3.1 Biological Molecules Flashcards

Question

Polysaccharide - Glycogen | Describe its structure (1 point)

Answer 1

Has shorter chains to starch and is more highly branched so is readily hydrolysed

Answer 2

Animals and Bacteria | Never in Plants

Answer 3

Major carbohydrate storage of excess glucose in animals Stored as small granules mainly in muscles and liver Small mass of carbohydrate stored as fat is main storage molecule in animals

Answer 4

It is insoluble so does not draw water into cells by osmosis It is insoluble so does not diffuse out of cells It is compact so can be stored in small space It is more highly branched so has more ends that can be acted on by enzymes so can be more rapidly broken down to form glucose monomers used in respiration. This is important to animals with higher metabolic rate and higher respiratory rate than plants as they are more active

Answer 5

Made of monomers of beta-glucose held by 1,4 glycosidic bonds

Answer 6

Cellulose has straight unbranched chains which run parallel to each other, allowing hydrogen bonds to form cross-linkages between adjacent cells. The hydrogen bonds are weak but lots together are strong Cellulose molecules are grouped together to form microfibrils which are arranged in parallel groups called fibres Every second beta glucose is inverted (rotated 180') to form straight linear chain structure instead of helical structure

Answer 7

In plant cell walls

Answer 8

It is a structural polysaccharide in plants Due to its strength it is a valuable structural material Provides rigidity to plant cell and prevents cell from bursting (cell lysis) as water enters by osmosis It does this by exerting an inward pressure that stops any further influx of water. Therefore living plant cells are turgid and push against one another, making parts of plant rigid It is important for maintain stems and leaves in turgid state so they can provide maximum surface area for photosynthesis

Answer 9

The cellulose molecular chains run parallel to each other and are cross linked by hydrogen bonds to add collective strength These molecules are grouped to form microfibrils which are grouped to form fibres which all provide more strength

Answer 10

Triglycerides (fats and oils) Phospholipids Cholesterol Steroids

Answer 11

``` Substrate for respiration Storage of energy Insulation Protection of organs Buoyancy and streamlining in aquatic mammals Cell membranes Hormones Water proofing ```

Answer 12

Lipids are insoluble in water | Lipids are soluble in organic solvents (alcohol and acetone)

Answer 13

Fats are solids at room temperature whereas oils are liquids | Fats are saturated whereas oils are unsaturated

Answer 14

O (Carbon atom links fatty acid to glycerol) \\ C---R (Variable R group hydrocarbon tail) / HO

Answer 15

Saturated fatty acids don't have any double bonds between their carbon atoms

Answer 16

Unsaturated fatty acids have at least one double bond between carbon atoms which causes chain to bend the molecule so they cannot pack as tightly together. This makes them a liqid at room temperate

Answer 17

The glycerol molecule joins to a fatty acid by a condensation reaction 3 ester bonds are formed (when a carboxylic group -COOH reacts with hydroxyl group -OH) and molecule of water released All have a carboxyl group and a hydrocarbon chain attached

Answer 18

One molecule of glycerol with three fatty acids attached to it Fatty acid molecules have long tails made of hydrocarbons. The tails are hydrophobic (repel water molecules). These tails make lipids insoluble in water

Answer 19

Triglycerides are mainly used as energy storage molecules. They are good for this because: 1. The long hydrocarbon tails of fatty acids contain lots of chemical energy so a lot of energy is released when they are broken down. Therefore lipids contain twice as much energy per gram as carbohydrates. 2. They're insoluble so don't affect the water potential of the cell and cause water to enter by osmosis. The triglycerides clump together as insoluble droplets in cells because the fatty acid tails are hydrophobic so the tails face inwards, shielding themselves from water with their glycerol heads 3. Have high ratio of energy storing C-H bonds to C atoms so is an excellent energy store 4. Low mass: Energy so large amounts of energy stored in small space so animals carry less weight 5. High hydrogen: Oxygen atoms so release water when oxidised for desert animals

Answer 20

Phospholipids

Answer 21

Only have 2 fatty acids attached to glycerol as one is replaced by a phosphate group. The phosphate group is hydrophilic (attracts water) But the tails are hydrophobic (repels water)

Answer 22

Phospholipids make up the bilayer of cell membranes which contol what enters and leaves the cell Their heads are hydrophilic and their tails are hydrophobic, so they form a double layer with their heads facing out towards the water on either side The centre of the bilayer is hydrophobic, so water-soluble substances can't easily pass through it. The membrane acts as a barrier to those substances

Answer 23

Both are lipids Both have glycerol Both have fatty acids Both have ester bonds

Answer 24

Triglycerides have 3 fatty acids whereas phospholipids only have 2 as 3rd fatty acid is replaced by a polar hydrophilic phosphate group

Answer 25

Hydrophilic head of phospholipid molecule asscociates itself with water but hydrophobic tail does not. Therefre hydrophilic head is closest to water and hydrophobic tail furthest away. This forms a spherical structure called micelles If not in globular form they form a phospholipid bilayer

Answer 26

Shake the test substance with ethanol for a minute so that it dissolves Pour the solution into water If lipids are present a milky emulsion will show

Answer 27

Long chains of amino acids

Answer 28

When two amino acids join together

Answer 29

When more than two amino acids join together

Answer 30

1 or more polypeptide chains

Answer 31

