monomers, polymers, carbohydrates and lipids

what four things do all living things primarily consist of

carbohydrates, lipids, proteins, nucleic acids. These biological molecules are organic, so they contain the element carbon

what is hydrogen bonding

Hydrogen bonds are weak attractions that occur between a hydrogen atom covalently bonded to a highly electronegative atom (like oxygen or nitrogen) and another electronegative atom.

define monomers 

Smaller units that combine to make a large molecule (polymer). 

define polymers 

molecules made from a large number of monomers joined together 

give 3 examples of monomers

monosaccharides, amino acids, nucleotides

define condensation reaction

A condensation reaction joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water.

what is the monomer and polymer of proteins, carbohydrates and nucleic acids

carbohydrates monomer- monosaccharides, polymer- polysaccharides

proteins monomer- amino acids, polymer- polypeptides 

nucleic acids monomer- nucleotides, polymer- polynucleotides 

define hydrolysis reaction

A hydrolysis reaction breaks a chemical bond between two molecules and involves the use of a water molecule

what are larger carbohydrates made of (polysaccharides)

their monomer is monosaccharides

name three common monosaccharides and give monosacharide function and number of subunits 

glucose, galactose and fructose

• main function is energy source

• one sub unit (monomer)

what type of bond is formed when two monosaccharides join in a condensation reaction 

glycosidic bond 

how are disaccharides formed? name the three reactions. give main function and number of sub units 

Disaccharides are formed by the condensation of two monosaccharides- pair

• glucose + glucose = maltose

• glucose + fructose = sucrose

• glucose + galactose = lactose
  

• two sub units (dimer)

• form of transport 

draw the structures of the two isomers of glucose- a-glucose and b-glucose

define isomer 

molecules which have the same molecular formula but a different arrangement of atoms in space.

how are polysaccharides formed and give function and number of sub units. what properties make them useful in cells

many monosaccharides join in a condensation reaction 

• many (polymer )

• energy storage form 

• large and insoluble- good as doesnt interfere with osmosis and water potential in the cell

what is a hexose sugar and give an example

contains 6 carbons eg glucose

name 3 polysaccharides and function

glucose, startch , cellulose

• startch and glycogen are large energy storage molecules which cannot leave cells

• cellulose gives strength in the cell wall for plant and agal cells

how is cellulose fomed

condensation of b-glucose molecules

how is startch anf glycogen formed

condensation reactions between a - glucose molecules

what are monosaccharides

sweet tasting, soluble substances that have the genera formula (CH*2O)n

define polysaccharide- size, type, composed of, what bonding, what reaction

• Polysaccharides are large, complex carbohydrates composed of many repeated, monosaccharides joined by glycosidic bonds through condensation reactions​.

what property of polysaccharides make them suitable for storage

they are insoluble

describe glycogen- it is a storage molecule in ********, what are they made uo of, what is their structure, 4 factors that made them useful (branching, size, compactness, and solubility)

• storage molecule in animals

• they are made up of many a-glucose monomers

• highly branched structure

• more highly branched than starch- enzymes can easily hydrolyse the glycosidic bonds to rapidly release glucose

• large- cannot diffuse out of cells

• compact- a lot of glucose can be stored in a small space

• insoluble- It does not affect the water potential of cells, and so water does not enter cells by osmosis.

differences between monosaccharides and polysaccharides

• polysaccharides- 3+ sugar unit, glycosidic bond present, condensation reaction present, not sweet. examples are glycogen and starch

• monosacharides- single sugar unit, no glycosidic bond present, no condensation reaction present. examples are glucose, fructose, galactose

what is starch used for 

storing excess glucose in plants - can be hydrolysed back inot glucose when plants require energy

name the two forms starch exists in

amylose and amylopectin

describe amylose and amylopectin and how their structure is helpful for starch

amylopectin is branched with 1,4 and1,6 glycosidic bonds, allowing rapid hydrolysis by enzymes to release glucose for respiration

amylose is helical, unbranched structure with 1.4 glycosidic bonds making it compact. This means lots can be stored in a small space 

name four properties of starch

• Insoluble, preventing osmotic effects in plant cells​ as it does not affect the water potential.

• Large molecule meaning it cannot diffuse out of cells.

• Insoluble, preventing osmotic effects in plant cells​ as it does not affect the water potential.

