Chapter 3 - Biological Molecules Flashcards

Question

What are hydrogen bonds, and what causes them?

Answer 1

* Hydrogen bonds are relatively weak interactions * They are caused by polar molecules interacting with each other and forming bonds - hydrogen bonds

Answer 2

* Liquid * Density * Solvent * Cohesion and surface tension * High specific heat capacity * High latent heat of vaporization

Answer 3

The hydrogen bonds between water molecules make it more difficult for them to escape to become a gas

Answer 4

* Provides habitats for living things in rivers, lakes and seas * Forms a major component of the tissues in living organisms * Provides a reaction medium for chemical reactions * Provides an effective transport medium e.g. in blood and vascular tissue

Answer 5

Usually the solid is more dense than the liquid form of a substance. However ice is less dense than water because as water goes from 4C to freezing point, the water molecules form a structure that is less dense than liquid water

Answer 6

* If water was less dense, aquatic organisms would find it very difficult to float **Ice floats on water so:** * Aquatic organisms have a stable environment to live through in winter * Ponds are insulated against extreme cold because the ice layer reduces heat loss from the pond

Answer 7

* As it is polar, the positive and negative parts of the water molecules are attracted to the oppositely charged parts of the solute * Water molecules cluster around the charged parts of the solute molecules or ions, which helps to separate them and keep them apart

Answer 8

* Molecules andirons can move around and react together in water e.g. as in the cytoplasm of cells, which is >70% water * Molecules and ions can be transported around living things whilst dissolved in water

Answer 9

* Water molecules demonstrate **cohesion** because hydrogen bonding between the molecules pulls them together * Water molecules demonstrate **surface tension** because they are more attracted to the water molecules beneath them than air molecules above, so the water contacts, giving the surface of the water the ability to resist a force applied to it

Answer 10

* Columns of water in plant vascular tissue are pulled up the xylem tissue together from the roots due to cohesion * Insects like pond-skaters can walk on water due to surface tension

Answer 11

* Water molecules are held together quite tightly by hydrogen bonds * Therefore you need to put in a lot of heat energy to increase their kinetic energy and temperature * This means that water doesn’t heat up or cool down easily

Answer 12

* Living things need a stable temperature for enzyme-controlled reactions to happen properly * Aquatic organisms need a stable environment in which to live

Answer 13

Because the water molecules are held together by hydrogen bonds, a relatively large amount of energy is needed for water molecules to evaporate

Answer 14

**Water can help to cool living things and keep their temperature stable e.g.** * Mammals are cooled when sweat evaporates * Plants are cooled when water evaporates from mesophyll cells

Answer 15

**It is a reactant in reactions such as photosynthesis, and in hydrolysis reactions such as digestion of starch, proteins and lipids** * Plays a very important role in the digestion and synthesis of large biological molecules

Answer 16

Organic polymers composed of the elements carbon, hydrogen and oxygen, usually in the ration **Cx(H2O)y**. Also known as saccharides or sugars

Answer 17

A single sugar molecule e.g. glucose, fructose and ribose

Answer 18

A molecule comprising two monosaccharides joined together by a glycosidic bond

Answer 19

* C6H12O6 * Hexose monosaccharide (because it has 6 carbons) * Polar and soluble in water due to the hydrogen bonds that form between the OH group and water molecules * Means glucose is dissolved in the cytosol of the cell

Answer 20

*⍺ glucose - OH group is below carbon 1 *ß glucose - OH group is above carbon 1

Answer 21

* The OH groups on C1 and C4 reacted forming a 1,4 glycosidic bond (covalent) * Condensation reaction because a water molecule is formed (lost)

Answer 22

1. Maltose 2. Sucrose 3. Lactose 4. Cellobiose

Answer 23

* Sugars that contain 5 carbon atoms * e.g. ribose which is the sugar present in RNA nucleotides * e.g. deoxyribose which is the sugar present in DNA nucleotides

Answer 24

A polysaccharide formed from alpha glucose molecules either joined to form amylose or amylopectin. Found in plants

