Biological Molecules

What do carbohydrates contain?

Carbon, Hydrogen and oxygen.
They are 'hydrated carbon' meaning for every carbon there are two hydrogen atoms and one oxygen atom.

What is the function of carbohydrates?

They are three-fold. They act as a source of energy ( glucose) , a store of energy (starch and glycogen) and as structural units (cellulose)

What are the three main groups of carbohydrates?

Monosaccharides , disaccharides and polysaccharides.

What are monosaccharides?

They are the simplest carbohydrates, they are a source of energy. They are sugars.

Where are monosaccharides soluble?

Monosaccharides are soluble in water, and are insoluble non-polar solvents.

What is the chemical arrangement of monosaccharides?

They have a backbone of single bonded carbon atoms, with one double-bonded oxygen- carbonyl group.

Hexose sugars have...

6 carbon atoms and exist in rings

Pentose sugars have...

5 carbon atoms exist in rings

Triose sugars have...

3 carbon atoms and exist in straight chain

What is glucose?

Glucose is a monosaccharide hexose sugar, they are monomers that can bond to form disaccharides and polysaccharides.

What are disaccharides?

-They are when two monosaccharides join together. When they join a condensation reaction occurs to form a glycosidic bond.
- A glycosidic bond is when a water molecule is removed leaving an oxygen acting as a link between the two monosaccharides.

How are disaccharides broken?

They are broken by hydrolysis , the addition of water. The water provides the hydroxyl group and a hydrogen , which helps the glycosidic bond to break.

What is a-glucose + a-glucose

maltose

What is a-glucose + sucrose

sucrose

What is b-glucose + a-glucose

lactose

What sugar is hexose and what is their role?

-a-glucose: energy source and component of starch and glycogen acting as energy stores
-b-glucose component of cellulose for structural support in plants.

What sugar is a pentose and what is their role?

Ribose : component of ribonucleic acid (RNA) ,ATP and NAD.
Chemical formula: C5H10O5

What are polysaccharides?

They are polymers of monosaccharides

How are polysaccharides made into energy stores?

-Joining lots of glucose molecules together into polysaccharides can create a store of energy.
-Examples of energy stores: starch in plants in chloroplast. Glycogen in cells of liver and muscle cells.

What is starch and chloroplast made up of?

Amylose and amylopectin

Why are polysaccharides less soluble in water than monosaccharides?

-They have a larger size,the amylose may form a double helix structure which is hydrophobic.
-Furthermore, if many water molecules did dissolve in cytoplasm , the water potential would decrease and excess water would diffuse in.

What are 3 examples of polysaccharides?

-Amylose (plants)- forms long chains of a-glucose and have glycosidic bonds between carbon 1-4. -Amylopectin (plants) - forms a-glucose with glycosidic carbon bonds 1-4. But has branches between carbon 1-6. -Glycogen (in animals) : like amylopectin , it has carbon 1-4 bonds and branches formed by glycosidic bo

What is cellulose ?

It's a homopolysaccharide made from long chains made from long chains of up to 15000 b-glucose molecules bonded together through a condensation reaction to form glycosidic bonds

How are glycosidic bonds formed?

It's formed by the removal of water , a condensation reaction.

What are cellulose beta glucose like?

-Cellulose chains are straight and lie side by side.
-The hydrogen and hydroxyl groups on carbon 1 are inverted compared to a-glucose
-The hydrogen bond is rotated - gives additional strength and stops spiralling
-Hydroxyl groups on carbon 2 sticks out , enabling hydrogen bonds to be formed between them

What is the arrangement of cellulose chains?

The microfibrils are embedded in pectins to form the wall
Macrofibrils run in all directions criss-crossing the wall for extra strength

What is the structure of plant cell walls?

-microfibrils and Macrofibrils have very high tensile strength due to glycosidic bonds and hydrogen bonds
-Microfibrils run in all directions cross-crossing the wall for extra strength
-It is difficult to digest cellulose - due to its glycosidic bonds

What is the function of plant cell walls?

-each cell provides strength as plants don't have a rigid skeleton
-There is a space between Macrofibrils for water and mineral ions to pass into and out of the cell. Making cell fully permeable
-Cell had high tensile strength , prevents cell from bursting when turgid
-Macrofibril reinforced with other substances , eg lignin, makes cell wall waterproof

What are bacterial cell walls like?

The cell wall is not made of cellulose but peptidoglycan, lie in parallel , cross linked by short peptide chains

What are lipids?

-lipids contain C,H,O
-They are insoluble in water as they aren't polar
-They dissolve in alcohol
-The three most important lipids are : triglycerides, steroids and phospholipids
-They are examples of macromolecules

What are triglyceride's structure

1 glycerol backbone with 3 fatty acid tails.

What is glycerol

Glycerol has 3 carbon atoms. It is an alcohol so it has 3-OH , which are important to the structure of triglycerides

What are fatty acids?

