Cell Structure 1

Question 1

What are the 4 types of tissues in the body?

Answer 1

1. Nervous
2. Epithelial
3. Connective
4. Muscle

Question 2

What are the germ layers from which all tissues develop?

Answer 2

1. Ectoderm
2. Endoderm
3. Mesoderm

Question 3

What types of tissues does the ectoderm give rise to?

Answer 3

Nervous and epithelial

Question 4

What types of tissues does the endoderm give rise to?

Answer 4

Epithelial

Question 5

What types of tissues does the mesoderm give rise to?

Answer 5

Epithelial, connective, and muscle

Question 6

What does amphipathic mean?

Answer 6

Has both polar (hydrophilic) and nonpolar (hydrophobic) regions attached to it.

Question 7

What is the purpose of the cell membrane’s fluidity?

Answer 7

To allow lateral diffusion of lipid molecules and membrane proteins.

Question 8

Describe membrane permeability.

Answer 8

Impermeable to charged ions.

Permeable to small nonpolar and small polar molecules.

Question 9

What are some functions membrane proteins perform?

Answer 9

Transport, signaling, adhesion

Question 10

Name the two parts of the phospholipid head and their charges.

Answer 10

Amino alcohol: positive

Phosphate: negative

Question 11

Name the backbone of the phospholipid.

Answer 11

Glycerol

Question 12

What are phospholipids named after?

Answer 12

The amino-alcohol that forms the head group.

Question 13

A kink in the unsaturated fatty acid chain helps with…

Answer 13

maintaining membrane fluidity, preventing phospholipids from packing too closely together.

Question 14

What are the components of phospholipids?

Answer 14

Two fatty acid tails (one unsaturated); glycerol backbone; phosphate bridge (head); amino alcohol (head).

Question 15

What are the components of cholesterol?

Answer 15

One fatty acid tail; a rigid, planar, steroid ring structure; a polar head group (hydroxyl)

Question 16

Where does cholesterol go?

Answer 16

Intercollates b/w phospholipids.

Question 17

What does cholesterol do?

Answer 17

• reduces permeability to small molecules
• stiffens membrane for mechanical strength
• at high concentrations, prevents further packing of phospholipid
• contributes to formation of lipid rafts

Question 18

With an increase in cholesterol, fluidity…

Answer 18

decreases, then plateaus after a certain point. (Adding in cholesterol reduces fluidity as low as it can go.)

Question 19

Lipid rafts are…

Answer 19

concentrations of specific proteins crucial for cell-cell recognition on lipid membrane

Question 20

Name the components of glycolipids.

Answer 20

2 fatty acid chains, polar head, carbohydrates attached to head group.

Question 21

What do glycolipids do?

Answer 21

Contribute to the glycocalyx.

Question 22

Where are glycolipids present?

Answer 22

Only in outer leaflet of lipid bilayer. Form a sugar coating around membrane of most cells.

Question 23

What happens in Tay-Sachs disease?

Answer 23

Defect in metabolism of gangliosides (complex lipids) in neurons. Inability to turn over gangliosides results in buildup to toxic levels, causing neurons to die. Defect in enzyme that metabolizes gangliosides.

Question 24

What are the two forms of membrane proteins?

Answer 24

Integral: embedded in or traverse membrane
Peripheral: associated with integral proteins but not directly embedded in membrane; adherent to cytoplasmic or extracellular surface of membrane.

Question 25

What are the functions of membrane proteins?

Answer 25

1. Transport of ions and molecules 2. Cell-cell recognition and adhesion 3. Signal transduction

Question 26

What is the purpose of freeze fracturing?

Answer 26

Allows us to visualize which side of the lipid bilayer proteins adhere primarily to.

Question 27

What are the two resultant sides of freeze fracturing, and which do most proteins cling to?

Answer 27

P-face (protoplasmic): most integral membrane proteins stick with this side because they are anchored to the cytoplasmic side of the bilayer/interacting w/ some part of the cytoskeleton. E-face (extracellular)

Question 28

What are the two sources of carbohydrates in the glycocalyx?

Answer 28

Glycolipids and proteins (either integral or secreted by other cells and absorbed to membrane)

Question 29

What are the functions of the glycocalyx?

Answer 29

1. Prevent infection: it is strongly negatively charged (polyanionic) on the outer surface to repulse bacteria that have been coated in negatively-charged antibodies. 2. Protects cell from chemical or mechanical damage by acting as a barrier above the delicate lipid membrane. 3. Important for cell-cell recognition: carbohydrate composition helps identify what kind of cell it is so it can interact or not interact w/ other cells.

Question 30

Movement of ions and small molecules across membrane is controlled by:

Answer 30

``` Transport proteins (e.g. ion channels) Carrier proteins ```

Question 31

Movement of macromolecules and particulate matter across membranes is controlled by:

Answer 31

Endocytosis (outside to inside) | Exocytosis (inside to outside)

Question 32

What are the 3 types of endocytosis?

Answer 32

Pinocytosis (cell drinking) Receptor-mediated endocytosis Phagocytosis

Question 33

What is pinocytosis?

Answer 33

Bulk uptake of fluids from extracellular medium into interior of cell and sent to destinations w/in cells by vesicles.

Question 34

What is receptor-mediated endocytosis?

Answer 34

Capturing of specific molecules that the cell needs by having receptors on the cell surface that bind to those molecules and capture them, then bring them into the cell through the cytoplasmic vesicle.

Question 35

What is phagocytosis?

Answer 35

Only performed by special phagocytic cells that have target receptors for bacteria or cell debris. Taking up of large particles via pseudopodia that engulfs the particle and brings it in via a large phagocytic vesicle to fuse with lysosomes. NOT clathrin-driven; pseudopodia driven by changes in actin cytoskeleton.

Question 36

What drives invagination during pinocytosis?

Answer 36

Clathrin coating on cytoplasmic side of cell membrane.

Question 37

What drives pinching off of endocytic vesicles in pinocytosis?

Answer 37

Dynamin: a GTPase that forms a collar to form the missing side of the vesicle.

Question 38

What are the purposes of pinocytosis?

Answer 38

To bring nutrients into the cell and to help maintain membrane's surface area, shape, and size by taking out old, worn parts of membrane.

Question 39

How does receptor-mediated endocytosis work for cholesterol?

Answer 39

The cell produces LDL receptors and implants them on the extracellular surface to bind LDL. When LDL binds to receptors inside a clathrin-coated pit, the clathrin causes invagination of the membrane into a coated vesicle. The clathrin dissociates, and the vesicle becomes a CURL (component for uncoupling of receptor and ligand - acidic) to dissociate the LDL from the receptors. The receptors return to the cell surface with the membrane, while the LDL in the endosome proceeds to fuse w/ a lysosome that can break down the LDL and release cholesterol.

Question 40

What is phagocytosis limited to?

Answer 40

MACROPHAGES AND NEUTROPHILS

Question 41

What is a phagosome?

Answer 41

the large vesicle containing engulfed material in phagocytosis

Question 42

What is the purpose of exocytosis?

Answer 42

Export of material out of the cell (synthesized materials made in the cell) packaged in vesicles

Question 43

What materials travel in exocytosis and where?

Answer 43

Things that are going to be secreted from the cell are inside the vesicles; integral membrane proteins are located on the vesicle membrane itself and will then merge with the cell membrane upon release of vesicle contents.

Question 44

What catalyzes the fusion of exocytic vesicles with the cell membrane?

Answer 44

Fusogenic proteins (differ from cell to cell)