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A Level Bio Processes > 2.1.2 Biological Molecules (Foundations in Biology) > Flashcards

2.1.2 Biological Molecules (Foundations in Biology) Flashcards

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1
Q

What’s the role of water in the body?

A
  • provide a medium for reactions to occur
  • transport medium e.g. blood
  • maintain osmotic balance
  • cooling mechanism i.e. sweating
  • waste removal
  • formation of urine
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2
Q

What are the roles of carbohydrates in the body?

A

Simple Sugars (monosaccharides and disaccharides):

  • use in respiration to provide energy for cells
  • other roles e.g. attracting animals to eat fruit

Complex Carbohydrates (polysaccharides):

  • starch and glycogen are energy stores
  • cellulose: plant cell walls
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3
Q

What are the roles of lipids in the body?

A

Fats and Oils (triglycerides):

  • insulation
  • protection of organs
  • stored energy

Cholesterol:

  • component of cell membranes

Steroid Hormones:

  • testosterone, oestrogen, progesterone (sex hormones)
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4
Q

What are the roles of proteins in the body?

A
  • enzymes
  • some hormones
  • antibodies
  • blood clotting
  • muscles
  • structural roles e.g. keratin in hair and collagen in skin
  • channel protein and protein pumps
  • haemoglobin (transports oxygen)
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5
Q

What are the role of nucleic acids in the body?

A

DNA: - stores genetic info

  • codes for proteins

RNA: - protein synthesis

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6
Q

Draw a water molecule

A
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7
Q

What is meant by ‘water is a polar molecule’?

A
  • it has negative and positive regions
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8
Q

What are hydrogen bonds?

A
  • a weak interaction which happens between slightly negatively charged atom and slightly positively charged hydrogen
  • they form between adjacent water molecules
  • weaker than covalent bonds
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9
Q

Draw how water molecules are joined by hydrogen bonds

A
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10
Q

Name six properties of water related to its importance for organisms

A
  • liquid at room temperature
  • density
  • solvent
  • cohesion and surface tension
  • high specific heat capacity
  • high latent heat of vaporisation
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11
Q

Describe and Explain why water being a liquid of room temperature is important to organisms

A
  • as the water molecules move, they continually make and break hydrogen bonds
  • the hydrogen bonds make it more difficult for them to escape to become a gas
  • even with H bonds, water has quite a low viscosity so flows easily
  • provides habitats
  • provide a medium for chemical reactions
  • major componenet of tissues in organism
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12
Q

Describe and Explain why the density of water is important to organisms

A
  • water behaves differently from other liquids
  • as it goes from 4 degrees celsius to freezing point, due to its polar nature, the water molecules align themselves in a structure which is less dense than liquid water
  • aquatic animals live in a stable environment
  • bodies of water are insulated against extreme cold, layers of ice reduce rate of heat loss
  • organisms can live on ice
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13
Q

Describe and Explain why water being a solvent is important to organisms

A
  • water is a good solvent for many substances found in living things (e.g. ionic solutions NaCl)
  • since water is polar, positive and negative parts of water molecules are attracted to the negative and positive parts of the solute
  • water molecules cluster around these parts of the solute molecules or ions and will help separate them and keep them apart
  • so they dissolve and a solution is formed
  • molecules and ions can move around and react together in water e.g. in cytoplasm of cell
  • molecules and ions can be transported around living things whilst dissolved in water
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14
Q

Describe and Explain why cohesion and surface tension of water is important to organisms

A
  • water molecules show cohesion, which is when H bonds between them pull them together
  • this happens at the surface of the water as well: surface of the water contracts as molecules are pulled inwards and gives the surface of the water the ability to resist forced applied to it surface tension
  • transport in the xylem relies on cohesions between water molecules sticking together
  • surface tension allows small insects to walk on water
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15
Q

Describe and Explain why high specific heat capacity of water is important to organisms

A
  • water require a lot of energy to increase its temperature
  • a lot of energy is needed to break the hydrogen bonds between water molecules
  • this means that water does not change temperature easily
  • organisms need a stable temperature for enzyme-controlled reactions to happen properly
  • aquatic organisms need a stable environment to live
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16
Q

Describe and Explain why high latent heat of vaporisation of water is important to organisms

A
  • when water evaporates, heat energy, the latent heat of vaporisation, helps the molecules to break away from each other to become a gas
  • because the molecules are held together by hydrogen bonds, a relatively large amount of energy to needed fro water molecules to evaporate
  • water can help to cool living things and keep their temperature stable
  • liquid water remains as liquid despite temperature changes e.g. oceans exist
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17
Q

What are carbohydrates?

