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MED 103- BIOLOGY I > 23. TRANSMEMBRANE PROTEINS > Flashcards

23. TRANSMEMBRANE PROTEINS Flashcards

1
Q
  1. What are Transmembrane proteins?
A
  • they are proteins that completely span the membrane (1 or more times)
  • they contain alpha helices
  • they penetrate the hydrophobic core of the lipid bilayer
  • their hydrophobic region contains non-polar amino acids
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2
Q
  1. What are Lipid- Bound Proteins?
A
  • they are attached to a membrane lipid
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3
Q
  1. What two types of Secondary Structures does the Transmembrane Protein have?
A
  1. alpha helical structures:
    - Growth Factor Receptors (EGFR)
    - Insulin
    - Membrane Immunoglobulins
  2. beta pleated sheet structures (beta barrels):
    - Bacterial Porin Proteins
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4
Q
  1. What are Epidermal Growth Factor Receptors ?
    (EGFR)
A
  • they are over expressed in many cancers
    (such as breast cancer)
  • they are a single pass transmembrane protein
  • they have alpha helical structures
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5
Q
  1. What are Porin Beta Barrel Structures?
A
  • they are attached to the plasma membrane through a covalent bond
  • it is bonded to a lipid molecules
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6
Q
  1. What are the two types of attachment of Integral Lipid- Bound Proteins?
A
  1. Directly Attached
  2. Indirectly Attached
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7
Q
  1. What are directly attached integral lipid-bound proteins?
A
  • they are directly attached to the lipids
  • this happens at the internal side of the plasma membrane
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8
Q
  1. What are indirectly attached integral lipid-bound proteins?
A
  • they are indirectly attached to phosphatidyl-inositol
  • this happens at the external site of the plasma membrane
  • it happens through an oligosaccharide chain
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9
Q
  1. What are the two functions of Integral Lipid-Bound Proteins?
A
  • hydrolases
  • receptors
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10
Q
  1. What are Peripheral Proteins?
A
  • they are loosely bound to the surface of the membrane
  • they interact with the polar surfaces of the membrane
  • they can also interact with the proteins embedded in the
    membrane
  • they can be bound to either the external or the internal side of the membrane
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11
Q
  1. What are internal membrane proteins connected to?
    Give an example.
A
  • they are connected with the cytoskeleton
  • EG: Erythrocyte Spectrin
    : this is found in blood cells
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12
Q
  1. List the 6 major functions of the membrane proteins.
A
  1. Transport
  2. Enzymatic Activity
  3. Signal Transduction
  4. Cell-cell Recognition
  5. Intercellular Joining
  6. Attachment to the Cytoskeleton
    Attachment to the Extra Cellular Matrix
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13
Q
  1. What is Transport?
A
  • TRANSPORT TO THE LEFT:
    • a protein that spans the membrane may provide a
      hydrophilic channel
    • this channel is across the membrane
    • the membrane is selective for a particular solute
  • TRANSPORT TO THE RIGHT:
    • other transport proteins shuttle a substance from one
      side to the other by changing shape
    • some of these proteins hydrolyse ATP as an energy
      source
    • this is so that they can actively pump substances
      across the membrane
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14
Q
  1. What is Enzymatic Activity?
A
  • a protein built into the membrane may be an enzyme
  • this is with its active site exposed to the substances in the
    adjacent solution
  • IN SOME CASES:
    • several enzymes in a membrane are organised as a
      team
    • they carry out sequential steps of a metabolic pathway
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15
Q
  1. What is Signal Transduction?
A
  • a membrane protein may have a binding site with a
    specific shape
  • this fits the shape of a chemical messenger perfectly
  • the external messenger (signal) may cause a conformational change in the protein (the receptor)
  • this relays the message to the inside of the cell
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16
Q
  1. What is cell-recognition?
A
  • some glycoproteins serve as identification tags
  • they are specifically recognised by other cells
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17
Q
  1. What is Intercellular Joining?
A
  • the membrane proteins of the adjacent cells may hook together in various kind of junctions
  • EG: gap junctions
    : tight junctions
18
Q
  1. What is the Attachment to the Cytoskeleton and the Extracellular Matrix?
A
  • microfilaments or other elements of the cytoskeleton may
    be bonded to membrane proteins
  • this is a function that helps maintain the cell shape
  • it also stabilises the location of the certain membrane
    proteins
  • proteins that adhere to the ECM can coordinate extracellular and intracellular changes
    (such as integrids)
19
Q
  1. Where are Membrane Carbohydrates located?
A
  • they are located on the external side of the cell membrane
  • they interact with the surface molecules of the other cells
  • this facilitates cell recognition
20
Q
  1. What is Cell Recognition?
A
  • it is the cell’s ability to distinguish one type of neighbouring cell from another
21
Q
  1. Name the 3 type of membrane-associated carbohydrates?
    (Glycocalyx)
A
  1. Glycoproteins
  2. Glycolipids
  3. Proteoglycans
22
Q
  1. What are Glycoproteins?
A
  • they are carbohydrates that are covalently bonded to proteins
  • there is a greater amount of proteins than carbohydrates in their structure
  • they are found in the membrane and the ECM
23
Q
  1. What are Glycolipids?
A
  • they are carbohydrates that are covalently bonded to lipids
  • they have a greater amount of lipids than carbohydrates in their structure
  • they are found in the membrane only
24
Q
  1. What are Proteoglycans?
A
  • they are proteins that are covalently linked to carbohydrates
  • they have more carbohydrates in their structure than proteins
  • they are found in the ECM only
25
Q
  1. What is a Glycocalyx?
A
  • the carbohydrates that cover the external side of the cell membrane
  • they protect the cell surface from mechanical and chemical damage
26
Q
  1. What is an example of a Glycocalyx?
A
  • the human red blood cell types
  • A, B, AB , O
  • they reflect in variation in the red blood cell surface carbohydrates
27
Q
  1. Where are lipids synthesised?
A
  • in the smooth Endoplasmic Reticulum
28
Q
  1. Where are Carbohydrates synthesised?
A
  • in the Golgi Apparatus
29
Q
  1. Where are Membrane Proteins synthesised?
A
  • in the rough endoplasmic reticulum
30
Q
  1. What are the three characteristics of the Cell Membrane?
A
  1. Selective Permeability
  2. Hydrophobic Molecules
    (Non-Polar)
  3. Hydrophilic Molecules
    (Polar)
31
Q
  1. What is the selective permeability a result of?
A
  • the plasma membrane
  • it controls the molecule exchange of the cell materials with its surroundings
32
Q
  1. What are two characteristics of Hydrophobic Molecules?
    Give three examples of these kinds of molecules.
A
  • they are lipid soluble
  • they can pass through the membrane rapidly

