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OCR A-Level Biology > Chap 3 - Biological Molecules > Flashcards

Chap 3 - Biological Molecules Flashcards

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1
Q

Describe the structure of a water molecule

A
  • two hydrogen atoms bonded covalently to an oxygen atom
  • the covalent bond is polar - oxygen is slightly -tive and the hydrogen atoms are slightly +tive
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2
Q

What is the bond that links two water molecules together?

A

hydrogen bond

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3
Q

Explain what a hydrogen bond is and what molecules it can join

A

electromagnetic attraction between partially positively charged hydrogen atoms attached to a highly electronegative atom (oxygen, nitrogen)

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4
Q

Explain how a H bond links water molecules together

A

slight positive charge of a hydrogen atom of one molecule is attracted to the slight negative charge of an adjacent oxygen atom from another molecule

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5
Q

What are hydrogen bonds responsible for

A

holding together DNA, proteins, and other macromolecules.

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6
Q

Explain why water is polar

A
  • oxygen and hydrogen atoms are bonded covalently - they share electrons
  • oxygen has a larger positive nucleus, the electrons are shared unequally and they spend more time closer to it than the small nucleus of hydrogen which means the bond is polar
  • causes the oxygen to become slightly negative because has greater share of negative electrons, meaning hydrogen is slightly positive (positive nucleus which has a smaller share of electrons)
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7
Q

Define electronegativity

A

the tendency of an atom or molecule to draw electrons towards itself.

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8
Q

Define dipole

A

a bond or molecule whose ends have opposite charges.

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9
Q

List the 5 roles that water plays in life

A
  • solvent - most biological reactions happen in aqueous solution (cell cytoplasm is mainly water)
  • reactant - hydrolysis, condensation
  • transport medium - in blood, lymphatic system, excretory system, digestive system, vascular tissues, etc
  • coolant - helps buffer temperature changes during chemical reactions in cells
  • insulating layer - ice freezes and floats which insulates the water so seas do not freeze solid, providing aquatic organisms with a constant environment
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10
Q

Explain why the polar nature of water allows it to be a useful solvent

A
  • excellent solvent for ions & polar molecules
  • water mols are attracted to them, collect around them and separate them
  • chemicals are then free to react with other chemicals in the solution
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11
Q

Explain why water cannot dissolve lipids & why that is useful

A
  • because water molecules are attracted to each other, so push the non-polar molecules together.
  • important to maintain stability of membrane structures which are mainly made of lipid molecules - water does not dissolve them
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12
Q

Explain why the polar nature of water allows it to be a useful transport medium.

A
  • hydrogen bonds allow for thermal stability - remains a liquid over a big range of temperatures
  • cohesion between water molecules means that when water is transported through the body, molecules stick together (hydrogen bonds between water molecules)
  • cohesion and adhesion allow for capillary action
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13
Q

Explain why the polar nature of water allows it to be a useful coolant.

A
  • because of its high thermal stability (high specific heat capacity) meaning it requires a lot of heat gain or loss to change its temperature
  • tt also has a high latent heat of vaporisation (large amount of energy is needed to convert liquid water into gas)
  • hydrogen bonding holds water molecules together, it takes a lot of energy to overcome them in order to release the particles and cause water to melt/evaporate
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14
Q

Explain why the polar nature of water allows it to be a useful reactant.

A
  • in hydrolysis it is able to split up polymers or join them together by being removed from them
  • this is due to the partial positive charge on the hydrogens, one of them splits away from the OH and binds to one part of the polymer while the OH binds to the other part
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15
Q

Why is water a good habitat?

A
  • high thermal stability due to the hydrogen bonds helps keep the temperature stable - good environment for life
  • because ice is less dense than liquid water, it floats forming an insulating layer - prevents seas from freezing
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16
Q

Why does ice float on water?

