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A-Level Biology > 2.1.2 Biological Elements > Flashcards

2.1.2 Biological Elements Flashcards

1
Q

Main elements present in living organisms

A

Carbon, Hydrogen, Oxygen and Nitrogen (4 main)
Phosphorous and Sulfur (2 extra)
Sodium Potassium and Calcium and Iron (extra)

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2
Q

Biological elements in Carbohydrates

A

Carbon, Hydrogen and Oxygen (use glucose as example of ration)

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3
Q

Biological elements in lipids

A

Carbon, hydrogen and oxygen

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4
Q

Biological elements in Proteins

A

Carbon, hydrogen, oxygen, nitrogen and sulfur

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5
Q

Nucleic acids

A

Carbon, hydrogen, oxygen, nitrogen and phosphorous

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6
Q

How are carbohydrates polymers?

A

Long chain molecules linking multiple individual molecules (called monomers) in a repeating manner

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7
Q

Monomers in carbohydrates

A

Saccharides (sugars)

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8
Q

Monomers in proteins

A

Amino acids

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9
Q

What causes polarity?

A

Uneven sharing of electrons in a covalent bond between two atom - making one side delta positive and another side delta negative (regions of positivity and negativity)

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10
Q

O-H bond polarity

A

Oxygen has a greater share of electrons which makes hydroxyl group polar - O is more negative relative to hydrogen

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11
Q

Water molecule

A

Polar molecules including water interact with each other as negative and positive regions of the molecule attract each other and form hydrogen bonds

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12
Q

Hydrogen bonds

A

Relatively weak interactions which break and reform between the constantly moving water molecules - hydrogen bonds are weak interactions but when they occur in high numbers they are strong (giving unique characteristics)

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13
Q

Why does water have a high boiling point?

A

This is due to hydrogen bonding between water molecules which takes a lot of energy to break the bonds and cause it to become gaseous (evaporate) - therefore latent heat of vaporisation is very high (in order to change state)

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14
Q

Density of water characteristic

A

More dense in liquid state than solid - as water is cooled BELOW 4 degrees Celsius, hydrogen bonds and the polarity causes repulsion thus producing an open (tetrahedral) lattice which increases the volume and thus decreases density

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15
Q

Cohesion property and example

A

Water moves as one mass because molecules are attracted to each other (cohesion) due to polarity and in this way plants are able to draw up water through roots (and suck a straw)

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16
Q

Adhesion property and example

A

Water molecules’ polarity causes it to be attracted to other materials (when you wash your hands, your hands become wet and water does not run straight off)

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17
Q

What causes surface tension?

A

Water molecules cohesivenss’ to each other > they are adhesive to the air ; creating a “skin” of surface tension

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18
Q

Water as a solvent?

A

Because it is polar - many organic solvents can be dissolved in it (cytosol of prokaryotes etc) ; many solutes are also polar molecules such as amino acids and proteins therefore water acts as a medium for chemical reactions and helps in the transport of dissolved compounds into and out of the cell

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19
Q

Water as a transport medium?

A

Cohesion between water molecules means that they stick together
Adhesion means attraction between water and other polar molecules
Effects of adhesion + cohesion results in CAPILLARY ACTION = allowing water to rise up a narrow tube AGAINST Gravity

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20
Q

Water as a coolant?

A

Because of it’s high SHC and Latent Heat, it helps to buffer temperatures during chemical reactions in prokaryotic and eukaryotic cells because of the large amount of energy required to overcome hydrogen bonding (MAINTAINS constant temperatures in cellular environments - enzymes only active in a narrow temperature range)

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21
Q

Life support for organisms/animals

A
  • Wtaer is stable (temerpature wise too) allowing a constant environment for fish to live in
  • Because ice floats it forms on the surface of ponds and lakes rather than at the bottom ; producing an insulating layer above the water below ; aquatic organisms will not be able to survive if entire habitat frozen solid
  • Surface tension is strong enough to support pond skaters (small insects)
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22
Q

Carbohydrates formula

A

Cx(H2O)y

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23
Q

Single sugar unit is called

A

Monosaccharide

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24
Q

Examples of monosaccharides

A

Glucose, fructose and ribose

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25
Q

Disaccharide

A

2 monosaccharides linked together ; lactose and sucrose

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26
Q

Polysaccharide

A

When two or more monosaccharides are linked they form a polymer called a polysaccharide ; glycogen cellulose and starch

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27
Q

Glucose molecule

A

C6H12O6 - 6 carbons in a ring therefore hexose monosaccharide

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28
Q

How are carbons numbered?