EG: CO2, O2, Hydrocarbons

33
Q
  1. What are two characteristics of Hydrophilic Molecules?
    Give two examples of these kinds of molecules.
A
  • they are not lipid soluble
  • they do not cross the membrane rapidly

EG: sugars, ions

34
Q
  1. What are two characteristics of Transport Proteins?
A
  • they allow the passage of hydrophilic substances across the membrane
  • most are extremely specific for the substance that they are transporting
  • this means that there are different transport proteins for different agents
35
Q
  1. What are the two types of Transport Proteins?
A
  1. Channel Proteins
  2. Carrier Proteins
36
Q
  1. What are Channel Proteins?
A
  • they are transport proteins
  • they have a hydrophilic channel
  • certain molecules or ions can pass through this channel
  • such as: aquaporins, ion channels
37
Q
  1. What are Aquaporins?
A
  • they are special transport proteins for water
38
Q
  1. What are Ion Channels?
A
  • they transport proteins for ions
39
Q
  1. What are Carrier Proteins?
    Give an example of these kinds of proteins
A
  • they are transport proteins
  • they bind to molecules
  • they change the shape of these molecules
  • they shuttle them across

EG: glucose transporters

40
Q
  1. What type of hydrocarbon tails make the plasma membrane fluid?
A
  • bending hydrocarbons
  • they have tails with kinks
  • they are unsaturated

MED 103- BIOLOGY I (53 decks)

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