrane is permeable to the solute, it will move down its gradient
Dependant on concentration gradient

Question 21

Facilitated diffusion definition

Answer 21

Requires a specific membrane protein channel

Still flows down its concentration gradient just cannot cross the membrane by itself

Question 22

Active transport definition

Answer 22

Requires energy and a specific membrane protein

Solute is going against its concentration gradient

Question 23

Secondary active transport definition

Answer 23

If the gradient generated by a primary active transporter is used by a second active transporter (uses the energy from one thing to drive another)

Question 24

Simple diffusion example

Answer 24

Paracellular pathway

Question 25

Facilitated diffusion examples

Answer 25

AQP | GLUTs

Question 26

Primary active transport examples

Answer 26

Na+/K+

Question 27

Secondary active transport examples

Answer 27

SGLT1, SGLT2

Question 28

Channel vs transporter

Answer 28

Transporter: requires a conformational change to move the solute from one side of the cell to the other CAN BE SATURATED Channel: pore in membrane allowing flow of specific solute

Question 29

Na absorption is initiated by? Or How is the electrochemical gradient created?

Answer 29

Na+/K+ ATPase on basolateral side generating a gradient of low Na inside the cell and high on lumenal side

Question 30

Electrochemical gradient

Answer 30

Drive for different processes

Question 31

SGLT1 and SGLT2 help get glucose in the cell how?

Answer 31

these secondary active proteins use the Na gradient and couple glucose influx

Question 32

Electric gradient is generated by

Answer 32

Na+/K+ ATPase kicks out more Na than puts in K+ 3Na+/2K+ creating a negative charge on the inside, further electrically attracting Na+ from the lumenal side into the cell

Question 33

Why does Cl- move paracellularly from the lumen to interstitium?

Answer 33

The basolateral side has become more positive from movement of Na and K and therefore Cl- is pulled and creates the osmotic gradient which therefore pulls water transcellularly and paracellularly to move down osmotic gradient