Biological Molecules Flashcards

Question

What are single, paired and large chain of monomers called

Answer 1

Monosaccharide Disaccharide Polysaccharide

Answer 2

Glycosidic bonds

Answer 3

Glucose (hexose monosaccharide) Ribose (Pentose monosaccharide) Galactose Fructose

Answer 4

Alpha-glucose Beta- glucose

Answer 5

They have the same chemical formula but have slightly different structures. If the carbon 1 hydroxyl pointes above the ring we call this isomer beta glucose If the carbon 1 hydroxyl points below the ring we call this isomer alpha glucose

Answer 6

Isomers are molecules with the same chemical formula but have different structures.

Answer 7

Glucose is a hexose sugar- a monosaccharide with six carbon atoms in each molecule There are two types of glucose, glucose A and B which have the same chemical formula but have different structures

Answer 8

Maltose Sucrose Lactose

Answer 9

Maltose is a disaccharide formed by condensation of two glucose molecules Sucrose is a disaccharide formed by condensation of glucose and fructose Lactose is a disaccharide formed by condensation of glucose and galactose

Answer 10

A polysaccharide is a macromolecule consisting of more than 2 sugars - often a long chain of polymers joined together by glycosidic bonds

Answer 11

Glycogen Starch cellulose

Answer 12

- Glycogen is formed by the condensation of alpha glucose molecules. - Starch is formed by the condensation of alpha glucose molecules. - Cellulose is formed by the condensation of beta glucose molecules.

Answer 13

• These chains may be: • Branched or unbranched. • Folded (making the molecule compact which is ideal for storage eg. starch and glycogen). • Straight (making the molecules suitable to construct cellular structures e.g. cellulose) or coiled.

Answer 14

The glucose storage molecule is glycogen and the major stores of glycogen are found in the liver and in the muscle cells

Answer 15

- It is a multi-branched alpha glucose polymer joined together by 1, 4 and 1, 6 glycosidic bond. It is stored in the muscle and liver - It has a large number of side branches meaning that energy can be released quickly as enzymes can act simultaneously on these branches. -Glycogen is more branched than amylopectin which makes glycogen a very compact molecule . -Glycogen has large number of branches thus a lot of free ends. This means that enzymes can convert glycogen back to glucose very rapidly -Glycogen is insoluble in water. Glycogen does not draw water into the cell by osmosis . Additionally, being a a large molecule glycogen cannot diffuse out of the cell

Answer 16

-Glycogen is the main energy storage molecule in animals which is stored in the muscles and in the liver. In times of high energy usage, these organs hydrolyse the glycogen stored and break it down into glucose molecules which can be used in respiration -It is a relatively large but compact molecule thus maximising the amount of energy it can store. Makes it optimal for an energy storage molecule. -Finally being insoluble means it will not affect the water potential of cells and cannot diffuse out of cells being a large molecule . -Glycogen has a a large number of branches + free ends thus enzymes can convert glucose very rapidly

Answer 17

• Starch is constructed from two different polysaccharides: - Amylose (10 - 30% of starch) • Unbranched helix-shaped chain with 1,4 glycosidic bonds between α-glucose molecules • The helix shape enables it to be more compact and thus it is more resistant to digestion - Amylopectin (70 - 90% of starch) • 1,4 glycosidic bonds between α-glucose molecules but also 1,6 glycosidic bonds form between glucose molecules creating a branched molecule

Answer 18

Amylose forms a tight helix which make starch compact.. Thus the starch can store a large amount of glucose molecule for its size. Amylopectin and amylose are polymers which are too large to diffuse through the cell membrane and pass out of the cell. Thus starch is insoluble in water and does not cause water to enter the cell by osmosis. As amylopectin has a large number of branches it has a large number of ends thus enzymes can break down starch rapidly by breaking the glycosidic bonds at the end of molecules.

Answer 19

Amylose is a polymer of alpha glucose molecules. The amylose molecule twists into a compact helix with hydrogen bonds forming between glucose molecules along the chain. Amylose contain hundreds or thousands of alpha glucose molecules which are joined together by 1,4 glycosidic bonds.

Answer 20

Amylopectin is a polymer of alpha glucose joined together by 1,4 glycosidic bonds. However, amylopectin chains have a branch every 25-30 glucose molecules. The branch is connected to the main chain by a glycosidic bond which is connected to carbon 1 of one glucose molecule and carbon 6 of another (1,6 glycosidic bond).

