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BIOL 107 > TOPIC 3: Membranes > Flashcards

TOPIC 3: Membranes Flashcards

1
Q

What are the 4 factors that affect membrane fluidity?

A

1) tempurature
too cold=more viscous,
too hot=more fluid-like

2) fatty acid tail saturation
Saturated=more viscous
Unsat.=more fluid

3) tail length
Longer tail=more viscous
Shorter=more fluid

4) prescense of steroids (helps to stabilize fluidity)

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2
Q

Why do animal cells have cholesterol in their membrane bilayer?

A

The cholesterol in the bilayer moderates tempurature and ensures that the phopholipids aren’t too close or far from eachother.

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3
Q

What does the cholesterol in the bilayer help revent

A

Prevents:

1) freezing (stops phospholipids from being too close together)

2) melting (by restraining phospholipid movement and filling in the gaps)

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4
Q

Cell membranes have a variation in lipid composition due to what?

A

Adaptations to environmental conditions

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5
Q

Can organism change their lipid composition as tempurature changes?

A

Yes

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6
Q

What are two types of membrane proteins?

A
  • peripheral proteins
  • integral proteins
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7
Q

What are peripheral proteins?

A

Proteins in which that hang out on top or on the surface of the membrane (they touch the membrane)

They are polar amino acids

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8
Q

What are integral proteins

A

Proteins that are penetrate the hydrophobic core. These proteins are INTEGRATED and embedded in the membrane

These proteins include hydrophillic (1 or 2 parts) and hydrophobic parts

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9
Q

If the integral protein spans the whole membrane then its called ______

A

Transmembrane protein

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10
Q

Describe the structure of a transmembrane protein

A

It consists of a sequence of amino acids (it includes polar and non polar chunks and it goes in a pattern)

Hydrophilic region and hydrophobic regoin to match the region outside (refer to the diagram in the notes)

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11
Q

What are the 6 functions of membrane proteins?

A
  • help molecules transport across membrane
  • enzymes
  • signalling
  • cell to cell recognition (recognizes molecules)
  • cell-cell joining)
  • anchoring
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12
Q

What matters in the selectively permeable bilayer?

A
  • size
  • polarity
  • charge
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13
Q

What kind of molecules can pass through the lipid bilayer?

A
  • small non polar molecules (O2, N2, CO2)
    (They get in very fast)
  • small uncharged polar molecules (H2O, glycerol) (slower acces )
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14
Q

What kind of molecules have a hard time or can’t pass through the membrane?

A
  • ions (will be fully rejected) Cl-, K+, Na+
  • large uncharged polar molecules
    (Glucose sucrose)
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15
Q

What are the two types of transport in a cell?

A

Passive and active transport

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16
Q

What is passive transport?

A

Transport that is based on diffusion and moves with/down the concentration gradient (high [ ] to low [ ])

Imagine a ball rolling down an incline. The high represents the concentration (high and low)

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17
Q

What is active transport?

A

Transport in which that requires energy to go from a place of low [ ] to a place of high [ ]

  • moves agaisnt or up the concentration gradient

Imagine pushing a ball up an incline, it requires energy to push the ball to get to a high [ ]

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18
Q

Define osmosis

A

The diffusion of water across a seletively permeable membrane.

For an example refer the the diagram in the notes

19
Q

Name the four kinds ofwater balance in a cell

A

Tonicity, isotonic, hypertonic, and hypotonic

20
Q

What is tonicity

A

The ability of a currounding solution to cause a cell to gain or lose water

21
Q

Define isotonic

A

When there is equillibrium of concentration inside and out of the cell

No net water movement across the plasma membrane

22
Q

Define hypertonic

A

When a cell loses water

Because the solute concentration is greater than that inside of the cell

23
Q

Define hypotonic solution

A

When the celll gains water

Because there is a high concentration of solutes inside the cell

24
Q

What kind of solution do animal cells prefer

A

Isotonic

25
Q

What kind of solution do plant cells prefer?

A

Hypotonic solutions because it keeps the plants in a standing state because of the pressure (turger pressure)

This is why plants flop when they aren’t watered

26
Q

What is a channel protein

A

Proteins that act like a a tunnel

They provide tunnels to allow a specific molecule or ion to cross the membrane bilayer

27
Q

What is a carrier protein

A

Protein that can change its shape (conformation) to help a molecule get across

Think of it as a revolving door that opens and closes

28
Q

What are aqua porins

A

A type of channel protein specifically designed for water molecules only to move across the membrane.

This protein is only for the process of diffusion, the aquaorin speeds up diffusion

29
Q

What does active transport require

A

Transport proteins

30
Q

True or false: sometimes passive transport needs transport proteins

A

True

31
Q

What are some characteristics of transport proteins?

A

1) work with many kinds of different molecules

2) can become saturated (all available proteins are in use)

3) can be open or closed (something which the cell controls)

32
Q

Does active transport allow cells to maintain their concentration gradients that differ to their surroundings? Give an example if you said yes

A

Yes

Example is a sodium-potassiom pump
- allows cells to generate [] gradients

33
Q

The sodium potassium pump is a specific case of ________ transport

A

Active

34
Q

The sodium potassium pump is a major component of _____ cells

A

Animal

35
Q

Refer to the sodium potassium pump diagram in the notes

A

Gotcha

36
Q

What is the purpose of the sodium potassium pump?

A

Helps maintain membrane potential (coltage difference inside and outside of the membrane)

37
Q

Sodium and potassium entering the pump has high ________

A

Affinity (attraction)

38
Q

A release of a phosphate group is called _______

A

Dephosphorization

39
Q

______ is created by the differences of distribution of + and - charged ions across the membrane. This leads to the ______

A

Voltage

Electrochemical gradient

40
Q

What is cotransport

A

When active transport is driven by a concentration gradient (coupled trnasport)

41
Q

What is bulk transport

A

When large molecules (such as polysaccharides and proteins) cross a membrane via vesicle (in exocytosis or exo)

This requires energy

42
Q

What is exocytosis

A

A transport vesicle exiting the membrane

43
Q

What is endocytosis

A

When a cell allows a macormolecule to enter the cell by forming a vesicle around it from the plasma membrane

44
Q

Steps of endocytosis

A
  1. Phagocytosis (vesicle “eats” cell) or plasma membrane grabs macromolecule
  2. Pinocytosis ( sipping or drinking )
  3. Specific cytosis

BIOL 107 (5 decks)

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