A
  • they are molecules made up of sugar units
  • general formula: CnH2nOn
  • include sugars, starch/glycogen and cellulose

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18
Q

What are monosaccharides?

A
  • carbohydrates whose molecules contain just one sugar unit
  • monosaccharides are the monomers of carbohydrates
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19
Q

How are larger carbohydrates made?

A
  • by joining monomers, the monosaccharides, together
  • a condensation reaction occurs to form a glycosidic bond
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20
Q

What are the properties of monosaccharides?

A
  • sweet-tasting
  • soluble
  • crystalline
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21
Q

How are monosaccharides grouped?

A
  • grouped according to the number of carbon atoms in the molecules
  • e.g. triose sugars have 3 carbon atoms
  • pentose 5
  • hexose 6
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22
Q

What is the most common monosaccharide group?

A
  • hexoses
  • includes glucose, fructose and galactose
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23
Q

What is the role of glucose?

A
  • used in respiration to release energy
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24
Q

What is the role of fructose?

A
  • in fruit and nectar attracts animals to disperse seeds/pollen
  • used by plants to make sucrose (glucose and fructose)
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25
Q

Give two important pentose sugars

A
  • ribose (a component of RNA)
  • deoxyribose (component of DNA)
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26
Q

Explain the difference between alpha and beta glucose and draw one out

A
  • in α glucose, the OH at C1 is below plane
  • in β glucose, the OH at C1 is above the plane
  • leads to very different properties
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27
Q

Draw the structure of ribose

A
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28
Q

What are disaccharides?

A
  • two monosaccharide molecules can join together in a condensation reaction to form a disaccharide
  • a new covalent bond called a glycosidic bond is formed and water is removed
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29
Q

What are the properties of disaccharides?

A
  • soluble in water
  • taste sweet
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30
Q

What is α glucose + α glucose?

A
  • maltose
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31
Q

What is ß glucose + galactose?

A
  • lactose
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32
Q

What is α glucose + fructose?

A
  • sucrose
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33
Q

What is an alpha 1,4-glycosidic bond?

A
  • the glycosidic bond is between carbon atom 1 of one molecule and carbon atom 4 of the other
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34
Q

What happens when carbohydrates are digested and what is that called?

A
  • glycosidic bonds are broken by carbohydrases (enzymes)
  • this is a hydrolysis (meaning water breaking apart) reaction using a water molecule
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35
Q

Define monomer

A
  • a single, small molecule that may combine with other monomers to build up larger molecules called polymers
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36
Q

Define polymer

A
  • a large molecule built up from many similar monomers joined together by covalent bonds to form a chain or a branched chain
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37
Q

Define condensation reaction

A
  • a chemical reaction where two molecules are joined together by a covalent bond, forming a larger molecule and releasing one molecule of water
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38
Q

Define hydrolysis

A
  • a chemical reaction where the covalent bond between two molecules is broken with the addition of a water molecule, separating the two molecules
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39
Q

What are polysaccharides?

A
  • large complex organic molecules made up of many hundred monosaccharide subunits

there are two types:

  • homopolysaccharides: made solely of one kind of monosaccharidge (e.g. starch)
  • heterepolysaccharides: made of more than one monosaccharide (hyaluronic acid)
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40
Q

What differs in polysaccharides from monosaccharides and disaccharides?

A
  • they are insoluble in water
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41
Q

What roles do polysaccharides provided in plants and animals

A
  • storage and structural roles
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42
Q

What are the stores of potential energy?

A
  • starch and glycogen
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43
Q

What is starch?

A
  • the energy storage polysaccharide in plants
  • a polymer of α glucose
  • it is actually a mixture of two different polysaccharides: amylose and amylopectin
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44
Q

How is amylose formed?