Answer 25

* Found in plants * Alpha glucose * Glycosidic bonds between C1 and C4 * Coils into a spiral shape held together by hydrogen bonds * OH groups on C2 inside of the coil, making the molecule less soluble and allowing hydrogen bonds to form to maintain the coil’s structure

Answer 26

* Found in plants * Alpha glucose * Has glycosidic bonds between C1 and C4, and also has branches formed by glycosidic bonds between C1 and C6 * Coils into a spiral shape held together by hydrogen bonds, but with branches coming out of the spiral

Answer 27

A branched polysaccharide formed from ⍺ glucose A chemical energy store in animals

Answer 28

* Found in animals * Like amylopectin with glycosidic bonds between C1 and C4, and branches formed by glycosidic bonds between C1 and C6 * The C1 C4 bonded chains are smaller than in amylopectin so glycogen has less tendency to coil * Has more branches than amylopectin making it more compact * Easier to remove monomer units as there are more ends

Answer 29

* The OH groups on C1 and C4 are to far away to react, so each alternate beta glucose molecule must be turned upside down to reach * It is unable to could or form branches * A straight chain molecule called cellulose is formed

Answer 30

* Cellulose molecules make hydrogen bonds with each other forming microfibrils * Microfibrils join together to form macrofibrils that combine to produce fibres * The fibres are strong and insoluble and are used to make cell walls

Answer 31

* Microfibrils and macrofibrils have very high tensile strength because of the glycosidic bonds and hydrogen bonds * macrofibrils run in all directions, criss-crossing the wall for extra strength * Space between macrofibrils for water and mineral ions to pass in and out of the cell, making the cell wall full permeable

Answer 32

Non-polar macromolecules contains the elements carbon, hydrogen and oxygen. Soluble in alcohol rather than water. Include triglycerides, phospholipids and sterols.

Answer 33

Lipids composed of one glycerol (C3H8O3) molecule and three fatty acids. Fatty acids are carboxylic acids that consist of a carboxyl group (-COOH) which a hydrocarbon chain attached.

Answer 34

* The hydroxyl groups in the fatty acid molecule and glycerol molecule react * This leads to the formation of 3 water molecules and bonds between the fatty acid and glycerol molecule * The bonds are called ester bonds, and the reaction is called esterification * Esterification is an example of a condensation reaction

Answer 35

* Fatty acid chains that have no double bonds between the carbon atoms are saturated, and vice versa * If there’s 1 double bond = monounsaturated * If there’s 2 or more double bonds = polyunsaturated

Answer 36

* Changes the bond angle and causes the molecule to kink or bend * Therefore the molecules cannot pack so closely together * Makes them liquid at rtp rather than solid, so they are oils rather than fats

Answer 37

Unsaturated triglycerides, which normally occur as oils

Answer 38

Unsaturated triglycerides are healthier for human than triglycerides or (solid) fats.

Answer 39

Modified triglycerides, where one fatty acid has been replaced with a phosphate group. They are found in the cytoplasm of very cell.

Answer 40

* Have a non-polar end (the fatty acid chains) which are hydrophobic and repelled by water * Have a charged head (the phosphate PO43-) which are hydrophilic and attracted to water

Answer 41

* Form a layer on surface of water with phosphate heads (hydrophilic) in the water and fatty acid tails (hydrophobic) sticking out * Can form structures based n a bilayer with all the hydrophobic tails pointing towards the centre of the sheet, protected by from the water by hydrophilic heads

Answer 42

The bilayer arrangement means that they can separate the aqueous environment in which cells usually exist, from the aqueous cytosol within the cells

Answer 43

Steroid alcohols. Complex alcohol molecules based on a 4 carbon ring structure with a hydroxyl (OH) group at one end.

Answer 44

Have a dual hydrophilic/hydrophobic characteristics. The hydroxyl group is polar and therefore hydrophilic, and the rest of the molecule is hydrophobic.

