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BIO 101 > Topic 4 - Lipids, Membranes, and Membrane Transport > Flashcards

Topic 4 - Lipids, Membranes, and Membrane Transport Flashcards

1
Q

Lipid

A

Macromolecule that is nonpolar and insoluble in water (hydrophobic); hydrocarbons that include mostly nonpolar carbon-carbon or carbon-hydrogen bonds

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2
Q

List four functions of lipids

A
  1. Energy storage
  2. Insulation from environment in plants and animals
  3. Building blocks of many hormones
  4. Form plasma membrane
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3
Q

What are some examples of lipids?

A

Fats and oils (aka triglycerides), phospholipids, steroids, waxes, etc.

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4
Q

What are the main components of a fat molecule?

A

Glycerol and three fatty acids

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5
Q

Saturated fatty acid

A

Single bonds between neighboring carbons in the hydrocarbon chain - i.e. saturated with hydrogen; compact, solid at room temperature, and inflexible in cold temperature
Ex. butter

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6
Q

Unsaturated fatty acid

A

Hydrocarbon chain contains a double bond (C=C); fluid, liquid at room temperature, flexible in cold temperature
Ex. vegetable oil

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7
Q

Monounsaturated

A

One double bond (C=C)

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8
Q

Polyunsaturated

A

Multiple double bonds

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9
Q

What causes an unsaturated fatty acid to be liquid at room temperature?

A

Double bonds cause a bend/”kink” that prevents fatty acids from packing tightly, keeping them liquid at room temperature.

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10
Q

Why are fats (triglycerides) important?

A

Fats are an excellent source of stored energy, may be used for insulation and cushioning

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11
Q

Phospholipids

A

Plasma membrane constituents that comprise cell’s outermost layer; glycerol backbone linked to a modified phosphate group (polar, hydrophilic head) and 2 fatty acid tails (nonpolar, hydrophobic)
- Tails may be saturated or unsaturated
- Spontaneously form micelles or bilayers in water

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12
Q

Steroids

A

Chemical messengers; precursors to water-insoluble vitamins (A, K, D, and E) and hormones (testosterone and estradiol)
- Composed of 4 carbon rings

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13
Q

Cholesterol

A

Sterol found in the plasma membrane of animal cells; located within phospholipid bilayer

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14
Q

Fluid mosaic model

A

Plasma membrane is a mosaic of components - including phospholipids, cholesterol, proteins and carbohydrates - that gives the membrane a fluid character (i.e. lipids are fluid, mosaic is made of proteins)

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15
Q

Phospholipid bilayer

A

Barrier that separates the inside of the cell from the outside environment; comprised of phospholipids

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16
Q

Functional membranes must be…

A

Fluid

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17
Q

What affects the fluidity of the bilayer?

A

Temperature, size of protein, protein attachment to cytoskeleton, saturation of hydrocarbon tails, and cholesterol

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18
Q

What is the function of cholesterol in the membrane?

A

Prevents lower temperatures from inhibiting fluidity and higher temperatures from increasing fluidity too much

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19
Q

What are the functions of integral proteins (transmembrane proteins)?

A
  • Transporting/channeling molecules across membrane
  • Cell-surface receptors - cell recognition, signal transduction
  • Cell-to-cell adhesion; carbohydrate chains attached to some proteins act as labels that identify cell type
  • Enzymatic activity
  • Attachments to cytoskeleton
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20
Q

What are the functions of peripheral proteins?

A
  • Enzymatic activity
  • Attachments to cytoskeleton
  • Cell recognitions sites - cell-specific proteins
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21
Q

Integral proteins are found…

A

Embedded in lipid bilayer

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22
Q

Peripheral proteins are found…

A

On the periphery of lipid bilayer, attached to either integral proteins or phospholipids

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23
Q

Cell surface markers

A

Classify cells according to their markers

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24
Q

What are the functions of carbohydrates in the cell membrane?

A
  • Cell recognition (“self” vs. “non-self”)
  • Glycoproteins and glycolipids - AKA glycocalyx
  • Hydrophilic - attracts H2O to cell’s surface
  • Cell-to-cell adhesion
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25
Q

Selective permeability / semipermeability

A

Plasma membranes allow some substances to pass through but not others

26
Q

Passive transport

A

A type of membrane transport that does not require energy (ATP) to move substances across cell

27
Q

Diffusion

A

A type of passive transport where substances move down their concentration gradient (high to low)

28
Q

What are the requirements for simple diffusion?

