Block 1: Cell Biology

Question 1

Describe the structural characteristics of the smooth endoplasmic reticulum

Answer 1

while the SER is continuous with the RER, it does not have ribosomes embedded on the membrane surface and is not as abundant. the SER still has cisternae, which are tubular, saclike interconnected channels of vesicles

Question 2

Describe the function of the smooth endoplasmic reticulum

Answer 2

functions in lipid biosynthesis, detoxification of potentially harmful materials, and storage calcium

Question 3

Describe the structure of the rough endoplasmic reticulum

Answer 3

Rough ER has ribosomes embedded on the membrane

Question 4

Describe the function of the rough endoplasmic reticulum

Answer 4

production of membrane associated proteins, proteins of membranous organelles, and proteins to be secreted by exocytosis.

Question 5

Describe the overall structure and function of the endoplasmic reticulum

Answer 5

structure: membranous network enclosing intercommunicating channels called cisternae
f(x): major site for biosynthesis of lipids and proteins

Question 6

Describe the role of the smooth ER in hormone synthesis and detoxification

Answer 6

hormone synthesis: in cells that secrete steroid hormones (i.e. adrenal cortex) SER occupies a large portion of the cytoplasm

detoxification: SER enzymes, including those of the cytochrome p450 family, allow detoxification of harmful molecules by solubilizing them to allow them to be excreted by cells

Question 7

Describe the role of smooth ER in the storage of calcium

Answer 7

smooth ER vesicles are responsible for the storage and controlled release of Ca2+, which is part of the rapid response of cells to various stimuli. Particularly in striated muscle cells, SER has a special name–sarcoplasmic reticulum.

Question 8

Describe the structure of the golgi complex.

Answer 8

many smooth, membranous cisternae containing enzymes and proteins being processed.

cis face (receiving face, convex face): located closest to RER, receives vesicles from ER

trans face (shipping face, concave face): exports finished/packaged products to the cell, located away from the RER

Question 9

What is the function of the golgi complex?

Answer 9

posttranslational modification (glycosylation, phosphorylation, sulfation, proteolysis), initation of some packaging

Question 10

What is the relationship of the golgi apparatus to the rough ER

Answer 10

transport vesicles from the RER are received by the cis face of the golgi apparatus

Question 11

What is the role of COPI and COPII surface proteins?

Answer 11

COP I Facilitates the retrograde movement of vesicles through the golgi apparatus

COP II facilitates the forward movement of vesicles in the cis golgi network

Question 12

Predict functional outcomes of deficient/altered structure or function of smooth ER

Answer 12

smooth ER functions to detoxify potentially harmful drugs and many drugs are metabolized by enzymes situated in the smooth ER; without this the body can’t metabolize those drugs

sarcomere contraction would be impaired. leading to muscle weakness.

phospholipid synthesis would be decreased.

Question 13

Describe the structure of mitochondria

Answer 13

mitochondria are membrane enclosed organelles with a double membrane; the inner membrane projects internal shelves called cristae that increase the surface area The inner membrane also holds the electron transport chain complexes as well as ATP synthases.

2 functional compartments: matrix and intermembrane space

Question 14

Describe the mitochondrial matrix

Answer 14

a gel that’s the location of the enzymes for the CAC and fatty acid beta oxidation. the matrix also contains DNA, tRNA, rRNA and mRNA

Question 15

Describe the intermembrane space

Answer 15

very H+ rich.

Question 16

Describe the relationship between the intermembrane space and the mitochondrial matrix

Answer 16

the intermembrane space is very H+ rich. movement of electrons from the matrix to the intermembrane space produces an electrochemical gradient across the membrane, leading to a large proton motive force that moves H+ through ATP synthase

Question 17

Describe the outer mitochondrial membrane

Answer 17

sieve like w/ transmembrane proteins called porins that form a small channel molecules can pass from the cytoplasm to the IM space

Question 18

Function of cristae

Answer 18

increase the membrane SA to increase reaction space

Question 19

List structural/genetic mitochondrial disorders

Answer 19

myoclonic epilepsy w/ ragged red fibers (MERF)

other mitochondrial cytopathy syndromes

Question 20

Describe MERF

Answer 20

myoclonic epilepsy w/ ragged red fibers (MERF)

a family of mitochondrial cytopathy syndromes where aggregates of normal mitochondria provide a ragged appearance of red muscle fibers. These patients have a defect in the MT-TH gene and results in structural abnormalities of muscle tissue including muscle fatigue

Question 21

Describe the mechanisms behind mitochondrial cytopathy syndromes

Answer 21

mitochondrial DNA is completely maternally derived. abnormal mitocDNA can impair mitochondrial function, leading to defective cell function, which mainly results in structural abnormalities of muscle and nervous system as well as metabolic abnormalities derived from failure of oxphos

Question 22

Describe the structure and function of endosomes

Answer 22

s(x): spherical, enclosed by a single membrane
f(x): can be viewed as stable cytoplasmic organelles or transient structures formed as the result of endocytosis. they either return to the plasma membrane (early endosomes) or travel deeper and mature into lysosomes (late endosomes)

Question 23

Describe the structure of lysosomes.