Answer 21

Cellulose is a polymer of beta glucose The structure of beta glucose is similar to alpha glucose. However, the hydroxyl on carbon 1 points above the plane of the ring. Glycosidic bonds cannot form between carbon 1 and 4 as the hydroxyl groups point in different directions. As a result when a molecule of cellulose is formed every second beta glucose molecule flips. Thus a 1,4 glycosidic bond is formed Cellulose is an unbranched polysaccharide joined by glycosidic bonds in a condensation reaction

Answer 22

Cellulose forms a straight chain without any branches. This allows cellulose molecules to get close together. Hydrogen bonds can now form between neighbouring chains. As a result a large number of hydrogen bonds are formed which makes cellulose extremely strong. Cellulose cell wall is permeable to molecules The contents of the plant cell push against the turgid cell of the cellulose cell wall. The strength of the cell wall resists the outwards pressure due to the cells contents, This prevents plants cell from bursting. Plant cells filled with water become rigid. These turgid cells give the plant an upright structure.

Answer 23

Monosaccharides such as glucose, amino acids and nucleotides

Answer 24

Molecule of water contains one atom of oxygen chemically bonded to two atoms of hydrogen. The bonds between atoms are covalent bonds

Answer 25

Molecule of water contains one atom of oxygen chemically bonded to two atoms of hydrogen. The bonds between atoms are covalent bonds

Answer 26

Water’s polarity makes it a very good polar solvent for many biological molecules. E.g: in ionic calcium chloride, the positive Ca2+ will be attracted to the negative pole of a water molecule, and Cl- will be attracted to the positive pole. Many metabolic reactions occur in water.

Answer 27

water is a reactant in many different reactions such as hydrolysis reactions and photosynthesis Water is also produced in certain metabolic reactions. These include condensation reactions and aerobic respiration

Answer 28

They are soluble in water. This is because they contain a large number of OH groups within their structure (hydroxyl groups). As a result the hydroxyl group will form hydrogen bonds with water molecules which cause the molecule to be soluble (hydrophilic) Hydrophilic= water loving (hydrophilic molecules dissolve in water)

Answer 29

A molecule of water is produced which is formed from hydrogen atom from one of the monosaccharides and a hydroxyl group from the other

Answer 30

A molecule of water is produced which is formed from hydrogen atom from one of the monosaccharides and a hydroxyl group from the other

Answer 31

If water is added to a disaccharide we can break the glycosidic bond. This converts the disaccharide back to the original monosaccharides This is called hydrolysis reaction.

Answer 32

Glucose is extremely soluble in water. It contains a large number of hydroxyl groups which are polar. As a result hydroxyl groups can form hydrogen bonds with water molecules. This makes glucose soluble in water. However,if a cell contains a large amount of dissolved glucose this can cause water to move into the cell through osmosis. As a result plant store glucose as starch.

Answer 33

Polymer of 10,000 beta glucose molecules in a long unbranched chain is called a microfibril (long cellulose chains)

Answer 34

Microfibrils group together to form a larger structures called macofibrils

Answer 35

Polymer of 10,000 beta glucose molecules in a long unbranched chain is called a microfibril (long cellulose chains)

Answer 36

Macrofibrils grouped together form a cellulose fibre

Answer 37

Macrofibrils grouped together form a cellulose fibre

Answer 38

Carbon-C Hydrogen-H oxygen-O Nitrogen-N

Answer 39

A covalent bond is the sharing of two or more electrons between two atoms The electrons can be shared equally forming a nonpolar covalent bond or unequally (where an atom can be more electronegative δ-) to form a polar covalent bond

Answer 40

Covalent bonding occurs when pairs of electrons are shared by atoms. Atoms will covalently bond with other atoms in order to gain more stability, which is gained by forming a full electron shell (valence shell is formed)

Answer 41

An atom or molecule in which the total number of electrons is not equal to the total number of protons is called an ion.

Answer 42

Cations are ions with a positive charge, meaning they have lost electrons. Anions are ions with a negative charge, meaning they have gained electrons.

Answer 43

Ionic bonds form between a positively charge atom and a negatively charged atom

Answer 44

Ionic bonds are formed between two or more atoms by the transfer of one or more electrons between atoms. Electron transfer produces negative ions called anions and positive ions called cations

Answer 45

Organic substances contain carbon covalently bonded to a hydrogen atom. (CH4) Inorganic substances lack C-H bonds. (NH4)

Answer 46

Lipids are macromolecules that contains carbon, hydrogen and oxygen atoms. Unlike carbohydrate, lipids contain a lower proportion of oxygen

Answer 47

Triglycerides (main components of fats and oils) Phospholipid

Answer 48

They contain carbon, hydrogen and oxygen- lots of of energy can be released The proportion of carbon to oxygen and hydrogen is smaller than in carbohydrates They are insoluble in water They are soluble in organic solvents such as alcohol and acetone

