Module 2 Section 2: Biological Molecules Flashcards

Question

Structure of unsaturated fatty acids

Answer 1

Unsaturated fatty acids have at least one double between carbon atoms, which cause the chain to kink Liquid at room temperature

Answer 2

Cn H(2n+1) COOH

Answer 3

Phospholipids are also macromolecules They are similar to triglycerides except one of the fatty acid molecules is replaced by a phosphate group The phosphate group is hydrophilic ( it attracts water molecules ) whereas the fatty acid tails are hydrophobic

Answer 4

In animals and plants, triglycerides are mainly used as energy storage molecules Some bacteria use triglycerides to store bond energy and carbon They are good for storage because: 1). The long hydrocarbon tails of the fatty acids contains lots of chemical energy - lots of energy is released when they are broken down Because of these tails, lipids contain about twice as much energy per gram as carbohydrates 2). They are insoluble, so they don’t cause water to enter the cells by osmosis which would make them swell The triglycerides bundle together as insoluble droplets in cells because the fatty acids tails are hydrophobic - the tails face inwards, shielding themselves from water with their glycerol heads

Answer 5

Found in the cell membranes of all eukaryotes and prokaryotes They make up the phospholipid bilayer Cell membranes control what enters and leaves a cell 1) Phospholipid 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 2) 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 6

Cholesterol is another type of lipid - it has a hydrocarbon ring structure attached to a hydrocarbon tail The ring structure has a polar hydroxyl ( OH ) group attached to it In eukaryotic cells, cholesterol molecules help to regulate the fluidity of the cell membrane by interacting with the phospholipid bilayer 1) Cholesterol has a small size and flattened shape - this allows cholesterol to fit in between the phospholipid molecules in the membrane 2) At higher temperature, they bind to the hydrophobic tails of the phospholipids, causing them to pack more closely together This helps to make the membrane less fluid and more rigid 3) At lower temperatures, cholesterol prevents phospholipids from packing too close together, and so increases membrane fluidity (Orange hydrophilic, rest hydrophobic)

Answer 7

They are polymers like carbohydrates Amino acids are the monomers in proteins

Answer 8

A dipeptide is formed when two amino acids join together A polypeptide is formed when more than two amino acids join together Proteins are made up of one of more polypeptides

Answer 9

All amino acids have the same general structure: A carboxyl group: COOH Amino group: NH2 The difference between different amino acids is the variable group ( R group ) they contain All amino acids contain the chemical elements carbon, oxygen, hydrogen and nitrogen Some contain sulfur

Answer 10

Amino acids are linked together by peptide bonds to form dipeptides and polypeptides A molecule of water is released during the reaction - its a condensation reaction The reverse of this reaction adds a molecule of water to break the peptide bond - its a hydrolysis reaction

Answer 11

Primary structure Secondary structure Tertiary structure Quaternary structure

Answer 12

Sequence of amino acids in the polypeptide chain Different proteins have different sequences of amino acids in their primary structure A change in just one amino acid may change the structure of the whole protein

Answer 13

The polypeptide chain doesn’t remain flat and straight Hydrogen bonds form between nearby amino acids in the chain This makes it automatically coil into an alpha (α) helix or fold into a beta (β) pleated sheet

Answer 14

The coiled or folded chain of amino acids is often coiled and folded further More bonds form between different parts of the polypeptide chain For proteins made from a single polypeptide chain, the tertiary structure forms their final 3D structure

Answer 15

Some proteins are made of several different polypeptide chains held together by bonds The quaternary structure is the way these polypeptide chains are assembled together E.g. haemoglobin is made of four polypeptide chains, bonded together For proteins made from more than one polypeptide chain, the quaternary structure is the protein’s final 3D structure

Answer 16

Computer modelling can create 3D interactive images of proteins This is useful for investigating the different levels of structure in a protein molecule

Answer 17

Primary structure proteins are held together by the peptide bonds between amino acids

Answer 18

Secondary structure proteins are held together by hydrogen bonds

Answer 19

Tertiary structure proteins’ are affected by different kinds of bonds: Ionic bonds: attractions between negatively charged R groups and positively charged R groups on different parts of the molecule Disulfide bonds: whenever two molecules of the amino acid cysteine come close together, the sulfur atom in one of the cysteine bonds to sulfur in the other cysteine, forming a disulfide bond Hydrophobic and hydrophilic interactions: when hydrophobic R groups are close together in the protein, they tend to clump together. This means that hydrophilic R groups are more likely to be pushed to the outside, which affects how the protein folds up into its final structure Hydrogen bonds: these weak bonds form between slightly positively charged hydrogen atoms in some R groups and slightly negatively charged atoms in other R groups on the polypeptide chain

