Biological Molecules

Question 1

Describe what is meant by water is a polar molecule.

Answer 1

-Although water has no overall charge, the distribution of electrons is uneven because the oxygen atom draws them away from the hydrogen atoms.
-Oxygen has a slightly negative charge (delta negative), while hydrogen atoms have a slightly positive charge (delta positive).

Question 2

What does dipolar mean?

Answer 2

-Atoms has both - and + poles so therefore it is dipolar.

Question 3

Draw a Hydrogen Bond.

Question 4

What is a hydrogen bond?

Answer 4

-A weak attraction between the partially negative oxygen of one molecule and the partially positive hydrogen atom of the next molecule.

Question 5

List all the properties of water.

Answer 5

-High specific heat capacity.
-High latent heat of vaporisation.
-Cohesion and surface tension in water.
-The density of water.
-Transparency.
-Water in metabolism.
-Water as a solvent.
-Water as a lubricant.
-Water giving support.

Question 6

Describe waters property of high specific heat capacity.

Answer 6

-Because of the H bonds that occur between water, it takes a lot of energy to heat a given mass of water. This is why water exists at room temperature.
-Water acts as a buffer against sudden temperature changes leading to a stable aquatic environment for many organisms.

Question 7

Describe waters property of high latent heat of vaporisation.

Answer 7

-It takes a lot of energy to evaporate water.
-Sweat in mammals is a very effective means of cooling because body heat is used to evaporate the water.

Question 8

Describe waters property of cohesion and surface tension.

Answer 8

-The tendency of molecules to stick together is known as cohesion. With its hydrogen bonding, water has large cohesive forces, these allow it to be pulled up through a tube, such as xylem in plants.
-Water molecules at the surface of a body of water tend to be pulled back into the body of water rather than escaping it, this is called surface tension.

Question 9

Describe the density of water.

Answer 9

-Water is less dense in the form of ice than when liquid, due to the lattice structure formed to the hydrogen bonds.
-It acts as an insulating layer that delays the freeing of water beneath it.

Question 10

What are biological molecules?

Answer 10

-They are very large and have been built up by the living organisms from smaller sub-units joined by bonds called condensation bonds.

Question 11

What are the polymers of monomer sub-units:
-Amino acids
-Simple sugars (Monosaccharide)
-Nucleotides
-Fatty acids + Glycerol

Answer 11

-Polypeptides (proteins)
-Polysaccharides (carbohydrates)
-Nucleic acids (DNA + RNA) (polynucleotides)
-Lipids (macromolecules)

Question 12

What is a condensation reaction?

Answer 12

-When the monomer sub-units join. Water molecules are produced as one of the products + bonds are formed.

Question 13

What is a hydrolysis reaction?

Answer 13

-A reverse reaction that breaks the polymer back into the monomer subunits and here a water molecule is used up.

Question 14

What is a catabolic reaction?

Answer 14

-Breaking larger molecules into simpler ones.

Question 15

What is an anabolic reaction?

Answer 15

-making larger molecules from simpler ones.

Question 16

What chemical elements are present in carbohydrates?

Answer 16

-Carbon
-Hydrogen
-Oxygen

Question 17

Sate the general formula of a carbohydrate.

Answer 17

(CH2O)n

Question 18

Sate the general formula of glucose.

Answer 18

(C6H12O6)

Question 19

Draw Alpha-glucose.

Question 20

Draw Beta-glucose.

Question 21

What is an isomer?

Answer 21

-Compounds that have the same molecular formular but different structural formula.

Question 22

Describe the difference in the structure between alpha and beta glucose. (ABBA)

Answer 22

-For alpha glucose the OH group is below the ring on carbon number 1, butt beta glucose it is above the ring on carbon number 1.

Question 23

What are the names for carbon sugars: 3,5,6 ?

Answer 23

• 3 carbon bonds- carbon sugars = Trioses
• 5 carbon bonds- carbon sugars = Pentoses
• 6 carbon bonds- carbon sugars = Hexoses

Question 24

What are the functions of carbohydrates?

Answer 24

-Energy source - glucose
-Energy store - starch glucose
-Support and structure - cellulose in plant cell wall
-As constituents of DNA and RNA - deoxyribose and ribose

Question 25

What is the general formula for ribose?

Answer 25

(C5H10O5)

Question 26

Draw ribose and deoxyribose.

Question 27

What is ribose and deoxyribose?

Answer 27

-Ribose is a pentose sugar that is found in RNA. -A closely related molecule is called deoxyribose that is a component of DNA. It has one less oxygen on carbon number 2.

Question 28

Describe the process of how a glycosidic bond is formed?

Answer 28

--Monosaccharides can be linked by special covalent bonds called glycosidic bonds in a condensation reaction. -A hydroxyl group attached to a carbon atom of one of the monosaccharides is removed with a hydrogen atom from another hydroxyl; on another monosaccharide, making a water molecule as a product. -This leaves an oxygen 'bridge'. Here carbons 1 and 4 are linked so its a 1-4 glycosidic bond.

Question 29

What monosaccharides form maltose?

Answer 29

Glucose + glucose = maltose

Question 30

What monosaccharides form sucrose?

