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Biology > 3. Lipids, membranes and transport > Flashcards

3. Lipids, membranes and transport Flashcards

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

Biology (23 decks)

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