A

Substances must be small, nonpolar, and lipid-soluble

29
Q

Dynamic equilibrium

A

Lack of concentration gradient (no net movement)

30
Q

Facilitated diffusion

A

Process in which integral proteins allow membrane diffusion to be selective

31
Q

Transport proteins

A

Integral proteins involved in facilitated diffusion; function as either channels for the material or carriers

32
Q

Channel proteins

A

Membrane proteins that allow a substance to pass through its hollow core across a plasma membrane
- Hydrophilic interior allows polar compounds, ions and/or water to pass through, which avoids the nonpolar central layer of the plasma membrane

33
Q

Aquaporins

A

Channel proteins that allow water to pass through the membrane at a high rate

34
Q

Ion channels

A

Allow ions to pass through membrane; diffusion depends on charge (membrane potential), concentration, open/closed status of gate
- Na+, K+ channels in nerve impulses
- Ca2+ channels in muscle cells

35
Q

Gated channels

A

Transport proteins that open a “gate,” allowing a molecule to pass through a membrane
- Stimulus (chemical/electrical signals, temperature, mechanical force) causes gate to open/shut

36
Q

Carrier proteins

A

Assist specific molecule to pass through by changing shape
- Binds to a substance, triggering a change in shape and moves bound molecule across membrane
Ex. glucose transporter in RBC

37
Q

Osmosis

A

The movement (diffusion) of water across a semipermeable membrane down its concentration gradient

38
Q

Solutions

A

Solute: substance dissolved in solvent
Solvent: dissolving agent (water)

39
Q

Tonicity

A

Amount of solute in a solution

40
Q

Hypertonic

A

Higher solute concentration

41
Q

Hypotonic

A

Lower solute concentration

42
Q

Isotonic

A

Equal solute concentration

43
Q

Cells without a cell wall will _____ when placed in a hypotonic solution

A

Lyse/burst

44
Q

Cells with a cell wall will _____ when placed in a hypotonic solution

A

Become turgid (firm)

45
Q

Cells without a cell will _____ when placed in a hypertonic solution

A

Shrivel/crenate

46
Q

Cells with a cell wall will _____ when placed in a hypertonic solution

A

Plasmolyze (shrivel)

47
Q

Animal cells do best in a _____ environment

A

Isotonic

48
Q

Plant cells do best in a _____ environment

A

Hypotonic

49
Q

How is osmotic balance maintained?

A
  • Contractile vacuoles pump water out
  • Isosmotic regulation - regulation of solutes in the body
  • Turgor prevents plant cells from bursting due to pressure from cell wall
50
Q

Active transport

A

Method of transporting material the requires energy (ATP, diffusion gradient or light)

51
Q

ATP stands for…

A

Adenosine triphosphate

52
Q

ATP moves substances _____ their concentration gradient

A

Against

53
Q

What carrier proteins are involved in active transport?

A
  • Uniporter: carries one specific ion/molecule
  • Symporter: carries two different ions/molecules in same direction
  • Antiporter: carries two different ions/molecules in a different direction
54
Q

Give an example of an active transport pump

A

Na+-K+ ATPase

55
Q

Electron flow

A

Proton pumps: H+ is pumped across membrane using electron flow; H+ gradient is used to make ATP as H+ diffuses

56
Q

Light-driven

A

Light drives H+ out of cell, H+ gradient is harvested to make ATP

57
Q

Coupled transport

A

Gradient of one molecule is used to transport another molecule; maintained indirectly by ATP

58
Q

Endocytosis

A

A type of active transport that moves particles, such as large molecules, parts of cells, and whole cells, into a cell

59
Q

Phagocytosis

A

“Cell eating”
Process by which a cell engulfs large particles via invagination

60
Q

Pinocytosis

A

“Cell drinking”
Process by which a cell takes in molecules, including water, from extracellular fluid

61
Q

Receptor-mediated endocytosis

A

Variation of endocytosis that involves using specific binding proteins in the plasma membrane for specific molecules/particles (e.g. hormones)

62
Q

Exocytosis

A

Process of passing bulk material out of a cell
- Vesicles fuse with membrane, releasing contents

BIO 101 (15 decks)

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