Answer 30

Glucose + fructose = sucrose

Question 31

What monosaccharides form lactose?

Answer 31

Glucose + galactose = lactose

Question 32

What does starch consist of?

Answer 32

- 2 polysaccharides joined.

Question 33

Describe the structure of amylose and what causes it to happen?

Answer 33

-Amylose is a chain of alpha glucose units. -The 1-4 glycosidic bonds cause the chain to turn and coil into a helix shape. -Therefore, amylose has a unbranched and long structure.

Question 34

Describe the structure of amylopectin and what causes it to happen?

Answer 34

-Amylopectin is made of alpha glucose, that forms both 1-4 and 1-6 glycosidic bonds. -Therefore, it produces a branched structure.

Question 35

List the structure, properties and functions of glycogen.

Answer 35

-Structure - A polysaccharide made of repeating alpha glucose monomers. A highly branched structure with 1-4 and 1-6 glycosidic links. -Properties - Even more compact than amylose. Side branches are easily accessible to the enzymes needed to break the glycosidic bonds. -Functions - Highly compact so more can be stored in animal cells compared to starch in plants, an important feature of highly active animals (more metabolically active). Branches allow for the glucose molecules to be added and release quickly.

Question 36

List the structure, properties and functions of glucose.

Answer 36

-Structure - single, hexose monosaccharide. -Properties - small molecule, sweet tasting, Molecules are polar and soluble, so they can dissolve in the cytosol of the cell. -Functions - used in respiration in all organism to provide the cell with ATP for active processes such as active transport and protein synthesis.

Question 37

List the structure, properties and functions of starch.

Answer 37

-Structure - polysaccharide made of repeating alpha glucose monomers. Two combined polysaccharides, amylose and amylopectin. -Properties - insoluble, so it doesn't affect the osmotic potential of the cell where its stored. Compact. The side branches of amylopectin are easily accessible to the enzymes needed to break the glycosidic bonds. -Functions - when glucose is made during photosynthesis in plants it can be stored as starch, a chemical energy store. Compact, so it can be stored in a small space. Glucose molecules can be added and release quickly and easily.

Question 38

List the structure, properties and functions of cellulose.

Answer 38

-Structure - polysaccharide made of repeating beta glucose monomers. Every other glucose is rotated 180 degrees to form 1-4 beta glycosidic links creating a flat chain. Chains join by H bonds to form cellulose fibres. -Properties - cellulose fibres are strong and insoluble. -Functions - make cell wall in plant cells. Important feature in animals diet. Cellulose fibres cannot be digested and pass through the system as 'fibre'. Important to keep the system healthy.

Question 39

Draw the structure of glycerol.

Question 40

What is a saturated fat?

Answer 40

-In a saturated fat the hydrocarbon chain of the fatty acid consists only of repeating CH2 groups, so the carbons are all linked to each other by single bonds. (C-C bonds). -Tend to be animal fats that are solid at room temperature.

Question 41

What is an unsaturated fat?

Answer 41

-In a unsaturated fat there will be 1 or more double bonds between the carbon atoms in the fatty acid. If there is a single double bond it is a monounsaturated fat, if there is more than one double bond its a polyunsaturated fat. -The double bond causes the hydrocarbon tail to kink and so they pack together less tightly. -These fats tend to be vegetable oils and are liquid at room temperature.

Question 42

What is a lipid and what is the difference between a fats and oils?

Answer 42

-Lipids: a group of compounds that are insoluble (because they have no positive or negative areas) in water but soluble in alcohols such as ethanol. -Fats: lipids that are solid at room temperature. -Oils: lipids that are liquid at room temperature.

Question 43

What is a triglyceride and how is it formed?

Answer 43

-Formed when a glycerol becomes linked to 3 fatty acids by a condensation reaction. The condensation reaction is known as esterification, as it results in the formation of 3 ester bonds, where each fatty acids joins to the glycerol. -3 water molecules are release.

Question 44

Draw the formation of a triglyceride and label the ester bond.

Question 45

How does a phospholipid form?

Answer 45

-A phosphate group (PO43-) replaces one of the three fatty acids.

Question 46

List all functions of a triglyceride.

Answer 46

-Energy source: high proportion of carbon-hydrogen bonds and a low proportion of oxygen, fats yield twice as much energy as carbohydrates or proteins when respired. -Thermal insulation: fats are stored in the body as a store of energy, to insulate and keep warm. -Protection: fats are stored around organs that help protect them (cushioning). -Buoyancy: fats are less dense than water so will provide buoyancy for aquatic organisms. -Water-proofing: lipids form waterproof cuticles of plant leaves and water proofing feathers of birds.

Question 47

List all functions of a phospholipid.

Answer 47

-Membrane formation: phospholipids have hydrophilic head and a hydrophobic tail, which affects the way they orientate themselves in a watery medium. If only a few molecules are involved they will form 'micelles' in water. If the number of phospholipid molecules are large, they orientate into a bilayer with their hydrophilic heads outwards. -Electrical insulation: Neurones are wrapped by the many layers of the cell surface membrane of cells called Shawn cells. This provides electrical insulation to the neurones (myelin sheath).