2.2 Biological molecules

Question 1

What type of molecule is water?

Answer 1

Dipolar molecule- oxygen end slightly negative and hydrogen end slightly positive (oxygen has more electrons so is negative)

Question 2

Why is water described as dipolar?

Answer 2

There is a greater amount of electrons by the oxygen molecule, creating a negative end, as oxygen’s nucleus has a greater charge than hydrogen therefore attracting more electrons

Question 3

A substance is polar if?

Answer 3

It dissolves in water and has a slight charge
Non-polar doesn’t dissolve

Question 4

What type of bonding is between water molecules?

Answer 4

Hydrogen bonds- individually weak but water has a lot so very strong in numbers

Question 5

The negative parts of a water molecule attract to the positive parts of another water molecule to from hydrogen bonds, which constantly break and reform between moving water molecules. What does this mean?

Answer 5

That water has cohesive properties - it moves as one mass as the molecules are attracted to each other

Question 6

How does water also has adhesive properties?

Answer 6

Adhesion is when a charge attracts to a neutral, like with how a water molecule attracts to a neutral xylem vessel wall

Question 7

How do substances dissolve in water?

Answer 7

Molecules orientate themselves when ions dissolve in water (pos to neg and vice versa), and this pulls ions apart to separate the ionic compound

Question 8

Why does water has a high specific heat capacity and latent heat of vaporisation ?

Answer 8

Its high amount of hydrogen bonds that need lots of energy to broken

Question 9

Why is it important that water has a high specific heat capacity /latent heat of vaporisation?

Answer 9

Useful for aquatic organisms who cannot make their own body heat. You need a lot of energy to heat up a large amount of water like an ocean so having these properties means regulated conditions in water and the aquatic organisms survive (temp doesn’t fluctuate) temp of the ocean then won’t change to account for fish not being able to make their own body heat

Question 10

How does water make a good transport medium?

Answer 10

Its molecules sticking together when transported (cohesion) and water being attracted to other polar molecules/surfaces (adhesion) means it exhibits capillary action (ab rise up a tube against gravity, like in a xylem vessel)

Question 11

How does water act as a coolant?

Answer 11

It buffers temp changes during chemical reactions in pro/eu cells due to the large amount of energy needed to break its hydrogen bonds- keeping temp constant in cells is important as enzymes often only active in a small temp range

Question 12

How does ice form?

Answer 12

The hydrogen bonds orientate molecules to take up more space so it has a higher volume- allows max number of hydrogen bonds to form showing water expands as it freezes (ice less dense than water proven using Density=mass÷volume as volume increased so density decreased)

Question 13

What is good about water being less dense than ice?

Answer 13

Ice floats in water- this provides habitats for arctic organisms like polar bears and creates an insulating layer for organisms below, keeping in heat so their habitat isn’t frozen solid

Question 14

Water molecules at the surface attract to those below. Why is this good?

Answer 14

It creates surface tension to allow insects like pond skaters to inhibit the surface

Question 15

How does water act as a solvent?

Answer 15

Many of the solutes in an organism dissolve in water- metabolic processes rely on chemicals reacting together in a solution (water is a medium for chemical reactions), cytosol of pro/eu cells mainly water, cytoplasm mainly water (where metabolic reactions occur)

Question 16

What is the difference between alpha and beta glucose?

Answer 16

The hydroxyl group at the first carbon is switched- on alpha the H points up, on beta OH points up

Question 17

What elements make up carbohydrates and lipids?

Answer 17

Carbon, hydrogen, oxygen

Question 18

What elements make up nucleic acids?

Answer 18

Carbon, hydrogen, oxygen, nitrogen, phosphorus

Question 19

What elements make up proteins?

Answer 19

Carbon, hydrogen, oxygen, nitrogen, sulphur

Question 20

What is a condensation reaction?

Answer 20

The formation of 2 molecules releasing a water molecule in the process

Question 21

What is a hydrolysis reaction?

Answer 21

The breakdown of a molecule into 2 smaller ones using a water molecule

Question 22

Glucose formula vs disaccharide formula

Answer 22

C6 H12 O6 vs C12 H22 O11
(because of the H2O molecule that was taken away

Question 23

General formula of carbohydrates

Answer 23

(CH2O)n

Question 24

What bond joins molecules in saccharides

Answer 24

A 1,4 glycosidic bond, formed by a condensation reaction and broken by a hydrolysis reaction

Question 25

Properties sa/disaccharides

Answer 25

Soluble in water Small Tastes sweet Crystalline when solid (appears whitish)

Question 26

Properties of polysaccharides

Answer 26

Non-crystalline when solid White Big chain Most insoluble

Question 27

What is the structure of ribose?