``` Structure e.g. collagen and keratin Enzymes e.g. amylase Some hormones e.g. insulin Membrane transport Antibodies Mass transport e.g. haemoglobin Receptors Cell recognition ```

Answer 32

Are the monomers that form the polymers called polypeptides Polypeptides join together to make proteins There are 20 amino acids that occur natuarally in proteins The fact that the same 20 occur in every living organism is proof for evolution

Answer 33

``` All have: Central carbon atom Amino group Carboxyl group Hydrogen atom R (variable side) group ``` Only difderence is each amino acid has a different R group ``` H H O / / // H ---- N ----C ---- C ---- OH / R group ```

Answer 34

The R-group composition of each amino acid varies greatly Each of the 20 amino acids has a different side chain structure Side chains contain mainly hydrogen, carbon and oxygen but some amino acids have nitrogen atoms in R group

Answer 35

Formed through condensation reactions | A peptide bond is formed C-N

Answer 36

Where amino acids join by a series of condensation reactions

Answer 37

The sequence of amino acids in the polypeptide chain

Answer 38

Weak hydrogen bonds form between the amino acids in the chain due to the O of the -C=O having a negative charge and the H of the -NH group having a positive charge and are slightly attracted to each other This causes the chain to coil into an alpha helix or fold into a beta pleated sheet

Answer 39

The secondary structure is folded and coiled more to create a 3D structure The structure is maintained by strong disulphide bridges/bonds between two molecules of the amino acid cysteine as the sulphur atoms bond Also has ionic bonds between carboxyl and amino acid not involved in forming dipeptide bonds. They are weaker than disulphide and easily broken as pH changes Also has lots of hydrogen bonds which are easily broken

Answer 40

Large proteins made from many individual polypeptide chains bonded together Includes non-protein (prosthetic) groups e.g. haem group

Answer 41

Roughly spherical shaped due to tight folding of polypeptide chains They’re soluble and often have roles in metabolism e.g. digestive enzymes break down food molecules whilst other enzymes synthesise large molecules

Answer 42

Involved in the immune response Made up of two light polypeptide chains and two heavy polypeptide chains bonded together. Antibodies have variable regions and the amino acid sequences in these regions vary greatly

Answer 43

Channel proteins are present in cell membranes. Contain hydrophobic and hydrophilic amino acids, which cause protein to fold up and form a channel. These proteins transport molecules and ions across membranes

Answer 44

Are physically strong Consist of long polypeptide chains lying parallel to each other with cross-links between them Includes keratin and collagen

Answer 45

Have structural features Form long chains which run parallel to each other E.g. Collagen

Answer 46

Carry out metabolic functions Not structural E.g. Haemoglobin and enzymes

Answer 47

Found in tendons. Tendons join muscles to bones. When a muscle contracts the bone is pulled in direction of contraction. Collagen controls this

Answer 48

Primary structure = unbranched polypeptide chain Secondary structure = Polypeptide chain very tightly wound. Lots of amino acid glycine helps close packaging Tertiary structure = Chain is twisted into second helix Quaternary structure = Made up of 3 polypeptide chains wound together

Answer 49

Quaternary structure makes it suitable molecule for tendons as individual collagen polypeptide chains in fibres are held together by cross-linkages between amino acids of adjacent chains Cross linkages increase strength and stability of collagen fibre as points where collagen molecule ends and next one starts are spread throughout fibre instead of in one place Arrangement of collagen is necessary for efficient functioning of tendon because each polypeptide forms long, unfolded strand. Individual polypeptide strands are wound tightly around each other. Long fibrous molecular shape

Answer 50

Efficiently transports oxygen

Answer 51

Primary structure = consists of 4 polypeptide chains Secondary structure = In each of polypeptide chains is a coiled helix Tertiary structure = Each polypeptide chain folded into precise shape to be able to carry oxygen Quaternary = All polypeptide chains linked together to form spherical molecule

Answer 52

Readily associates with oxygen at the surface where gas exchange takes place Readily dissociate from oxygen at tissues requiring it Haemoglobin changes its affinity for oxygen because its shape changes in presence of certain substances due to having different amino acid sequences

Answer 53

Add a few drops of sodium hydroxide solution to food sample to make it alkaline Then add some copper (II) sulphate solution If protein is present the solution turns purple If no protein is present, the solution stays blue

Answer 54

