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AP Bio 1 > Cell communication > Flashcards

Cell communication Flashcards

Ch. 7, 11

1
Q

What is selective permeability

A

Some substances can cross a barrier while others cannot

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2
Q

What deos amphipathic mean

A

A substance with both a hydrophobic and a hydrophillic region

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3
Q

What is the fluid mosaic model

A

The membrane is a mosaic where the phospholipids are the liquid and the embedded proteins are the mosaic pieces

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4
Q

What type of bonds hold together the phospholipid bilayer

A

Hydrophobic interactions

Weaker than covalent bonds

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5
Q

What are two ways in which we can increase membrane fluidity

A
  1. Increase temperature
  2. Increase amount of unsaturated fatty acids
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6
Q

How does cholesterol act in plasma membranes

A

Cholesterol acts as a fluidity buffer as it hinders the close packing of fatty acids in the membrane

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7
Q

Why must a membrane be fluid to work properly

A

The fluidity affects the permeability and ability of membrane proteins to move

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8
Q

What are integral proteins

A

Proteins that penetrate the membrane and have hydrophobic regions that are found inside the membrane
Some span the entire membrane while others do not

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9
Q

What are transmembrane proteins

A

Integral proteins that protrude on both sides of the plasma membrane

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10
Q

What are peripheral proteins

A

Proteins that are loosely bound to membrane surface and are often bound to integral proteins

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11
Q

What are the 6 functions of membrane proteins

The red elephant crossed an island

A
  1. Transport
  2. Receptors
  3. Enzymes
  4. Cell-cell recognition
  5. Intercellular joining
  6. Attachment to cytoskeleton
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12
Q

Explain how membrane proteins function as transport proteins

A

Proteins may provide selective passage through hydrophilic channels,or else shuttle through shape-changing proteins

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13
Q

Explain how membrane proteins function as enzymes

A

Enzymes with active sites exposed to a substance may carry out steps of metabolic pathways

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14
Q

Explain how membrane proteins function in a signal transduction pathways

A

Receptor proteins may have binding site with specific chemical messangers. These may cause proteins to change shape, relaying message inside the cell

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15
Q

Explain how membrane proteins function in cell-to-cell recognition

A

Glycoproteins may serve as ID tags to be specifically recognized by proteins of other cells

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16
Q

Explain how membrane proteins function through intercellular joining

A

Proteins of adjacent cells may hook together (gap/tight junctions)

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17
Q

Explain how membrane proteins function in cytoskeleton attachement

A

They help mainain shape / stabilize location of other proteins (eg fibronectins). They coordinate intra/extracellular changes

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18
Q

What kind of molecules can pass through the lipid membranes easily

A

Small and hydrophobic

Hydrophillic / polar molecules canNOT pass

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19
Q

What are channel proteins

A

Hydrophillic channels that certain molecules or ions use as a tunnel through the membrane

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20
Q

What is an aquaporin

A

A channel protein that facilitates H2O movement through membrane

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21
Q

What are carrier proteins

A

A protein that holds substances and change shape to shuttle substances across membrane

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22
Q

True or false:
Transport proteins are specific to the substances they shuttle

A

True

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23
Q

What is diffusion

A

The movement of particles* of any substance so that they spread out randomly into available space

This does not require energy and is therefore a passive transport

  • This is because of thermal energy of individual molecules
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24
Q

What is a concentration gradient

A

The region along which the density of a chemical substance increases / decreases

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25
Q

What is osmosis

A

The diffusion of free H2O across a selectively permeable membrane

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26
Q

What does isotonic mean

A

Balanced H2O molecule concentration on either side of a plasma membrane

H2O may move across membrane but with no net movement

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27
Q
A
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28
Q

What does hypertonic mean

A

The solution in a cell has a high solute concentration and therefore a low H2O concentration

H2O will move to a hypertonic region

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29
Q

What does hypotonic mean

A

The solution in a cell has a low solute concentration and a high H2O concentration

H2O will leave the hypotonic region

30
Q

What is osmoregulation

A

The regulation of H2O : solute concentrations

31
Q

What does turgid mean

A

The healthy state for most plants → The plant cell wall is hypotonic and therefore the inside of the cell has an excess amount of water and exerts a pressure against the cell to maintain pressure

32
Q

What does flaccid mean

A

Plant is limp; wilted → Isotonic surroundings and no net flow of water

33
Q

What is plasmolysis

A

The plant cell dies → The cell is in a hypertonic solution and the cell membrane pulls away from the cell wall

34
Q

What does lysed mean in animal cells

A

The cell surroundings are hypotonic, meaning water will enter the cell, leading to a burst

35
Q

What does shrivelled mean in terms of animal cells

A

The cell is placed in a hypertonic solution and water leaves the cell, leading to the shrivelling of the cell

36
Q

What is facillitated diffusion

A

Passive transport through membrane proteins of polar (hydrophillic) molecules and ions