Answer 45

* A type of sterol * The body primarily manufactures it in the liver and intestines * Vitamin D, steroid hormones and bile are all manufactured using cholesterol

Answer 46

* Positioned between the phospholipids with the hydroxyl group at the periphery of the membrane * Adds to the stability of cell membranes

Answer 47

Keeps membranes fluid at low temperatures and stops them becoming too fluid at high temperatures

Answer 48

* Membrane formation and the creation of hydrophobic barriers * Hormone production * Electrical insulation necessary for impulse transmission * Waterproofing, e.g. in birds’ feathers and on plant leaves

Answer 49

* Long-term energy storage Stored under the skin and around vital organs where they provide: * Thermal insulation to reduce heat loss, e.g. in penguins * Cushioning to protect vital organs e.g. heart and kidneys * Buoyancy for aquatic animals like whales

Answer 50

1. One or more polypeptides arranged as a complex macromolecule 2. Chains of two or more amino acid molecules 3. Bond formed between two amino acids 4. Monomer used to build polypeptides and thus proteins

Answer 51

* The hydroxyl in the carboxylic acid group of one amino acid reacts with a hydrogen in the amine group of another amino acid * A peptide bond is formed between the amino acids and water is produced (condensation reaction) * The resulting compound is a dipeptide

Answer 52

* When many amino acids are joined together by peptide bonds * This reaction is catalysed by the enzyme peptide transferase present in ribosomes, the sites of protein synthesis

Answer 53

* Different R-groups interact with each other (R-group interactions) forming different types of bond * These bonds lead to polypeptides folding into complex structures (proteins)

Answer 54

Different structures with different shapes being produced The very specific shapes of proteins are vital for the many functions proteins have within living organisms

Answer 55

* The sequence in which the amino acids are joined * Directed by information carried within DNA * The amino acids in the sequence will influence how the polypeptide’s fold to give the proteins final shape, and determine its function * The only bonds here are peptide bonds

Answer 56

* The oxygen, hydrogen, and nitrogen atoms of the amino acids (excluding R groups) interact * A result of hydrogen bonds and forms at regions along long protein molecules depending on the amino sequences

Answer 57

* **Alpha Helix** - Hydrogen bonds form within the amino acid chain, pulling it into a coil shape called an alpha-helix * **Beta Pleated Sheet**- Polypeptide bonds lie parallel to each other joined by hydrogen bonds, forming sheet-like structures.The pattern formed by individual amino acids makes the structure appear pleated

Answer 58

* The folding of a protein into its final shape * Often includes sections of secondary structure * The coiling or folding of sections of proteins into their secondary structures brings R-groups of different amino acids closer together so they can interact

Answer 59

* **Hydrophobic and hydrophilic interactions** - weak interactions between polar and non-polar R-groups * **Hydrogen bonds** - these are the weakest of bonds formed * **Ionic bonds** - stronger than hydrogen bonds and form between oppositely charged R-groups * **Disulfide bonds/bridges** - covalent and the strongest of the bonds but only form between R-groups that contain sulphur atoms

Answer 60

* Protein structure where a protein consists of more than 1 polypeptide chain, e.g insulin has a quaternary structure * Results from the association of 2 or more individual proteins called subunits * The interaction between subunits are the same as in tertiary structure except between different protein molecules rather than within one molecule * The protein subunits can be identical or different

Answer 61

* Proteins are assembled in the aqueous environment of the cytoplasm * The way a protein will fold also depends on whether the R-groups are hydrophilic or hydrophobic * Hydrophilic groups arena the outside, whilst hydrophobic are on the inside of the molecule (away from the cytoplasm)

Answer 62

* Globular proteins * Conjugated proteins * Fibrous proteins

Answer 63

**Compact, spherical, water-soluble proteins** * Form when proteins fold into their tertiary structures so that the hydrophobic R-groups on the amino acid are kept away from the aqueous environment * Hydrophilic R-groups on the outside of the protein meaning the proteins are soluble in water * e.g. Insulin

Answer 64

**Globular protein ** * Hormone involved in regulation of blood glucose concentration * Hormones are transported in the bloodstream so need to soluble * Hormones have to fit into specific receptor on cell-surface membranes to work, therefore need to have precise shapes

Answer 65

**Globular proteins that contain a prosthetic group** Lipids or carbohydrates can combine with proteins forming lipoproteins or glycoproteins. Metal ions and molecules derived from vitamins also form prosthetic groups * e.g. Haemoglobin and Catalase both contain prosthetic harm groups (Fe2+)