Answer 49

Storage of energy for long term use (e.g triglycerides) or adipose tissue in humans. Hormonal roles (e.g steroid such as oestrogen and testosterone) Insulation- both thermal (triglycerides) and electrical (sphingolipids). Furthermore, adipose tissue in humans help to insulate the body, reducing heat loss to the environment. Protection of internal organs (triglycerides and waxes). Furthermore, adipose tissue is found around organs to protect it from injury Structural components of cells (phospholipids , cholesterol, mitochondria, ) Lipids are used for water proofing- oils which coat the feathers of aquatic birds ( this is because the molecule is uncharged therefore non-polar. This means it is hydrophobic adn does not dissolve in water)

Answer 50

Triglycerides form when a condensation reaction occurs between one glycerol and three fatty acid chains -the 3 hydroxyl group of the glycerol molecule combine with a carboxylic group of 3 fatty acid molecules to form an ester linkage (esterfication) This condensation reaction results in the formation of three water molecules

Answer 51

Animals tend to store triglycerides as fat (solids) plants tend to store triglycerides as oils (liquids)

Answer 52

Fatty acids are long hydrocarbon chains that are found in certain types of lipids (triglycerides and phospholipids) They differ in length (2-24 carbons) and in the number of double bonds Contains a carboxylic group on one end Fatty acids with no double bonds are saturated

Answer 53

This generates fats that are usually solid at room temp Saturated fats are usually linear in structure, originate from animal sources (I.e fats)

Answer 54

Fatty acids with double bonds are unsaturated- either monounsaturated (1 double bonds) or polyunsaturated (> 1 double bond) Contains a carboxylic group on one end

Answer 55

Unsaturated fatty aids are bent in structure, originate from plant sources (I.e oils) Unsaturated fatty acids are usually liquid at room temperature and are called oils

Answer 56

Hydrogenated vegetable oils Fast foods Cakes/pastries Chocolate Deep fried food

Answer 57

Vegetable fats: Coconut Palm oil Condensed milk Animal fats: Poultry skin Fatty meat Butter Ghee

Answer 58

Polyunsaturated: Com oil Soybean oil Sunflower oil Seeds Monounsaturated: Olive oil Cannoli oil Peanut oil

Answer 59

Structure similar to triglyceride, but one Fatty acid chain is replace with a Phosphate group PO4^3-group

Answer 60

Phospholipids are amphipathic (contain both a hydrophobic and hydrophilic)- the phosphate head is negatively charged and thus is polar (hydrophilic) whereas the two fatty acids tails these are non-polar (hydrophobic) Phospholipids have both mono layers and bilayers

Answer 61

Phospholipids play a crucial role in forming the plasma membrane of cells: • In an aqueous environment being polar means a bilayer can be formed. • They form a bilayer with the FA tails facing into each other, and the polar heads facing outwards and dissolving in the aqueous intra- and extracellular fluids. • The hydrophilic heads of the phospholipids can be used to hold at the surface of the cell surface membrane. • Their structure allows them to form glycolipids with carbohydrates which are important on the cell surface membrane for cell recognition. • They are ideal for forming cell surface membranes as they enable integration of other molecules into the ‘mosaic’ and help to regulate the movement of molecules in and out of the cell.

Answer 62

No. Fatty acids tails: 2 / 3 Presence of phosphate: yes / no Polar / non-polar: polar phosphate head / non-polar No,water molecules released when formed : 3 / 3 Function: Cell membrane components / energy storage

Answer 63

Cholesterol is an important component of the cell membrane and helps to regulate its fluidity: High levels of cholesterol in the membrane can lead to a decrease in fluidity and stability. Low levels of cholesterol can cause the membrane to become more fluid and lead to disruptions in cell function.

Answer 64

Has a 4 carbon ring structure with a hydroxyl (OH) group at one end Comes from the family of sterols

Answer 65

• Cholesterol is important in the formation and fluidity of cell surface membranes and in theproduction of certain hormones e.g.testosterone and oestrogen . Hormones (oestrogen and testosterone) are able to pass through cell membranes and interact with receptors inside the cell as they are based on cholesterol Cholesterol creates vitamin D in the skin in response to UV light (needed for the development of bones) Cholesterol is used in the liver to create bile which increase the rate of digestion of lipids by the enzyme lipase Forms a small, thin molecule that fits into a lipid bilayer giving strength and stability Cholesterol can insert into cell membranes by using its hydrophilic hydroxyl group to interact with the head groups of phospholipids. While the rest of it interacts with the hydrophobic fatty acids tails

Answer 66

The hydroxyl group is hydrophilic. However the rest of the molecule is hydrophobic. Therefore, the cholesterol can insert itself into the cell membrane. The hydrophilic hydroxyl group on the cholesterol molecule can interact with the heads of the phospholipids. While the rest of the cholesterol molecule can interact with the hydrophobic fatty acid tails. (Not soluble in water)

Answer 67

Low-density lipoproteins (LDL) High-density lipoproteins (HDL)

Answer 68

• Low density lipoproteins (LDL) carry cholesterol from the liver to the rest of the body • LDLs bind to receptors on cell surface membranes before being taken up by the cells where the cholesterol is involved in the synthesis and maintenance of cell membranes.