A
  • amylose is formed by a series of condensation reactions that bond alpha glucose molecules together into a long chain
  • forms many alpha 1, 4-glycosidic bonds
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45
Q

What shape is amylose in and why?

A
  • once the amylose chain is formed, it coils into a helix
  • it stays in a helix because of the hydrogen bonding between molecules, keeping the helix in place
  • it is more compact and stores more glucose
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46
Q

What is amylopectin?

A
  • amylopectin consists of a straight chain of alpha glucose units with branch points along the chain
  • also coils into a spiral shape, held together by H bonds, but with branches emerging from the spiral
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47
Q

How is starch made?

A
  • the highly branched amylopectin is wrapped around the amylose to make up starch
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48
Q

Where in plants is starch stored?

A
  • root tubers e.g. potatoes
  • leaf cells
  • chloroplasts
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49
Q

What makes starch and glycogen good storage materials?

A
  • compact due to helix form and doesn’t take much space.
  • occurs in dense granules within the cell
  • insoluble: keep glucose in the right place (i.e. not used or transported). glucose is stored in a cell as a free molecule would dissolve and reduces the water potential of the cell which would affect osmotic balance
  • easily hydrolysed by enzymes to release glucose when needed
  • branched structure provides easy access for enzymes to ‘strip off’ glucose when needed
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50
Q

What is glycogen?

A
  • the energy storage polysaccharide in animals
51
Q

What is the glycogen’s structure same as?

A
  • same overall structure as amylopectin, but there is more branching in glycogen
52
Q

Where is glycogen stored?

A
  • muscles: needs to be used when glucose runs out and needs to be converted
  • liver: many reactions so needs a lot of glucose
53
Q

Explain the importance of the difference in structure between glycogen and starch

A
  • glycogen is more space efficient than starch: due to more branching
  • more glucose can be released from glycogen than the same amount of starch: so more energy is obtained from it, advantage in animals as they are more metabolically active
54
Q

If glucose is needed for fuel, why store it as glycogen?

A
  • compact due to helix form and doesn’t take much space.
  • insoluble: keep glucose in the right place (i.e. not used or transported). glucose is stored in a cell as a free molecule would dissolve and reduces the water potential of the cell which would affect osmotic balance
  • easily hydrolysed by enzymes to release glucose when needed
  • branched structure provides easy access for enzymes to ‘strip off’ glucose when needed
  • glycogen is insoluble so doesn’t affect the water potential of cell
  • our muscles and over cells need a store of glucose to use even if we haven’t recently eaten sugar
55
Q

What is cellulose?

A
  • a polymer of beta glucose units where each glucose molecule is inverted with respect to its neighbour
  • the orientation of the beta glucose units places many hydroxyl (OH) groups on each side of the molecule
56
Q

Describe the structure of cellulose

A
  • each glucose molecule is inverted with respect to its neighbour
  • the orientation of the beta glucose units places many hydroxyl (OH) groups on each side of the molecule
  • many parallel chains of beta glucose units form and each chain forms hydrogen bonds between the OH groups of adjacent chains
57
Q

How does cellulose form the plant cell wall?

A
  • cellulose chains that align parallel have H bonds between them
  • when 60-70 chains are bound, they form microfibrils (10-30nm in diameter)
  • up to 400 microfibrils are bundles together into macrofibirls
  • it is then embedded in pectoris to form plant cell walls
  • macrofibrils run in all directions, criss-crossing the wall
58
Q

What are triglycerides?

A
  • fats and oils
  • made up of glycerol and three fatty acids
59
Q

What elements are in all lipids?

A
  • carbon
  • hydrogen
  • oxygen
60
Q

What are the fatty acid molecules made of?

A
  • hydrocarbons
  • they can vary from 2 to 20 carbons long
  • contain a carboxyl group
  • rest of molecule is a hydrocarbon chain
61
Q

What are the properties of fatty acids?

A
  • the tails are hydrophobic (repel water molecules)
  • they make lipids insoluble in water
62
Q

How are triglycerides formed?

