Membranes + epithelial tissues

Question 1

Define diffusion

Answer 1

A function of concentration gradients as solutes move from a high conc. to a low conc.

Question 2

State what molecules can undergo simple diffusion

Answer 2

Lipid soluble molecules

Question 3

State what molecules undergo facilitated diffusion

Answer 3

Large/water soluble molecules/ions move through protein channels
-> leak channels enable free movement of ions

Question 4

Explain the function of carrier proteins

Answer 4

Have specific receptor site that a molecule must bind to to open the protein + enable similar molecules to move across eg. glucose
-> must exhibit specificity

Question 5

Define osmosis

Answer 5

Net movement of water molecules across a semi-permeable membrane to a higher solute concentration
-> moves through channels called aquaporins

Question 6

State the osmolarity of normal plasma

Answer 6

285 osmol/L

Question 7

Define tonicity

Answer 7

Effect of osmotic solutions on cells

Question 8

Define active transport

Answer 8

Movement of molecules ‘up’ a concentration gradient, requiring ATP

Question 9

Describe the sodium-potassium exchange pump

Answer 9

Moves Na+ out of cell + K+ in
-> b/c ions move down gradients therefore Na+ moves in -> cell X want Na+

Question 10

Explain the process of secondary active transport

Answer 10

• glucose binds to protein / Na+ binds to carrier protein -> move across membrane
• Na+ pumped back out of cell
• enables glucose + amino acid absorption in digestion as moves specific substrate down conc. gradient then pumps Na+ back out

Question 11

Explain the process of receptor-mediated endocytosis

Answer 11

• ligand binds to receptors in PM which migrate to clathrin coated pits
• ligand receptor areas form deep pockets in PM surface
• pockets pinch off, forming clathrin coated vesicles
• clathrin recycles back into PM + endosomes fuse w/ primary lysosomes to form secondary lysosomes
• ligands removed + absorbed into cytoplasm
• lysosomal + endosomal membranes separate
• endosomes fuse w/ PM, receptors again available for ligand binding

Question 12

Describe the process of vesicular transport

Answer 12

• material is taken up by neuron at synapse -> transported to cell body (retrograde transport)
• material made at cell body released at axon terminal (anterograde transport)

Question 13

Define exocytosis

Answer 13

Movement of material out of the cell

Question 14

Define tissue

Answer 14

A collection of cells + cell products that perform specific, limited functions

Question 15

Describe the 2 epithelial tissues

Answer 15

Epithelia = layers of cells covering internal/external surfaces
Glands = structures that produce secretions -> attached to/derived from epithelia

Question 16

List 4 functions of epithelial tissues

Answer 16

• provide physical protection
• controls permeability
• provides sensation
• produce specialised secretions

Question 17

Describe the structure + characteristics of epithelial tissues

Answer 17

• apical surface = exposed to internal/external environment -> have microvilli
• basal surface = bottom surface attached to basement membrane
• basement membrane = specialised form of extracellular matrix -> enables sticking together

Avascular

Question 18

Describe the intercellular connection of cell adhesion molecules

Answer 18

• connects large areas of PM to adjacent cells via connecting basal surface w/ basement membrane

Question 19

Describe the function of gasp junctions b/t cells

Answer 19

Permit free diffusion of ions + small molecules b/t 2 cells -> contain connexons
-> coordinate muscle contraction

Question 20

Describe the function of tight junctions b/t cells

Answer 20

• prevents movement of water + solutes b/t cells
• protects basal surface from contents of lumen (enzymes, acids + wastes)

Question 21

Describe the function of desmosomes b/t cells

Answer 21

Connections that resist stretching + twisting
-> link 2 cells via CAMs + proteoglycans to cytoskeleton
eg. superficial layers of skin

Question 22

State how an epithelial cell attaches to the basement membrane

Answer 22

Via hemidesmosomes which attach the cell to extracellular filaments in basement membrane

Question 23

State how epithelial cells are repaired/maintained

Answer 23

Structure maintained via division of stem cells located near the basement membrane

Question 24

Describe the location + function of simple squamous epithelia

Answer 24

Location = lining of heart, blood vessels + alveoli
Function = reduce friction, controls vessel permeability, absorption + secretion

Question 25

Describe the location + function of stratified squamous epithelia

Answer 25

Location = surface of skin, lining of mouth + throat
Function = physical protection against abrasion, pathogens + chemicals

Question 26

Describe the location + function of simple cuboidal epithelia

Answer 26

Location = glands, ducts
Function = secretion + absorption

Question 27

Describe the location + function of stratified cuboidal epithelia (rare)

Answer 27

Location = lining of some ducts
Function = protection, secretion + absorption

Question 28

Describe the location + function of transitional epithelia

Answer 28

Location = urinary bladder, renal pelvis, ureters
Function = permits repeated cycles of stretching w/out damage

Question 29

Describe the location + function of simple columnar epithelia

Answer 29

Location = lining of stomach, intestine, gall bladder
Function = protection, secretion + absorption

Question 30

Describe the location + function of stratified columnar epithelia (rare)

Answer 30

Location = pharynx, mammary glands, salivary ducts
Function = protection

Question 31

Describe the location + function of pseudostratified ciliated columnar epithelia

Answer 31

Location = lining of nasal cavity , trachea + bronchi
Function = protection, secretion, move mucous

Question 32

Describe the function of endocrine glands

Answer 32

Release hormones directly into the interstitial fluid eg. pituitary gland

Question 33

Describe the function of exocrine glands

Answer 33

Release of secretions onto epithelial surfaces eg. sweat, mammary + sebaceous glands

Question 34

Describe the function + location of unicellular glands

Answer 34

Function (goblet cells) = make + secret mucous to protect epithelia
Location = airways + intestines

Question 35

Differentiate b/t serous glands + mucous glands

Answer 35

Mucous glands release mucous whereas serous glands release watery solutions