Answer 20

Tends to be determined by the tertiary structure of the individual polypeptide chains being bonded together Because of this, it can be influenced by all the bonds mentioned in tertiary structure proteins

Answer 21

Heating a protein to a high temperature will break up its ionic and hydrophobic/ hydrophilic interactions and hydrogen bonds In turn this will cause a change in the protein’s 3D shape

Answer 22

Round and compact The hydrophilic groups on the amino acids tend to be pushed to the outside of the molecule This is caused by the hydrophobic and hydrophilic interactions in the protein’s tertiary structure This makes the globular proteins soluble, so they’re easily transported in fluids

Answer 23

Globular proteins have a range of functions in living organisms: Haemoglobin Insulin Amylase

Answer 24

Haemoglobin is a globular protein that carries oxygen around the body in red blood cells It’s known as a conjugated protein - this means it’s a protein with a non-protein group attached The non-protein section is called a prosthetic group Each of the 4 polypeptide chains in haemoglobin has a prosthetic group called haem A haem group contains iron, which oxygen binds to

Answer 25

A hormone secreted by the pancreas It helps to regulate the blood glucose level It’s solubility is important - it means it can be transported in the blood to the tissues where it acts An insulin molecules consists of two polypeptide chains, which are held together by disulfide bonds

Answer 26

Amylase is an enzyme that catalyses the breakdown of starch in the digestive system It is made up of a single chain of amino acids It’s secondary structure contains both alpha-helix and beta-pleated sheet sections Most enzymes are globular proteins

Answer 27

Fibrous proteins are strong and insoluble They’re structural proteins and are fairly unreactive ( unlike many globular proteins )

Answer 28

Collagen Keratin Elastin

Answer 29

Found in animal connective tissues, such as bone, skin and muscle It is a very strong molecule due to triple helix polypeptide arrangement Minerals can bind to the protein to increase its rigidity e.g. in bone

Answer 30

Keratin is found in many of the external structures of animals, such as skin, hair and nails, feathers and horns It can either be flexible ( as in skin ) or hard and tough ( as it is in nails )

Answer 31

Elastin is found in elastic connective tissue, such as skin, large blood vessels and some ligaments It is elastic, so it allows tissues to return to their original shape after they have been stretched

Answer 32

An ion is an atom ( or group of atoms ) that has an electric charge A positive ion is called a cation A negative ion is an anion

Answer 33

An inorganic ion is one which doesn’t contain carbon ( although there are a few exceptions to this rule ) Inorganic ions are really important in biological processes

Answer 34

Calcium: Ca2+ Sodium: Na+ Potassium: K+ Hydrogen: H+ Ammonium: NH4 +

Answer 35

Nitrate: NO3 - Hydrogencarbonate: HCO3 - Chloride: Cl- Phosphate: PO4 3- Hydroxide: OH-

Answer 36

Involved in transmission of nerve impulses and release of insulin from the pancreas Acts as a cofactor for many enzymes e.g. those involved in blood clotting. Is important for bone formation

Answer 37

Important for generating nerve impulses, for muscle contraction and for regulating fluid balance in the body

Answer 38

Important for generating nerve impulses, for muscle contraction and for regulating fluid balance in the body Activates essential enzymes needed for photosynthesis in plant cells

Answer 39

Affects pH substances ( more H+ ions that OH- ions in a solution creates an acid ) Also important for photosynthesis reactions that occur in the thylakoid membranes inside chloroplasts

Answer 40

Absorbed from the soil by plants and is important source of nitrogen ( which is then used to make, e.g. amino acids, nucleic acids )

Answer 41

Absorbed from the soil by plants and is an important source of nitrogen ( which is then used to make, amino acids, nucleic acids )

Answer 42

Acts as a buffer, which helps to maintain the pH of blood

Answer 43

Involved in the ‘chloride shift’ which helps to maintain the pH of the blood during gas exchange Acts as a cofactor for the enzyme amylase Also involved in some nerve impulses

Answer 44

Involved in photosynthesis and respiration reactions Needed for the synthesis for many biological molecules, such as nucleotides ( including ATP ), phospholipids and calcium phosphate ( which strengthen bones )

Answer 45

Affects the pH of substances ( more OH- ions than H+ ions in a solution creates an alkali )