A

Clockwise - carbon 1 to carbon 6 (on carbon 5)

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29
Q

Alpha glucose structure describe

A 
Carbon 1 - OH group down
2 - down
3 - up
4 - down
5 - Ch2OH up
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30
Q

Beta glucose structure describe

A 
Carbon 1 - OH group up
2 - down
3 - up
4 - down
5 - ch2oh up
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31
Q

Are glucose molecules soluble?

A

Yes because of the hydrogen bonds formed between hydroxyl groups and water molecules ; glucose can be dissolved into the cytosol of the cell

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32
Q

Condensation reaction between 2 alpha glucose

A

Carbon 1 and Carbon 4 - OH groups both down close together ; they react to form O bond with H2O as by-product
Bond forms between 1 and 4 - 1,4 glycosidic bond ( COVALENT BOND)

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33
Q

2 a-glucose bonded together

A

Maltose - disaccharide

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34
Q

Other hexose monosaccharides

A

Fructose (fruit) and galactose

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35
Q

Sucrose?

A

Disaccharide formed by fructose + glucose

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36
Q

Lactose?

A

Glucose + galactose (milk) - disaccharide

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37
Q

Ribose?

A

It is a pentode monosaccharides - 5 carbon atoms ; present in RNA nucleotides and deoxyribose in DNA nucleotides

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38
Q

What is starch?

A

Made up of two polysaccharides and glucose made by photosynthesis in plant cells is stored as starch ; it is a chemical energy store

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39
Q

Amylose

A

Polysaccharide made by alpha glucose molecules joining together using 1-4 glycosidic bonds ; allowing it to twist to form a helix which is further stabilised by hydrogen bonding between different molecules making it more compact and thus less soluble than the glucose molecules

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40
Q

Amylopectin

A

Also made up of 1-4 bonds between alpha glucose BUT there are also some glycosidic bonds between carbon 1 and carbon 6 causing amylopectin to have a branched structure with the branching occurring every 25 glucose subunits

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41
Q

Glycogen

A

Functionally equivalent energy storage molecule to starch in animals and fungi BUT is more branched than amylopectin which means it is more compact and less space is needed for storage ; cooling is ideal for storage in animal. Branching results in many free ends where glucose molecules can be added or removed which speeds up the processes of storing or releasing glucose molecules (for respiration maybe) by the cell

42
Q

Key properties of branched polysaccharides

A

Insoluble, compact and branched allowing them to carry out storage roles

43
Q

Hydrolysis reactions

A

Exothermic reaction - when during respiration the stored energy is released as ATP for the organism to use ; this is caused due to hydrolysis, addition of water molecules to break up the glycosidic bond (CATALYSED BY ENZYMES)

44
Q

Beta glucose molecules

A

Unable to join together same as alpha glucose because hydroxyl groups too far apart therefore every alternate beta glucose molecules is turned upside down

45
Q

Beta glucose switched

A 
ANTI-CLOCKWISE 
Carbon 1 - hydroxyl group down
Carbon 2- hydroxyl group up
3 - down
4 - up
5 - ch2oh down
46
Q

Cellulose

A

Polysaccharide unable to twist or coil or form branches so it is a straight chain ; cellulose chains form hydrogen bonds with each other (OH and O) forming microfibrils - join together to form macrofibrils which are combined to produce fibres -> strong and insoluble and used to make cell walls which are also a part of our diet ; break down to form roughage etc

47
Q

Benedicts test for reducing sugars

A

All monosaccharides are reducing sugars (and maltose and lactose - disaccharides)
Benedicts reagent is alkaline copper sulfate ; place sample in boiling water with equal volume of benedicts and heat for 5 minutes
If reducing sugars are present then they will cause Cu2+ ions to gain an electron forming Cu+ (reduction) which forms a brick red precipitate
More reducing sugars = more precipitate and less Cu2+ ions left ; this is QUALITATIVE

48
Q

Range of colours in benedicts

A

Green - low concentration of reducing sugars
Yellow/amber - medium concentration
Red - high concentration

49
Q

Non-reducing sugars

A

Negative with benedicts because not reducing (SUCROSE)
If sucrose is boiled with HCl it is hydrolysed to glucose and fructose which are both monosaccharides and thus reducing sugars giving a positive result

50
Q

Iodine test for starch

A

Few drops of iodine dissolved in potassium iodide - if solution changes colour from yellow to purple/black then starch is present in sample

51
Q

Reagent strips

A

Can be used to test for presence of reducing sugars (glucose) and ADVANTAGE IS THAT MORE ACCURATE CONCENTRATION OF SUGAR CAN BE MATCHED TO COLOUR PRODUCED

52
Q

Lipids contain what elements?