Answer 27

C5 H10 O5, deoxyribose has one less oxygen at carbon 2 pointing down (isn't OH just H for deoxyribose)

Question 28

Maltose

Answer 28

Made of alpha glucose x2, 1,4 glycosidic bond, formed by amylase on starch during digestion, made during germination of seeds- food source for seeds

Question 29

Sucrose

Answer 29

Made of alpha glucose and fructose, 1,2 and occasional 1,4 glycosidic bond, used as a soluble transport system in plants (in phloem), storage in some plants like onions, concentrated in sugar cane

Question 30

Lactose

Answer 30

Beta glucose and galactose, 1,4 glycosidic bond, present in mammalian milk so important in infants' diets

Question 31

Starch-amylose

Answer 31

Unbranched chain wound into a helix, 1,4 glycosidic bond, compact so good for storage (in vacuole of plants) as insoluble, alpha glucose is constituent monomer (made of it), function same as amylo-pectin

Question 32

Starch-amylo-pectin

Answer 32

Coiled chain with occasional branches, 1,4 and rarely 1,6 glycosidic bonds, alpha glucose is constituent monomer, function same as amylose

Question 33

Glycogen

Answer 33

Coiled chain with occasional branches (more branches than starch-amlyo-pectin), alpha glucose is constituent monomer, 1,4 and more frequent 1,6 glycosidic bonds, storage as an energy source (animal cell)- usually found in liver/muscle cells

Question 34

Cellulose

Answer 34

Straight unbranched chain, every 2nd glucose flipped so OH groups are closer and carbon 1 and 4 bond, 1,4 glycosidic bond, beta glucose is constituent monomer, forms cell walls in plants

Question 35

How are cell walls made?

Answer 35

Hydrogen bonds form between long chains of cellulose to form microfibrils. These join up forming macrofibrils, which combine to produce fibres/cellulose fibres. The fibres are strong/insoluble and used to make cell walls. There are gaps between microfibrils which allow water to pass easily through

Question 36

What are some examples of reducing/non-reducing sugars?

Answer 36

Reducing- glucose, fructose, maltose Non-reducing- sucrose

Question 37

What is a triglyceride made of?

Answer 37

One glycerol molecule and 3 fatty acids

Question 38

Bonding in triglycerides

Answer 38

Condensation/esterification reaction between glycerol and fatty acids (H from glycerol and HO from fatty acids create 3 H2O molecules), bonds formed are called ester bonds

Question 39

Uses of triglycerides

Answer 39

Long term energy storage/source: Cushioning around vital organs like the heart for protection Buoyancy for aquatic animals like whales Thermal insulation to reduce heat loss (as they're a bad heat conductor) like in penguins

Question 40

Saturated fatty acids

Answer 40

Fatty acid chains with no double bonds between carbon atoms as the carbons form the max number of bonds with the hydrogen atoms

Question 41

Unsaturated fatty acids

Answer 41

Fatty acids have double bonds between some of the carbons- just one double bond means its monosaturated, more means its polysaturated

Question 42

How does a fatty acid having double carbon bonds change it?

Answer 42

Carbon bonds causes the molecule to kink/bend so it cannot pack closely together (makes them liquid at room temp so described as oils not fats)- the more double bonds between carbons, the more kinks, the harder it is to make the molecules pack closely together

Question 43

Uses of lipids

Answer 43

Membrane formation Hormone production Electrical insulation to speed up impulses (myelin sheath) Waterproofing like the waxy cuticle on a leaf

Question 44

What type of molecule are triglycerides and phospholipids?

Answer 44

Macromolecules

Question 45

Structure of phospholipids

Answer 45

Polar, soluble, hydrophilic phosphate heads that attract water and 2 non-polar, insoluble hydrophobic fatty acid tails that repel water

Question 46

Why are the properties of phospholipids important in membrane formation?

Answer 46

They form a bilayer with the tails pointing towards each other and the heads on the outside/ layer of the membrane to separate the aqueous environment cells exist in to the aqueous cytosol in cells-

Question 47

What are sterols?

Answer 47

Steroid alcohols, a type of lipid in cells- not fats or oils, complex alcohol molecules based on a 4 carbon ring structure with an OH group at one end- OH group is hydrophilic and rest of molecule is hydrophobic

Question 48

Importance of cholesterol in membranes

Answer 48

It strengthens the phospholipid bilayer- like a phospholipid with a philic and phobic end which interact with the phospholipid parts to pull the bilayer together, in between phospholipids, adds stability/flexibility to membrane, maintains fluidity (prevents membrane from being too stiff/fluid),

Question 49

Globular protein

Answer 49

Forms unique shapes like active sites, usually an enzyme or a hormone/signalling molecule Very folded, complex tertiary structure compact, often irregular

Question 50

Fibrous protein

Answer 50

Structured proteins which support cell structures like microfilaments Have a straight, regular, reoccurring structure