Answer 66

* Red, oxygen-carrying pigment in red blood cells * Quaternary protein made from 4 polypeptides (2 alpha and 2 beta subunits) * Each subunit contains a prosthetic hem group * The Fe2+ ions in the haem groups are each able to combine reversibly with an oxygen molecule which enables haemoglobin to transport oxygen around the body

Answer 67

* An enzyme * A quaternary protein containing 4 prosthetic harm groups * The presence of Fe2+ ions in the haem groups allow catalase to interact with hydrogen peroxide and speed up its breakdown * Hydrogen peroxide is a common byproduct of metabolism but damaging to cells and cell components, so catalase makes sure it doesn’t accumulate

Answer 68

**Long insoluble, structural proteins** * Due to the presence of a high proportion of amino acids with hydrophobic R-groups in their primary structures * Amino acid sequence in primary structure is usually very repetitive leading to very organised structures * Are NOT folded into complex 3D shapes like globular proteins * E.g. Keratin, Elastin and Collagen

Answer 69

* Group of fibrous proteins presenting hair, skin and nails * Large proportion of the sulfur-containing amino acid cysteine leading to many strong disulphide bonds forming strong, inflexible, insoluble materials * Hair contains fewer disulphide bonds than nails, so is more flexible

Answer 70

* Fibrous protein found in elastic fibres * Elastic fibres are present in the walls of blood vessels and in the alveoli of the lungs * Give these structures flexibility to expand when needed but also to return to their normal size * Quaternary protein made from many stretch molecules called tropoelastin

Answer 71

* Fibrous protein * Connective tissue found in skin, tendons, ligaments and the nervous systems * Many different forms but all are made up of 3 polypeptides wound together in a long and strong rope-like structure * Like rope, collagen has flexibility

Answer 72

1. Add iodine solution (in potassium iodide) to a sample 2. If starch is present, you will see a colour change from yellow-brown to blueback * When dissolved in potassium iodide, the iodine (I2) forms a triiodide I3-, which slips into the middle of the amylose helix, causing a colour change

Answer 73

1. Place the sample in a boiling tube. If its not liquid, grind it up or lend it in water 2. Add an equal volume fo Benedict’s solution 3. Heat the mixture gently in a boiling water bath for 5 minutes **Blue > Green > Yellow > Orange > Red** * Benedict’s reagent is an alkaline solution of copper (II) sulphate * The more reducing sugar present, the more brick-red precipitate formed and the less blue Cu2+ ions left in solution

Answer 74

1. Do Benedict’s test for reducing sugars, the result will be negative 2. Sucrose is the most common non-reducing sugar 3. If sucrose is first boiled with dilute hydrochloric acid then it’ll give a positive result when warmed with Benedict’s solution * This is because the sucrose has been hydrolysed by the acid to glucose and fructose, both reducing sugars

Answer 75

1. Mix the sample with ethanol 2. The resulting solution is mixed with water and shaken 3. If a white emulsion forms as a layer on top the solution, this indicated the presence of a lipid 4. If the solution remains clear, the test is negative

Answer 76

1. Add Biuret A (sodium hydroxide) and then Biuret B (copper sulphate) to the sample 2. If a protein is present, the colour changes from light blue to lilac/ mauve

Answer 77

Large polymers formed from nucleotides. Contain the elements carbon, nitrogen, hydrogen, phosphorus, and oxygen.

