Lecture 2

Question 1

Cells are held together physically and functionally by…

Answer 1

junctions which are made up of different types of proteins —> nuts and bolts that anchor cells to one another and anchor cells to their environment (ECM)

Question 2

what is the ECM

Answer 2

Extracellular Matrix (ECM)
E- outside
C-cell
M- the stuff we live on

Question 3

The ECM can have variable consistency. Give 2 examples

Answer 3

Both are connective tissue
Bone:
- made up largely of protein and is mineralized
- so super solid ECM
Blood
- very liquidy because it has a lot of water

Question 4

Name the 3 types of junctions

Answer 4

1. Gap junction
2. Tight junction
3. Anchoring junction

Question 5

Define gap junctions

Answer 5

• little pores, little holes that allow stuff (mostly ions) to move from one cell to its neighboring cell
• enable communication between cytoplasms of adjacent cells
• found in cardiac muscle
• connexion proteins build a gap junction

Question 6

Define tight junctions

Answer 6

• adjacent cell membranes are partly fused together creating a barrier
• tightly link cells
• claudin and occludin proteins

Question 7

Define anchoring junctions

Answer 7

• anchor cells to each other or the ECM or provide strength when tissue is under mechanical stress
• cadherin proteins

Question 8

what are the 4 major tissue types in the body?

Answer 8

1. Epithelial
2. Connective tissue cells
3. Muscle
4. Neural

Question 9

Describe epithelial tissue

Answer 9

function: protects the internal environment of the body and regulates the exchange of materials between external/internal environments

cell types: exchange, transporting, protective, ciliated, secretory

Question 10

Define connective tissue cells

Answer 10

function: provides structural support and creates a barrier
- found within the extensive ECM
- made up of collagen

cell types: blood, bone, fibroblasts

Question 11

Define muscle tissue

Answer 11

function: generate contractile force
cell types: cardiac, skeletal, and smooth

Question 12

Define Neural tissue

Answer 12

function: neurons carry information in the form of chemical and electrical from one part of the body to another

glial cells are support cells for neurons

Question 13

Different types of connective tissue

Answer 13

1. loose connective tissue
   - elastic tissue beneath the skin and between some cells
2. dense connective tissue
   - provides strength and flexibility (tendon and ligaments)
3. blood
4. bone
5. adipose tissue
6. cartilage

Question 14

cell membranes are ___________

Answer 14

selectively permeable

Question 15

what determines the permeability of a molecule

Answer 15

• Presence of transporters or channels for substance
• Size of substance
• Charge of substance
• Hydrophilicity of substance

Question 16

Highly permeable:

Answer 16

gases, small lipophilic (hydrophobic) molecules, water

Question 17

impermeable:

Answer 17

ions, lipophobic (polar) and large molecules

Question 18

Diffusion

Answer 18

• moves from an area of high concentration to a low
• down a concentration gradient
• no use of ATP

Question 19

Diffusion can be divided into two types across a cell membrane

Answer 19

1. Simple diffusion: directly across the phospholipid membrane (small lipophilic molecules)
2. Facilitated diffusion: protein-mediate transport

Question 20

factors affecting diffusion rate

Answer 20

• lipid solubility
• molecular size
• membrane surface area
• concentration gradient

Question 21

Facilitated diffusion

Answer 21

• protein-mediated channel
• passive transport
• molecule move down their concentration gradient towards equilibrium

Question 22

Active transport

Answer 22

• requires energy
• molecules move against their concentration gradients
• systems move away from equilibrium

Question 23

Channels

Answer 23

• water-filled pores linking the extracellular and intracellular environment
• facilitated diffusion (always passive transport
  Selective about the substances they allow to pass:
• small molecules
• water channels
• ion channels
• most have gates to regulate the flow
• fast

Question 24

Transporters

Answer 24

• open to one side of the membrane or the other
• may be selective: can carry larger molecules than channels
• facilitated diffusion or active transport
• transport is much slower than channels

Question 25

Types of channels

Answer 25

1. passive/leak channels
   - always open and conducting (K+)
2. Voltage-gated channels
   - open and close due to changes in membrane potential
3. Ligand-gated channels- open when a specific chemical molecule binds to the channel protein
4. Mechanically-gated channel: open and close in response to physical disturbance of the membrane

Question 26

Give an example of ions that use membrane carrier proteins

Answer 26

sodium-glucose transporter

Question 27

Type of carrier proteins

Answer 27

1. uniport carriers (transport one kind of substrate)
2. symport carriers (move two or more substrates in the same direction)
3. antiport carriers (move substrates in opposite directions)

Question 28

active transport

Answer 28

• molecules move against a concentration gradient and the system moves away from equilibrium

2 types:
- primary active transport (uses ATP)
- secondary active transport (uses potential energy stored in concentration gradient)

Question 29

example of secondary active transport

Answer 29

sodium-glucose transporter

Question 30

Transcellular transport

Answer 30

transport through cells via diffusion, facilitated diffusion, active transport, and endo/exocytosis

ions or molecules pass through apical or basolateral membranes

Question 31

paracellular transport

Answer 31

• molecules that pass between adjacent cells to get to or from the lumen
• regulated by the presence of tight junctions