• Large molecule meaning it cannot diffuse out of cells.

describe the structure of cellulose (what kind of chains, what are the chains held by, micro**** s are joined together to make macro*****s)

made up of many b(beta)- glucose molecules

• it is a long, straight, unbranched chains with 1,4 glycosidic bonds 

• the straight chains are held together by many hydrogen bonds to form microfibrils.

• Microfibrils are joined together to make macrofibrils.

• Many hydrogen bonds help give structural strength to cellulose and plant cell walls, preventing plant cells from bursting under osmotic pressure​.

if two beta- glucose molecules line up next to eachother. the hydroxyl groups on carbon 1 and carbon 4 are too far apart from eachother to react. For the formation of cellulose, how do they beta - glucose molecules join? and what does this allow to form between the individual chains

To fix this, every other beta-glucose molecule is inverted by 180° (flipped upside down). This brings the hydroxyl groups (OH) close enough together to react. The alternating inversion of the beta glucose molecules also allows for hydrogen bonds to form between individual chains. Although each hydrogen bond itself is relatively weak, the huge number of these bonds provides great strength to cellulose as a whole.

how is cellulose adapted for it’s role (structure of chains. bonding, *******s)

1. Long, straight, and unbranched chains - These provide rigidity to the cell wall.

2. Hydrogen bonds - These cross link the chains to add collective tensile strength.

3. Microfibrils - These provide additional strength.

describe an explain how the structue and properties of polysaccharides make them useful as energy storage molecules in animals and plants 

• Polymers of glucose that can be used for respiration 

• large so insoluble so doesn’t affect the water potential

• amylose is coiled- so its compact so it doesnt take up too much space and more can be stored in a smaller area 

• glycogen is branched, it’s able to be hydrolysed rapidly by enzymes to release glucose 

• 1,4 glycosidic bonds - so they are easy to break down

name which of the 3 polysaccharides arefound in animals and which are found in plants

ONLY GLYCOGEN in animals, starch and cellulose in plants

which of the two polysaccharides contains a-glucose

startch and glycogen- cellulose is made up of beta glucose

true or false- stach, glycogen and cellulose are all structural molecules 

false 

only cellulose

true or false- starch, glycogen and celluloseare all storage molecules

false only starch and glycogen are. Cellulose is not

which of S, G, C has branched chains

statch and glycogen

which of S , G , C is tightly coiled

starch

describe the iodine test for starch

1. Place 2 cm³ of your food sample into a test tube.

2. Add a couple of drops of iodine solution and shake.

3. If starch is present, the solution will turn from orange to blue-black.

4. if not, it will stay orange

what is a reducing sugar 

• Reducing sugars include all monosaccharides and some disaccharides such as maltose and lactose.

• A sugar that can donate electrons to another chemical.

what are non- reducing sugars

Non-reducing sugars include some disaccharides such as sucrose and all polysaccharides

describethe test for a reducing sugar

1. Place 2 cm³ of your food sample into a test tube.

2. Add an equal volume of Benedict's reagent.

3. Heat the mixture in a gently boiling water bath for 5 minutes at 80 degrees

4. If a reducing sugar is present, the mixture will change from a blue solution to a brick red precipitate.

what is the spectrum of colours that indicate concentration of sugars from the benedicts test for reducing sugars 

• Blue - This indicates no reducing sugar is present.

• Green - This indicates a low concentration.

• Orange - This indicates a medium concentration.

• Brick-red - This indicates a high concentration.

name two more accurate methods that determine the concentration of reducing sugars

• Use a colorimeter to measure the absorbance of each solution.

• Filter the solution and weigh the precipitate.

what result will non-reducing sugars give for the bendicts reagent

they will give a negative result (blue solution)

Why do lipids form an emulsion in the emulsion test?

Lipids are insoluble in water but soluble in ethanol. When mixed with water, lipid droplets disperse, forming a white emulsion​

benedicts test is considered semi-quantative. Why?

it is an approx indication and is subjective

describe the test for non-reducing sugars

1. Add dilute hydrochloric acid (HCl) and heat to hydrolyse glycosidic bonds. Heat the solution in a water bath gently for 5 mins

2. Neutralise with sodium hydrogen carbonate (NaHCO₃) which is alkaline..

3. Repeat the Benedict’s test.

4. Positive result: Colour change from blue → brick red​.

describe the test for lipids

1. Add ethanol to the sample and shake well.

2. Pour the mixture into a test tube containing water.

3. Positive result: A white, milky emulsion forms​.

Describe how a student could carry out a chemical test for reducing sugar and suggest how he could estimate the amount of reducing sugar in the sample (the student did not have a colourimeter). (5 marks)