Answer 78

* A pentose monosaccharide containing 5 carbon atoms * A phosphate group, (PO42-) and inorganic molecule that is acidic and negatively charged * A nitrogenous base - a complex organic molecule containing 1 or 2 carbon rings in its structure, as well as nitrogen

Answer 79

* By condensation reactions * Phosphate group at the 5th carbon of the pentose sugar (5’) of one nucleotide forms a covalent bond with the hydroxyl (OH) group at the 3rd carbon (3’) of the pentose sugar of another nucleotide * These bonds are called phosphodiester bonds * Forms a long, strong sugar-phosphate ‘backbone’ * Phosphodiester bonds are broken by hydrolysis

Answer 80

** The molecule responsible for the storage of genetic information ** * The sugar is deoxyribose, which has 1 less oxygen atoms than a ribose sugar * The nucleotides each have 1 of 4 different bases: Adenide, Thymine, Guanine, or Cytosine

Answer 81

* Single-ringed, nitrogenous bases that form part of a nucleotide * Smaller bases * Thymine (T) and Cytosine (C)

Answer 82

* Double-ringed, nitrogenous bases that form part of a nucleotide * Larger bases * Adenine (A) and Guanine (G)

Answer 83

* Made up of 2 strands of polynucleotides coiled into a helix * The 2 strands are held together by hydrogen bonds between the bases * Each strand has a phosphate group (5’) at one end, and a hydroxyl group (3’)at the other end * The 2 parallel strands run in opposite directions - antiparallel

Answer 84

Specific hydrogen bonding between nucleic acid bases. A binds to T or U, C binds to G * A and T form 2 hydrogen bonds so always join with each other * C and G form 3 hydrogen bonds so always join with each other

Answer 85

* A small pyrimidine base always binds to a larger purine base; this arrangement keeps a constant distance between the DNA backbones, resulting in parallel polynucleotide chains * DNA always has equal amounts of adenine and thymine, and cytosine and guanine

Answer 86

Polynucleotide molecules involved in the copying and transfer of genetic information from DNA. The monomers are nucleotides consisting of a ribose sugar and 1 of four bases: Adenine, Uracil, Cytosine, or Guanine

Answer 87

Similarities: * RNA nucleotides form polymers in the same way as DNA nucleotides - by the formation of phosphodiester bonds Differences: * In RNA the pentose sugar is ribose, meanwhile in DNA it’s deoxyribose * In RNA, the thymine base is replaced with Uracil

Answer 88

The semi-conservative process of the production of identical copies of DNA molecules

Answer 89

DNA replication results in one old strand and one new strand present in each daughter DNA molecules

Answer 90

1. The enzyme DNA helicase travels along the DNA backbone, catalysing reactions that breaks the hydrogen bonds between complimentary base pairs 2. After the ‘unzipping’, free DNA nucleotides will then pair with their complimentary bases, which have been exposed as the strands separate 3. Hydrogen bonds are formed between the new complimentary bases 4. The enzyme DNA polymerase catalyses the formation of phosphodiester bonds between adjacent new nucleotides

Answer 91

A change in the genetic material which may affect the phenotype of the organism. Happen due to random error in the replication of DNA that lead to a change in the sequence of bases

Answer 92

The sequences of baes in DNA are the ‘instructions’ for the sequences of amino acids in the production of proteins

Answer 93

The genetic code is a sequence of three nucleic acids bases, called a codon. Each codon codes for one amino acids. A section of DNA that contains the complete sequence of baes (codons) to ode for an entire protein is called a gene.

Answer 94

* There are 64 different base triplets or codons possible, but there are only 20 amino acids * Therefore, many amino acids can be coded for by more than one codon

Answer 95

* There’s a start codon (ATG) that signals the start of a sequence that codes for a protein (if it’s in the middle of a gene it codes for methionine) * Having a start codon means that codons are read ‘in frame’, so the genetic code is non-overlapping * There are 3 stop codons that don’t code for any amino acids, and signal the end of the sequence

Answer 96

The process of copying smaller sections of DNA base sequence to produce smaller molecules of mRNA, which can be transported out of the nucleus via the nuclear pores, to the site of protein synthesis

Answer 97

1. A gene unwinds and unzips, aided by DNA helicase, and the hydrogen bonds between complimentary nucleotide bases break 2. The sense strand (5’ to 3’) codes for the protein, whilst the antisense strand (3’ to 5’)acts as the template strand during transcription 3. RNA polymerase catalyses the formation of temporary hydrogen bonds between RNA nucleotides and their complimentary DNA bases on the template strand 4. The strand of RNA produced is complimentary to the template strand, so is a copy of the sense/ coding strand 5. Messenger RNA (mRNA) passes out of the nucleus, through the nuclear envelope, whilst the DNA double helix reforms