They have a carboxyl group (-COOH) on one end, attached to a hydrocarbon tail.
The carbon chains can be up to 2-20 carbons long. The carboxyl group ionises into H+ and COO- groups. Therefore this is an acid due to free H+ ions.

What are saturated fatty acids like?

-no C=C Bonds in molecule
-Forms straight chains
-solid at room temperature , high melting point

What are single C=C bonds called?

monounsaturated

What are more than one C=C called?

polyunsaturated

What are unsaturated fatty acids like?

-Forms a kink in the chain where double bond is
-These kinks push the molecules apart slightly, making them more fluid.
-more unsaturated fatty acids , the lower the melting point

How are ester bonds formed?

-Condensation reaction happens between the -COOH group of fatty acids and the -OH group of the glycerol.
-Due to the 3 -OH group, three fatty acids will bond. A water molecule is produced and the covalent bond, the ester bond

What are the functions of triglycerides?

-Energy source - Triglycerides are broken down in respiration to release energy and generate ATP. -The ester bonds are hydrolysed and then glycerol and fatty acids can be broken down completely
-Triglycerides are insoluble in water- so can be stored without affecting the water potential
-Insulation - Adipose in whales (blubber), lipid in nerve cells act as an electrical insulator, animals prepare for hibernation
-Buoyancy - fat is less dense than water so used by aquatic molecules to help them float
Protection - protect vital organs .

What is the structure of phospholipid?

-glycerol, two fatty acids, and a phosphate group
-One of the three -OH groups on the glycerol forms an ester bond by a condensation reaction
-2 hydrophobic tails and hydrphilic head (due to the charged phosphate making it polar)

What are examples of steroid hormones and what are they made from?

-Testosterone, oestrogen, vitamin D are all made from cholesterol
-They are small and hydrophobic so they can pass through the cell membrane and any other membrane inside the cell.
-Steroid hormones are abundant in plants and in ingestion and absorption some can be converted into animal hormones.

Where is cholesterol made?

Liver

How are ester bonds broken?

hydrolysis reaction

What are amino acids?

Monomers of all proteins , and all amino acids have the same basic structure

What are peptide bonds?

A bond formed when two amino acids are joined by a condensation reaction

What are proteins?

Proteins are large polymers of long chain amino acids.

What properties of amino acids give them a variety of functions?

They form structural components of animals in particular like muscles Their tendency to adopt specific shapes in  enzymes , antibodies and some hormones Membranes have protein constituents that act as carries and pores for active transport and facilitated diffusion

What elements do amino acids contain?

C,H,O,N and sometimes sulphur

What does each protein chain of amino acids have?

Amine group (-NH2) at one end and a carboxyl (-COOH) group at the other end

What do the names of almost all amino acids end in?

-ine

The R group does not stand for ……..

A particular element

What is the element in glycine in the R group?

H

How do amino acids act as a buffer?

When dissolved in water , the amine group and carboxyl group can ionise.

The amine group can accept an H+ ion to change from NH2 to NH3+ . The carboxyl group can give up an H+ ion to change from COOH to COO-

What are peptide bonds and what type of bond are they?

Amino acids are joined together by peptide bonds

How are peptide bonds made?

They are made by condensation reactions

How are peptide bonds broken?

They are broken by hydrolysis

How do the making and breaking of peptide bonds occur and give an example?

Enzymes catalyse the reaction of peptide bonds.

For example protease enzymes break peptide bonds during digestion. They also break down protein hormones so their effects are not permanent.

Draw the bond of amino acids + amino acids to form dipeptide molecules and water 

Draw the hydrolysis of dipeptide molecules to form two amino acids

What are two amino acids joined together?

Dipeptides

What are multiple amino acids together?

Polypeptides

What is the definition of the primary structure of proteins?

The sequence of amino acids found in a molecule

What is the definition of tertiary protein structure and its boding?

The overall 3D shape of a protein molecule. Its shape arises due to interactions including hydrogen bonding, disulfide bridges,ionic bonds, and hydrophobic interactions

Why is the number and order of amino acids important?

Changing just one amino acid can alter the function of the protein

How many possible ways are there of ordering amino acids?

There are 20¹⁰⁰ possible ways of ordering amino acids

The order of amino acids in the primary structure will determine its shape in the………

Secondary, tertiary and quaternary structure

In the secondary structure are the shapes of amino acids twisted or straight.

They are twisted

What are secondary structure proteins twisted into and what are they held together by?

They are twisted into a-helix coil with 36 amino acids per 10 turns of the helix. They are held together by hydrogen bonds between -NH on one amino acid and -CO group on another further down the strand

Why are the a-helix and b-pleated sheets stable at optimal temperature and pH even though they have hydrogen bonds in secondary structure protein?

Many hydrogen bonds are formed

What forms the tertiary structure of proteins?

When coils and pleats start to fold along with areas of straight chain of amino acids.

How are the shapes of the tertiary structure proteins?

The tertiary structure is a very precise shape which is held together in place by bonds between amino acids which lie close together.

