Biological Molecules Flashcards

Question

How can we test for the presense of reducing sugars?

Answer 1

Add 2cm3 of benedicts solution to 2cm3 of reducing sugar. Copper (II) sulphate in alkaline solution. Blue Colour Reaction requires heating at 90degrees celcius. if reducing sugar is present: Cu2+🡢Cu+ (in benedicts solution) Blue, soluble🡢red, insoluble Forms brick-red precipitate (if high concentrations of reducing sugars are present)/

Answer 2

testing for the presense of non-reducing sugars (e.g sucrose) some disaccharides such as sucrose are not reducing sugars so you would get a negative result from benedicts test. In such a case you should then carry out a test for a non-reducing sugar. in the non reducing sugars test, the disaccharide is first broken down into its two monosacharide constituents. The chemical reaction is hydrolysis and can be brought about by adding hydrochloric acid. The consitutent monosacharides will be reducing sugars and their presense can be tested for using bendicts test after the acid has been neutralised. Procedure 1.Add 2cm3 of sample 2cm3 of acid to hydrolyse glycosidic bonds🡢monosaccharides. 2.Heat at 90 degrees celcius 3.Neutralise using 2cm3 of sodium hydroxide. 4.Add 2cm3 of benedicts solution to the mixture 5. Heat at 90 degrees celcius. Results: Brick red precipiate=non redcuing sugar even after hydrolysis remains blue colour=Not sugar.

Answer 3

Made of carbon, hydrogen, oxygen and sometimes Phosphorus. Important for: 1. Energy storage (lipids have many C-H bonds, can generate more-E than carbs). 2. Structural component of membranes. 3. Other specific biological functions (certain hormones are made up of lipids.

Answer 4

Glycerol: Has 3 carbons 3-OH groups Functional group is a hydroxyl group. Fatty acid Has an acid "head" (-COOH group)+ a long hydrocarbon chain 🡢many C-H bonds. Hydrocarbon chain is hydrophobic and non-polar. | you need to be able to draw and recognise fatty acids.

Answer 5

saturated fatty acids. No double bonds. Unsaturated fatty aics Has double bonds Mononsaturated FA= 1 double bond Polyunsaturated FA>1 double bond Results in kink in hydrocarbon tail lesser C-H bonds. Lower melting point-liquid at room temperature.

Answer 6

3 fatty acids + 1 glycerol Linked by ester bonds Formed via condensation reactions by removal of three water molecules (H from glycerol and OH from fatty acid). FA can be saturated or unsaturated.

Answer 7

Insoluble in water Bcs of the long hydrocarbon tails of the fatty acid. Non-polar, hydrophobic Soluble in organic solvents for e.g ether, chloroform, ethanol.

Answer 8

1) source of energy 🡢Many C-H bonds (more than hydrocarbohydrates) 🡢Higher porportion of hydrogen 🡢Insoluble and compact 🡢more energy can be produced per unit mass 2) metabolic source of water 🡢high ratio of H to O atoms 🡢release water during fat oxidation 🡢especially for desert animals 3) Insulator 🡢 Below dermis 4) Protection of organs 5) Buoyancy 🡢blubber

Answer 9

Composed of 1 glycerol 2 fatty acids 1 phosphate gp (PO4-) May also have other groups attached to phosphate gp (represented by R). a)They have a hydrophillic head phospahte groups Charged, polar Forms h-bonds with water 2)Hydrophobic tails Fatty acid residues Hydrocarbon chair are insoluble and non polar repels water

Answer 10

1)Forms a phosphlopid bilayer with a hydrophobic core barrier to water-soluble substances at membrane lipid soluble substances can pass through 2) allow regulation of membrane fluidity Double bonds in unsaturated fatty acis tails increases fluidity sat FA decreases fluidity 3) Helps to hold membrane proteins in place Hydrophobic interaction with "floating" membrane proteins. 4) Can combine with carbohydrates to form glycolipids. Important in cell recognition.

Answer 11

Emulsion test for lipids. 1) Shake sample with ethanol 2) Pour mixture into a tube with water Results: Transparent-no lipids White and cloudy-lipids present 🡢Lipid molecules clump together 🡢Forming little groups dispersed throughout the liquid 🡢Emulsion

Answer 12

The three most common disacharides are maltose (alpha glucose+ alpha glucose), sucrose (alpha glucose + beta fructose) and lactose (glucose + galactose).

Answer 13

Made of C,H,O, N (sometimes, S) Examples of structures made of proteins * Haemoglobin * Collagen * Components of cell membranes * Enzymes * Antibodies * Keratin Monomer: amino acids Dimer: dipeptide Polymer: Polypeptide

Answer 14

H I HOOC-C-NH2 I R amine group, carboxylic acid group and r group

Answer 15

The simplest amino acid is glycine R group=H Another onme to remember is cysteine R group=contains sulphur (-CH2-SH) | dont need to draw only identify cysteine.

Answer 16

A peptide bond forms between C of -COOH and the N of -NH2. Peptide bond is o=C-N

Answer 17

Many amino acids undergo condensation reaction will give you a polypeptide. Many peptide bonds. Synthesised at the ribosome. Condensation reaction. How to identify central carbon: First find peptide bond and circle The carbon atoms directly next to peptide bond are central carbons.

Answer 18

peptide bonds (present in all polypeptides) 1. Hydrogen bonds 2. Disulfide bonds 3. Ionic bonds 4. Hydrophobic interactions Arranged in order of weakest to strongest= Hydrophobic Interactions H bonds Ionic bonds Cocalent Bonds e.g. disulphide and peptide bonds.

Answer 19

very strong Covalent bonds Between C and -COOH and N of -NH2 Result of condensation reaction present in all polypeptides.

