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BIO1140 > Lecture 5: Cell Membranes > Flashcards

Lecture 5: Cell Membranes Flashcards

1
Q

Lipids are the one class of biomolecules that do not form ________.

A

Polymers

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2
Q

The unifying feature of lipids is that they have ___________________________ (_________), this is because they consist mostly of _______ which are ________.

A

Little or no affinity for water (hydrophobic); hydrocarbons; nonpolar

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3
Q

What are 4 functions of lipids?

A
  1. Long-term energy stores (very rich)
  2. Provide insulation from the environment for plants and animals
  3. Serve as building blocks for some hormones
  4. Important component of cellular membranes
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4
Q

What are the biologically important classes of lipids?

A
  1. Fats
  2. Waxes
  3. Steroids
  4. Phospholipids
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5
Q

Fats (also known as ______ or ______) are constructed from ______ and _______________.

A

Triacylglycerol; triglyceride; glycerol; 3 fatty acids

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6
Q

_______ is a 3-carbon alcohol with a hydroxyl attached to each carbon

A

Glycerol

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7
Q

What is glycerol?

A

A 3-carbon alcohol with a hydroxyl attached to each carbon

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8
Q

________ consist of a carboxyl group linked to a long hydrocarbon chain.

A

Fatty acids

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9
Q

What is a fatty acid?

A

A carboxyl group linked to a long hydrocarbon chain.

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10
Q

Fatty acids vary in:

A

Length
Number of double bonds
Location of double bonds

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11
Q

_______ do not have double bonds, and is solid at room temp.

A

Saturated fatty acids

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12
Q

______ have one or more double bonds, and may be liquid at room temp.

A

Unsaturated fatty acids

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13
Q

What is an unsaturated fatty acid?

A

have one or more double bonds, and may be liquid at room temp.

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14
Q

What is a saturated fatty acid?

A

do not have double bonds, and is solid at room temp.

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15
Q

What is a wax?

A

Waxes are long fatty acid chains esterified to long chain alcohols. They are hydrophobic and prevent water from sticking to its surface.

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16
Q

Where can waxes be found?

A

On feathers of some aquatic birds and on the surface of leaves from certain plants.

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17
Q

What type of lipids are found on some aquatic birds and on the surface of leaves from certain plants?

A

Waxes

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18
Q

______ are long fatty acid chains esterified to long chain alcohols. They are ________ and prevent water from sticking to its surface.

A

Waxes; hydrophobic

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19
Q

What are steroids?

A

Steroids are lipids with a carbon skeleton consisting of four fused rings.

20
Q

______ are lipids with a carbon skeleton consisting of four fused rings.

A

Steroids

21
Q

What is cholesterol?

A

A component in animal cell membranes and a precursor for many types of steroid hormones.

22
Q

_______ a component in animal cell membranes and a precursor for many types of steroid hormones.

A

Cholesterol

23
Q

A ________ (also known as _______) has 2 fatty acids and a phosphate group are attached to glycerol. The 2 fatty acid tails are hydrophobic. The phosphate head group is hydrophilic. The phosphate may be modified by the addition of charged or polar chemical groups.

A

Phospholipid; diacylglycerol

24
Q

Regions of the plasma membrane called “lipid” rafts have high concentrations of cholesterol and sphingomyelin. Consequently, the proteins in lipid rafts:
A. Diffuse more freely
B. Tend to stay clustered together
C. Are able to flip across the lipid balayer from inside to outside and vice versa
D. Cannot function as receptors

A

B

25
Q

A phospholipid (also known as diacylglycerol) has _________ and _______ are attached to _____. The 2 ______ tails are _______. The _________ head group is ________ which may be modified by the addition of _______ groups.

A

2 fatty acids; a phosphate group; glycerol; fatty acid; hydrophobic; phosphate; hydrophilic; charged or polar chemical

26
Q

Phospholipids are major constituents of the plasma membrane because when added to water, they __________________, due to ________. Phospholipids contribute to the _____ nature of the plasma membrane.

