3. Lipids, membranes and transport Flashcards

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1
Q

What elements are in Lipids

A

C H O

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2
Q

What are lipids

A

Group of non-polar molecules
Insoluble in water
dissolve easily in organic solvents

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3
Q

What are the important groups of lipids

A

Triglycerides and phospholipids

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4
Q

What is a triglyceride

A

Made of 3 fatty acids and 1 molecule of glycerol

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5
Q

How is a triglyceride formed

A

Glycerol has 3 OH- groups.
Each bind to a fatty acid
Condensation reaction
Produce 3 molecules of H2O
Ester bonds between OH and COOH

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6
Q

What is a fatty acid made from

A

A COOH- group and a long hydrocarbon chain (Unsaturated or Saturated)

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7
Q

Why are triglycerides not classified as polymers

A

They are not made of monomers.
They are made of 2 different types of molecules

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8
Q

What are the biological roles of triglycerides

A

Storage of energy
Insulation - electrical and heat
Protection

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9
Q

How do the structure and properties of a triglyceride relate to its function

A

High ratio of energy storing C-H bonds to C atoms = good source of energy
Low mass to energy ratio = Good storage molecules as lots of energy stored in small volume
Large, non-polar, insoluble in water molecules = no osmotic effect and dont effect water potentiels

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10
Q

What is a phospholipid

A

Lipids where one fatty acid is substituted for phosphate group
- Polar/hydrophilic head (Glycerol and phosphate)
-2 Non-Polar/hydrophobic tails (Fatty acids)

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11
Q

What is the test for lipids

A

Ethanol emulsion test
- Add ethanol to the sample to be tested
- Shake thoroughly to dissolve any lipid in sample
- Then add water to sample and shake gently
-A milky white emulsion indicates the presence of lipid

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12
Q

What are the 3 functions of plasma membranes

A
  • Control the transport of substances into and out of cell or organelle - Partially permeable
  • Act as a receptor site - Recognise chemicals that need to enter the cell
  • Separate off the cell from the environment and the different reactions - Different concs can be maintained
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13
Q

What molecules do plasma membranes not let through

A

Water-soluble
Charged
Polar

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14
Q

What molecules are in a membrane structure

A
  • Phosphlipids
  • Membrane proteins
    -Glycoproteins
  • Glycolipids
    -Cholesterol
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15
Q

What do phospholipids do in the membrane structure

A

Form a bilayer
Hydrophobic tails point towards eachother
Hydrophilic head point out into the water

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16
Q

What do membrane proteins do in the membrane structure

A

Float about in bilayer - fluid mosaic structure
May be in one layer (Extrinsic) or across the whole membrane (Intrinsic) .
May be fixed in one place or float about
Often have hydrophilic channels in the middle

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17
Q

What is the function of an Intrinsic protein

A

Transport - channels and carriers

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18
Q

What is the function of extrinsic proteins

A

Enzymes
Receptors
Antigens

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19
Q

What is a glycoprotein and its function in the membrane structure

A

Short, branching carbohydrate chains attached to proteins in the membrane.
Act as receptors for hormones and neurotransmitters or antigens

20
Q

What is a glycolipid

A

Made of a carbohydrate covalently bonded to a lipid.
Act as recognition sites
Help maintain stability of the membrane and help cells attach to one another forming tissues

21
Q

What is cholesterol

A

Restrict the movment of other molecules in the membrane
Increase the strength and stability of membranes by making them less flexible
Prevents loss of water and dissolved ions

22
Q

What is the fluid mosaic structure

A

Fluid = All different molecules can move
Mosaic = Different types of molecules. Some can float within the bilayer

23
Q

What can molecules in the plasma membrane do

A

-Move sideways
-Leave the membrane to form vesicles
-Join memranes from vesicles

24
Q

Why does should a membrane be fluid

A

Cells can change their shapes e.g phagocytes

25
Q

What are 4 ways substances can be exchanged

A

Diffusion
Osmosis
Active transport
Endo/Exocytosis

26
Q

What is diffusion

A

The movement of substances from a region of higher concentration to a region of lower concentration down a concentration gradient

27
Q

How does surface area affect rate of diffusion

A

The greater the surface area of the membrane over which diffusion occurs the greater the rate of diffusion

28
Q

How does the thinckness of exchange surface affect the rate of diffusion

A

the thinner the surface the faster the rate of diffusion (shorter diffusion pathway)

29
Q

How does the conc gradient affect the rate of dissusion

A

the steeper the gradient the faster the rate of diffusion

30
Q

How does the size of the diffusing molecule affect rate of diffusion

A

the smaller the molecule the faster the rate of diffusion (can diffuse through the phospholipid bilayer easier)

31
Q

How does temperature affect the rate of diffusuion

A

the higher the temperature the faster the rate of diffusion (more kinetic energy)

32
Q

How does water solubility/ polarity affect the rate of diffusion

A

Molecules that are water-soluble/polar/ charged generally diffuse slower than lipid-soluble/non-polar/uncharged ones (non-polar can pass through hydrophobic region of the phospholipid bilayer easier)

33
Q

What is Ficks law

A

Rate of diffusion (is proportional to) (SA x difference in conc) / thickness of exchange surface

34
Q

How do you increase the rate of diffusion

A
  • Maximise the SA
  • Maximise concentration difference
  • Minimise the thickness of exchange surface
35
Q

What is simple diffusion

A

Diffusion of substances directly across the phospholipid bilayer
Molecules that are non-polar and smaller can diffuse through

36
Q

What is facilitated diffusion

A

Molecules diffuse through bilayer through intrinsic proteins.
The substances are specific to the proteins
Passive
Moves charges, polar or hydrophilic substances.
Channel proteins for ions, carrier proteins for others

37
Q

What is osmosis

A

the movement of water across a partially permeable membrane down a water potential gradient from higher (less negative) to lower (more negative) water potential.

38
Q

What is water potentiel

A

The tendency for water to move from one place to another
Measure in KPa
Pure water has WP of zero, all others are negative

39
Q

What happens to an animal cell in a hypertonic solution

A

lower water potential than the cell
Water leaves cell
cell shrinks (crenate)

40
Q

What happens to an animal cell in a hypotonic solution

A

Higher WP than cell
water enters cell
Cell swells and bursts - osmotic lysis

41
Q

What happens to an animal cell in isotonic solution

A

Same WP as cell
no net osmotic movment

42
Q

What happens to a plant cell in hypertonic solution

A

Lower WP than cell
Water leaves cytoplasm and vacuole
Cytoplasm shrinks away from cell wall and leaves a gap
Gap filled with concentrated salt solution
Plasmolysis

43
Q

What happens to a plant cell in a hypotonic solution

A

Higher WP than cell
water enters the cell
Cytoplasm and vacuole gain water
Due to high tensile strength of cell wall - cell will not burst
Turgid

44
Q

What happens to a plant cell in an isotonic solution

A

Same WP
No net osmotic movment

45
Q

What is active transport

A

Needs ATP
Movment against a concentration gradient
Needs specific proteins carriers/ pumps
Factors affecting respiration affect AT

46
Q

When does endo/exocytosis occur

A

When a cell needs to transport large amounts of materials across their plasma membrane

47
Q

What is endo/exocytosis

A

Cells make containers out of the plasma membrane
Makes vesicles
Endocytosis is importing materoials into the cell
Excocytosis is exporting materials out of the cell
Both require ATP