A
  • triglycerides are synthesised by the formation of an ester bond between each fatty acid and the glycerol molecule
  • each ester bond is formed by a condensation reaction (in which a water molecule is released)
  • the process of triglyceride synthesis is called esterification
  • triglycerides break down when the ester bonds are broken
  • each ester bond is broke in a hydrolysis reaction (water molecule is used up)
63
Q

What are saturated fatty acids?

A
  • they don’t have any double bonds between their carbon atoms
  • fatty acid is saturated with hydrogen
64
Q

What are unsaturated fatty acids?

A
  • they have at least one double bond between carbon atoms, which cause the chain to kink
  • these kinks push the molecules apart slightly, making htem mor fluid
65
Q

What are phospholipids?

A
  • they are also macromolecules
  • similar to triglycerides except one fatty acid molecule is replaced by a phosphate group
  • a condensation reaction between an OH group on a phophoric acid molecule (H3PO4) and on of the OH on glycerol
66
Q

Are phospholipids hydrophobic or hydrophilic?

A
  • the phosphate group is hydrophilic
  • but the fatty acid tails are hydrophilic
  • meaning the molecule is amphipathic
67
Q

What are the functions of triglycerides?

A
  • energy source: triglycerides can be broken down in respiration to release energy and generate ATP
  • hydrolyse ester bonds, then both glycerol and fatty acids can be broken down to CO2 and water. respiration of lipid produces more water than respiriation sugar.
  • energy store: insoluble in water, so can be stored without affecting water potential of cell. 1g of fat releases twice as much energy as 1g of glucose due to higher proportion of H atoms
  • insulation: adipose tissue a storage location for whales. lipiids in nerve cells act as electrical insulator.
  • buoyancy: fat is less dense than water, helps aquatic mammals stay afloat
  • protection: humans have fat around delicate organs, such as kidneys, to act as shock absorber. peptidoglycan cell wall of some bacteria is covered in lipid-rich outer coat
68
Q

What are the functions of phospholipids?

A
  • phospholipids are found in the cell membranes of all eukaryotes and prokaryotes
  • they make the phospholipid bilayer, which controls what enters and leaves the cell
  • the phospholipid heads are hydrophilic and tails are hydrophobic so they form a double layer with head facing out
  • the centre of the bilayer is hydrophobic so water soluble substances can’t easily pass through it, acting as a barrier to these substances
69
Q

What is cholesterol and its structure?

A
  • a steroid alcohol
  • a type of lipid not made from glycerol and fatty acids
  • has a hydrocarbon ring structure attached to a hydrocarbon tail
  • ring structure has a polar hydroxyl (OH) group attached to it
  • mainly made in the liver in animals
70
Q

What is the function of cholesterol?

A
  • in eukaryotic cells, cholesterol molecules help strengthen the cell membrane by interacting with the phospholipid bilayer
  • cholesterol has a small size and flattened shape, allowing it to fit between phospholipid molecules in the membrane
  • they bind to the hydrophobic tails of phospholipids, causing them to pack more closely together, making the membrane less fluid and more rigid
71
Q

What are proteins?

A
  • they are large polymers
  • comprised of long chains of amino acids
72
Q

What are the monomers of proteins?

A
  • amino acids
73
Q

What is a polypeptide?

A
  • when more than two amino acids join together
74
Q

What differentiates one amino acid from another amino acid

A
  • all amino acids have the same general structure
  • a carboxyl group (-COOH) and an amino group (NH2) attached to a carbon atom
  • the difference is the variable group (R)
75
Q

What chemical elements are in amino acids?

A
  • all contain carbon, oxygen, hydrogen and nitrogen
  • some contain sulfur
76
Q

How are amino acids joined together?

A
  • they are linked together by peptide bonds to form dipeptides and polypeptides
  • the carboxyl group from one amino acid bond with the amine group from another to form a peptide bond
  • a molecule of water is released during the reaction, called a condensation reaction
  • the reverse is the hydrolysis reaction, which is when a molecule of water is added to break the peptide bond
77
Q

What are the four protein structural levels?