Answer 46

Add Benedict’s reagent (blue) and heat it in a water bath until it starts to boil A positive test will form a coloured precipitate The higher the concentration of reducing sugar, the further the colour change goes to (blue->green->yellow->orange->brick red) You can use this to compare the amount of reducing sugar in different solutions

Answer 47

If the result For reducing sugars is negative, they could still be a non-reducing sugar present To test for non-reducing sugars, like sucrose, first you have to break them down into monosaccharides You do this by getting a new sample the test solution, adding dilute hydrochloric acid and carefully heating them in a water bath until they start to boil The neutralise it with sodium hydrogencarbonate, Then just carry out the Benedix test as you would for a reducing sugar If they test positive it will form coloured precipitate, if the test negative the solution will stay blue, which means it doesn’t contain any sugar at all

Answer 48

Can be tested for using test strips coated in a reagent Strips are dipped in a test solution and change colour if glucose is present The colour change can be compared to a chart to give an indication of the concentration of glucose present The strips are useful for testing a person’s urine for glucose, which may indicate they have diabetes

Answer 49

Add iodine dissolved in potassium iodide solution to the test sample If starch is present, the sample changes from browny-orange to blue-black If there’s no starch it stays browny orange

Answer 50

The buiret test has two stages The solution needs to be alkaline, so first you add a few drops of sodium hydroxide solution Then add some copper (II) sulfate solution - if protein is present the solution turns purple - if there is no protein the solution stays blue

Answer 51

Use the emulsion test Shake test tube with ethanol for a minute, then pour the solution into water If the lipid is present, the solution will turn milky The more lipid there is, the more noticeable the milky colour will be If there’s no lipid, the solution stays clear

Answer 52

Use Benedict’s reagent and a colorimeter to get a quantitative estimate of how much glucose ( or another reducing sugar ) there is in a solution A colorimeter measures the strength of a coloured solution by seeing how much light passes through it A colorimeter measures absorbance ( the amount of light absorbed by the solution ). The more concentrated the colour of the solution, the higher the absorbance is It’s easiest to measure the concentration of the blue Benedict’s solution that’s left after the test ( the paler the solution, the more glucose there was ) So, the higher the glucose concentration, the lower the absorbance of the solution

Answer 53

Make 5 serial dilutions with a dilution factor of 2, starting with an initial glucose concentration of 40mM 1. Line up 5 test tubes in a rack 2. Add 10cm3 of the initial 40mM glucose solution to the first test tube and 5cm3 of distilled water to the other 4 test tubes 3. Use a pipette to transfer 5cm3 of the solution from the first test tube, add it to the distilled water in the second test tube and mix the solution. This gives 10cm3 of solution that’s half as concentrated as the solution in the first test tube (it’s 20mM) 4. Repeat this process three more times to create solution of 10mM, 5mM and 2.5mM

Answer 54

After you have the glucose solutions from serial dilution: 1. Do a Benedict’s test on each solution (plus a negative control of pure water), use the same amount of Benedict’s solution in each case 2. Remove any precipitate - either leave for 24hrs ( so ppt settles ) or centrifuge them 3. Use a colorimeter ( with red filter ) to measure the absorbance of the Benedict’s solution remaining in each tube 4. Use the results to make the calibration curve, showing absorbance against glucose concentration You can then test the unknown solution in the same way as the known concentrations and use the calibration curve to find its concentration

Answer 55

Used to separate solutions in a mixture Once it’s separated out, you can often identify the components E.g. can be used separate out and identify biological molecules such as amino acids, carbohydrates, vitamins and nucleic acids

Answer 56

Paper chromatography and thin layer chromatography

Answer 57

Mobile phase: where the molecules can move In both paper and thin layer chromatography the mobile phase is a liquid solvent such as ethanol or water Stationary phase: where the molecules can’t move In paper chromatography the stationary phase is a piece of chromatography paper In thin layer chromatography the stationary phase is a thin layer of solid, e.g. silica gel, on a glass or plastic plate

Answer 58

The mobile phase moves through or over the stationary phase The components in the mixture spend different amounts of time in the mobile phase and the stationary phase The components that spend longer in the mobile phase travel faster or further The time spent in the different phases is what separates out the components of the mixture

Answer 59

Glycogen Starch Cellulose

Answer 60

Reducing sugars include all monosaccharides (e.g. glucose) and some disaccharides (e.g. maltose and lactose)

Answer 61

A more accurate way is to filter the solution and weigh the ppt