BIOLOGY A - (3.1.1 - 3.2) BIOLOGICAL MOLECULES

MONOMERS AND POLYMERS (3.1.1)

MONOMERS AND POLYMERS (3.1.1)

How to calculate the number of water molecules released in a polymer

(n-1) where n is the number of monosaccharides

Define monomers

Small, repeating subunits that form larger, complex polymers (monosaccharides)

Define Polymers

Molecules made a large number of monomers joined together

What are the 3 monomers we need to know about

Monosaccharides

Amino acids

Nucleotides

What are the 5 polymers we need to know

Starch

Cellulose

Glycogen

Protein

DNA and RNA

What happens during a condensation reaction

One water molecule is eliminated per chemical bond formed as two monomers are joined together. (Anabolic reaction)

What is the name of the bond formed in a condensation reaction between two monosaccharides

A glycosidic bond (One oxygen atom holding the two saccharides together)

What is hydrolysis

Opposite of a condensation reaction and is a chemical reaction that uses water to break a compound into two or more smaller molecules

Define carbohydrates

Molecules that only consist of carbon, hydrogen and oxygen which are large chains of sugar units called saccharides

Define monosaccharides

The simplest forms of carbohydrates, composed of a single sugar unit

Define isomers

Molecules with the same chemical formula but with a different strucuture

What is the formula for glucose

C₆ H₁₂ O₆

Where are the carbons located on a glucose molecule

In the corners of the hexagon

Carbon one is the middle corner on the right and we count clockwise from there. The last carbon atom is not in the final corner but sticks out from the 5th carbon atom

Name the two isomers of glucose and their difference

Alpha (H on top) and Beta (H on bottom) glucose

What does fructose look like

50p coin with oxygen atom at the centre

Name 3 common monosaccharides

Glucose

Fructose

Galactose

Name 3 qualities of these monosaccharides

Sweet tasting

Soluble

Crystalline with general formula (CH₂O)n where “n” can carry any number from 3 - 7

Define disaccharide

Two monosaccharides joined together in a condensation reaction

What is maltose formed by

Condensation of two alpha glucose molecules which are held together by glycosidic bond

What is sucrose formed by

Condensation of alpha glucose and fructose

What is lactose formed by

Formed by condensation of alpha glucose and galactose

What is cellulose formed by

Condensation of two beta glucose molecules (Only thing in the world made from beta glucose)

What are sucrose and lactose both

Disaccharides / Simple sugars

What is cellulose

Polysaccharide / Complex sugar

Give of starch the: Bonding, Function, Location, Structure

1-4 GB in amylose and 1-4/1-6 GB in amylopectin

Store of glucose

Plant cells

Made of amylose (straight chained helix) and amylopectin (branched molecule)

How does the structure of starch lead to its function

Helix is compact which allows lots of glucose to be stored in small place

Branches structure increases surface area for rapid hydrolysis back to glucose (allows glucose to be accessed)

Insoluble - Wont affect water potential

Give of cellulose the: Bonding, function, location and structure

1-4 GB

Structural strength for cell wall

Plants - Cell wall

Long straight chains held in parallel by many hydrogen bonds to form fibrils

How does the structure of cellulose lead to its function

Many hydrogen bonds provide collective strength

Insoluble - Wont affect water potential

Give of glycogen the: Bonding, Function, Location and structure

1-4/1-6 GB

Store of glucose

Mammalian muscle and liver cells

Highly branched molecule

How does the structure of glycogen link to its function

Branched structure increases surface area for hydrolysis back into glucose

Insoluble so won’t affect the water potential

What is the test for reducing sugars

Add benedict’s reagent AND heat

A positive test is when solution goes from blue to green, yellow, orange or brick red

What colour does glucose and Benedict’s solution go

Brick red/Orange

What colour does sucrose and Benedict’s go

Blue

Is glucose reducing or non reducing

Glucose is reducing because it gives the Cu²⁺ an electron which makes it Cu⁺ and “reduces” it. This causes the colour of the copper solution to change from blue to brick red/orange