Answer 69

• Triglycerides (from fats in our diet) combine with cholesterol and proteins to form LDLs which transport the cholesterol to our body cells.

Answer 70

Excess LDL overload on these membrane receptors, results in high blood cholesterol levels, which may be deposited in the artery walls forming atheromas. Therefore it is desirable to maintain a higher HDL:LDL ratio in the blood. As HDLs reduce blood cholesterol deposition

Answer 71

HDLs are made when triglycerides (from fats in diet) combine with cholesterol and proteins.

Answer 72

High density lipoproteins (HDL) scavenge excess cholesterol in the body tissues and carry it back to the liver where it is broken down. • This lowers blood cholesterol levels, and helps to remove the fatty plaques of atherosclerosis.

Answer 73

High intake of certain types of fast will differently affect cholesterol levels in the blood: • Saturated fats increase LDL levels within the body, raising blood cholesterol levels • Trans fats increase LDL levels and decrease HDL levels within the body, significantly raising blood cholesterol levels • Unsaturated (cis) fats increase HDL levels within the body, lowering blood cholesterol levels

Answer 74

Saturated fats: studies have shown they increase LDL and HDL cholesterol, however increase in LDL cholesterol is greater. Monounsaturated fats:Help the removal of LDLs from the blood Polyunsaturated fats: Increase the activity of the LDL receptor sites so the LDLs are actively removed from the blood

Answer 75

Amino aids are formed from an amine group and a carboxyl group attached to a single carbon atom. The R group attached to the carbon is different for each of the 20 amino acids

Answer 76

Carbon,hydrogen, nitrogen and oxygen Some contain sulfur

Answer 77

Two amino acids can react together and form a chemical bond. This is known as a ** peptide bond **. A molecule of water is produced from this reaction (condensation reaction) The molecule formed is called a dipeptide as it contains two amino acids which are bonded together

Answer 78

If three or more amino acids bond together a polypeptide is formed (Consist of hundred of amino acids formed together)

Answer 79

A peptide bond is formed through a condensation reaction where water is produced. The peptide bond can be broken by adding a molecule of water (hydrolysis reaction) This reaction is carried out by protease enzymes in the digestive system

Answer 80

In order to be classed as a protein a polypeptide has to fold into a complex, 3-dimensional shape Once a polypeptide has folded into the correct shape it carries out its function e.g as an enzyme or hormone. It is then considered to be a protein molecule. Protein consist of several different polypeptides forming a large and complex molecule. It also contains other molecules to support its function (eg haemoglobin)

Answer 81

The primary structure is simply the specific order of amino acids in a polypeptide It helps to determine the final 3 dimensional shape of the protein molecule which is critical for its function

Answer 82

The primary structure for a polypeptide is determined by the DNA sequence of the gene which encodes the polypeptide

Answer 83

Within a polypeptide chain there are C=O groups and N-H groups The oxygen atoms in C=+O groups have a small negative charge and the hydrogen atoms in the N-H groups have a small positive charge. This means they attract to each other and a hydrogen bonds form between amino acids all along the polypeptide chain The polypeptide chain will twist and fold into shapes and scientists call this the secondary structure

Answer 84

Alpha-helix Beta-pleated sheet

Answer 85

The polypeptide chain is twisted into a helical shape held in place by hydrogen bonds

Answer 86

The polypeptide chain folds into a flatter, sheet-like structure. The hydrogen bonds between the amino acids hold the shape into place.

Answer 87

The type of secondary structure formed depends on the primary structure in that region

Answer 88

Many proteins have regions with alpha helices and regions with beta pleated sheets. Certain amino acid tend to be found in alpha helices and other in beta-pleated sheets

Answer 89

The regions of secondary structure determines how the tertiary structure continues folding forming the final tertiary structure

Answer 90

It is the overall 3-dimensional shape of a polypeptide chain

Answer 91

It is the overall 3-dimensional shape of a polypeptide chain It is critical for how a protein function e.g the active site of an enzyme depends on the protein forming a very specific tertiary structure If the tertiary structure of an enzyme is changed (e.g by heating) the shape of the active site changes. Thus the enzyme no longer function effectively (denatured)

Answer 92

It is critical for how a protein function e.g the active site of an enzyme depends on the protein forming a very specific tertiary structure If the tertiary structure of an enzyme is changed (e.g by heating) the shape of the active site changes. Thus the enzyme no longer function effectively (denatured)