A
  • as water cools down, the kinetic energy the molecules have gets reduced - they move less and therefore take up less space
  • above 4*C, interactions between molecules are short, hydrogen bonds keep forming and breaking quickly
  • below 4*C, the energy of water molecules falls below the energy of hydrogen bonds - they form much more frequently than they break
  • this causes a lattice to be formed where the molecules are more spread out than in liquid water - less dense than disordered liquid water therefore it floats
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17
Q

Define hydrophillic

A

substance attracted to water
- water can dissolve them, tend to be polar molecules/ions

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18
Q

Define hydrophobic

A

substance that repels water
- water cannot dissolve them, tend to be non-polar molecules

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19
Q

Define cohesion

A

the ability of a substance to stick to a like substance

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20
Q

Define adhesion

A

the ability of a substance to stick to an unlike substance

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21
Q

List 3 examples of how water is used by prokaryotes and eukaryotes

A
  • cytoplasm is made up primarily from water - where most metabolic reactions happen
  • water being a solvent allows for molecules/ions to flow freely in the cytoplasm allowing for movement of substances in/out of cells
  • supports plant cells thanks to turgor - water pressure inside of plant cells
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22
Q

List 6 examples of how water is used in plants, animals and fungi

A
  • in animals with sweat glands - secrete sweat (made up of water
  • hydrostatic skeleton - octopuses, snails which is made up of water-filled tubes which can expand and contract but pushing water in/out
  • synovial fluid - in joints mostly made up of water, acts as lubricant in the joint
  • circulatory system - blood is mostly water which allows animals to transport substances inside the organism
  • xylem and phloem - thanks to capillary action, nutrients can be transported against the force of Gravity up to the top of the plant
  • seminal fluid in animals - acts as a medium for the sperm cells to swim to the egg
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23
Q

Explain how water is used in unicellular and multicellular organisms

A

water is used by all organisms for hydrolysis and condensation of polymers

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24
Q

Explain why water can dome above the level of the glass container it is in? Explain the shape it makes.

A
  • glass is made up of polar molecules to which water molecules are attracted to (hydrophilic) - adhesion
  • while the water is in the container, some molecules touch glass which is above the level of water and they stick to it - adhesion
  • other molecules stick to that molecule due to cohesion and stay like that while the original molecule is stuck to the glass, resulting in a concave meniscus shape
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25
Q

Explain how capillary action occurs.

A
  • one H2O molecule gets pulled up because of the adhesion of water to the walls of a vessel
  • this pulls H2O molecules which are below it, upwards due to cohesion between H2O molecules, causing a continuous stream
  • this means that there is a net movement upwards, against gravity
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26
Q

List the main properties of water.

A
  • adhesion & Cohesion
  • hydrogen bonding
  • high specific heat capacity & latent heat of vaporisation
  • solvent
  • polar covalent bond
  • surface tension
  • solid is less dense than liquid
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27
Q

Define monomer

A

a molecule (repeating unit) that can be covalently bonded to other identical molecules to form a polymer.

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28
Q

Define polymer

A

chains of repeating units (monomers) joined together by a covalent bond through a condensation reaction

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29
Q

Define macromolecules

A

molecules containing a very large number of atoms.

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30
Q

Define dimer

A

a molecule or molecular complex consisting of two identical molecules linked together.

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31
Q

Define oligomer

A

a polymer whose molecules consist of relatively few repeating units.

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32
Q

Describe a condensation reaction

A

reaction between two molecules resulting in the formation of a larger molecule and the release of a water molecule

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33
Q

Describe hydrolysis

A

the breakdown of a molecule into two smaller molecules requiring the addition of a water molecule

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34
Q

Define metabolism

A

the sum of the chemical reactions that take place within each cell of a living organism consisting of anabolism and catabolism

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35
Q

Describe catabolic reactions

A

metabolic reactions where larger molecules are broken down into smaller units
- release energy

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36
Q

Describe anabolic reactions

A

metabolic reations where molecules are constructed from smaller units
- require energy

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37
Q

What are the main categories of biological molecules?

A
  • carbohydrates
  • lipids
  • proteins
  • nucleic acids
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38
Q

Define single bond

A

a chemical bond in which one pair of electrons is shared between two atoms.

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39
Q

Define double bond

A

a chemical bond in which two pairs of electrons are shared between two atoms.