A

Spontaneously self-assemble into a bilayer; their structure (hydrophilic face fluid environments/ hydrophobic face billard centre region); dynamic

27
Q

Does the relative proportion of membrane components remain the same from cell to cell?

A

No

28
Q

Which of the following explains what is happening when sodium chloride dissolves in water?
A. More hydrogen bonds are forming between water molecules.
B. Na & Cl atoms are separating from one another
C. Hydration shells are forming around the Na and Cl ions
D. Covalent bonds are breaking and reforming

A

C

29
Q

Ceviche is prepared by marinating fresh raw fish in citrus juice for several hours, until the flesh becomes opaque and firm, as if cooked. How does citrus juice render the seafood safe to eat?
A. Acidic pH denatures (unfolds and inactivates) proteins by disrupting their hydrogen bonds
B. Acidic pH denatures proteins by disrupting their ionic bonds
C. Acidic pH contains enzymes that hydrolyse peptide bonds to break apart proteins
D. Acidic pH dissolves cell membranes by disrupting hydrophobic interactions

A

A

30
Q

Will membranes be more fluid at high temperatures with or without cholesterol?

A

Without

31
Q

The plasma membrane of human red blood cells is __% lipid.
The mitochondrial inner membrane contains __% protein and __% lipid.
Myelin contains __% protein and __% lipid.

A

30
76; 24
28; 76

32
Q

The plasma membrane of _______ is 30% lipid.
The _________ contains 76% protein and 24% lipid.
______ contains 18% protein and 76% lipid.

A

human red blood cells; mitochondrial inner membrane; Myelin

33
Q

What is a myelin?

A

An outgrowth of specialized cells’ membrane that insulates neuronal axons.

34
Q

_______ is an outgrowth of specialized cells’ membrane that insulates neuronal axons.

A

Myelin

35
Q

Are plasma membranes static? ___, since _____&_____ in the plasma membrane can move within the _______. Most move _______, rarely do they _______.

A

No; phospholipids; proteins; bilayer; laterally; switch bilayers

36
Q

Which membrane will be more fluid at room temperature? The one with:
A. 20% saturated and 80% unsaturated fatty acids
342
B. 80% saturated and 20% unsaturated fatty acids
18
C. 50% saturated and 50% unsaturated fatty acids

A

A

37
Q

The temperature at which a membrane solidifies depends on its ____________.

A

lipid composition

38
Q

Why are unsaturated hydrocarbon tails more fluid than saturated hydrocarbons?

A

Because unsaturated hydrocarbon tails have double bonds that cause them to have a bend in their tail which prevents tight packing of hydrocarbons allowing more space thus causing them to be more fluid. Whilst saturated hydrocarbons are single bonded tails that are straight and can thus pack closely together, creating a more timely packed structure limiting fluidity.

39
Q

Describe the effects of the steroid lipid cholesterol on membrane fluidity at different temps.

A

At warm temp: cholesterol restrains movement of phospholipids = membrane is less fluid
At cold temps: cholesterol prevents tight packing = membrane maintains fluidity

40
Q

Variations in the lipid composition of cell membranes of many species are likely due to ____.

A

adaptations to specific environmental conditions

41
Q

The ability of ____ has evolved by organism that live in temperature that vary from season to season.

A

To change membrane lipid composition

42
Q

Plasma membranes are ____, the inner surface ____ the outer surface.

A

Asymmetrical; differs from

43
Q

What are some organelles that are found on the inner surface or the outer surface of the plasma membrane?

A

OUTER: exterior proteins, glycoproteins, glycolipids,

INNER: interior proteins

44
Q

When is the asymmetrical distribution of plasma membrane components determined?

A

When the membrane is synthesized and is assembled by the ER and Golgi

45
Q

An oligosaccharide covalently linked to a lipid in the lumen of the rough ER may end up on the

A

Extracellular face of the plasma membrane

46
Q

What is the difference in phospholipid composition in the outer vs inner plasma membrane?

A

Outer: has more phosphatidylcholine and sphingomyelin
Inner: has more phosphatidylethanolamine, phosphatidylserine, and inositol

BIO1140 (5 decks)

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