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Biology - Metabolsim And Enzymes > Chapter 4 > Flashcards

Chapter 4 Flashcards

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1
Q

What is the importance of selectively permeable membranes?

A

They separate internal and external contents while allowing specific exchange of molecules/ions.

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2
Q

What are the qualities required for a barrier in cellular membranes?

A
  • Impermeable to most molecules and ions
  • Ability to exchange specific molecules/ions
  • Insoluble in water
  • Permeable to water
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3
Q

What are the main components of a cellular membrane?

A
  • Phospholipids
  • Glycolipids
  • Sterols (cholesterol, ergosterols, phytosterols)
  • Membrane proteins
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4
Q

What types of membrane proteins exist?

A
  • Integral proteins (transmembrane)
  • Peripheral membrane proteins
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5
Q

What is the Fluid Mosaic Model of membranes?

A

It describes membranes as fluid lipid bilayers with embedded proteins that float freely.

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6
Q

True or False: Membranes are rigid structures.

A

False

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7
Q

What does polarity in water molecules refer to?

A

Uneven distribution of charge due to electronegative oxygen and electropositive hydrogen.

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8
Q

What does hydrophilic mean?

A

Water-loving substances that can form hydrogen/ionic bonds with water.

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9
Q

What does hydrophobic mean?

A

Water-fearing substances that do not dissolve in water.

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10
Q

What is a solvent?

A

A fluid in which another substance (solute) can be dissolved.

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11
Q

What is the significance of hydrophobic interactions?

A

They drive the folding of molecules, assembly of structures, and membrane organization.

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12
Q

What are phospholipids characterized by?

A

They are amphipathic with a hydrophilic head and two hydrophobic tails.

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13
Q

How does temperature affect membrane fluidity?

A
  • Low temperature: membrane becomes viscous
  • High temperature: membrane becomes too fluid
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14
Q

What role do desaturases play in membrane fluidity?

A

They produce unsaturated fatty acids, allowing regulation of membrane fluidity.

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15
Q

What do sterols do in membranes at high temperatures?

A

They restrain movement of lipids, preventing excessive fluidity.

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16
Q

What do sterols do in membranes at low temperatures?

A

They disrupt fatty acid associations, slowing the transition to a semisolid state.

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17
Q

What can organisms change to optimize membrane fluidity?

A
  • Fatty acid desaturation
  • Cholesterol content
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18
Q

What are integral membrane proteins?

A

Proteins embedded in the phospholipid bilayer, often coiled into alpha helices.

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19
Q

What are peripheral membrane proteins?

A

Proteins located on the membrane surface, held by noncovalent bonds.

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20
Q

What is passive transport?

A

Movement of molecules across a membrane without using chemical energy.

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21
Q

What drives passive transport?

A

Diffusion, the net movement from higher to lower concentration.

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22
Q

What is simple diffusion?

A

Passive transport of small uncharged molecules without a transporter.

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23
Q

What factors impede the crossing of membranes for larger or charged molecules?

A

Their size and charge may strongly hinder their movement.

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24
Q

What are the two types of passive transport?

A
  • Simple diffusion
  • Facilitated diffusion
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25
Q

Define simple diffusion.

A

Movement of molecules across a membrane without involvement of a transporter.

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26
Q

What factors influence simple diffusion?

A
  • Molecular size
  • Lipid solubility
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27
Q

Which types of molecules move rapidly through simple diffusion?

A

Small uncharged molecules.

28
Q

What is facilitated diffusion?

A

Diffusion of molecules across a membrane with the help of a transporter.

29
Q

What is osmosis?

A

Passive diffusion of water molecules across a selectively permeable membrane.

30
Q

In osmosis, water moves from a _______ solution to a _______ solution.

A

hypotonic; hypertonic

31
Q

What occurs when solutions on each side of a membrane are isotonic?

A

No osmotic movement of water in either direction.

32
Q

What is active transport?

A

Transport of molecules across a membrane against a concentration gradient.

33
Q

What is required for active transport?