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40
Q

Name the elements present in carbs

A

C, H, O

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41
Q

What is the general formula for carbohydrates

A

(CH2O)n
n is 3 or more

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42
Q

Define monosaccharides

A

a single sugar unit which cannot be hydrolysed into a simpler sugar
- (CH2O)n , n is 3 or greater up to 6

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43
Q

Define disccharides

A

carbohydrates formed when two monosaccharides link together
- general formula: C12H22O11

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44
Q

Define polysaccharides

A

consist of 10 or more monosaccharides that are linked together
- they are polymers

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45
Q

Define pentose and hexose sugars

A

pentose: monosaccharides with five carbon atoms.
hexose: monosaccharides with six carbon atoms.

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46
Q

What is a triose sugar with an example

A

monosaccharides with three carbon atoms.
- example: triose phosphate

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47
Q

What is a furanose ring

A

five-membered ring consisting of four carbon atoms and oxygen atom.

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48
Q

What is a pyranose ring

A

a six-membered ring consisting of five carbon atoms and one oxygen atom.

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49
Q

Define isomer

A

compounds with the same number of atoms (empirical formula) but a different structure.

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50
Q

Describe the difference between and alpha and beta glucose

A

alpha: -OH on C1 is below the ring and on the same side as -OH on C4
beta: -OH on C1 is above the ring and on the opposite side to -OH on C4

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51
Q

List 3 examples of dissaccharides and for each state which monosaccharides they are composed of.

A

maltose: made up of two alpha glucose molecules
sucrose: made up of alpha glucose and fructose
galactose: made up of beta glucose and galactose

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52
Q

List the properties and functions of glucose.

A
  • hexose monosaccharide
  • chemical formula: C6H12O6
  • can exist in cyclical (pyranose) or linear structure
  • soluble in water bc it can form hydrogen bonds between its hydroxyl groups and water molecules
  • main respiratory substrate, product of photosynthesis
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53
Q

State the properties and functions of fructose.

A
  • hexose monosaccharide
  • chemical formula: C6H12O6
  • five member ring structure (furanose)
  • soluble in water
  • plant transport sugar
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54
Q

State the properties and functions of galactose

A
  • hexose monosaccharide
  • chemical formula: C6H12O6
  • found in milk, soluble
  • six member ring structure (pyranose)
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55
Q

State the properties and functions of maltose

A
  • disaccharide composed of two alpha glucose molcules
  • chemical formula; C12H22O11
  • alpha 1, 4 glycosidic bond is present
  • soluble in water
  • it is an intermediate in the intestinal digestion of glycogen and starch
  • found in germinating grains
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56
Q

State the properties and functions of sucrose

A
  • disaccharide composed of alpha glucose and fructose molecules
  • chemical formula; C12H22O11
  • glycosidic bond holds them together
  • the only non-reducing sugar, its components cant convert to open-chain form with an aldehyde group
  • soluble in water
  • transport sugar in phloem in plants
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57
Q

State the properties and functions of lactose

A
  • disaccharide composed of beta glucose and galactose
  • chemical formula; C12H22O11
  • beta 1,4 glycosidic bond between them
  • glucose and galactose are flipped w respect to each other
  • soluble in water
  • main sugar in milk
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58
Q

Describe how hydrolysis of maltose occurs and why water is needed

A
  • water is needed to break the glycosidic bond between the two glucoses
  • after bond is broken, OH (from water) binds to carbon 1 of first glucose
  • remaining H atom binds to carbon 4 of second glucose so water gets used up and becomes part of the monosaccharides
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59
Q

Explain why alpha glucose link together to form starch

A
  • two alpha glucoses next to each other can an alpha 1,4 glycosidic bond
  • hydroxyl groups on C1 and on C4 on neighboring glucose are on the same side of the ring and therefore can react in condensation and bond together
  • they can even form alpha 1,6 glycosidic bonds because the molecules are not flipped resulting in amylopectin branching
  • the helical strucrture forms because of intramolecular hydrogen bonds between -OH of C3 and -OH of C2 in the next glucose unit
  • conclusion: two alpha glucoses form alpha 1,4 glycosidic bonds which allow intramolecular hydrogen bonding, forming a helical structure - amylose and can form 1,6 glycosidic bond branches too - amylopectin
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60
Q

Explain why beta glucose link together to form cellulose.

