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Building Bodies > 1. Cell Membrane, RER and SER, Ribosomes > Flashcards

1. Cell Membrane, RER and SER, Ribosomes Flashcards

1
Q

What are the main functions of the plasma membrane

A
  1. Separates cell from extracellular environment
  2. Maintains structural integrity
  3. Movement and expansion
  4. Regulates exchanges between the cell and the extracellular environment
  5. susceptible to chem. and phys. variation
  6. receiving signals from outside + sending signal transduction inside
  7. regulation of cell to cell and cell to extracellular protein contacts (adhesion)
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2
Q

What is the current plasma membrane model

A

Fluid Mosaic model

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3
Q

What does the fluid mosaic model state

A

States that components of the plasma membrane move fluidly (side to side/laterally) in the membrane layer.

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4
Q

What is the evidence supporting the Fluid Mosaic Model

A

Proteins are free to diffuse in the membrane, thus in an hour 2 proteins will form hybrid cells and then become mixed proteins

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5
Q

Is the plasma membrane a selective or non selective barrier

A

Selective barrier

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6
Q

What are the principle components in the plasma membrane

A
  • Lipids –> phospholipids and carbohydrates (40%)
  • Membrane proteins (50%)
  • Carbohydrate groups (10%)
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7
Q

What is a phospholipid

A

glycerol, 2 fatty acid tails and phosphate linked head group

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8
Q

What is the phospholipid bilayer

A

Forms main membrane component, the barrier.

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9
Q

structure of phospholipid bilayer

A

Is composed of 2 phospholipids with tails pointing inwards.
- hydrophillic head faces outwards contacting aq soln inside + outside cell (forms electrostatic interactions w H2o)
- Hydrophobic tail face inwards to avoid interactions with water
P substances cannot cross hydrophobic centre, creating barrier

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10
Q

What are the 2 types of phospholipids in the plasma membrane

A

Phosphoglycerides (based on glycerol) and

Sphingolipids (+phosphoglycerides based on amino alcohol sphingosine)

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11
Q

Can water pass through the plasma membrane?

A

Yes through protein channel aquaporins at a slow rate

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12
Q

What are the 2 types of membrane proteins

A

Integral and peripheral proteins

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13
Q

What are the types of integral proteins

A

Integrated and transmembrane proteins

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14
Q

Functions of membrane proteins

A
  • transporters
  • connectors
  • receptors
  • enzymes
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15
Q

Functions of integral proteins

A
  • cell surface receptors
  • adhesion molecules
  • transporters
  • ion channels
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16
Q

What do carbohydrates attach to on the outside of the cell membrane to form

A

Carbohydrates attach to lipids to form glycolipids, and they attach to proteins to form glycoproteins

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17
Q

What is the function of carbohydrates in the plasma membrane

A

Form cellular markers, allowing the body to differentiate between body cells and foreign cells which it may need to attack

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18
Q

What is glycocalix

A

Glycocalix is a mixture of glycolipids and glycoproteins (also called cell coat). It is a mucus layer

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19
Q

What does the mucous in glycocalix consist of

A
  • glycosaminoglycans and glycoproteins and sometimes enzymes.
  • Thickness up to 50nm
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20
Q

What is the function of glycocalix?

A

A molecular filter (barrier) and is involved in cell to cell adhesion (may contain enzymes)

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21
Q

What is the importance of the mucus barrier in the intestinal homeostasis

A

Breach in mucus barrier allows microbiota to pass. This activates the intestinal immune system causing harmful iflammation.

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22
Q

What is the role of sugar on the plasma membrane surface

A

When neutrophil detects sugar it realises the cell is healthy, therefore at the side of infection, the sugar molecules on the plasma membrane are disrupted and the neutrophil can detect that this is the cell that requires help (reaches site of infection)

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23
Q

What are the types of proteins in the bilayer

A

Integral membrane proteins (integrated in the membrane)

Peripheral membrane protein (attached on the outside of the membrane, non-covalently associated)

24
Q

Functions of integral membrane proteins

A
  • cell surface receptors
  • adhesion molecules
  • transporters
  • ion channels (allows ions through the membrane)
25
Q

Overall functions of membrane proteins

A
  • transporters
  • connectors
  • receptors
  • enzymes
26
Q

What are the 3 forms of transport across the membrane

A

Passive - simple diffusion, facilitated diffusion

Active - active transport

27
Q

Simple diffusion

A

Materials move down conc. gradient through pplbl,

  • doesn’t require energy
  • moves from high to low concentration
  • eg O2 or H20 diffusing into cell, Co2 diffusing out
28
Q

Facilitated diffusion

A

Passage of material aided by conc. gradient and by transport protein

  • doesn’t req. energy
  • uses transport protein to move from high to low conc.
  • eg. glucose or amino acids moving from blood into a cell (aquaporin transport protein for H2o)
29
Q

Active transport

A

Molecules move through transport protein with energy must be released/used to move it against the concentration gradient