Enzymes are proteins that speed up chemical reactions by acting as biological catalysts

Answer 55

Catalyse metabolic reactions both at a cellular level (e.g. respiration) and for the organism as a whole (e.g. digestion in mammals). Since they ae a catalyst they are not used up in the reaction They lower the activation energy of a reaction which speeds up the rate of a reaction Enzyme action can be intracellular or extracellular Enzymes can affect structures in an organism (e.g. involved in production of collagen) as well as functions (e.g. respiration)

Answer 56

When a substrate fits into the enzymes active site it forms an enzyme-substrate complex which lowers activation energy because: 1. If two substrate molecules need to be joined, being attached to enzyme holds them close together, reducing repulsion between molecules so can bond more easily. 2. If the enzyme is catalysing a breakdown reaction, fitting into the active site puts a strain on bonds in the substrate, so the substrate molecule breaks up more easily

Answer 57

Enzymes are made from a long folded chain of amino acids so is a globular protein Hydrogen bonds hold the chain in the correct shape DNA dictates the order in which amino acids join The different amino acids fold in different ways to give enzymes a specific shape

Answer 58

A specific and complementary substrate binds to an enzymes active site to form an enzyme-substrate complex. The enzyme then breaks down the substrate to form the products of the reaction

Answer 59

Outlines that the substrate fits into the enzyme in the same way a key fits into a lock It correctly identifies concept of active site where substrate binding and catalysis occurs Explains specificity of enzymes for particular substrates

Answer 60

Does not fully explain how products are released | Does not explain why some enzymes act on a small number of similar substrates

Answer 61

This shows that the active site changes shape as substrates bind at the same time causing a change in the shape of the substrate This results in a tight fit where the active site is now complementary to the altered substrate The change in substrate shape induces strain in the substrate bonds which lowers the activation energy required for the reaction to occur by lowering the amount of energy needed to break the bonds in the substrate

Answer 62

As temperature increases, kinetic energy of the enzymes molecules increases. The molecules move faster and collide more often. Enzymes and substrates successfully collide more often creating more enzyme-substrate complexes. If the temperature increases above 37˚C the molecules vibrate more which breaks some of the bonds holding the enzyme in shape. The enzymes active site loses its shape and the enzyme becomes denatured as the enzyme and substrate no longer fit together.

Answer 63

Altering the pH causes a change in charges on amino acids that form active site so substrate can no longer attach to active site, so enzyme-substrate complexes are not possible Changing pH can break the ionic bonds involved in enzymes tertiary structure which causes a change in shape of active site so the substrate can no longer fit, and the enzyme is denatured

Answer 64

At low substrate concentration, rate of reaction is slow as there are too few substrate molecules to fill all enzyme active sites so there is a limited number of collisions and enzyme-substrate complexes that can form. As substrate concentration increases, rate of reaction increases up to a point. There are more substrate molecules so more chances of collisions, so more enzyme-substrate complexes formed, and more products released At high substrate concentrations, rate levels off as reaction is proceeding as fast as possible but addition of extra substrate molecules doesn’t make difference as active sites are fully occupied only addition of enzymes increase rate

Answer 65

As enzyme concentration increases, rate of reaction increases as due to having more enzyme molecules in the solution it is more likely a substrate molecule will collide with an active site and form an enzyme-substrate complex. Plateau (Vmax) occurs when the number of substrates is limited so no more collisions occur. To increase rate more substrates must be added

Answer 66

When the rate of reaction is at its maximum as all available active sites have been occupied at one time

Answer 67

When molecules have a similar shape to substrate molecules so compete with the substrate molecules to bind to active site, but no reaction takes place. Instead they block the active site so no substrate molecules can fit in it. If there's a high concentration of inhibitor it'll take up nearly all active sites and hardly any of substrate will bind to the enzyme If there's a higher concentration of substrate then it is easier for the substrate to bind to the active site so increasing concentration of substrate will increase rate up to a point

Answer 68