A
  • two beta glucoses next to each other cannot bond like alpha glucses can
  • hydroxyl groups on C1 and C4 are on diff sides of the ring and therefore cannot react in condensation and bond - theyre too far away
  • this is why one glucose molecule must be flipped 180 degrees with regards to the other
  • this forms a beta 1,4 glycosidic bond
  • there is no helical structure because each beta glucose monomer is upside down with respect to its neighbor - linear structure
  • conclusion: two beta glucoses must be flipped with respect to each other which allows for a beta 1,4 glycosidic bond, this means only intermolecular hydrogen bonds can form - molecule will have linear structure - cellulose
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61
Q

List the diff polysaccharides that make up starch with their proportions.

A

amylose - 20% of starch
amylopectin - 80% of starch

62
Q

Explain why glycosidic bonds are called 1,4 or 1,6

A

because they either bond at the 1st and 4th carbons or the 1st and 6th carbons

63
Q

Explain how to calculate the number of glycosidic bonds in a carbohydrate given the number of monosaccharides.

A

number of monosaccharides - 1 because a glycosidic bond involves TWO monomers.

64
Q

Describe the structure of a cellulose fibre

A
  • they consist of macrofibrils of cellulose which are made up of many microfibrils
  • microfibrils contain about 80 cellulose molecules
  • cellulose molecules have hydrogen bonds between them because they are parallel
  • cellulose molecules themselves are made up of beta glucose monomers
65
Q

Relate structural properties to the functions of starch w/ solubility and size

A
  • insoluble - does not affect water potential & does not cause osmotic swell
  • too large of a molecule, overcomes water’s hydrogen bonds attempting to separate the molecules (amylose - 300 glucose molecules, amylopectin - 3000 glucose molecules)
  • makes it good for storage - stays inside the plant cells without dissolving into the system
  • many glucose units stored in one molecule - more energy dense than storing them separately
66
Q

Relate structural properties to the functions of starch with bonding and presence of side chains.

A
  • amylose - only alpha 1,4 glycosidic bonds which have a bond angle that makes it form a helical structure further stabilised by intramolecular hydrogen bonds (between -OH groups between neighboring monomers) meaning it is more compact than if a straight chain - energy dense
  • amylopectin - alpha 1,4 glycosidic bonds, every ~20C - alpha 1,6 glycosidic bond which forms a branched structure of helical chains - even more energy stored
  • 1,6 glycosidic bonds allow for more branch endings for enzyme activity - easy to hydrolyse and release the glucose for energy quickly
67
Q

Relate structural properties to the functions of glycogen wrt solubility, size

A
  • insoluble - does not affect water potential & does not cause osmotic swell
  • too large of a molecule, overcomes water’s hydrogen bonds attempting to separate the molecules (up to 60000 glucose molecules)
  • makes it good for storage - stays inside animal cells without dissolving into the system
  • many glucose units stored in one molecule - more energy dense than storing them separately
68
Q

Relate structural properties to the functions of glycogen with bonding and presence of side chains.

A
  • 1,4 glycosidic bonds that cause a helical structure (reinforced by hydrogen bonds between -OH groups between neighboring monomers) due to the bond angle and every ~10C a 1,6 glycosidic bond branch - compact energy storage compared to straight chain
  • every ~10C branch - highly branched structure - lots of branch endings for enzymes to hydrolyse for quick glucose access, more branched than starch because animals are more metabolically active and need more energy more quickly
69
Q

Relate structural properties to the functions of cellulose wrt solubility, size

A
  • insoluble - does not dissolve away - forms good barrier between cytoplasm and exterior
  • too large of a molecule, overcomes water’s hydrogen bonds attempting to separate the molecules (~10000 glucose molecules in a chain)
  • length of chain gives it good tensile strength - supports cells, preventing them from bursting allowing cells to become turgid which gives plant tissue support and strength
70
Q

Relate structural properties to the functions of cellulose with bonding and presence of side chains.

A
  • composed of beta glucose molecules, each consecutive one is flipped forming beta 1,4 glycosidic bonds
  • because each consecutive glucose is flipped wrt previous one there is no helical structure or intramolecular hydrogen bonds between different -OH groups - linear chains
  • each chain is parallel to each other - form intermolecular hydrogen bonds - 80 of them form microfibrils which form macrofibrils - additional strength
  • cellulose fibrils run in different directions - give cell wall extra support
  • water can fill space between fibrils - fully permeable allowing for ions/molecules to enter cell
71
Q

Define inorganic material and inorganic compound

A

inorganic material: material not consisting of or deriving from living matter.

inorganic compound: compound that is not organic (do not contain carbon-hydrogen bonds)

72
Q

Define cation

A

ion with a positive charge

73
Q

Define anion

A

ion with a negative charge

74
Q

What is the symbol for calcium ions? List one biological process it is involved in.

