Epithelial Tissues III

Question 1

cell junctions are present on the _______ surfaces of epithelial cells, generally towards the _______ side

Answer 1

• lateral

- apical

Question 2

Tight junctions (or the zonula occludens): provide a _______ barrier that limits or prevents _______. These also limit/control _______.

Answer 2

• highly selective
• diffusion of substances between epithelial cells
• diffusion of membrane proteins through the plasma membrane bilayer

Question 3

Key core proteins of tight junctions are _______ and _______:

Answer 3

occludins and claudins

Question 4

In some epithelia the “tightness” of this barrier is regulated. Tight barriers ensure that

Answer 4

substances absorbed or secreted must pass through the epithelial cell by specific transport pathways

Question 5

Adherence junctions (zonula adherens): Promote _______, but also _______, _______ and _______

Answer 5

• attachment
• polarity
• mophological organization and cell behavior within the epithelial sheet

Question 6

Adherence junctions contain specific _______ that link to actin filaments and other adapter/signaling proteins in the cytoplasm.

Answer 6

cadherins

Question 7

Cadherins are

Answer 7

transmembrane proteins with extracellular domains that interact with each other, and cytoplasmic tails that bind adapters and actin filaments.

Question 8

Some cadherin-associated proteins (e.g. ______ and ______) control various aspects of epithelial polarity, development, and function.

Answer 8

beta catenin and protein kinases

Question 9

Adherence junctions contain specific cadherins that link to _______ and other _______ in the cytoplasm.

Answer 9

• actin filaments

- ther adapter/signaling proteins

Question 10

Adherence junctions contain specific cadherins that link to actin filaments and other adapter/signaling proteins in the _______.

Answer 10

cytoplasm

Question 11

Desmosomes (macula adherens): Promote

Answer 11

mechanical strength and resist shearing forces and promote the structural organization of the epithelial sheet

Question 12

Core components of desmoses include

Answer 12

a different class of cadherins that link to intermediate filaments and other adapter proteins

Question 13

Gap junctions: Promote

Answer 13

rapid communication between epithelial cells, through diffusion of ions and small molecules

Question 14

The plasma membrane in the apical domain contains distinct membrane proteins and a distinct phospholipid content compared to the membrane in the basal domains. Key membrane proteins that localize to specific domains include:

Answer 14

transporter enzymes, ion channels, receptors for exocytosis/endocytosis, signaling receptors and effectors, and proteins that mediate cell-cell and cell-lamina attachments.

Question 15

The tight junction complexes tend to reside near the _______ surface in these cells.

Answer 15

-apical

Question 16

the membrane surrounding the lateral and basal side is often called the basal-lateral (or basolateral) membrane because _______.

Answer 16

the protein and lipid content is similar on both the lateral and basal sides

Question 17

2 key aspects of polarity

Answer 17

1. the PM composition is locally segregated into domains

2. the cytoplasm is polarized

Question 18

The cytoskeleton (particularly microtubules) is

Answer 18

asymmetric or polar in orientation. Organelles are distributed in a precise polarized pattern; secretory vesicles in the apical domain are usually different from those in the basal domain, and they move in specific directions.