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Membranes and Signalling > Membranes > Flashcards

Membranes Flashcards

1
Q

Regarding the nucleus membrane which are false
A- it has a single bilayer surround it wit h two rows of phospholipids
B- its role is to protect nuclear material and control what comes in and out
C- it has a perinuclear space
D- it has a non-membrane bound area Calle the nucleolus

A

A

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2
Q

Regarding the nucleolus which are false
A- its role is in RNA processing
B- its role is in DNA storage

A

B

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3
Q

Regarding the ER which are false
A- it is continuous with the nuclear membrane and the largest organelle
B- it has a role in lipid synthesis and protein synthesis
C- it forms contacts with organelles but not the plasma membrane

A

C

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4
Q

Regarding protein folding in the ER which are false
A- a modification is signal peptide addition
B- a modification is N-linked glycosylation
C- a modification is disulphide bond breaking
D- cycles of glycosylation and folding/misfolding occurs before the protein is released

A

A and C

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5
Q

Regarding the Golgi which are false
A- its consists of 3 compartments (cis, medial and trans)
B- it is composed of 40-100 stacks of cristae
C- the trans Golgi is where proteins are packed in vesicles for lysosomes, secretory vesicles/intermediates or cell surface

A

B

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6
Q

Regarding the mitochondria which are false
A- it has a double membrane
B- the inter membrane space is important for the citric acid cycle
C- the matrix is a fluid with enzymes responsible for the citric acid cycle

A

B

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7
Q

Regarding phospholipids which are false
A- they are amphipathic
B- they contain a fatty acid, glycerol and polar phosphate head
C- the phosphate head is positively charged

A

B and C

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8
Q

Regarding fatty acids which are false
A- they have a terminal carbonyl group
B- they usually have an uneven number of CH^2 atoms
C- the two fatty acid chains in a phospholipid tend to be asymmetric
D- a double bond causes a 45 degree bend in the chain
E- polyunsaturated fatty acids mean a more fluid membrane and lower melting point (kinks in the chains incase distance between the phospholipids

A

A, B and D

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9
Q

Regarding glycerophopholipids which are false
A- it is composed of glycerol-3-phosphate
B- phosphoryl group usually linked to another polar group
C- C2 and C3 of the glycerol esterified with fatty acids

A

C

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10
Q

Regarding different types of glycerophospholipids which are false
A- phosphatidylinsositol can be phosphorylated up to 3 times
B- Phosphatidylserine usually faces the outside on the plasma membrane but faces the cytosol during cell death to signal macrophages
C- phosphatidylcholine is the least abundant phospholipid
D- phosphatidylethanolamine has a small head group size making it easier for proteins to be positioned in the membrane

A

C

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11
Q

Regarding sphingolipids which are false
A- plays no part in protecting cells from harmful environmental factors or signalling
B- they are phospholipids with amide bond between a fatty acid and sphingosine
C- sphingosine bound to fatty acid makes a ceramide
D- sphingomyelin is largely found on the ectoplasmic leaflet
E- they are not phospholipids
F- their fatty acids are longer than glycerophospholipids (up to 26 carbons)

A

A and E

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12
Q

Regarding cholesterol which are false
A- its essential for membrane structural integrity and fluidity
B- interaction between cholesterol polar COOH group and polar phospholipid head group holds the membrane together
C- at high temps they repel each other, preventing the membrane breaking down
D- important for membrane dynamics such as vesicle fusion/endocytosis
E- prevent membrane becoming too rigid at low temp by stopping phospholipids coming too close due to steric reasons

A

B and C

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13
Q

Regarding glycolipids which is false
A- they are the least common type of membrane lipid
B- they are a lipid with a carbohydrate attached via an ester bond
C- they have a role in membrane stability and cell recognition
D- they cannot extend into the extracellular space or act as recognition site for particular chemicals
E- they allow cell attachment and tissue formation

A

B and D

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14
Q

Regarding lipid composition and membrane/vesicle properties which are false
A- pure sphingomyelin bilayers are thinner than those formed by glycerophospholipids
B- cholesterol enhances PC bilayer through lipid ordering
C- PE forms flat monolayers whilst PC forms conical shaped layers
D- varying endo/exoplasmic concentrations of PC and PE result in membrane curvature
E- cholesterol and sphingolipids are incapable of clustering with specific proteins to for lipid rafts
F- membrane lipids can undergo lateral diffusion and typically exchange place with heir neighbours 10 million times a second