A

Ca2+
- part of enamel and bone structure
- cofactor in blood clotting

75
Q

What is the symbol for sodium ions? List one biological process it is involved in.

A

Na+ - has an essential function in nerve transmission

76
Q

What is the symbol for potassium ions? List one biological process it is involved in.

A

K+
- nerve transmission
- essential in water reabsorption in loop of Henle and collecting duct

77
Q

What is the symbol for hydrogen ions? List one biological process it is involved in.

A

H+
- involved in hydrolysis and condensation reactions
- involved in ATP formation

78
Q

What is the symbol for ammonium ions? List one biological process it is involved in.

A

NH4+
- intermediate ion in deamination of proteins

79
Q

What is the symbol for nitrate ions? List one biological process it is involved in.

A

NO3-
- nitrogen source for green plants to manufacture proteins

80
Q

What is the symbol for hydrogen carbonate ions? List one biological process it is involved in.

A

HCO3-
- involved in carbon dioxide transport in the blood with H+

81
Q

What is the symbol for chlorides? List one biological process it is involved in.

A

Cl-
- shift of chloride ions into and out of red blood cells maintains pH balance during CO2 transport

82
Q

What is the symbol for phosphate ions? List one biological process it is involved in.

A

PO43-
- in phospholipids, they form part of cell membranes
- constituent of ATP and nucleic acids

83
Q

What is the symbol for hydroxide ions? List one biological process it is involved in.

A

OH-
- involved in hydrolysis and condensation

84
Q

What are the chemicals used in Benedict’s test?

A
  • qualitative Benedict’s solution (alkaline solution of copper(II)sulfate)
  • solution you are testing (reducing/non-reducing sugar)
85
Q

Outline the method for using Benedict’s solution

A
  • sugar being tested must be in solution so that reducing sugar molecules can expose their aldehyde group in linear form
  • add qualitative benedicts solution in equal volume to sample being tested - reactants will be in excess so reaction will be complete
  • heat mixture to 80+ deg C - catalysing reaction
86
Q

Describe the appearance of a negative/positive result using Benedict’s test

A
  • brick red precipitate - Cu2+ ions reduced to Cu+ - brick red color - positive result
  • no color change - solution stays blue - negative result
87
Q

Describe the appearance of a negative/positive result using Benedict’s test

A
  • brick red precipitate - Cu2+ ions reduced to Cu+ - brick red color - positive result
  • no color change - solution stays blue - negative result
88
Q

Define qualitative test

A

the process of determining whether or not a particular chemical is present in a sample
- does not determine quantity of chemical

89
Q

Define semi-qualitative test

A

process of determining whether or not a particular chemical is present and its quantity, but not precisely.
- result is an estimate of the quantity present

90
Q

Define quantitive test

A

test that determines the precise quantity of a particular chemical present in the sample

91
Q

How can Benedict’s test for reducing sugars act as a semi-quantitative test?

A
  • you can get an estimate of the relative concentration present
  • resulting color gives an idea of concentration of reducing sugars, more red = higher conc
92
Q

Give 5 examples of reducing sugars.

A
  • glucose
  • lactose
  • fructose
  • maltose
  • ribose
93
Q

Give one example of a non-reducing sugar.

A

sucrose

94
Q

Explain why reducing sugars are called reducing sugars.

A

sugars that have an aldehyde group which can reduce another molecule or ion.

95
Q

Describe what reagent test strips are with an example of how they are used.

A

determine the concentration/presence of an ion/compound in solution (or air)
- example: test for presence of reducing sugars (glucose) - using color coded chart - can determine conc

96
Q

Describe in principle how a colorimeter works.

A
  • piece of equipment used to quantitatively measure the absorbance/transmission of light by a colored solution by shining a light thru it
  • more concentrated solutions will absorb more light and transmit less - used to calculate concentrations
97
Q

Define the terms percentage absorbance and percentage transmission in relation to data provided by a colorimeter.