  • requires energy
  • uses transport protein to move from low to high conc.
  • eg. Na+/K+ pump –> pumping Na+ ions out and K+ ions in against strong conc. gradients
30
Q

Endocytosis

A

Capturing things from outside

31
Q

Exocytosis

A

Moving things out from the cell

32
Q

What are the main features of cell membranes (plasma membrane)

A
  • Fluidity
  • Asymmetry
  • Discontinuity
  • Selectivity
33
Q

Expand on fluidity in the cell membrane

A

Lipids can move laterally in the layer where they are inserted

34
Q

Expand on asymmetry in the cell membrane

A

lipids, proteins and are not symmetrical on the inner and external side

35
Q

Expand on discontinuity in the cell membrane

A

membrane structure interrupted by integral proteins (not symmetrical(

36
Q

Expand on selectivity in the cell membrane

A

Membrane is permeable with strict selection

37
Q

What is the name given to organelles that make up the intracellular membrane

A

The endomembrane system

38
Q

What organelles make up the intracellular membrane

A
  • endoplasmic reticulum
  • golgi apparatus
  • lysosomes and vesicles
  • nuclear envelopes
39
Q

The endoplasmic reticulum includes

A

The rough endoplasmic reticulum (RER) and the smooth endoplasmic reticulum (SER)

40
Q

What is the structure of the Rough endoplasmic reticulum

A
  • Made up of interconnected, flattened membrane sacs. - -
  • Contains ribosomes bound to the outer layer of the membrane
  • very abundant in cells undergoing high protein synthesis (glands, plasma cells, neurons)
41
Q

What is the function of the RER

A
  • after receiving proteins made by ribosomes, amino acid chains pass through connected, flat sacs of RER and are folded + modifies (then sent to Golgi)
  • post-translational modifications of protein (proteolysis, glycosylation, phsophorylation)
  • giving proteins secondary, tertary and quaternaty structure
  • start protein glycosylation, completed in golgi apparatus
  • hydroxylation of lysine and proline residues
42
Q

Free ribosomes function

A

synthesise proteins for nucleus, mitochondria, cytoskeleton, peroxisomes, and cytoplasmic side of the plasma membrane

43
Q

RER ribosomes function

A

synthesise proteins for the membrane, secreted proteins and lysosomes. Proteins formed in RER are ‘export proteins’, ie are shipped around the cell

44
Q

How do proteins synthesised in the ribosome enter the lumen of the ER

A

First 5-30 amino acids encode a signal peptide (red),

45
Q

Eukaryote protein synthesis

A 
Major subunit made of:
- 49 proteins, 3RNA molecules
- 60S (sedimentation coefficients in Svedberg units)
minor subunit:
- 33 proteins, 1 RNA molecule
- 40S
During protein synthesis Major and Minor subunit combine:
- 82 proteins, 4 RNA molecules,
- 80S
*15-20nm
46
Q

Prokaryote protein synthesis

A 
Major subunit
- 34 proteins, 2 RNA molecules
- 50S
Minor subunit
- 21 proteins, 1 RNA molecule
- 30S
During protein synthesis major and minor subunit combine:
- 55 proteins
- 3 RNA molecules
- 70S
47
Q

Which ribosomes are responsible for protein synthesis

A
  • ribosomes on the cytosilic side of nuclear envelope

- ribosomes on RER

48
Q

How are proteins imported into the RER

A

First 5-30 amino acids encode a signal peptide (red) –> recognised by and bound to signal recognition peptide (SRP, brown) –> SRP binds to receptor of ER membrane (green)

49
Q

soluble proteins vs membrane proteins

A
  • soluble proteins present in cytoplasm/mitochondria/nucleus. Outer part contains hydrophilic AA which interact with solvent and help solubilize the protein. hydrophobic aa buried inside the protein
  • membrane proteins are present in the membrane, have hydrophobic aa interact with membrane centre w anchored proteins having some linked lipid molecule attached
50
Q

Functions of the smooth endoplasmic reticulum

A
  • synthesis of steroids and lipids
  • biogenesis (making of) of cell membranes
  • storage of ions such as calcium
  • involved in detoxifying processes of the cell
  • glycogen metabolism
51
Q

Where are steroid hormones synthesised

A

In the SER in gonads and adrenal glands

52
Q

What is the cell detoxifying process (SER)

A

contains enzymes that add OH groups to toxic compounds, favouring elimination

53
Q

Where are Ca ions stored and where do they go

A

Stored in SER (particularly in striated muscle cells) and go to/from cytoplasm

54
Q

Where do lipids synthesised by SER go

A

into the cell membrane
- can synthesis “flippase” enzyme which catalyze flip flop movement and bring newly synthesised molecules to opp. side of bilayer

55
Q

What is glycogen metabolism (SER)

A

Breaking down glycogen granules into glucose (mainly occurs in liver cells and skeletal muscle cells)

56
Q

What are the steps in Glycogen metabolism

A
  1. glycogen granule (branches of glycogen)
  2. becomes glycogen phosphorylase
  3. phosphoglucomutase
  4. glucose-6-phosphatase
  5. glucose?

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