A
  • primary
  • secondary
  • tertiary
  • quaternary
78
Q

Describe the primary structure of proteins

A
  • the sequence of amino acids in a protein chain is its primary structure
  • this is determined by the sequences of bases on a gene
  • a change in one amino acid could lead to a different protein/prevent protein function
79
Q

Describe the secondary structure of proteins

A
  • formed when amino acid chain coils or folds
  • either to form an α helix or ß-pleated sheet
  • hydrogen bonds holds the structures in place
  • they are weak bonds, but there are many, so give great stability
  • these bonds form between different amino acids in the chain
80
Q

Describe the tertiary structure of proteins

A
  • the coiled or folded chain of amino acids is often coiled and folded further to form the final 3D shape of the protein
  • structure is held in place by a number of different bonds between R-groups
  • vital to the function of protein as it gives it the specific shape
81
Q

Describe the quaternary structure of proteins

A
  • some proteins are made of several different polypeptide chains held together by bonds
  • quaternary structure is the way polypeptide chains are assembled together
  • it is the interaction between R groups on different chains that hold the quaternary structure in place
82
Q

What can computer modelling do?

A
  • it can create 3D interactive images of proteins
  • good for investigating different levels of structure in a protein molecule
  • predicts the occurrence of binding sites on a protein can help identify new medicines
83
Q

What kind of bonds hold together the primary structure of proteins?

A
  • peptide bonds between amino acids
84
Q

What kind of bonds hold together the secondary structure of proteins?

A
  • hydrogen bonds
85
Q

What kind of bonds hold together the tertiary structure of proteins?

A
  • ionic bonds: attraction between negatively-charged R groups and positively-charged R groups on different parts of molecule - disulfide bonds: the sulphur atom from one cysteine bond and another sulphur atom come close and form a disulphide bond - hydrophobic and hydrophilic interactions: when hydrophobic R groups are close together in the protein, they tend to clump together, meaning hydrophilic R groups are more likely pushed to outside, affecting how proteins fold up into its final structure - hydrogen bonds: weak bonds between slightly positively-charged hydrogen atoms in some R groups and slightly negatively charged atoms in other R groups
86
Q

What kind of bonds hold together the quaternary structure of proteins?

A
  • determined by the tertiary structure - can be influenced by all the other levels
87
Q

Describe the structure of globular proteins

A
  • the hydrophilic R groups on the amino acids tend to be pushed outside the molecule due to hydrophobic and hydrophilic interactions - this makes the globular proteins soluble, so they’re easily transported in fluids
88
Q

Describe the function of the haemoglobin protein

A
  • a globular protein that carries oxygen around the bond in red blood cells - a conjugated protein (protein with a non-protein group attached) - the attached is a prosthetic group, and it binds to haemoglobin, which contains iron, which O2 binds to
89
Q

Describe the function of the protein hormone insulin

A
  • secreted by pancreas - helps to regular blood glucose level - soluble is important - can be tranported in the blood to tissues - consists of two polypeptide chains, held together by disulphide bonds
90
Q

describe the function of the protein amylase

A
  • an enzyme that catalyses the breakdown of starch in the digestive system - made of a single chain of amino acids - secondary structure contains both alpha helix sections and beta pleated sheet section - globular
91
Q

What are fibrous proteins?

A
  • they’re structural proteins - fairly unreactive - are insoluble and strong
92
Q

Describe the function of the protein collagen

A
  • found in a animal connective tissues, such as bone, skin muscle - very strong molecule - minerals can bind to the protein to increase its rigidity
93
Q

Describe the function of the protein keratin

A
  • found in many of the external structure of animals such as skin hair nails - can either be flexible or hard and tough
94
Q

Describe the function of elastin

A
  • found in elastic connective tissues, such as skin, large blood vessels and some ligaments - elastic, so allows tissues to return to their original shape after stretched
95
Q

What is an ion?

A
  • an atom that has an electric charge
96
Q

What is an ion with +

A
  • cation
97
Q

What is an ion with -

A
  • anion
98
Q

What is an inorganic ion

A
  • an ion that doesn’t contain carbon
99
Q

What is the role of calcium in biological processes?