Answer 93

The quaternary structure shows how the individual subunits are arranged to form a larger three dimensional structure It only applies to proteins with at least two subunits Some protein contain other non-protein molecules forming part of the structure. These are called prosthetic groups and they help the protein to carry out its role Protein with a prosthetic group are called conjugated proteins. They show the arrangement of subunits and the position of any prosthetic group

Answer 94

RBCs contains the prosthetic group haemoglobin which binds to oxygen

Answer 95

A polypeptide chain will have two amino acids with R groups containing a hydroxyl Due to the slight positive and negative changes present on the hydroxyl a hydrogen bond can form these two R groups and this contributes to the 3 dimensional shape of the polypeptide chain Hydrogen bonds are weak and are easily broken by high temperature or by pH changes

Answer 96

Several amino acids have uncharged R groups we call these non-polar amino acids which aren’t attracted to water (hydrophobic). These cluster work to exclude water molecules (hydrophobic interactions). These tend to be in the centre of proteins away from water molecules Hydrophilic amino acids tend to be found on the surface of proteins where they can interact with water molecules. Both hydrophobic and hydrophilic interactions are relatively weak bonds

Answer 97

Ionic bonding occurss between amino acids with charged R groups An amino acid will be a positively charged R group and the other will be a negatively charged R group These opposite charges attract each other and form an ionic bond. This holds different parts of the polypeptide chain together and contributes to protein structure Ionic bonds are broken by pH. This is why enzymes can denature under acidic or alkaline conditions

Answer 98

A polypeptide contains two molecules of an amino acid called cysteine. The R group of cysteine contains a sulfur atom. The sulfur atom in the two cysteine molecule form a covalent bond. This is called a disulfide bond. Disulfide bonds are relatively strong and are not broken by high temperatures or pH changes

Answer 99

They’ll be involved in tertiary structure

Answer 100

They’ll be involved in quaternary structure

Answer 101

The structure of a protein is critical to its function

Answer 102

Globular proteins fibrous proteins

Answer 103

They have an approximately spherical shape They are surrounded by hydrophilic amino acids There are hydrophobic amino acids deep in the centre of the protein away from water molecules

Answer 104

They are soluble in water - This is due to hydrophilic amino acids surrounding the surface. This means that hydrophilic R groups can interact with water molecules. Therefore, globular proteins are soluble in water Contains hydrophobic amino acids within the centre of the protein away from water molecules.

Answer 105

Each haem group contains a fe2+ ion where the oxygen binds. Thus one haemoglobin molecule can bind to four oxygen molecules. This supports the function of haemoglobin in the RBC as it role is to bind reversibly to oxygen in the lungs to release oxygen in the body tissue. Furthermore, as oxygen attaches to the haemoglobin, the quaternary structure of the protein changes slightly. This makes it easier for more oxygen to attach. Thus more oxygen traveling across the body to muscle tissue

Answer 106

Haemoglobin is a polypeptide with four polypeptide subunits. Two are called the alpha subunit and the other two are called the beta subunit . Each subunit contains a prosthetic group haem. Therefore, haemoglobin is a conjugated protein. Each haem group contains a fe2+ ion where the oxygen binds.

Answer 107

Insulin consist of two polypetide chains. The chains are linked by a disulfide bonds.

Answer 108

The hormones like insulin carry out their function by binding to specific receptor molecules. These receptor are proteins found on the cell membrane of target cells The shape of the insulin molecule mean that it fits perfectly within its receptor even slight changes to the shape of the molecule could prevent it from binding effectively . The shape of protein hormones such as insulin are critical for how they bind to receptor and carry out their effects. Insulin can support blood glucose concentration

Answer 109

Lysozyme consist of a single polypeptide chain. The chain folds to form a groove along the surface. This groove is called the active site. The shape of active site fits perfectly to substrate molecule in the bacterial cell wall.

Answer 110

Found in Saliva and tears Enzymes (lysozyme) can only react with a specific substrate molecule. This specificity is due to the structure of the enzyme. Lysozyme consist of a single polypeptide chain. The chain folds to form a groove along the surface (active site). The shape of active site fits perfectly to substrate molecule in the bacterial cell wall. As a result the lysozyme and the active site work together to catalyse the breakdown of a molecule in the bacterial cell wall. This helps defend the body against bacteria Surrounding the substrate are amino acids which work to hold the substrate in place. Lysozymes contain regions where amino acids catalyse reaction.

Answer 111

They play a structural role e.g bones, tendons or wall of blood vessels

Answer 112

Forms long, rope like molecules e.g collagen

Answer 113

Fibrous proteins are insoluble in water

Answer 114

Collagen is found in tendon, which connects muscle to bones and ligaments which connects bones to each other It is also found in skin

Answer 115

It is a strong molecule due to its structure. The polypeptide chains in collagen wrap tightly together to form a triple helix.