When molecules bind to the enzyme away from its active site. This causes the active site to change shape so the substrate molecules can no longer bind to it. They don't compete with the substrate molecules to bind to active site as they are different shape. Increasing concentration of substrate won't make difference to reaction rate as enzyme activity will still be inhibited

Answer 69

DNA is a polymer of repeating nucleotides (a polynucleotide) | Scientific name is DeoxyriboNucleic Acid

Answer 70

Genetic information to make new cells, control their function and make proteins

Answer 71

Nucleus of a cell contains chromosomes which are made of genes which are sections containing DNA. Genes are sections of DNA which code for different proteins and different characteristics as a result

Answer 72

Two polynucleotide chains twisted around each other and held together with hydrogen bonds

Answer 73

A deoxyribose pentose sugar attached to a phosphate group and an organic nitrogenous base

Answer 74

Ester bond - 1st of the 2 condensation reactions occuring to release water

Answer 75

Glycosidic bond - 2nd of the 2 condensation reactions occurng to release water

Answer 76

Many nucleotides join together to form a polynucleotide | A condensation reaction occurs between the sugar of one mononucleotide and phosphate group of another

Answer 77

The bonded sugar of one mononucleotide and phosphate group of another

Answer 78

Phosphodiester bond

Answer 79

Adenine Thymine Cytosine Guanine

Answer 80

A pairs with T and has 2 hydrogen bonds C pairs with G and has 3 hydrogen bonds A and T, C and G should have equal amounts

Answer 81

S: DNA molecule is very long F: Stores lots of information S: Two strands are complementary F: Each starnd acts as a template for copying the other S: Two strands are held together by hydrogen bonds F: It is easy to separate the strands to transcribe the genes and replicate the DNA S: The bases are located on the inside of double helix F: The bases are partly protected from damage by free radicals

Answer 82

The phosphodiester backbone protects the more chemically reactive bases Hydrogen bonds join the bases forming bridges between the 2 phosphodiester uprights

Answer 83

A polymer of nucleotides | So has a pentose sugar attached to a phosphate group and a nitrogenous base

Answer 84

1. Messenger RNA (mRNA) - are copies of DNA produced in transcription that leave the nucleus through pores in membrane and give instructions to the ribosomes 2. Ribosomal RNA (rRNA) - makes up part of the ribosome structure (the rest is made of protein) 3. Transfer RNA (tRNA) - used to carry specific amino acids during the process of protein synthesis called translation

Answer 85

1. DNA helicase unzips the DNA molecule (breaks hydrogen bonds between bases) 2. mRNA takes a copy of the DNA template strand (transcription inside of nucleus) 3. mRNA leaves the nucleus through a nuclear pore 4. The ribosome attaches to the mRNA 5. tRNA molecules attach their complementary anti-codon which is attached to an amino acid (translation outside of nucleus) 6. Each amino acid joins together to form a polypeptide

Answer 86

1. DNA has a deoxyribose sugar present whereas RNA has a ribose sugar 2. DNA is structured as a double helix whereas RNA is single stranded 3. DNA has complementary base pairing Adenine with Thymine, Cytosine with Guanine whereas RNA has no base pairing and Thymine is replaced with URACIL 4. DNA is a larger and longer molecule whereas RNA is shorter and smaller 5. In DNA you can predict the percentage of bases present as A and T, C and G are equal whereas in RNA you cannot predict the percentage of other bases from percentage of 1 base

Answer 87

Growth Development/specialisation Reproduction

Answer 88

The original DNA double helix replicates to produce a newly synthesised material stranded double helix and an original parental DNA stranded doule helix

Answer 89

The original DNA double helix replicates to produce two double helixes each with each strand having parental DNA interspersed between two daughter molecules

Answer 90

The original DNA double helix replicates to produce two DNA double helices each double strand has one parental and one new strand This is the main theory we use today for DNA replication

Answer 91

1. The enzyme DNA helicase breaks the hydrogen bonds between bases on the two polynucleotide DNA strands which makes the helix unwind to form two single strands 2. Each original single strand acts as a template for a new strand. Complementary base pairing means that free-floating DNA nucleotides are attracted to their complementary exposed bases on each original template strand 3. Condensation reactions join the nucleotides of the new strands togeher by hydrogen bonds forming between bases on original and new strands to form a polynucleotide chain with a phosphodiester bond and strong sugar phosphate backbone formed (polymerisation). Catalysed by enzyme DNA polymerase 4. Each new DNA molecule contains one strand from original parental DNA molecule and one new strand

Answer 92