A

Carbon, hydrogen and oxygen

53
Q

Fats and oils difference

A

Fats are solid lipids at room temperature and oils are liquid lipids at room temperature

54
Q

Why does oil and water not mix?

A

Lipids are non-polar cause of the even distribution of outer electrons ; creating no positive or negative areas and thus nit being soluble in water

55
Q

What are lipids?

A

Macromolecules which are built from monomers like polysaccharides

56
Q

Triglyceride

A

Combines one glycerol molecule with 3 fatty acids which are alcohol (OH) with 3 carboxyl groups (COOH)

57
Q

Reaction to form triglycerides

A

Hydroxyl groups interact leading to the formation of 3 water molecules and bonds between the fatty acids and the glycerol molecule (O-C=O ester bond) ; this reaction is called esterification which is another condensation reaction

58
Q

Fatty acid structure

A

COOH - (CH2)n - ends chain with CH3

59
Q

Hydrolysis of triglycerides?

A

3 water molecules need to be supplied to reverse the reaction that formed the triglyceride ; hydrolysis

60
Q

Saturated

A

Fatty acid chains which are saturated have no double bonds present because all the carbon atoms form the maximum number of bonds with hydrogen atoms

61
Q

Monounsaturated

A

Single double bond

62
Q

Polyunsaturated

A

2 or more double bonds

63
Q

What does it mean for a fatty acid chain to be unsaturated?

A

The presence of double bonds causes the molecule to kink or bend and they therefore cannot pack so closely together which makes them liquids (oils) at room temperature instead of fats

64
Q

Plants contain what type of triglycerides?

A

Unsaturated - thus as oils which are healthier than saturated fats

65
Q

Elements in phospholipids

A

Carbon, hydrogen, oxygen and phosphorous ; they contain the PO43- ions which are found in the cytoplasm of every cell ; they are soluble in the cytosol ; one of the fatty acid chain in a triglyceride is replaced with a phosphate head to make it a phospholipid

66
Q

Polarity in a phospholipid

A

Non-polar tail (fatty acid chain - just C and H atoms so no proper difference in electronegativity) and a charged polar head with the phosphate group. The non polar tails repel water (hydrophobic) and the polar heads interact with water (hydrophilic)

67
Q

What does this difference in polarity cause?

A

They form a layer with the phosphate heads in the water and the fatty acid tails sticking out (surfactants) - they can also form structures based on a two layered i layer formation with all the hydrophobic tails pointing inwards (mycelle) and the hydrophilic heads on the outside ; this allows them TO SEPARATE AN AQUEOUS ENVIRONMENT FROM CYTOSOL ; endosymbiosis theory

68
Q

Sterols structure

A

Alcohol molecules based on a 4 carbon ring structure with an OH at the end ; resulting in dual hydrophilic/hydrophobic characteristics ; hydroxyl group is polar and thus rest is hydrophobic

69
Q

Cholesterol role

A

Manufactured in liver - positions itself between phospholipids with the hydroxyl group at the periphery of the membrane adding stability and regulating fluidity by keeping membranes fluid at low temperatures and stoping them becoming too fluid at high temperatures

70
Q

Roles of lipids

A 
Because they are non polar
Membrane formation - hydrophobic barriers
Hormone production
Electrical insulation 
Water proofing
71
Q

Lipids in long term energy storage

A

Thermal insulation to reduce heat loss - buoyancy for animals like whales and cushioning to protect vital organs

72
Q

Presence of lipids test

A

Emulsion test - sample is mixed with ethanol and the resulting solution is mixed with water and shaken, forming a white emulsion as a layer on top of the solution which indicates the presence of a lipid ; if it is clear it is negative

73
Q

Elements in protein

A

Carbon, hydrogen, oxygen and nitrogen

74
Q

What are peptides?

A

They are polymers made up of amino acid molecules - protein consists of one or more polypeptides arranged as a complex macromolecule and they have specific biological functions

75
Q

Structure of amino acids?

A

Central carbon atom attached to an amine NH2 group, a carboxyl COOH group, hydrogen and an R group (which differs)

76
Q

How many different amino acids found in the body?

A

20

77
Q

How does a peptide bond form?

A

Through a condensation reaction including amine and carboxyl idc acid groups - R groups are not involved - OH in the COOH reacts with H in NH2 ; forms water as a by product and a dipeptide is formed as a result (with a peptide bond)

78
Q

How is a polypeptide formed?

A

Many amino acids are joined together by peptide bonds - this is catalysed by the enzyme peptidyl transferase present in ribosomes

79
Q

What factors affect the shape of the polypeptide chains?

