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BIOL 112 > Lecture 5 > Flashcards

Lecture 5 Flashcards

1
Q

What does the endomembrane system consist of, and where is it found?

A

Nuclear membrane, endoplasmic reticulum, golgi apparatus and lysosomes.
Found in eukaryotic cells.

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2
Q

What is the SER involved in?

A

Drug detoxification, carbohydrate metabolism and the synthesis of fats, phospholipids and steroids.

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3
Q

Where are phospholipids made?

A

SER.

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4
Q

How does the SER detoxify lipid soluble drugs e.g. barbiturates?

A

Adds charged water soluble groups such as sulphate or glucuronic acid.

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5
Q

What is the SER in hepatocytes responsible for?

A

The breakdown of stored glycogen and the release of glucose.

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6
Q

What does the SER in muscle do and what is it called?

A

Sequesters calcium ions from cytosol.

Sarcoplasmic reticulum.

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7
Q

What is the calcium pump?

A

SR bound ATPase which pumps calcium ions into the SR lumen.

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8
Q

What do calcium ions bind to in the muscle?

What does this therefore enable?

A

A protein complex of tropomyosin and troponin which normally blocks interaction between the myosin heads and actin.
Therefore allows the myosin heads to interact with the actin filaments, so muscle contraction can occur.

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9
Q

Where does protein synthesis for rough ER destined proteins begin?

A

The cytosol.

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10
Q

What four types of proteins are synthesised in the rough ER?

A

Extracellular proteins, membrane proteins, lysosomal proteins and glycoproteins.

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11
Q

What is required from ribosome synthesising proteins to attach to the rough ER?
What does the N terminus of proteins usually contain?

A

A specific signal peptide sequence.

Signal peptide usually 20 to 30 amino acids long.

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12
Q

What doesn’t SRP attached to and what does it do?

A

Attaches to signal peptide.

Stops translation in the cytosol.

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13
Q

What does the SRP dock to on the ER membrane

A

SRP receptor.

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14
Q

What enzyme cleaves the signal sequence off? Where is this found?

A

Signal peptidase. Found in the ER lumen.

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15
Q

What does glycosylation mean?

A

The addition of sugars or oligosaccharides.

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16
Q

How many oligosaccharides are added to proteins in the ER?

What is it composed of, and where is it transferred to?

A

One.
N-acetylglucosamine, mannose on glucose residues containing 14 sugar residues.
Transferred to the proteins in the ER.

17
Q

What is quickly removed from the oligosaccharide of most proteins while still in the ER?

A

Glucose residues and one mannose residue.

18
Q

What happens usually after protein synthesis in the RER?

A

Most proteins are moved in small transport vesicles to the Golgi apparatus.

19
Q

What do the Golgi apparatus do?

A

Modifies and sorts proteins.

Mediates flow of proteins from RER to various destinations in endomembrane system.

20
Q

What is the default pathway of proteins synthesised in the RER?
When does this not happen?

A

Through the Golgi and then to the plasma membrane for secretion.
Some proteins tagged in the Golgi for specific destinations in the cell.

21
Q

Example of proteins tagged in the Golgi? What then happens to them?

A

Lysosomal enzymes’ mannose residues phosphorylated in the cis Golgi.
Mannose 6-phosphate receptor then binds in trans-Golgi reticulum, directing their transfer to lysosomes.

22
Q

What is the principal type of modification in the Golgi?

A

Glycosylation.

23
Q

What are lysosomes?

A

Vesicular structures surrounded by single smooth membrane containing 60 hydrolytic enzymes active at acidic pH.

24
Q

Where are hydrolytic enzymes manufactured? And will they break down almost all biomolecules?

A

ER.

Yes.

25
Q

Where do primary lysosomes originate from?

A

Trans face of the Golgi.

26
Q

What happens when a lysosome fuses with its target?

A

H+ ions pumped into secondary lysosome to reduce pH and activate enzymes.

27
Q

What three mechanisms do lysosomes carry out?

A

Autophagy - recycling of worn out organelles.
Phagocytosis
Autolysis during apoptosis

28
Q

What happens in Tay-Sachs disease?

A

Hexosaminidase A enzyme deficiency results in accumulation of lipid ganglioside.

29
Q

What causes clinical symptoms of Tay-Sachs disease?

A

The accumulation of ganglioside in nerve cells.

30
Q

When does death typically occur in Tay-Sachs disease?

A

2 to 3 years of age.

31
Q

What type of disease is Tay-Sachs?

A

Lysosomal storage disease.

BIOL 112 (6 decks)

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