``` DNA helicase to break apart strands Free nucleotides to synthesise new strand DNA template DNA polymerase to re-synthesise backbone Energy ```

Answer 93

Each end of a DNA strand is slightly diferent in its struture. In a DNA helix the strands run the opposite way (antiparallel) The active site of DNA polymerase is only complementary to 3' prime end so enzyme only adds nucleotides to the new strand at the 3' end so the new strand is made in a 5' to 3' direction. Therefore the DNA polymerase moves down the template strnd in 3' to 5' direction Because the strands in DNA double helix are anti-parallel, the DNA polymerase working on one of template strands moves in opposite direction to DNA polymerase working on other

Answer 94

1. Two samples of bacteria were grown - one in nutrient broth containing light nitrogen (N14) and one in broth containing heavy nitrogen (N15). As the bacteria reproduced, they took up nitrogen from the broth to help make nucleotides for new DNA. So the nitrogen gradually became part of the bacteria's DNA 2. A sample of DNA taken from each batch of bacteria and spun in centrifuge. DNA from heavier nitrogen bactria settled lower down he centrifuge tube than DNA from light nitrogen because its heavier 3. Bacteria grown in heavy nitrogen broth taken out and put in broth containing only light nitrogen. Bacteria left for one round of replication and then another sample of DNA taken out and spun in centrifuge 4. If replication was conservative the original heavy DNA which would still be together would settle at bottom and new light DNA settle at top 5. If replication semi-conservative new bacterial DNA molecules would contain ne strand old DNA with heavy nitrogen and one new with lighter nitrogen. So DNA would settle out between where light and heavy settle 6. However DNA settled in middle showing that DNA contained a mixture of heavy and light nitrogen so bacterial DNA had replicated semi-conservatively

Answer 95

Adenosine Triphosphate

Answer 96

A molecule of Ribose A molecule of Adenine Three Phosphate groups

Answer 97

It's a modified form of a nucleotide

Answer 98

Plant and animal cells release energy from glucose through respiration A cell can't get its energy directly from glucose So, in respiration the energy released from glucose is used to make ATP Once made, ATP diffuses to the part of the cell that needs energy The energy in ATP is stored in high energy bonds between the phosphate groups. Energy is released via hydrolysis reactions

Answer 99

When energy is needed by a cell, ATP is broken down into ADP (adenosine diphosphate) and Pi (inorganic phosphate) A phosphate bond is broken and energy released The reaction is catalysed by the enzyme ATP hydrolase