Answer 98

* 2 subunits, one large and one small * Almost equal amounts of protein and ribosomal RNA (rRNA)

Answer 99

* Maintaining the structural stability of the protein synthesis sequence * Biochemical role in catalysing the reaction

Answer 100

* Binds to a specific site on the small subunit of a ribosome * The ribosome holds mRNA in position while it is translated into a sequence of amino acids * This process is called translation

Answer 101

The process by which the complementary code carried by mRNA is decoded by tRNA into sequence of amino acids. This occurs at a ribosome

Answer 102

**Form of RNA that carries an amino acid specific to its anticodon to the correct position along mRNA during translation** * Single stranded polynucleotides, but can twist into a hairpin shape * At one end is a trio of nucleotide bases that recognises and attaches to a specific amino acid * At the loop is another triplet of bases called an anticodon that is complementary to a specific codon of bases on the mRNA

Answer 103

1. mRNA binds to the small subunit of the ribosome at its start codon (AUG) 2. A tRNA with the complementary anticodon (UAC) binds to the mRNA start codon. This tRNA carries the amino acid methionine 3. Another tRNA with the complementary anticodon, and carrying an amino acid, binds to the next codon on the mRNA. A maximum of 2 tRNAs can be bound at the same time 4. The 1st amino acid (methionine) is transferred to the amino acid on the 2nd tRNA by the formation of a peptide bond. This is catalysed by the enzyme peptidyl transferase, which is an rRNA component of the ribosome 5. The ribosome then moves along the mRNA, releasing the 1st tRNA. The 2nd tRNA becomes the 1st 6. Stages 3-5 are repeated until the ribosome reaches the end of the mRNA at a stop codon, and the polypeptide is released

Answer 104

**Adenosine triphosphate** A nucleotide composed of a nitrogenous adenine base, a pentose sugar, and 3 phosphate groups. The ‘universal energy currency’ for cells, because it is used for energy transfer in all cells.

Answer 105

* **Synthesis** - e.g. of large molecules such as proteins * **Transport** - e.g. pumping molecules or ions across cell membranes by active transport * **Movement** - e.g. protein fibres in muscle cells that cause muscle contraction

Answer 106

**Adenosine diphosphate** A nucleotide composed of a nitrogenous adenine base, a pentose sugar and 2 phosphate groups Formed by the hydrolysis of ATP, releasing a phosphate ion and energy

Answer 107

* The instability of the phosphate bonds * Fats and carbohydrates are better long-term energy stores * Energy released in the breakdown of these molecules (a process called cellular respiration) is used to create ATP * A phosphate group is reattached to an ADP molecule (phosphorylation which is an example of a condensation reaction)

Answer 108

* Due to the instability of ATP * Instead ATP is rapidly reformed by the phosphorylation of ADP * Interconversion of ATP and ADP is happening constantly in all living cells, so cells don’t need a large store of ATP * ATPis a good immediate energy store

Answer 109

1. When a cell needs energy, ATP is broken down to ADP and Pi 2. In the hydrolysis reaction, a phosphate bond is broken and energy released to be catalysed by the enzyme ATP hydrolase 3. ATP hydrolysis can be couple to other reactions in the cell - the energy can be used directly to make the coupled reaction happen (instead of being lost as heat) 4. The released phosphate can be added to another compound (phosphorylation) which often makes the compound more reactive 5. ATP can be re-synthesised in a condensation reaction between ADP and Pi. The enzyme ATP synthase catalyses it during both respiration and photosynthesis

Answer 110

* **Small** - moves easily into, out of, and within cells * **Water soluble** - energy requiring processes happen in aqueous environments * Contains **bonds between phosphates** with immediate energy: large enough to be useful for cellular reactions, but not so large that energy is wasted as heat * **Releases energy in small quantities** - quantities are suitable to most cellular needs, so that energy is not wasted as heat * **Easily regenerated** - can be recharged with energy

Chapter 3 - Biological Molecules Flashcards

Water, Carbohydrates, Lipids, Proteins, Nucleic Acids (134 cards)