• Add Benedict’s reagent

• Heat / boil 

• Forms precipitate / colour change from blue to, green / yellow / orange / brown / (brick) red;

Concentration estimated from EITHER 

• Observe degree of colour change

• Compare colour with known concentration solutions;

OR

• Filter and weigh the precipitate

• Greater mass/ weight = more reducing sugar present

what are lipids

Lipids are non-polar, hydrophobic molecules made primarily of carbon, hydrogen, and oxygen

when are lipids soluble/insoluble

• They are insoluble in water but soluble in organic solvents such as alcohols​.

are lipids polymers? why/ why not

Lipids are not made up of long chains of monomers, meaning they are not considered as polymers.

name two groups of lipids

triglyceride and phospholipid

what are most lipids made up of

fatty acids comined with an alcohol(usually glycerol)

draw and label the groups in a fatty acid

the R group can be unsaturated or saturated

describe a saturated fatty acid (+ describe why they are usually solid at room temp)

• These have hydrocarbon chains that are 'saturated' with hydrogen, meaning all carbon atoms are bonded to the maximum number of hydrogen atoms.

• The hydrocarbon chain has no carbon-carbon double bonds. 

• Lipids that contain saturated fatty acids have higher melting points and so are usually solid at room temperature (fats)- this is because there are mo double bonds to cause a kink in the chain. Saturated fatty acids have stronger intermolecular forces because they are more compact 

draw a saturated fatty acid

describe a unsaturated fatty acid (+ describe why they are usually liquid at room temp)

• These have hydrocarbon chains that do not contain the maximum number of hydrogen atoms bonded to the carbon atoms.

• The hydrocarbon chain has at least one carbon-carbon double bond, which causes the chain to kink - less compact and weak intermolecular forces

• Lipids that contain unsaturated fatty acids have lower melting points and so are usually liquid at room temperature (oils).

draw a unsaturated fatty acid

describe some roles of lipids

1. Energy supply - Lipids can be oxidised to provide energy to cells.

2. Structural components - Phospholipids are used in cell membranes.

3. Waterproofing - Insoluble lipids are used to form water-resistant barriers.

4. Insulation - Lipids can help retain heat or act as electrical insulators.

5. Protection - Delicate organs are surrounded by a layer of fat.

what is a triglyceride

A triglyceride is a type of lipid used as a store of energy in animals, plants, and some bacteria.

draw a triglyceride

describe the structure of a triglyceride

A triglyceride consists of a glycerol backbone attached to three fatty acid tails. Each fatty acid tail contains a hydrocarbon chain (R) which can vary in length and may be saturated or unsaturated.

how are triglycerides formed 

• Triglycerides are formed by the condensation of one glycerol molecule and three fatty acid molecules.- which can be saturated or unsaturated 

• The bond formed between glycerol and each fatty acid is called an ester bond.

• Reaction type: Condensation reaction (water is removed)​. 

what bond forms between glycerol and a fatty acid in a condensation reaction

ester bond

describe some features that allow the triglycerides to store energy efficiently

1. Long hydrocarbon tails - Their many carbon-hydrogen bonds can be broken to release energy.

2. Low mass to energy ratio - Lots of energy can be stored in a small volume.

3. Insoluble - They do not affect the water potential of cells as they are large and non-polar.

4. High ratio of hydrogen to oxygen atoms - Triglycerides will release water when oxidised.

in the condensation reaction between a glycerol and 3 fatty acids to form a triglycerid, where does the ester bond form? what happnes in the hydrolysis of this?

• The hydroxyl groups (OH) on the glycerol and on the three fatty acids react together to release three water molecules (H₂O).

• This results in three ester bonds between the glycerol and the fatty acids.

• The addition of three water molecules (H₂O) breaks the ester bonds.

• This separates the glycerol and the fatty acids.

how many numbers of fatty acid tails does a triglyceride have? how many for a phospholipid?

triglyceride- 3

phospholipid- 2

is a triglyceride and / or a phospholipid polar?

no, only phospholipid is

state the functional difference between a triglyceride and a phospholipid

triglycerides are a energy store, phospholipid is a structural component of a membrane 

what is a phospholipid