Answer 116

The polypeptide chains in collagen wrap tightly together to form a triple helix. In collagen polypeptides every third amino acid is glycine. The R group of glycerin is a hydrogen atom. Thus glycine has the smallest R group of any amino acid. This allows collagen polypeptides to wrap tightly around each other As it wraps around each other a large number of hydrogen bonds form between the polypeptide chains. This helps to stabilise the quaternary structure of the proteins. They are also joined to each other by strong crosslinks. A large number of these triple helical molecules join together to form large structures called microfibrils and fibrils. The molecules are staggered thus have no weak spots Cross linking between different triple helical molecules further strengthens collagen

Answer 117

It is found in hair, fingernails and the outer surface of skin

Answer 118

Keratin is extremely strong and insoluble in water

Answer 119

keratin consists of long stranded molecules with a high proportion of the amino acid cysteine. This is used to form disulfide bonds which are strong covalent bonds. Due to the high proportion of cysteine keratin molecules contains a large number of disulfide bonds which contributes to the strength of keratin molecules

Answer 120

The skin and walls of arteries

Answer 121

Elastin fibers stretch when blood passes through the artery and then recoil in between pulses, helping the artery to return to its original shape.

Answer 122

Elastin molecules are long strands, containing hydrophobic regions. These strands are cross linked to each other. The hydrophobic regions on different strands associated causing the elastin molecules to group together. However, when stretched the strands move apart but remain attached at the cross link. After stretching, the elastin molecules reassociate, springing back together. This makes elastin a very elastic molecule

Answer 123

We often carry out these test to determine which chemicals are present in different foods. However, these can be used for different purposes E.g: test plants for starch to see if they have carried out photosynthesis. Or Test urine for protein to diagnose kidney problems or for glucose to check diabetes.

Answer 124

Safety googles should be worn as potentially harmful chemicals are being used. To avoid contamination. Spills need to be cleaned with distilled water.

Answer 125

We have to grind our food with a small amount of distilled water in a mortar and pestle Once we have turned the food into a paste, we then add more distilled water and we stir the mixture (the mixture is going to be full of solid food particles and these could make the test results difficult to see) Therefore, we need to filter our mixture to remove these solid food particles. We carry out out test on the filtrate (food solutions which passes the filter)

Answer 126

We place 3cm^3 of our food tube into a solution into a test tube We then add 1cm^3 of a solution containing iodine adn potassium iodide. In the presence of starch, the iodine solution turns a blue-black colour. In the absence of starch the solution remain orange

Answer 127

We place 3cm^3 of our food tube into a solution into a test tube We then add 3cm^3 of dilute sodium hydroxide solution and mix Next we add ten drops of dilute copper (II) sulfate solution and mix again If protein is present then the solution turns purple or lilac. If protein is absent then the solution will remain blue. Important details: The sodium hydroxide solution and the copper (II) sulfate are premixed. This is called a blurted solution. This test detected peptide bonds therefore you get a positive results either proteins. However, a solution of amino acids would give a negative result as these do not contain any.

Answer 128

In this test the food mixture must not be filtered. That’s because the lipids can stick to the filter paper. Therefore, we can leave to food mixture for a while to allow the particles to settle. We add 3cm^3 of our food solution into a test tube We then add 3cm^3 of ethanol and water. We then shake the solution If lipids are present, then a white cloudy emulsion will form. If the solution stays clear, then lipids are not present . Be aware as the ethanol is flammable therefore the experiment must not be carried near any opens flames.

Answer 129

Reducing sugars can donate an electron to another molecule

Answer 130

All monosaccharides are reducing sugars Some disaccharides are reducing sugars (maltose , lactose)

Answer 131

* safety goggles should always be worn We should first grind the food with a mortar and pestle in distilled water. We should then filter away the solid food particles. We then place 3cm^3 of our food solution into a boiling tube and add 3cm^3 of Benedict’s solution. ( contains Cu2+ make the solution blue) We then place the boiling tube into a beaker of boiling water and leave it for five minutes. If the solution remains blue then there is no reducing sugar present . However, if reducing sugar is present then this adds an electron to the copper 2+ ion. This form a copper 1+ ion forming a red precipitate. If there is a very small amount of reducing sugar then only a very small amount of red precipitate forms. This causes the Benedict’ solution to turn green. If more reducing sugar is present then the colour yellow. A higher level of reducing sugar produces an orange colour. If a lot of reducing sugar is present then we see a brick red colour.