Answer 100

Water | ATP hydrolase

Answer 101

Energy ADP Inorganic Phosphate Group

Answer 102

``` Cellular reactions that are endergonic e.g. Active Transport Movement and Muscle contraction Breakdown and synthesis of new molecules Enzyme controlled reactions e.g. Respiration e.g. Photosynthesis e.g. Digestion ```

Answer 103

The energy released can be used directly to make the coupled reaction happen, rather than being lost as heat

Answer 104

It can be added to another compound (known as phosphorylation) which makes the compound more reactive

Answer 105

A condensation reaction occurs between ADP and Pi | Process is catalysed by enzyme ATP synthase

Answer 106

ATP synthase | Energy

Answer 107

Adenine Triphosphate

Answer 108

Photosynthesis | Respiration

Answer 109

Catabolic reactions that are exergonic

Answer 110

In mitochondria of all cells

Answer 111

A molecule of water (H2O) is made up of 2 atoms of hydrogen and one atom of oxygen by shared electrons

Answer 112

It has a partial negative charge on one side and a partial positive on the other Slight positive charge is caused by due to the shared negative hydrogen electrons being pulled towards the oxygen atom, the other side of hydrogen is left with positive charge Slight negative charge is caused by the unshared negative electrons on the oxygen atom

Answer 113

When the slightly negatively-charged oxygen atoms attract the slightly positively-charged hydrogen atoms of other water molecules

Answer 114

``` Surface tension Density Solvent High specific heat capacity/Temperature buffer Cohesion Adhesion High latent heat of vaporisation Metabolite ```

Answer 115

Surface tension is the uneven distribution of force at a boundary interface caused by molecular bonding The surface of water forms a skin which is strong enough to support small aquatic animals

Answer 116

Density is a measure of mass per unit of volume Because water freezes from top down, organisms are able to survive below surface of ice which acts as insulating layer. Changing density maintains circulation in large bodies of water to help nutrient cycling

Answer 117

A solvent is a liquid substance which can dissolve a wide range of molecules It allows water to act as a transport medium for polar molecules causing them to dissociate as the positive end of water is attracted to negative ion and negative end of water attracted to positive ion so ions are totally surrounded by water and dissolve It also removes metabolic wastes such as urea and ammonia

Answer 118

Specific heat capacity is the amount of heat required to raise 1kg of water by 1°C. High means it requires a lot of energy This is crucial for living organisms which need to maintain particular temperatures in order to optimise enzyme activity. High water content of cells and tissues helps them to maintain a constant temperature. In this way water acts as a temperature buffer

Answer 119

Cohesion is the tendency of molecules of a substance to attract one another Water molecules are very cohesive because they are polar which helps water flow, so water is good for transporting substances The cohesion allows water to move up the xylem

Answer 120

Adhesion is the tendency of molecules to be attracted to other molecules of a different type A strong force of attraction between the water molecules and the walls of the xylem allow transpiration to take place. This is what causes water to be wet

Answer 121

High latent heat of vaporisation means it requires a lot of energy to break hydrogen bonds between water molecules when water evaporates This is useful for living organisms as it means they can use water loss through evaporation to cool down without losing too much water

Answer 122

Many metabolic reactions involve condensation or hydrolysis reactions Hydrolysis requires a molecule of water to break a bond e.g. energy from ATP released through hydrolysis reaction Condensation releases a molecule of water when a new bond is formed e.g. amino acids are joined to make polypeptides (proteins) by condensation reactions

Answer 123

An atom or molecule that carries an electric charge An ion with positive charge is called a cation An ion with negative charge is called an anion

Answer 124

An ion which does not contain carbon

Answer 125

Buffering the blood | Controlling/altering pH (pH measured in units of moles per litre of hydrogen ions)

Answer 126

Proteins require optimum pH Proteins denature in incorrect pH Enzymes required for metabolic activities Channel proteins required for movement of ions and waste

Answer 127

Involved in several biological processes such as: - A component of haemoglobin - Involved in the electron transport chain in respiration Haemoglobin is a large protein that carries oxygen around the body, in the red blood cells It’s made up of 4 different polypeptide chains, each with an iron ion (Fe²⁺) The Fe²⁺ binds to the oxygen in haemoglobin

Answer 128

Sodium ions are important in the control of glucose and amino acids moving in or out of the cell in co-transport

Answer 129

DNA, RNA and ATP all contain phosphate groups The bonds between phosphate groups store energy in ATP The phosphate groups in DNA and RNA allow nucleotides to join up to form polynucleotides Phospholipids are important in cell membrane

Answer 130

Calcium is useful for strong bones and teeth and glue sticking plant cells together Magnesium is a component of chlorophyll and minerals in bones and teeth Nitrates are important in protein-synthesis in plants and nitrogenous bases in nucleotides