Protein transport in ER

Question 1

Function of Endoplasmic Reticulum

Answer 1

lipid and protein synthesis

Question 2

makes a major contribution to mitochondrial and peroxisomal membranes by producing most of their lipids

Answer 2

ER membrane

Question 3

an amino-terminal protein sequence that targets newly synthesized polypeptides to the endoplasmic reticulum (ER) for co-translational transfer and insertion into the ER membrane, or for translocation into the ER lumen.

Answer 3

ER signal sequence

Question 4

binds to the ER signal sequence, pausing translation and directing the ribosome to the rough ER

Answer 4

signal recognition particle (SRP)

Question 5

Function of RER

Answer 5

1. Surface for ribosomes
2. Formation of glycoprotein
   *Linking of sugars to protein to
   make glycoprotein
3. Synthesis of precursors
   *Produce enzyme precursors for
   the formation of lysosomes

Question 6

a chain-like structure composed of multiple sugar molecules (monosaccharides) linked together, forming carbohydrates or saccharides, and playing various roles in biological systems

Answer 6

glycan

Question 7

Temporary sugar added for quality control during glycoprotein folding.

Answer 7

Glucose

Question 8

A core sugar component

Answer 8

Mannose

Question 9

The base sugar directly linked to Asn

Answer 9

N-acetylglucosamine

Question 10

A lipid carrier embedded in the ER membrane that holds a pre-assembled oligosaccharide

Answer 10

Dolichol

Question 11

Enzyme that transfers the glycan onto the asparagine residue of a growing polypeptide

Answer 11

Oligosaccharide transferase

Question 12

Newly synthesized protein moving into the ER lumen through a translocation channel.

Answer 12

Translocating protein

Question 13

The glycosylation site where the oligosaccharide is attached

Answer 13

Asparagine (Asn)

Question 14

________ release ________ when the allergen is encountered

Answer 14

Mast cells; histamines

Question 15

glands that secrete substances, like sweat, tears, saliva, and digestive juices, onto an epithelial surface or into a duct that leads to the body’s surface or a cavity

Answer 15

Exocrine gland

Question 16

which organelle can we find vast amounts of protein

Answer 16

Rough ER

• exocrine cells of the pancreas
• antibody-secreting plasma cells
• insulin-secreting β cells

Question 17

Exocrine cells of the pancreas (____% rough ER)

• secrete digestive enzyme

Answer 17

60%

Question 18

Type of smooth ER:

• transport vesicles carrying newly synthesized proteins and lipids bud off for transport to the Golgi apparatus

Answer 18

Transitional ER

Question 19

Organelles that synthesize steroid hormones

Answer 19

Smooth ER

Question 20

• site of lipoprotein particles production
• functions in detoxification

Answer 20

Hepatocytes

Question 21

Carry lipids via the bloodstream to other parts of the body

Answer 21

lipoprotein particles

Question 22

Small ducts that collect bile from hepatocytes

Answer 22

canaliculi

Question 23

The main functional cells of the liver

Answer 23

Hepatocytes

Question 24

Specialized macrophages located in the liver sinusoids.

Engulf pathogens, dead cells, and debris, playing a role in immune defense

Answer 24

Kupffer cells

Question 25

Form the walls of liver sinusoids, allowing the exchange of nutrients and waste between the blood and hepatocytes.

Answer 25

Liver sinusoidal endothelial cells

Question 26

Most extensively studied of the detoxification reactions converts water-insoluble drugs or metabolites into water-soluble for excretion

Answer 26

Cytochrome 450

Question 27

Endoplasmic reticulum vs. Sarcoplasmic reticulum Which is an excitable cell

Answer 27

Sarcoplasmic reticulum

Question 28

is a specialized smooth ER found in muscle cells, primarily involved in calcium storage and release for muscle contraction

Answer 28

Sarcoplasmic reticulum

Question 29

releases Ca²⁺ rapidly upon stimulation

Answer 29

RyR (ryanodine receptor)

Question 30

actively pumps Ca²⁺ back into the SR to relax the muscle

Answer 30

SERCA pump

Question 31

The SR has junctional and longitudinal regions: Junctional SR is near T-tubules and facilitates rapid Ca²⁺ release. Longitudinal SR helps in Ca²⁺ reuptake.

Question 32

Synthesizes phospholipids (gonads and skin oil glands), steroid, and CHO

Answer 32

Smooth ER

Question 33

During transport in ER, a _______________ binds to ER signal Also state the processes undergone during transport in ER

Answer 33

Signal-Recognition Particle (SRP) 1. mRNA is being translated to the polypeptide tide chain with the signal sequence attached. 2. SRP binds to the signal sequence. 3. SRP binds to the SRP receptor (α - top part) located beside the closed translocon (sec61 complex). 4. GTP from SRP and GTP from SRP receptor is released forming GDP + Pi, releasing the SRP, and opening the translocon (sec61 complex). 5. Signal peptidase cleaves the signal sequence from the growing polypeptide chain. 6. Polypeptide continue to be translated into the ER lumen. 7. mRNA is released when ribosomal subunits detach, the translocon (sec61 complex) is closed, and protein is folded inside the ER lumen.

Question 34

consists of 3 or 4 protein complexes, each composed of 3 transmembrane proteins, that assemble into a donut-like structure. facilitates the translocation of proteins into the ER lumen or insertion into the ER membrane, acting as a crucial player in protein biogenesis.

Answer 34

Sec61 complex

Question 35

Import of proteins begins before the polypeptide chain is completely synthesized

Answer 35

Co-translational translocation

Question 36

Two modes of transport and which domain performs them (Bacteria, Archaea, Eukaryotes)

Answer 36

Co-translational translocation - Bacteria - Archaea - Eukaryotes Post-translational translocation - Bacteria - Eukaryotes