Answer 132

It only gives us a very appropriate idea of the amount of reducing sugar. This is because the Benedict’s test only shows a narrow range of colour changes and all humans perceive colour slightly differently - semi-quantitative. Goggles should always be worn during the test

Answer 133

First we should take a small amount of our unknown solution and carry out the Benedict’s test to check if it contains non-reducing sugars. ( we need to note down any colour changes and which takes place) We take a fresh boiling tube and add 3cm^3 of our unknown solution. Next we add 3cm^3 of dilute hydrochloric acid and gently boil the solution in the water bath for five minutes, If a non-reducing sugar is present then the acid hydrolyses the glycosidic bonds releasing the monosaccharides. Next we add 3cm^3 of a dilute alkali such as sodium hydroxide solution. We then use the pH paper to check the our solution is alkaline. That is because the Benedict’s test cannot work under acidic conditions. Finally we add 3cm^3 of Benedict’s solution and then hear it in the boiling water for five minutes. (Then note down any colour change)

Answer 134

We cannot test non-reducing sugars directly. We need to break the glycosidic bond releasing the monosaccharides. Because all monosaccharides reducing sugars we can test for them using the Benedict’s solution

Answer 135

Blue= negative ( reducing sugar not present) Orange= positive (non-reducing sugar present)

Answer 136

Green= positive ( very small amount of reducing sugar not present) Red = positive (non-reducing sugar present)

Answer 137

Red- positive (large amount of reducing sugar) Second Benedict’s solution test (not possible)- even if non-reducing sugar was present we would not be able to see a colour change beyond red. ( only can test for non-reducing sugar when there is either no reducing sugar present or a small amount)

Answer 138

Benedict’s reagent contains Cu^2= ions which make the solution blue When reducing in sugars such as glucose donate an electron it reduces the Cu^2+ ion to the Cu^+ ion forming a red precipitate. The red precipitate and the blue of the Benedict’s solution leads to a colour change. If the solution was left for several hours then the red precipitate would settle at the bottom. (Allows us to see the blue Benedict’s solution at the top) The Benedict’s solution will be less blue than it was before the test. That’s because some of the Cu2+ ions have reacted and are no longer in the solution ( a greater concentration of glucose would result in the solution to appear less blue at the end as there will be fewer cu^+ ions remaining in the solution0

Answer 139

Small changes to the blueness of the solution in the Benedict’ test are too subtle to be able to detect by the eye. Therefore, we quantify the blueness of the solution in by using a machine called a colorimeter.

Answer 140

Before we use a colorimeter, we first need to filter off the red precipitate leaving just the Blue Benedict’s solution If we shine white light than all colour will be absorbed apart from blue. That’s because Benedict’s solution allows blue light to pass through therefore is why it has a blue colour. This absorption of light can be used to quantify the levels of blueness- as it transmits through teh solution as is detected by a photoelectric cell (form of light detector) However, red light is the best as Benedict’s solution allows blue absorbs red most out of all the different colours as it is on the opposite end of the spectrum then blue. (Red is the complementary colour to blue) We can place a red filter in front of our lamp. This only allows red to pass through.

Answer 141

The sample could have been reacted with a very large amount of glucose. Therefore, has a small amount of Cu^+ ions. Little red light is absorbed by the solution therefore a lot is transmitted through and detected by the photoelectric cell ( light detector) The less red light is absorbed the greater the amount of glucose that must have reacted with out Benedict’s solution.

Answer 142

In order to accurately determine the concentration of glucose in a sample.

Answer 143

We need to prepare a whole range of glucose concentrations. We then react each solution with Benedict’s solution and filter off the red precipitate. We then use the colorimeter to see how much red light is absorbed by each solution. We carry out the same procedure with our unknown solution. By comparing our unknown solution with our known solution we can determine the concentration of glucose in our unknown solution. This is called a calibration curve.

Answer 144

We get six test tubes then start with a known concentration ( stock solution) of glucose (5mmol /dm^3) and create a range of dilutions from that. Using a syringe we use 5cm^3 of our stock solution into test tube This test tube contains a glucose solution with a concentration of 5mmol / dm^3. In test tube 2 we add 4cm^3 of our stock solution plus 1 cm^3 of distilled water. This contains a glucose solution of 4mmol / dm^3 In test tube 3 we add 3cm^3 of our stock solution plus 2 cm^3 of distilled water. This contains a glucose solution of 3mmol / dm^3 In test tube 4 we add 2cm^3 of our stock solution plus 3 cm^3 of distilled water. This contains a glucose solution of 2mmol / dm^3 In test tube 5 we add 1cm^3 of our stock solution plus 2 cm^3 of distilled water. This contains a glucose solution of 1mmol / dm^3 In test tube 6 we add 5cm^3 of our stock solution plus 6cm^3 of distilled water. This contains no glucose at all Next we set up a test tube containing 5cm^3 of our unknown concentration of glucose. At this stage we add 5cm63 of Benedict’s solution to each test tube and mix them thoroughly. We then place all the test tubes in a boiling water bath for five minutes. During this time the Benedict’s solution will react with the glucose producing a red precipitate. Finally, we filter each solution into a fresh test tube. This removes the precipitate, leaving the remaining Benedicts solution (a centrifuge can be used instead of a filer funnel)