A

relate to the amount of light of a particular wavelength that passed thru a volume of liquid, relative to maximum possible amount of light available at that wavelength.

98
Q

Explain how to convert % transmission to % absorbance.

A

If x% was transmitted, 100-x% will have been absorbed.

99
Q

Explain how a colorimeter can be used in a quantitative test for reducing sugars.

A
  • place filter into colorimeter
  • calibrate colorimeter using distilled water
  • perform normal Benedict’s test (with quantitative grade Benedict’s solution)
  • filter off the solutions to remove precipitate
  • measure % transmission for each of the solution of glucose
  • plot a calibration curve of transmission against known glucose conc
100
Q

Define the term calibration curve and explain how they are used to identify concentration of glucose in a solution.

A

method for determining the concentration of a substance in an unknown sample by comparing the unknown to a set of standard samples of known concentration.
- plot that shows how the instrumental response to changes with concentration of substance being measured
- match the corresponding y coordinate with the curve to find the glucose conc

101
Q

Describe in principle how biosensors work.

A

sensors that use biological components to determine the presence and conc of molecules such as glucose
- molecular recognition - a protein or single strand of DNA is immobilised to surface which will interact with or bind to the specific molecule under investigation
- transduction - interaction causes change in a transducer (detects changes in pH and produces response such as release of immobilised dye on a test strip or an electric current)

102
Q

Which elements are present in lipids (include phospholipids)?

A

C, H, O, (P)

103
Q

Define macromolecules

A

molecules containing a very large number of atoms

104
Q

What are the 3 categories of lipids?

A

triglycerides, phospholipids, sterols.
(Glycolipids, cholesterol, steroid hormones, lipid based vitamins)

105
Q

What are the components of a triglyceride?

A

glycerol, 3 fatty acid chains

106
Q

Describe the difference between saturated, monounsaturated and polyunsaturated fatty acids.

A
  • saturated - every carbon in the hydrocarbon chain has the maximum number of hydrogens. All C-C bonds are single bonds
  • monounsaturated - saturated except for one double/triple bond
  • polyunsaturated - contain several double/triple bonds between C-atoms
107
Q

Explain why saturated triglycerides tend to be solid at RTP whereas unsaturated triglycerides tend to be liquid.

A
  • unsaturated acids have one or more double/triple bond which cause a kink in the chain structure - it is not a straight line
  • saturated acids have single bonds only so their structure is a straight line
  • in packing of fatty acids, saturated can sit much closer together than unsaturated due to unsaturated bonds having a kink
108
Q

State the difference between the triglycerides found in non-fish animals and those in plants and fish.

A

in animals: rich in saturated fatty acids - solid at RTP
in plants & fish: rich in unsaturated fatty acids - oils are liquid at RTP

109
Q

State the property that each end of the phospholipid has.

A
  • charged hydrophilic head
  • non-polar hydrophobic tails
110
Q

Describe the diff between a triglyceride and a phospholipid.

A
  • contain 3 fatty acids, phospholipids contain 2 fatty acids
  • non-polar whereas phospholipids have a polar head and non-polar fatty acid tails
111
Q

What is the bond that holds the building blocks of a triglyceride together?

A

ester bond

112
Q

What is the reaction that forms triglycerides and the reaction that breaks them apart?

A

esterification - forms
hydrolysis - breaks down

113
Q

Explain how an ester bond is formed between glycerol and a fatty acid.

A
  • both molecules contain hydroxyl groups
  • the hydroxyl groups interact leading to the formation of 3 water molecules and ester bonds between fatty acids and glycerol molecule
114
Q

State the products of digestion of a triglyceride and state what would happen to the pH of the solution (and why).

A
  • products of digestion of a triglyceride are glycerol and 3 fatty acids
  • because the fatty acids are now free from the ester bond, they will lower the pH as they are acids
115
Q

Describe the structure of sterols/cholesterol.

A
  • complex alcohol molecules based on four carbon rings with a hydroxyl group at one end
  • the hydroxyl group is hydrophilic, rest of molecule is hydrophobic
116
Q

List the functions of triglycerides & relate them to their properties.