Is sucrose reducing or non reducing

Sucrose is a non reducing sugar because it gives no electrons to the Cu²⁺ So₄^2- solution

What is the test for non reducing sugars

Following negative benedict’s test where reagent remained blue

Add acid and boil (acid hydrolysis)

Cool the solution then add alkali to neutralise

Add benedict’s reagent and heat

A positive test + Solution goes from blue to orange/brick red

Why does solution not go green or yellow after non reducing test

You have split up the sucrose from disaccharide into the monosaccharides (fructose and glucose) and have doubled the sugar concentration which means it will be very high

Are monosaccharides reducing or non reducing sugars

Reducing sugars (ie glucose)

Are disaccharides reducing or non reducing sugars?

Non reducing sugars (ie sucrose)

Are lipids hydrophobic or hydrophilic

Lipids are hydrophobic

Are lipids soluble in water / ethanol

Water = NO (Float to top because of hydrophobia)

Ethanol = YES

Why do lipids not dissolve in water

To dissolve in water you need a charge and fats do not have a charge (non-polar) therefore they do not dissolve in water

What happens during a condensation reaction

During condensation, an enzyme is added to a solution which causes one monomer gives up its hydroxyl group and the other gives up its hydrogen group which makes a H₂ O molecule. The remaining bond holds the two monomers together

Where is glycogen stored and why is it highly branched

Mammalian liver and muscles

Not many places where it can be stored since it is stored as granules so it must be highly branched to fit as much as possible in the limited space available

What is cellulose a polymer of

Beta glucose

Why does cellulose have a HIGH tensile strength

Its long chains of glucose are held together by numerous hydrogen bonds, forming strong, parallel fibres called microfibrils. These microfibrils bundle together into a larger structure called a macrofibril

What is the name of the cell membrane

The cell SURFACE membrane

Why are amylose, glycogen and amylopectin all insoluble

So that there is no effect on the water potential/osmosis (Otherwise they would dissolve in the cell cytoplasm which would reduce the cells water potential and cause water to rush in)

No water goes in or out of cells

What kind of polymer is cellulose

Straight chained

How are the beta glucose monomers arranged in cellulose

They are inverted and form microfibrils (linear chains of B glucose monomers)

What keeps the monomers of beta glucose together then

Electrostatic forces between the monomers

What are proteins polymers of

Amino acids

How are amino acids held together

Amino acids are held together by peptide bonds which are formed in condensation reactions. The peptide bonds form between the hydroxyl from the carboxyl group of one amino acid and the amine group of another

LIPIDS (3.1.3)

LIPIDS (3.1.3)

What are lipids

Fats and oils

What are fats

Solid at room temperature (eg butter)

What are oils

Liquid at room temperature (eg oil)

What is the test for lipids

Mix/Shake the sample in ethanol

Add distilled water

Positive test observation = Cloudy white emulsion

What is a triglyceride made of

3 Fatty acids + Glycerol molecule

What does glycerol give up in a condensation reaction and what does the fatty acid give up

Glycerol gives up hydrogen from hydroxyl group

Fatty acid gives up hydroxyl group from its carboxyl group

What is the ester bond made of

An oxygen joining two carbon atoms with a carbon - oxgyen double bond on the fatty acid side

What functional group do fatty acids have

Carboxyl functional group

What type of bond is the bond between the glycerol molecule and the fatty acids

An ester bond

Why is the reaction of glycerol and a fatty acid not a polymer

Because the repeating units are not regular (there are multiple combinations of fatty acids)

Name the 3 types of fatty acids and their properties

Saturated fatty acid (only single bonds between carbons)

Mono saturated fatty acid (one C=C double bond)

Poly-unsaturated fatty acid (two or more C=C double bonds)