Answer 145

Some colorimeters have test tube which can be directly placed inside. However, in other colorimeters we need to transfer all your solutions into small plastic containers called cuvettes Curettes have two clear transparent sides and two sides which are translucent . We always place the cuvettes into the colorimeter so that the light passes through the transparent sides. First we should set the colorimeter on the red filter. That’s because red is the complementary colour to blue. (Red will be the colour most absorbed by the blue solution) We then set the colorimeter to measure absorption. In other words to see how much red light is absorbed by the solution. We then place a cuvettes contains just distilled water into the colorimeter and set the colorimeter to zero ( we telling the colorimeter to consider water to absorb zero red light) We then use the colorimeter to read the absorbances of all our solutions. We plot this information on a dilution serve on a graph. We use the calibration curve to determine the concentration of glucose in our unknown sample If the absorbance of the unknown sample is too great to read off the calibration curve then you need to dilute the solution and read the absorbance again. ( take the dilution factor into account when determining the concentration of glucose)

Answer 146

Glucose is used as the primary energy source in animals and plants.

Answer 147

It is soluble - The hydroxyl groups can form hydrogen bonds with water, so it can be transported around organisms. Its bonds store lots of energy - This energy is released when the bonds are broken.

Answer 148

Calcium ions: Ca^2+ Sodium ions: Na^+ Potassium ions: K^+ Hydrogen ions: H^+ Ammonium ions: NH4^+ Nitrate: NO3^- Hydrogen carbonate: HCO3^- Chloride: Cl^- Phosphate: PO4^3- Hydroxide: OH^-

Answer 149

Chromatography is a technique that can be used to separate a mixture into its individual components This method can be used to separate mixtures containing proteins, carbohydrates, vitamins and nucleic acids

Answer 150

Chromatography relies on differences in the solubility of the different chemicals (called ‘solutes’) within a mixture All chromatography techniques use two phases: The mobile phase The stationary phase The components in the mixture separate as the mobile phase travels over the stationary phase Differences in the solubility of each component in the mobile phase affects how far each component can travel Those components with higher solubility will travel further than the others This is because they spend more time in the mobile phase and are thus carried further up the paper than the less soluble components

Answer 151

A spot of the mixture (that you want to separate) is placed on chromatography paper and left to dry The chromatography paper is then suspended in a solvent As the solvent travels up through the chromatography paper, the different components within the mixture begin to move up the paper at different speeds. Larger molecules move slower than smaller ones This causes the original mixture to separate out into different spots or bands on the chromatography paper This produces what is known as a chromatogram

Answer 152

Paper chromatography can be used to separate a mixture of monosaccharides. Mixtures containing coloured molecules, such as ink or chlorophyll, do not have to be stained as they are already coloured Mixtures of colourless molecules, such as a mixture of monosaccharides, have to be stained first. A spot of the stained monosaccharide sample mixture is placed on a line at the bottom of the chromatography paper Spots of known standard solutions of different monosaccharides are then placed on the line beside the sample spot The chromatography paper is then suspended in a solvent.As the solvent travels up through the chromatography paper, the different monosaccharides within the mixture separate out at different distances from the line The unknown monosaccharides can then be identified by comparing and matching them with the chromatograms of the known standard solutions of different monosaccharides If a spot from the monosaccharide sample mixture is at the same distance from the line as a spot from one of the known standard solutions, then the mixture must contain this monosaccharides

Answer 153

Paper chromatography can be used to separate a mixture of amino acids. A spot of the unknown amino acid sample mixture is placed on a line at the bottom of the chromatography paper Spots of known standard solutions of different amino acids are then placed on the line beside the unknown sample spot The chromatography paper is then suspended in a solvent. Each amino acid will be more or less soluble in the mobile phase than others and will therefore separate out of the mixture travelling with the solvent at different times/distances from the line, depending on their: charge and size The unknown amino acid(s) can then be identified by comparing and matching them with the chromatograms of the known standard solutions of different amino acids.If a spot from the amino acid sample mixture is at the same distance from the line as a spot from one the known standard solutions, then the mixture must contain this amino acid In order to view the spots from the different amino acids, it may be necessary to first dry the chromatography paper and then spray it with ninhydrin solution (this chemical reacts with amino acids, producing an easily visible blue-violet colour)

Answer 154

Distance moved by solute ————————————- = Rf Distance moved by solvent