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cell processes > L21 > Flashcards

L21 Flashcards

1
Q

The cell membrane controls the passages of substances into and out of cells. This allows:

A
  1. Concentration gradients to be maintained;
  2. The spatial organisation of chemical and physical processes within the cell;

3.The controlled up-take of nutrients and discharge of waste prod ucts and the secretion of
molecules;

  1. The development of a membrane potential.
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2
Q

Membrane fluidity is determined by

A
  1. Number of double bonds: more increases fluidity
  2. Amount of cholesterol: more decreases fluidity
  3. Lipid tail length: longer, less fluid
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3
Q

What are the main membrane proteins?

A

1, Integral

  1. Peripheral
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4
Q

Membrane proteins can act as

A

A membrane protein is like somone just there: they
C (see) and R ef L E C T

  1. Receptors;
  2. Cell Identity Markers;
    3, Linkers;
  3. Enzymes;
  4. Channels;
  5. Transporters.
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5
Q

What is the membrane selective to? aka selective permeability

A
  1. Permeable to nonpolar, uncharged molecules: O, N2
  2. Permeable to lipid soluble molecules: steroids, fatty acids, some vitamins;
  3. Permeable to small polar uncharged molecules: water, urea, glycerol, CO2
  4. Impermeable to large uncharged polar molecules: glucose, amino acids;
  5. Impermeable to ions : Na+, K+, Cl-
    , Ca2+, H+.
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6
Q

What are the principals of Diffusion? aka the laws of diffusion

A
  1. More molecules move away from an area of high concentration to an area of low concentration.
  2. The greater the difference in concentration between the two sides of the membrane, the faster the rate of diffusion.
  3. The higher the temperature, the faster the rate of diffusion.
  4. The larger the size of the diff using substance, the slower the rate of diffusion.
  5. An increase in surface area increases the rate
    of diffusion.
  6. Increasing diffusion distance slows the rate of diffusion; so diffusion is only very fast
    over small distances.
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7
Q

Define diffusion

A

Diffusion is the random mixing of particles in a solution as a result of the particle’s kinetic energy

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8
Q

Explain Stored energy

A

Cells can maintain a difference in charged ions between the inside
& outside of membrane establishing an electrical gradient or membrane potential. Membranes
mimic capacitors and can separate and store charge. Cells use about 30% of resting energy to
maintain concentration and electrical gradients. These gradients represent stored energy. Ions
will be influenced by the membrane potential in addition to their concentration gradient. The net
movement of ions across a membrane will be influenced

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9
Q

Define Osmosis

A

Osmosis is the net diffusion of water across a semi-permeable membrane.

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10
Q

How thick is the membrane structure?

A

8nm

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11
Q

What is the fluid mosaic model

A

Fluid mosaic model describes membrane structure

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12
Q

What are the proportions of membrane, lipids, proteins in the membrane? and what holds these together?

A

membrane is 50 % lipid & 50 % protein

held together by hydrogen bonds

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13
Q

How are peripheral proteins connected to the membrane? and how can you break these off?

A

ionic chargers and using ionic solution

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14
Q

What are the main constituents of the cell membrane?

A

phospholipids and proteins

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15
Q

What is in the inside of a integral protein?

A

Non polar amino acids coiled into helices

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16
Q

What are the physical consequences of diffusion?

A

The rate of diffusion sets a limit on the size of cells of about 20 µm

To increase diffusion a cell can increase the membrane area available for exchange (diffusion) of a substance

Membrane thickness –the thicker the membrane the slower the rate of diffusion

Diffusion is very fast over small distances

17
Q

What are the gradients across the cell membrane?

A

Concentration gradient -non charged molecules will diffuse down their concentration gradients

Electrical gradient -ions will be influenced by membrane potential in addition to their concentration gradient. Movement of ions will be influenced by the electrochemical gradient

18
Q

What enables a difference in concentration or concentration gradient across the membrane to be established?

A

Selective permeability of the membrane

19
Q

How much resting energy do cells use to maintain concentration and electrical gradients?

A

around 30%

20
Q

What do gradients repersent?

A

stored energy

21
Q

When is the only time Osmosis can occur?

A

Only occurs if membrane is permeable to water but not to certain solutes

22
Q

Pw = ???

A

Pw = Pd (membrane is permeable to water but not to certain solutes) + Pf (aquaporins)

23
Q

What are the properties of Pd (through the lipid bilayer)?

A

Small

Mercury insensitive

Temp dependent (lipid fluidity

24
Q

What are the properties of Facillitated diffusion? (Through water channel)

A

Large

Mercury sensitive

Temp independent

25
Q

If the solution has the same osmolarity it is….

A

isomotic

26
Q

If the solution has a lower osmolarity it is

A

hypersmotic

27
Q

If the solution has a higher osmolarity it is

A

hypersmotic

28
Q

The concentration of body fl uids has an osmolarity of

A

280 mOsmol.

29
Q

What is tonicity?

A

The effect a solution has on cell volume is termed tonicity.

The tonicity of a solution depends on the
membrane permeability of the solute.

30
Q

In regards to tonicity, if it is a Isotonic solution there will be:

A

no change in cell volume;

31
Q

In regards to tonicity, if it is a Hypotonic solution there will be:

A

cause cell swelling and eventually cell lysis (haemolysis);

32
Q

In regards to tonicity, if it is a Hypertonic solution there will be:

A

causes cell shrinkage (crenation).

33
Q

Understand the fl uid mosaic model of membrane structure

A

refer to textbook - page 159

34
Q

Describe how the molecular structure of the membrane results in selective permeability

A

refer to textbook - pg 161

35
Q

Describe how the composition of the different fluid compartments act to store energy

A

refer to textbook - pg 162

36
Q

Understand the laws of diffusion that govern movement of ions and water across the
cell membrane

A

refer to textbook - page

37
Q

What type of property is osmosis?

A

Osmotic pressure is a colligative property. It depends only on the numbers and not the
types of particles in solution.

cell processes (4 decks)

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