Answer 20

Individually weak But many H bonds 🡢 cumulatively strong between H of -NH/-OH group and O of -OC group OR between R groups easily broken by: * High temperatures * pH changes

Answer 21

Very strong covalent bonds Between sulphur atoms of cysteine amino acids.

Answer 22

between ionized amine and carboxylic acid groups. 🡢-NH3+ and -COO-groups 🡢that are not involved in peptide bonding * or between charged R groups * weaker than disulphide bonds, but stonger than H bonds. * easily broken down by pH changes and high temp. | usually at end of polypeptide chain

Answer 23

Between non-polar/hyrdrophobic R groups Repel and move away from the water Weakest

Answer 24

Primary structure Secondary structure Tertiary structure Quaternary structure

Answer 25

Linear sequence of amino acids Held together by peptide bonds Specific sequence of amino acids 🡢Each with diff properties of R groups 🡢 Dictates folding of the polypeptide chain.

Answer 26

H bonds between amino acids. Not located directly next to each other. Of the same polypeptide chain Two conformations: 1) Alpha helix * Hydrogen bonding * Between h atom of the -NH group and O atom of the --CO group. * 4 places amino acid ahead * Forms spring-like structures 2) Beta pleated sheets * Hydrogen bonds * Between H atom of the -NH group and O atom of the -CO group. * straighter looser form * Parallel, flat sheets

Answer 27

.Coiling and folding of secondary structures.🡢into a precise 3D structure. Due to interactions between R groups. Only polypeptide chain only. Could be held by all 4 bonds-H bonds, disulfide bonds, ionic bonds and hydrophobic interactions.

Answer 28

Myoglobin * oxygen carrying molecule * Present in muscle cells 🡢gives it a red colour Made of 1 polypeptide chain Has a haem group=non amino acid group That binds 1 molecule oxygen

Answer 29

pretty much the same as tertiary structure except: Combination of two or more polypetide chains Held together by all four bonds for example collagen and haemoglobin.

Answer 30

Globular and Fibrous proteins

Answer 31

Spherical/ball shape Mostly tertiary, sometimes quatenary structure Soluble More functional roles For e.g. all enzymes, antibodies, some hormones, myoglobin, haemoglobin.

Answer 32

Long, parallel strands Mostly secondary structure (sometimes tertiary and quatenary) and form fibers. Insoluble More structural roles For example collagen and keratin

Answer 33

Amino acids with non-polar/hydrophobic R groups are inside Amino acids with polar/hydrophillic R groups face outside.

Answer 34

Has quaternary structure made of 4 polypeptide chains 2 alpha globin chains and 2 beta globin chains Globular Amino acids with non-polar/hydrophobic R groups are inside Amino acids with polar Hydrophilic R groups face outside Each polypeptide has a haem group Prosthetic group=non amino acid group Permanent part of haemoglobin Each haem has 1 iron ion (Fe2+) Each Fe2+can bind to one oxygen molecule. One haemoglobin can bind 4 molecules of O2

Answer 35

Structural protein High tensile strength Every 3rd amino acid of each collagen polypeptide is glycine. Usually Proline-Alanine-Glycine repeat Glycin has the samllest R group! 🡢so it can be tightly wound * 3 polypeptide chains form a triple helix collagen molecule. 🡢held by hydrogen bonds. Collagen molecules lie parallel and form covalent cross-links between R groups of Lysine. Staggered ends so no weak points. forms fibrils and fibres.

Answer 36

Bieuret reagent Copper (II) sulphate and dilute potassium hydroxide. Add 2cm3 of bieuret solution to 2cm3 of sample Purple-protein present Blue-no protein NH2 groups in amine react eith copper ions🡢Purple.

Answer 37

Dipole in nature 🡢O atom has slight negative charge 🡢H has slight positive charge Hydrogen Bonding 🡢Between the O and H atoms of different water molecules. 🡢Induvidually weak, cumulatively strong.

Answer 38

* Specific heat capacity=amount of heat required to raise the temperature of 1kg of water by 1 degrees celcius. * large amount of energy need to raise the temperature of water. 🡢Due to H bonding in water. 🡢Large energy needed to break the hydrogen bonds.. * Provide stable tempreature/enviroment. 🡢Acts as a buffer against sudden temperature change. 🡢Temperature of water does not chane quickly.

Answer 39

* Large amount of energy needed for water to evaporate 🡢 Due to H bonding in water * When water does evaporate it is able to remove a large amount of heat energy from surroundings. 🡢Important as a cooling mechanism.

Answer 40

* Water also needed to lose a large amount of heat to freeze. 🡢due to hydrogen bonds between water molecules 🡢Provide stable habitat for aquatic organisms, less likely to freeze. * Ice is less dense than water Water is most dense at 4 degrees celsius Floats🡢acts as an isulator on surface of frozen lakes.

Answer 41

water is dipolar Dissolve ions and polar molecules for example oxygen, CO2 and ammonia. Important for: Transport, removal of wastes, secretios, medium for enzymatic action. Not solvent for non-polar molcecules (lipids).

Answer 42

Water tends to stick to each other (cohesions) and stick to surfaces (adhesion) because of hydrogen bonds. Useful for: 1) transport of water in xylem tissue of plants 🡢long, unbroken coloumn of water 2) High surface tension 🡢Surface dwellers habitat for e.g. pond skater.

Answer 43

Beta Globin | Past paper question

Answer 44

R groups of glutamic acid is polar and R groups of valine is non polar. Change in tertiary structure. Change in quatenary structure of hameoglobin. Haemoglobin is less soluble. Haemoglobin is less effiencet and biding and transporting oxygen.

Biological Molecules Flashcards

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