Introduction to Biological Molecules

Question 1

What are biological molecules?

Answer 1

The building blocks of life

Question 2

Why is carbon the basis of living material?

Answer 2

It has the ability to form 4 bonds with other atoms and/or a wide variety of chemical groups

Question 3

What are 3 feature of carbon-based compounds?

Answer 3

Simple or very complex
Often large
Held together by strong covalent bonds

Question 4

How is a covalent bond formed?

Answer 4

Two atoms have separate electron clouds, these electron clouds merge to form a covalent bond, this is a molecule.

Question 5

What is valence?

Answer 5

Relates to how many electrons are in the outer shell

Question 6

What does tetravalent mean?

Answer 6

It can form 4 covalent bonds (carbon)

Question 7

What two features give carbon unique properties?

Answer 7

Valence and low atomic weight: account for diversity and stability of carbon-containing compounds and its role in biological molecules

Question 8

Describe the role of transfer of functional groups

Answer 8

Functional groups often attach to carbon-based compounds and dictate the function of the compounds
Different functional groups have specific chemical properties (therefore a different function)
Cellular chemical reactions often involve functional group transfer (loss or gain)
When covalent bonds are broken in carbon-based compounds energy is released which can be used to sustain life

Question 9

What are macromolecules?

Answer 9

Large biological molecules with repeating subunits and many functional groups

Question 10

Give 4 examples of biologically important macromolecules

Answer 10

Carbohydrates
Lipids
Proteins
Nucleic acids

Question 11

What are macromolecules composed of?

Answer 11

Monomers (building blocks)

Question 12

How are macromolecules formed?

Answer 12

Monomers join together via covalent bonding forming long chains (macromolecules) called polymers

Question 13

How are polymers formed?

Answer 13

Dehydration synthesis (condensation reaction), a molecule of water is formed and removed from reactants during the reaction and ATP is required

Question 14

How are polymers broken down?

Answer 14

Hydrolysis reaction, bonds between reactants are broken with the addiction of a water molecule and energy released from the bond is stored as ATP

Question 15

How is starch broken down?

Answer 15

By hydrolysis reaction which requires the help of enzymes, starch is digested to sugar molecules and then broken down further to be converted to energy in the form of ATP

Question 16

Why is starch broken down?

Answer 16

In order to be easily digested and absorbed across the gut

Question 17

What is an enzyme?

Answer 17

A biological catalyst that increases the rate of chemical reactions without being used up

Question 18

Why is water important?

Answer 18

Water is the most abundant molecule in the body and is the medium in which cellular reactions occur (plays a major role in living systems: growth and reproduction, hydration, nutrition, hygiene and health)

Question 19

How much of fresh mass of living organisms does water make up?

Answer 19

60-95%

Question 20

How does water act as a universal solvent and transporter?

Answer 20

All bodily fluids are mostly water and water aids movement of chemicals during diffusion

Question 21

How does water act as a lubricant?

Answer 21

At joints and on tissues, moistens epithelial surfaces (eyes, mouth) and water us a shock absorber (in brain: particularly sensitive to changes in CSF- cerebrospinal fluid)

Question 22

How does water regulate body temperature?

Answer 22

Requires heat to turn to vapour: sweat absorbs heat from skin when evaporating

Question 23

Why is it important for us to keep hydrated?

Answer 23

Body tissues are 62% water so we need approximately 1.5 litres of water a day. Dehydration is associated with many conditions (diarrhea and vomiting) and it can be fatal so should be treated quickly. A way to treat dehydration is by fluid replacement therapy- oral or intravenous (IV)

Question 24

Describe the bonding and atoms in a water molecule

Answer 24

A simple molecule: one oxygen covalently bonded (single bonds) to two hydrogen atoms

Question 25

Describe the polarity of a water molecule

Answer 25

Water molecules are polar (charged). The oxygen atom contains 8 protons in its nucleus whereas the hydrogen atoms only have one proton in their nucleus. Therefore, the electron pair shared in the O-H covalent bond is more strongly attracted to the oxygen atom’s nucleus (the electrons are pulled towards the oxygen) than either of the hydrogen atom’s nuclei. So there is a slightly negative pole where the oxygen atom is and a slightly positive pole where the hydrogen atoms are

Question 26

How does hydrogen bonding occur between water molecules?

Answer 26

The slightly positive region near the hydrogen atoms is attracted to the slightly negative region near the oxygen atoms of another water molecule

Question 27

Which are stronger: the covalent bonding in water molecules or the hydrogen bonding between water molecules?

Answer 27

Covalent bond > Hydrogen bonding

Hydrogen bonds are relatively weak, around 5-10% the strength of a covalent bond and easily broken (always breaking)

Question 28

Why does hydrogen bonding create a fluid?

Answer 28

As molecules are constantly changing which molecule they are bonded to

Question 29

How is water a powerful and universal solvent?

Answer 29

All polar (charged) molecules and ions are water soluble because they can form hydrogen bonds with water molecules.

Water is an important medium for chemical reactions because ions and polar molecules can move/ interact freely and take part in cellular chemical reactions

Question 30

What happens with non-polar molecules and water?

Answer 30

No electrical charge and cannot form hydrogen bonds with water.
Repel water molecules, non-polar molecules are hydrophobic (fats and oils)

Question 31

What does amphiphilic mean?

Answer 31

Some complex molecules have a mixture of hydrophilic and hydrophobic properties

Question 32

What is an example of an amphiphilic molecule?

Answer 32

Phospholipids

Question 33

What feature of biological molecules is influenced by hydrophobic forces?

Answer 33

The 3D shape

Question 34

Why does the plasma membrane have unique properties?

Answer 34

Comes from its fluidity and polarity

Question 35

What kind of molecules can move freely through the plasma membrane?

Answer 35

Small molecules and larger hydrophobic molecules (oxygen molecules, carbon dioxide and water)

Question 36

What is surface tension?

Answer 36

Tension of the surface film of a liquid caused by the attraction of the particles in the surface layer so as to reduce surface area
The elastic tendency of a fluid

Question 37

How does surface tension happen?

Answer 37

Air interfaces, results from the greater attraction of liquid molecules to each other (due to cohesion) than the molecules in the air

Question 38

What are surfactants?

Answer 38

Amphiphilic compounds which reduce the surface tension of a liquid in which they are dissolved

Question 39

What can surfactants reduce the surface tension of?

Answer 39

Two liquids, between a gas and a liquid or between a liquid and a solid

Question 40

What can surfactants act as?

Answer 40

Detergents, wetting agents, emulsifiers, foaming agents and dispersants

Question 41

Why can premature babies be prescribed surfactant inhaler therapy?

Answer 41

They lack surfactant and lack of surfactant can lead to atelectasis (lung collapse) because usually the alveoli would secrete surfactant to break surface tension in the lungs. When there is no surfactant to break the surface tension, the lung alveoli may collapse.