37
Q

What is an ion channel

A

Channel protein that transports ions

38
Q

What are gated channels

A

Channel proteins that open and close in response to stimuli

39
Q

What is active transport

A

Transport of a substrate against a concentration gradient and requires energy

40
Q

What reaction supplies most of the energy required in active transport

A

ATP hydrolysis

41
Q

The cytoplasmic side of the plasma membrane has what kind of charge and from where does this charge come

A

The cytoplasmic side has a negative charge that comes from an imbalanec in cations and anion concentrations

42
Q

What is the voltage potential

A

The voltage across a membrane

43
Q

What is an electrical chemical gradient

A

As cations and anions move towards their oppositely attracted regions they create an electrical gradient

44
Q

What is an electrogenic pump

A

A transport protein that generates voltage across the membrane

45
Q

What is a proton pump

A

A transport protein that moves H+ out of the cell

46
Q

What is cotransportation

A

The coupling of “downhill” diffusion of one substance with the “uphill” transport of another against a concentration gradient

47
Q

What is exocytosis

A

The fusion of vesicles to plasma membrane where inside substances leave the cell

Ex. cells in pancreas secreting insulin

48
Q

What is endocytosis

A

The uptake of substances into a cell by forming vesicles from the plasma membrane

49
Q

What are the three types of endocytosis

A
  1. Phagocytosis - cell engulfs food particles
  2. Pinocytosis - cell engulfs liquids
  3. Receptor mediated - substance binds to receptors and cell engulfs substance upon recognition
50
Q

BULK TRANSPORT

A
51
Q

What is endocrine signaling

A

Long-distance cell signaling in an organism

52
Q

What is paracrine signaling

A

Local cell signaling in an organism

53
Q

What is a growth factor

A

A local signal molecule in organisms that stimulate cell growth and division

54
Q

What is synaptic signaling

A

An electrical signal that passes through neural cells in organisms

55
Q

What are hormones

A

Plant and animal cell signaling molecules

56
Q

What is a ligand

A

A signaling molecule that specifically binds to a receptor molecule which causes a cascade of reactions in a cell

57
Q

GPCRs are what type of protein

A

Cell-surface, transmembrane protein that works with GTP

58
Q

Describe how a GPCR works when bound by a ligand

A
  1. When a ligand binds to the G protein-coupled receptor, causing activation and shape change, the affinity for G-proteins increases and
  2. they come together and GTP replaces GDP.
  3. The now-active G protein dissociates and binds to an enzyme, leading to further cell responses
59
Q

Describe how a RTK works when bound by a ligand

A
  1. The binding of a ligand causes dimerization in a receptor-tyrosine kinase, forming a dimer complex
  2. This activates tyrosine kinase regions as each region gains a phosphate group from ATP
  3. The fully active RTK is now recognized by other relay proteins which will lead to a cell response
60
Q

Explain how an ion-channel gated receptor works when bound by a ligand

A
  1. When a ligand binds to the channel, this causes a shape change to “open”, allowing certain ions to flow through, leading to a cell response
61
Q

A ligand must be one of two things to cross the hydrophobic barrier:

A
  1. Hydrophobic enough
  2. Small enough
62
Q

What are the three ligand molecules that are small enough and hydrophobic enough to cross the bilayer

A
  1. Steroid hormones
  2. Thyroid problems
  3. NO (nitric oxide)
63
Q

What is a protein kinase

A

An enzyme that transfers phosphate from ATP to proteins (typically a serine or threonine kinase)

64
Q

What is a phosphorylation cascade

A

A series of proteins in a path are phosphorylated in turn, with each protein adding a phosphate group to the next in line

65
Q

What is a protein phosphatase

A

An enzyme that removes phosphate from proteins (dephosphorylation) and deactivates the protein

66
Q

What is a second messanger

A

A small, non-protein, aqueous molecule involved in a signal transduction pathway (eg. cAMP, Ca2+)

67
Q

Explain how cAMP can act as a second messanger in an STP

A

The enzyme adenylyl cyclase embedded in the plasma membrane can covert ATP into cAMP. cAMP is broadcasted into the cytoplasm, sending signals from outside the cell (eg. from a ligand)

68
Q

Explain how IP3 and DAG are involved in the release of Ca2+ in the cell

A

A ligand signal travels to a phospholipase that cleaves an IP3 from the plasma membrane (initially IPI2) which diffuses and reaches the smooth ER and acts as a signal molecule for an IP3 gated Ca2+ channel, releasing Ca2+ into the cytoplasme

69
Q

Name four ways in which signal transduction pathway responses can be regulated

A
  1. Amplification → Multiple proceeding enzymes may be catalyzed at once
  2. Control points → Different cells have different proteins are thus respond differently to stimuli
  3. Scaffolding proteins → Large relay proteins may bind several relay proteins all together
  4. Signal termination → Proteins can change from active to inactive form
70
Q

What is apoptosis

A

Controlled cell suicide

71
Q

What is a death signal

A

A signal that comes from inside or outside the cell that signals for the cell to self destruct → activation of nuclease and capase

AP Bio 1 (7 decks)

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