Answer 23

Lysosomes are membrane walled vesicles containing hydrolytic enzymes, usually with a heterogenous appearance

Question 24

Describe the function of lysosomes

Answer 24

sites of intracellular digestion

Question 25

Describe how material from outside the cell is digested by lysosomes.

Answer 25

material from outside the cell is taken in by endocytosis and digested when the membrane of a phagosome or pinocytotic vesicle fuses with a lysosome. Their contents are acidified in the lysosome to facilitate digestion, and the lysosome is now called a heterolysosome.

Question 26

Describe how material from inside the cell is digested by lysosomes

Answer 26

excess organelles or large, nonfunctional macromolecules can be degraded in autophagy. During autophagy, a lipid bilayer membrane forms around and isolates the cytoplasmic portion to be removed, producing an autophagosome. Autophagosomes then fuse with lysosomes for digestion

Question 27

What happens if the enzymes in lysosomes are defective or absent?

Answer 27

substances that are normally digested by lysosomes would accumulate in large secondary lysosomes or in residual bodies filled with the indigestible material. These secondary lysosomes eventually interfere with normal cell or tissue function

Question 28

Describe the structure and function of peroxisomes

Answer 28

Peroxisomes are spherical, membrane enclosed organelles named for enzymes that decompose hydrogen peroxide as well as participate in lipid biosynthesis and catabolism by beta oxidation of long chain fatty acids

Question 29

Compare the alcohol handling function of peroxisomes to that of smooth ER

Answer 29

peroxisomes also have some enzymes that convert alcohol to acetaldehyes. also, some catalases inactivate various potentially toxic molecules

Question 30

Describe proteasomes.

Answer 30

proteasomes are multi protease complexes that digest proteins targeted for destruction by ubiquination, removing excess proteins or proteins that are misfolded.

Question 31

Compare targeted and non-targeted degradation of intracellular structures and debris

Answer 31

targeted: ubiquinated proteins are degraded by proteasomes
non-targeted: hydrolytic enzymes in lysosomes degrade substances derived from endocytosis and from the cell itself (autophagy)

Question 32

What is the most common lysosomal storage disease? describe it.

Answer 32

Tay Sachs Disease

caused by absence of lysosomal galactosidase that catalyzes a step of breakdown of gangliosides in neurons. this interferes with normal cell function, and children become vegetative die

Question 33

Describe peroxisomal disorders.

Answer 33

diseases due to defects in the peroxisomal enzyme responsible for processing very long chain fatty acids; usually presents w/ metabolic disturbances associated w/ acidosis or storage of abnormal lipids in susceptible cells

Question 34

What are some examples of peroxisomal disorders?

Answer 34

adrenoleukodystrophy

zellweger syndrome

Question 35

Describe adrenoleukodystrophy

Answer 35

caused by a defective
integral membrane protein needed for transport of very long chain fatty acids into the peroxisome for B oxidations. accumulation disrupts the myelin sheath, causing severe neurologic symptoms.

Question 36

Describe Zellweger syndrome

Answer 36

disease due to an inability of peroxisomes to incorporate peroxisomal enzymes b/c necessary targeting signal receptors are missing from the peroxisomal membrane.

Question 37

Inclusions

Answer 37

cytoplasmic structures or deposits filled w/ stored macromolecules that aren’t present in all cells

Question 38

glycogen droplet f(x)

Answer 38

used as an energy deposit that undergoes glycogenolysis to form glucose, which is converted to pyruvate for the CAC

Question 39

lipid droplet f(x)

Answer 39

catabolized into FA’s used for CAC for the formation of pyruvate; 1g lipid produces 2x ATP as 1 g glycogen

Question 40

Lipofuscin

Answer 40

yellow to brown pigment in long lived cells that are the indigestible remnants of lysosomal activity

Question 41

Hemosiderin

Answer 41

an iron storage complex found w/i the cytoplasm of many cells, most likely formed by the indigestible resides of hemoglobin; related to phagocytosis of RBCs