A

A direct or indirect input of energy derived from ATP hydrolysis or concentration gradients.

34
Q

What are the two kinds of active transport?

A
  • Primary active transport
  • Secondary active transport
35
Q

Define primary active transport.

A

The same protein that transports the molecules also hydrolyzes ATP to directly power the transport.

36
Q

What is the function of the Na+/K+ pump?

A

Moves 3 Na+ out and 2 K+ in for every pump cycle, creating a negative membrane potential.

37
Q

What is secondary active transport?

A

Transport that is indirectly driven by ATP hydrolysis using a favorable concentration gradient of ions.

38
Q

What are the two mechanisms of secondary active transport?

A
  • Symport
  • Antiport
39
Q

What is exocytosis?

A

Process where a secretory vesicle carries materials through the cytoplasm and fuses with the plasma membrane to release contents.

40
Q

What is endocytosis?

A

Process where materials outside the cell are enclosed in the plasma membrane, forming an endocytic vesicle.

41
Q

Define pinocytosis.

A

Endocytosis of solute and water molecules; also known as ‘cell drinking’.

42
Q

What is receptor-mediated endocytosis?

A

Process where molecules bind to receptor proteins, forming a coated pit that pinches off to form an endocytic vesicle.

43
Q

Define phagocytosis.

A

Endocytosis of large aggregates of molecules or whole cells; also known as ‘cell eating’.

44
Q

What are the essential elements for cell signaling?

A
  • Signal
  • Receptor
  • Signal Transduction
  • Response
  • Termination
45
Q

What is signal transduction?

A

The process of transferring the presence of a signal through the cell to elicit a response.

46
Q

What happens during the termination phase of cell signaling?

A

The cell turns off the response once the signal is gone.

47
Q

What are the three stages of signal transduction?

A
  • Reception
  • Transduction
  • Response
48
Q

True or False: Only cells with a receptor for a specific signal can respond to that signal.

A

True

49
Q

What type of receptors are involved in responses to steroid hormones?

A

Intracellular receptors.

50
Q

What are the three common stages of signal transduction?

A

Reception, transduction, and response

51
Q

What happens during the receptor activation stage in cell signaling?

A

The signal binds to a receptor, activating it

52
Q

What is the purpose of signal transduction in cell signaling?

A

To transmit the signal to the interior of the cell

53
Q

What occurs during the response stage of signal transduction?

A

The cell activates an enzyme or turns on gene transcription

54
Q

What is the termination stage in signal transduction?

A

The response is terminated to allow for new signals

55
Q

Fill in the blank: The binding of a signal molecule to a plasma membrane receptor activates a _______.

A

signalling cascade

56
Q

True or False: The signal molecule enters the cell during signal transduction.

A

False

57
Q

What role do protein kinases play in signal transduction?

A

They transfer a phosphate group from ATP to target proteins

58
Q

What is the function of added phosphate groups on target proteins?

A

They stimulate or inhibit the activities of target proteins

59
Q

What do protein phosphatases do in the signal transduction process?

A

They remove phosphate groups from target proteins

60
Q

Fill in the blank: Some signalling cascades involve the production of _______ messengers.

A

second

61
Q

What is a phosphorylation cascade?

A

A series of phosphorylation reactions catalyzed by protein kinases

62
Q

How does amplification occur in signal transduction pathways?

A

Each activated enzyme can activate hundreds of proteins in the next step

63
Q

What is the effect of just a few extracellular signal molecules in a signal transduction pathway?

A

They can produce a full internal response

64
Q

What is the first messenger in the example of glycogen breakdown stimulation?

A

Epinephrine

65
Q

How does epinephrine affect blood glucose levels?

A

It leads to an increase in blood glucose

66
Q

What physiological responses are included in the ‘fight or flight’ response?

A

Burst of energy, increased heart rate, dilated pupils

67
Q

How does one signal lead to multiple responses?

A

Through the activation of different pathways or target proteins

Biology - Metabolsim And Enzymes (3 decks)

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