• The shape is either super coiled (fibrous)

• The shape is either spherical (globular)

What does the quaternary structure describe ?

How polypeptide chains are arranged to make the complete protein molecule

What bonds are used to hold up the quaternary structure?

hydrogen bonding, disulfide bridges,ionic bonds, and hydrophobic interactions

What bonds primarily hold up the secondary structure?

Hydrogen bonds

What bonds hold up the primary structure?

Peptide bonds

What bonds hold up tertiary structure?

hydrogen bonding, disulfide bridges,ionic bonds, and hydrophobic interactions

What do the hydrogen bonds form between?

Between hydrogen atoms with slight positive and other atoms with slight negative.

• In amino acids form in hydroxyl and carboxyl

Where can hydrogen bonds form?

Between amino groups of one amino acid and carboxyl group of another  In polar areas of R groups on different amino acids

What are hydrogen bonds used for in proteins?

Keeping the tertiary and quaternary structure of protein in the correct shape.  The presence of multiple hydrogen bonds can give a protein molecules a lot strength

Where are ionic bonds formed in amino acids?

Between carboxyl and amino groups that are part of the R group. They also ionise into NH3+ and COO- groups - The positive and negative ions are strongly attracted to each other to form an ionic bond

What are disulfide bridges and how are they formed?

• The R group of the amino acid cysteine contains sulphur. 

• Disulfide bridges are formed between the R group of two cysteines These are strong covalent bonds

Describe the hydrophobic and hydrophilic interactions in protein?

Hydrophobic parts of R group tend to associate together in centre of the polypeptide to avoid water Hydrophilic parts are found at the edge of polypeptide close to water The hydrophobic interactions cause the twisting of the amino acid chain , which changes the shape of the protein.

Why are hydrophobic and hydrophilic interactions important in protein?

Most proteins are surrounded by water inside a living organism

What are fibrous proteins?

Has a relatively long , thin structure , is insoluble in water and metabolically inactive, and often have a structural role within an organism

What are globular proteins?

Has a spherical shape , soluble in water, have metabolic roles in organisms

What are prosthetic groups?

A non-protein component that forms a permanent part if a functioning protein molecule

What are the two categories of tertiary and quaternary structure of proteins?

Fibrous protein

Globular protein

Describe fibrous proteins

They have a regular , repetitive sequence of amino acids and are insoluble in water. This enables them to have a structural function eg collagen and elastin

Describe globular proteins

In a spherical shape.  Hydrophobic R groups are turned inwards towards centre of the molecule  . Hydrophilic group are on the outside This makes the protein soluble as water molecules cluster and bind around them. They often have specific shapes and take up roles such as enzymes, hormones and haemoglobin

What is the function of collagen?

Provide mechanical strength in: Artery walls : layer of collagen to prevent artery bursting and withstand high bp Tendons : made of collagen and connects muscles to bones, allowing them to pull on bones Bones are made from collagen , then reinforced with calcium phosphate making them hard Cartilage and connective tissues made from collagen

What  bonds are in keratin?

Rich in cysteine so lots of disulfide bridges form between polypeptide chains. Also hydrogen bonding , makes the molecule very strong

Where is keratin found?

Wherever a body part needs to be hard and strong like: nails, hooves, feathers, hair

What is the structure of elastin, how is it formed and where is it found?

Cross-linking and coiling makes the structure of elastin string extensible. 

It is found where living things need to stretch or adapt their shape as part of life processes

What are examples of elastin and function?

• Skin can stretch sound bones and muscles

• Elastin in lungs allow them to inflate and deflate

• Elastin in bladder hold urine

• Elastin in blood vessels help them to stretch and recoil as blood is pumped through them

What are examples of fibrous proteins?

Keratin and elastin

What is the structure of haemoglobin?

Quaternary structure Made up of four polypeptides : 2 a-globin chains and 2 b-globin chains- each has its own tertiary structure but fitted together forms one haemoglobin molecule On outside of each chain, there is a space where a haem group is help - called the prosthetic groups

What is the function of the prosthetic group in haemoglobin and what are these types of proteins called?

They are essential as without them proteins won’t function but they aren't made of amino acids They are called conjugated protein

What is the function of haemoglobin?

Carry oxygen from lungs to tissue Oxygen binds to iron in each of the four haem groups in haemoglobin molecule When it binds haemoglobin goes from purple red to bright red Oxygen is released by haemoglobin when it reaches tissue

What is the structure of insulin?

Made of two polypeptide chains Chain A begins with a section of a-helix and B ends with a section of B-pleat Both chains fold into tertiary structure , and are then joined together by disulfide links

Why is insulin soluble in water?

Amino acids with hydrophilic R groups are on the outside of the molecule making it soluble

How does insulin work with glycoprotein receptors?

Insulin binds to glycoprotein receptors on the outside of muscle and fat cells to increase their uptake of glucose from the blood , and increase rate of consumption of glucose