A
  • Ca2+ - involved in the transmission of nerve impulses and the release of insulin from the pancreas - a cofactor for many enzymes - important for bone function
100
Q

What is the role of sodium in biological processes?

A
  • Na+ - important for generating nerve impulses, for muscle contraction and regulating fluid balance in body
101
Q

What is the role of potassium in biological processes?

A
  • K+ - generating nerve impulses, muscle contraction and regulating fluid balance in body - activates essential enzymes needed for photosynthesis in plant cells
102
Q

What is the role of hydrogen in biological processes?

A
  • H+ - affects the pH of substances (more H+, more acidic) - important for photosynthesis reactions
103
Q

What is the role of ammonium in biological processes?

A
  • NH4+ - absorbed from the soil by plants - an important source of nitrogen
104
Q

What is the role of nitrate in biological processes?

A
  • NO3- - absorbed from the soil b plants - important source of nitrogen
105
Q

What is the role of hydrogencarbonate in biological processes?

A
  • acts as a buffer, helping to maintain pH of bloof
106
Q

What is the role of chloride in biological processes?

A
  • involved in the chloride shift, painting the pH of the blood during gas exchange - acts as a cofactor for the enzyme amylase - involved in some nerve impulses
107
Q

What is the role of phosphate in biological processes?

A
  • involved in photosynthesis and respiration reaction - needed for the synthesis of many biological molecules, such as nucleotides, phospholipids
108
Q

What is the role of hydroxide in biological processes?

A
  • affects the pH of substances (more OH-, more alkali)
109
Q

How do test for reducing sugars>

A
  • reducing sugars include all monosaccharides and some disaccharides - add benedictus reagent (blue) and heat above 90 degrees for at least 5 mins - blue to green to yellow to orange to brick red - a colour precipitate will form if positive - you can compare by weighting or looking at colour or colorimetert
110
Q

How to test for non-reducing sugars?

A
  • if the result for reducing sugars is negative, there could still be non-reducing sugars like sucrose - you have to break them down into monosaccharides - get a new sample of solution - add dilute HCl and heat in water bath that is boiling - neutralise with sodium hydrogencarbonate - carry out Benedict’s test like for reducing sugar - if it is positive, it will for coloured precipitate
111
Q

How to test for glucose?

A
  • test strips with reagent
112
Q

How to test for starch?

A
  • iodine test - add iodine dissolved in potassium iodide - if starch is present, sample changes from orange brqwn to dark, blue black colour - if not, it stays
113
Q

How to test for proteins?

A
  • biuret test - test solution needs to be alkaline, so first add few drops of sodium hydroxide solution - then add copper ii sulphate solution - if protein is present solution turns lilac - if no protein, solution stays blue
114
Q

How to test for lipids

A
  • emulsion test - test substance with ethanal then pour solution into water - if lipid present, solution will turn milky - more lipid, more mily - if no lipid, solution stays clear
115
Q

What is the Rf value?

A
  • distance travelled by spot / distance travelled by solvent
116
Q

Draw deoxyribose

A
117
Q

What are the properties and functions of cellulose?

A
  • provides great tensile strength to cell wall:
  • prevents cell bursting
  • enables turgidity: keeps plant upright when hydrated
  • cell wall is permeable
  • role in guard cells: opening and closing stomata
  • can be reinforced to make it more waterproof of for extra support (e.g. cutin, suberin, lignin)
118
Q

What are lipids?

A
  • a group of substances that are soluble in alcohol rather than water
  • includes triglycerides, phospholipids, glycolipids and cholesterol
119
Q

Draw a glycerol molecule

A
120
Q

What hormones are made from cholesterol and why is that helpful?

A
  • steroid hormones such as testosterone, oestrogen, vitamin D
  • they are small and hydrophobic, so can pass through the hydrophobic part of the cell membrane
121
Q

Draw the structure of an amino acid

A
122
Q

How many naturally occurring amino acids are there?

A
  • 20
123
Q

What bond joins amino acids together?

A
  • a peptide bond
  • covalent
124
Q

Which enzymes catalyse the breakdown of polypeptides in humans?

A
  • small intestine: trypsin
  • stomach: pepsin

A Level Bio Processes (14 decks)

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