A
  • source of energy - in respiration provide twice as much energy per gram than carbs or proteins
  • energy storage - for the equivalent amount of energy, lipids have half the mass of carbohydrates and proteins (facilitates movement in animals and seed dispersal in plants bc same amount of energy stored in less mass) & they dont affect water potential of cell - large amounts can be stored
  • buoyancy - lipids are less dense than water (aquatic mammals can ‘float’)
  • insulation - bad conduction of heat (aquatic mammals insulat themselves)
  • reducing water loss - bc hydrophobic they are insoluble (waxy cuticle on plants and insects)
  • (protection - vital organs have fat padding)
117
Q

List the functions of phospholipids & relate them to their properties.

A
  • membrane formation & creation of hydrophobic barriers - due to the non-polar nature (non-polar chains are in the middle, polar heads face the water so water cannot dissolve the membrane)
118
Q

List the functions of cholesterol & relate them to their properties.

A
  • important precursor for: steroid hormones, fat soluble vitamins, bile salts
  • found in phospholipid bilayer for membrane stability + fluidity - hydroxyl group is attracted to phosphate heads & carbon rings attracted to hydrophobic tails of phospholipids in the center of membrane - fits between them which prevents them aligning too closely & holds them together at the same time
119
Q

Describe how presence of cholesterol affects the properties of cell membranes.

A
  • cholesterol has one end attracted to the polar head of a phospholipid and the tail of another
  • this means cholesterol helps stabilise the bilayer
  • because it fits between phospholipids it also prevents them from aligning too close together at low temperatures - maintaining fluidity by preventing solidification
120
Q

Describe the structure of an amino acid

A

amine group, carboxyl group and R-group

121
Q

Identify the part of an amino acid which is variable.

A

r-group

122
Q

State how many amino acids occur in life.

A

20

123
Q

Describe the different types of amino acid in life.

A
  • non-essential (5) - our body can make them from other amino acids
  • essential (9) - only obtained from what we eat
  • conditionally essential (6) - only needed by infants and growing children
124
Q

Define polypeptide chain

A

many amino acids joined by peptide bonds

125
Q

Define protein

A

one or more polypeptides arranged as complex macromolecules with specific biological functions.
- contain C, H, O, N, (S)

126
Q

Describe how one end of a polypeptide chain differs from the other end.

A
  • one end - amino terminal (amine group)
  • other end - carboxyl terminal (carboxyl group)
127
Q

Define primary structure, describe how it is held together.

A

sequence in which the amino acids are joined together by peptide bonds

128
Q

Define secondary structure, the 2 types and how they are held together

A

initial folding of the polypeptide chain
- held together by hydrogen bonds between carboxyl group (δ-) and the amine group (δ+) of peptide bonds of different neighboring amino acids
- a-helix and b-pleated sheet

129
Q

Define tertiary structure and describe how it is held in place (all possible bonds).

A
  • final 3D structure of the polypeptide
  • coiling of polypeptide into secondary structure brings R-groups of diff amino acids closer together - can interact causing further folding
  • disulfide bonds - covalent bond between two sulfur containing amino acids
  • ionic bonds - between a basic and an acidic R-group
  • hydrophobic interactions - between non-polar R-groups (in aqueous env. they will be on the inside and hydrophilic on the outside)
  • hydrogen bonds - between polar/hydrophilic R-groups
130
Q

Define quaternary structure of a protein and describe how it is held in place (all possible bonds).

A
  • association of 2 or more polypeptide chains to form a fully functional protein
  • proteins do not have to have quaternary structure and those that do can have identical or different subunits
  • same bonds from tertiary are used to maintain the quaternary structure of the protein
131
Q

Define globular protein

A

compact, water soluble and roughly spherical proteins.
- carry out metabolic functions

132
Q

Define fibrous protein

A

long, insoluble structural proteins
- arent folded into complex 3D shapes (no tertiary structure)

133
Q

Define prosthetic group

A

non-protein component permanently attached to a protein

134
Q

Define conjugated protein

A

globular proteins that contain a prosthetic group

135
Q

Give 3 examples of fibrous proteins.