A

A, C and E

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15
Q

Regarding membrane lipid flipping which are false
A- p-type flippases require ATP, are specific and cause inward movement
B- spontaneous, bi-directional, non-specific flipping doesn’t occur
C- ABC flippases are bidirectional, ATP requiring and specific
D- scramblase is bidirectional, no energy needed, non-specific, CA^2+ dependant

A

B and C

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16
Q

Regarding lipids as energy stores which are false
A- triglycerides are stored in adipose tissue
B- complete oxidation of fatty acids provides high caloric content
C- adipocyte designed for continuous synthesis and breakdown of triglycerides controlled by hormone-dependant lipases

A

None

17
Q

Regarding lipids and intracellular signalling which is false
A- DAG and PIPs are involved in ATP-mediated activation of protein kinase C
B- prostaglandins are fatty acid derived eicosinoids that have a role in immunity and inflammation
C- sphingosine-1-phosphate, sphingolipid derived form ceramide, regulates calcium mobilisation, cell growth and apoptosis

A

A

18
Q

Regarding lipid droplets which are false
A- organelle, lipid ester core, surface phospholipid bilayer
B- Formed when lipid levels higher than for membrane needs
C- lipid/energy storage

A

A

19
Q

Regarding the SER which are false
A- enzymes embedded in its membrane allow it to produce cholesterol and phospholipids
B- it is unable to produce membrane lipids for itself but can transport newly made lipids elsewhere

A

B

20
Q

Regarding membrane synthesis which are false
A- occurs by expansion of existing membranes
B- early steps take place in the cytoplasm, water soluble intermediates
C- the final step takes place on enzymes in the Golgi membrane
D- major fatty acids contain 14,16,18 or 20 carbons

A

C

21
Q

Regarding unsaturated fatty acids which is false
A- double bond kinks mean less closely packed so less interactions between chains, lower melting point, liquid at room temp
B- most in nature are trans
C- desaturate enzymes remove two hydrogens creating a C=C
D- oleoyl-CoA formed by removal of 2H from stearoyl-CoA by stearoyl-CoA destaurase, forms cis C=C between 9th and 10th carbons

A

B

22
Q

Regarding the first stage of fatty acid synthesis which are false
A- catalysed by fatty acid synthase a multi enzyme protein
B- fatty acids are created from A
acetyl-CoA and NAD
C- it occurs in the lysosome
D- most acetyl-CoA comes from carbohydrates via the glycolytic pathway

A

B and C

23
Q

Regarding the 3 steps of cytosolic stage of fatty acid synthesis which are false
A- pyruvate is converted to acetyl-CoA, pyruvate loses one carbon which forms C02
B- during pyruvate breakdown electrons are transferred to NADP+ to produced NADPH which is used to be cells to make proteins
C- final stage of pyruvate breakdown, the acetyl group transferred to coenzyme A to produced acetyl-CoA

A

B

24
Q

Regarding the stage of fatty acid synthesis immediately after acetyl-CoA production which are false
A- one acetyl-CoA joins a bicarbonate, this requires energy from ATP catalysed by acetyl-CoA carboxylase
B- this is a reversible reaction not the committed step
C- this produced Malonyl-CoA

A

B

25
Q

Regarding Malonyl-CoA which are false
A- provides 2 carbon units to fatty acid chain
B- fatty acid synthase catalyses the synthesis of palmitate a 16 carbon long saturated fatty acid

A

None

26
Q

Regarding palmitate which are false
A- palmitate leaves the fatty acid synthesis cycle
B- palmitoyl protein thioesterases remove thioesterase linked fatty acyl groups from modified cytosine residues
C- addition of acetyl groups can generate stearate (C18) or longer chains
D- fatty acid elongation systems are present in the cytosol and mitochondria

A

D

27
Q

Regarding membrane synthesis which are false
A- during stage one two fatty acids are esterified to phosphorylated glycerol phosphate backbone
B- during stage two phosphatase coverts phophatidic acid into diacylglycerol, a glyceride with 2 fatty acids covalently bound to glycerol via glycosidic linkages
C- during stage 3 a polar head group is transferred via cytosine diphospho-(whatever the head group is)
D- during stage 4 flippases catalyse the movement of phospholipids from the cytosolic to endoplasmic leaflet

A

B

Membranes and Signalling (1 decks)

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