A

Different R groups interact forming different types of bonds (folding in different ways)
Presence of different sequences of amino acids leads to different structures with different shapes being produced ; VERY specific for the different functions

80
Q

Primary structure?

A

Sequence in which amino acids are joined ; this will influence how polypeptides fold to give the protein it’s final shape - in turn determining it’s function BUT ONLY BOND IS PEPTIDE BOND

81
Q

Secondary structure

A

The oxygen and hydrogen and nitrogen (NOT R GROUPS) interact and HYDROGEN BONDS may form

82
Q

Alpha helix

A

Hydrogen bonds within the amino acid chain pull it into a coil shape called an alpha helix

83
Q

Beta pleated sheet

A

The chains lie parallel to each other and hydrogen bonds join individual amino acids (H and O) together - forming a sheet like structure which makes it appear pleated

84
Q

Tertiary structure

A

Overall 3D shape ; folding of protein ; the coiling in the secondary structure brings R-groups close enough to interact, causing further folding to occur

85
Q

Interactions between R Groups

A

Hydrophobic and hydrophilic interactions - weak interactions between polar and non-polar R Groups
Hydrogen bonds - weakest
Ionic - oppositely charged R groups
Disulfide bridges - covalent and strongest (only form between R groups that contain sulfur atoms)

86
Q

Quaternary structure

A

Two or more polypeptide chains ; interactions between these subunits are the same as they are in the tertiary structure except between whole protein molecules rather than one amino acid/polypeptide chain

87
Q

Hydrophilic and hydrophobic interactions

A

Proteins are assembled in the aqueous environment of the cytoplasm so the way in which a protein folds will also depend on the R groups - hydrophilic groups are on the outside and the hydrophobic groups are on the inside of the molecule shielded from the water

88
Q

Breakdown of peptides

A

Peptides are created by amino acids linking together in condensation reactions - protease enzymes catalyse the reverse reaction turning peptides back into their constituent amino acids ; a water molecule is used to break the peptide bond in a hydrolysis reaction - reforming the amine and carboxylic acid groups

89
Q

Globular proteins

A

Compact, water soluble and usually roughly spherical ; R-groups interact so that hydrophobic R groups away from aqueous environment and hydrophilic R groups on outside (soluble)

90
Q

Insulin

A

Globular - hormone, soluble in blood stream and very specific on cell membrane to have effect and thus precise shapes

91
Q

Conjugated proteins

A

Globular proteins that contain non-protein components called prosthetic groups (without them they are called simple proteins)

92
Q

Types of conjugated proteins

A

Lipids or carbohydrates may combine with proteins forming lipoproteins or glycoproteins (Haem groups - Fe2+ ions are present in Catalase and haemoglobin)

93
Q

Structure of haemoglobin

A

4 polypeptides (quaternary structure) with 2 alpha and 2 beta subunits ; each subunit contains a prosthetic haem group and the iron is able to combine reversibly with oxygen allowing it to transport oxygen around the body and changing shape when delivering oxygen around the body

94
Q

Catalase structure

A

Enzyme with 4 haem prosthetic groups - presence of Fe2+ allows it to interact with hydrogen peroxide and speed up its breakdown to water and oxygen (catalyse prevents build up of hydrogen peroxide as a byproduct of metabolism so it does not damage cells)

95
Q

Fibrous proteins

A

Long, insoluble molecules due to a high proportion of amino acids with hydrophobic R groups in their primary structure; limited range of amino acids and this is quite repetitive => very organised structures reflected in the roles fibrous proteins may have (keratin, elastin, collagen etc) ; THESE ARE NOT FOLDED INTO 3D SHAPES LIKE GLOBULAR PROTEINS

96
Q

Keratin

A

Has a lot of cysteine which forms disulfide bridges forming inflexible and strong materials ; degree of disulfide bonds determines flexibility (hair more flexible than nails)

97
Q

Elastin

A

Present in walls of blood vessels allowing them to expand when needed (especially in arteries high blood pressure) - quaternary protein made from many stretchy tropoelastin molecules

98
Q

Collagen

A

Connective tissue - 3 polypeptides wound together in a rope like structure

99
Q

Elastin structure

A

Link many soluble teopoelastin proteins to make a very large stable cross linked structure- stretch and recoil because of aggregation of teopoelastin with interactions between hydrophobic areas (covalent cross linking stabilises structure)

100
Q

Collagen structure

A

3 polypeptide chains wound around each other to form a triple helix - every third amino acid is glycine which allows it to be closely packed and many hydrogen bonds form between polypeptide chains forming quaternary protein with staggered ends

A-Level Biology (37 decks)

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