A
  • elastin
  • collagen
  • keratin
136
Q

Compare the structure of globular and fibrous proteins

A

globular: round/spherical, can be tertiary or quaternary, irregular shapes
fibrous: long, narrow, secondary, regular shapes

137
Q

Compare the properties of globular and fibrous proteins

A

globular: exact shape/structure determines function, more sensitive to pH and temp changes, soluble
fibrous: strong, more durable to pH and temp changes, insoluble

138
Q

Compare the functions of globular and fibrous proteins

A

globular: metabolic functions
fibrous: structural functions (making up tissues)

139
Q

List the properties and functions of glucose,

A

properties:
- monosaccharide
- 6-membered ring structure
- can be alpha/beta glucose
- water soluble

function:
- main respiratory substrate (energy source)
- monomer for starch, cellulose and glycogen
- product of photosynthesis

140
Q

List properties and functions of starch.

A

properties:
- polysaccharide
- made up of 20% amylose, 80% amylopectin
- insoluble in water
- amylopectin - branched every ~20 carbons
- amylose - helical structure
- compact and energy dense

function:
- storage carbohydrate in plants found in chloroplasts, amyloplasts, storage organs (tubers and seeds)
- source of energy

141
Q

List the properties and functions of cellulose.

A

properties:
- polysaccharide
- made up of beta glucose molecules, each consecutive unit is flipped wrt previous
- insoluble in water
- fully permeable
- high tensile strength

function:
- component of plant and algal cell walls
- provides support for plants - they do not have a skeleton
- mixed w cutin for waxy cuticle covering of leaves
- mixed w suberin in endodermis of roots
- mixed w lignin in xylem walls to make the cell wall impermeable

142
Q

List the properties of glycogen.

A
  • polysaccharide
  • made up of alpha glucose molecules that form branches every ~10 carbons
  • insoluble in water
  • more easily digestible than starch bc there are more branch endings for enzyme activity
  • compact and energy dense
143
Q

Identify key structural components, properties and functions of a conjugated protein.

A

structural components:
- quaternary structure
- 2 alpha subunits
- 2 beta subunits
- each subunit contains prosthetic heam group
- Fe2+ present in each heam group

properties:
- iron ion able to pick up oxygen and release it

function:
- transport of oxygen throughout the body

144
Q

Identify key structural components, properties and functions of an enzyme.

A

structural components:
- quaternary structure
- contains four prosthetic heam groups
- Fe2+ present in each heam group

properties:
- iron ion allows catalase to interact with hydrogen peroxide and speed up its breakdown

function:
- catalyst for breakdown of hydrogen peroxide
- gets rid of it bc buildup can be toxic to cells and cell components

145
Q

Identify key structural components, properties and functions of a peptide hormone.

A

structural components:
- quaternary structure
- consists of two subunits
- subunits linked by two disulfide bonds

properties:
- soluble
- has precise shape to fit onto cell receptors

function:
- regulation of blood glucose concentration

146
Q

Describe structure, properties, location and function of keratin.

A

structure:
- group of fibrous proteins
- high proportion of sulfur containing cysteine that form strong disulfide bonds making it strong, inflexible and insoluble

properties:
- strong
- inflexible
- insoluble

location:
- hair
- skin
- nails

function:
- protective barrier
- formation of hair, skin, nail tissue

147
Q

Describe structure, properties, location and function of elastin.

A

structure:
- quaternary protein
- made from many stretchable molecules (tropoelastin) that are cross linked by covalent bonds involving lysine

properties:
- elastic
- insoluble

location
- walls of blood vessels
- alveoli of lungs

function
- give tissues flexibility to expand when needed and to return to normal size

148
Q

Describe structure of collagen.

A
  • three polypeptides wound together in long rope-like triple helix structure
  • every third amino acid is glycine that allows close packing
  • hydrogen bonds between pp chains form long quaternary proteins with staggered ends - allow them to join end to end to form long tropocollagen fibrils
  • tropocollagen cross link to produce strong fibres
  • high proportion of proline and hydroxyproline that repel each other giving stability
149
Q

Describe properties of collagen

A

strong, flexible

150
Q

State the location of collagen

A

skin, tendons, ligaments, nervous sys,

151
Q

State the function of collagen

A

connective tissue

152
Q

Describe the functions of glycogen

A
  • storage carbohydrate found in animal cells
  • cells that contain the most: kidney, liver, muscle, neurons (most metabolically active)

OCR A-Level Biology (16 decks)

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