What are good fats

Polyunsaturated fats

Monounsaturated fats

What are some bad fats

Saturated fatty acids (Bad Cholesterol)

Trans fats

What is a phospholipid

Glycerol molecule + Phosphate group + 2 fatty acids

What is the phosphate group and why does this make it hydrophilic

PO₄ ^{3 -}

The phosphate group has a charge which attracts it to the water in an attempt to dissolve

What is a phospholipid bi - layer

A layer formed by the phosphate ‘heads’ which are hydrophilic as they are charged and fatty acids hanging out like ‘tails’ as they are hydrophobic

Why does this arrangement work

It allows the charged phosphate heads to be exposed to the water in the cytoplasm and reduces the non polar fatty acids contact with water

Is there water in the cytoplasm

YES

Why is there cholesterol in the phospholipid bi layer

To regulate the membrane fluidity - preventing it becoming too rigid or soft

Also makes the membrane impermeable to small molecules which keeps cells internal conditions normal

How does glucose get through the phospholipid bilayer

Carrier proteins transport it

(In muscle cells at rest there are less carrier proteins visible as the muscle requires less glucose)

What is the role of channel proteins in the phospholipid bi layer

These form hydrophilic pores which allow specific ions to pass through the membrane

PROTEINS (3.1.4.1)

PROTEINS (3.1.4.1)

What four elements are amino acids made from

Carbon, hydrogen, nitrogen and oxygen

What is the amine group formula

NH₂ 

What is the general structure of an amino acid

Central carbon - C

Amine group - NH₂

Carboxyl group - COOH

R group - R (20 options)

What is the carboxyl functional group formula

COOH

What is the term for two amino acids joined together by a peptide bond

A dipeptide

When does this dipeptide chain become a protein

When it folds

How are folded amino acid chains joined together

Via bonds

What are the 4 bonds that hold these dipeptide chains together

Hydrogen bonds (oxygen attracted to hydrogen)

Ionic Bonds (Electrostatic forces between negatively and positively charged R - groups)

Hydrophilic/Phobic interactions

Disulphide bonds (Proper covalent bonds)

What types of proteins are made from the strong disulphide bond

Strength proteins such as collagen and keratin

What is an INTRA disulphide bond

Bond formed within one polypeptide

What is an INTER disulphide bond

Bond between two different chains

What is the primary structure of a protein

The order and sequence of amino acids (only bond at this point is peptide bonds)

What is the secondary structure of a protein

Protein starts to fold into ALPHA helix (very coiled) or BETA pleated sheet (stretched coil)

Only bond present at this point is a hydrogen bond and peptide bonds between amino acids

What is the tertiary structure of a protein

The further folding of the secondary structure that makes the 3D shape of the polypeptide but with 1 polypeptide chain

All types of bonds found in this structure

Quaternary structure

Two or more polypeptide chains wound together

Give 3 examples of quaternary proteins

Haemoglobin

Antibodies

Keratin/Collagen

Why is the primary structure so important

If even one amino acid in the sequence is different, it will cause the ionic/hydrogen/disulphide bonds to form in a different location resulting in a different tertiary (3D) structure

What is the impact of the tertiary structure changing on active sites

This will cause the shape of the active site to change which will mean it is no longer complimentary to the substrate which means it can no longer form (ESCs) and catalyse the reaction

What is the impact of the tertiary structure changing on carrier proteins

Carrier proteins will have different shaped binding site (molecules such as glucose no longer complimentary and so cannot be transported across the membranes)

What is the test for proteins

Add sodium hydroxide and copper sulphate to sample

Shake well

If proteins are present, the solution will go from blue to purple

What makes strength proteins such as keratin and collagen (contained in hair and nails) so strong

Because it has disulphide bridges which are strong covalent bonds

ENZYMES (3.1.4.2)

ENZYMES (3.1.4.2)

What are enzymes

Tertiary structure proteins that catalyse reactions by lowering the activation energy