Week 2

Question 1

Essential elements -

Answer 1

Make up 96% of living matter
C, H, O, N

Question 2

Trace elements -

Answer 2

0.01% of living matter

are required by an organism in only minute quantities

ex: Fe, I, Se, Cu

Question 3

Iodine deficiency can lead to

Answer 3

goiter

Question 4

Iodine (I) deficiency -

Answer 4

Hypothyroidism

Iodine is an essential trace element for production of the thyroid hormones (thyroxine and triiodothyronine)

Question 5

Iron (Fe) deficiency -

Answer 5

Iron deficiency anaemia

Fe is a part of the haemoglobin structure

Question 6

Radioisotopes used in medicine:

Answer 6

C¹⁴, H³ (tritium)

Question 7

Clinical applications of radioisotopes (4):

Answer 7

• Disease diagnosis (imaging)
• Disease treatment (ex: I¹³¹ for thyroid cancer, hyperthyroidism)
• Assessment of degree of disease severity
• Treatment monitoring

Question 8

Nuclear medicine imaging

Answer 8

• PET scan - Positron Emission Tomography
• Based on the use of radioactive isotopes
• produces a 3D image of functional processes in the body
• Detection of γ-rays emitted by a radioisotope (tracer) introduced into the body as part of a biologically active molecule (ex - F¹⁸-FDG fluoro-deoxy-glucose)

Question 9

Chemical bonds and their diff

Answer 9

covalent bonds - sharing e b/w atoms

ionic bonds - transfer e from one atom to another

covalent > ionic

Question 10

Electronegativity

Answer 10

the tendency of an atom to attract electrons towards itself

Question 11

Anions

Answer 11

negatively charged ions

Question 12

Cations

Answer 12

positively charged ions

Question 13

Strong chemical bonds:

Answer 13

• Covalent
• Ionic

bonds b/w atoms

Question 14

Weak Chemical Bonds

Answer 14

• Hydrogen Bonds
• Van der Waals interactions

Bonds between atoms or molecules

Question 15

Hydrogen bonds

Answer 15

• Interaction between neighboring molecules
• Form between a hydrogen atom (Η) covalently bonded to an electronegative atom of a molecule and an electronegative atom (oxygen, nitrogen or fluoride) of another molecule

Question 16

Van der Waals Interactions (3):

Answer 16

• Attractive forces → developed between molecules or atoms of a molecule (other than covalent bonds, ionic bonds and hydrogen bonds)
• Occur when transiently positive and negative regions of molecules attract each other
• Weaker than H-bonds
  ex: tertiary structure of protein - folding

Question 17

Role of weak chemical bonds

Answer 17

– Reinforce the shapes of large molecules
– Help neighbouring molecules adhere to each other

Question 18

Molecular Shape and Function

Answer 18

The precise shape of a molecule is important to its function in the living cell (ex: protein shape)

Question 19

molecule -

Answer 19

consists of 2 or more atoms held together by covalent bonds
ex: H2

Question 20

compound -

Answer 20

combination of 2 or more different elements

ex: H2O

Question 21

Cells consist of ____ water

Answer 21

70-95%

Question 22

Why is water a polar molecule?

Answer 22

it contains polar covalent bond: opposite ends have opposite charges

Question 23

Why is polarity impt f/ water molecules?

Answer 23

• it allows to form H-bonds with neighboring molecules, contributes to various properties of H₂O

Question 24

4 properties of water contribute to Earth’s fitness for life

Answer 24

1. Cohesion
2. Temperature moderation
3. Evaporative cooling
4. Versatility as a solvent

Question 25

Cohesion -

Answer 25

– the bonding of water molecules to neighboring molecules – occurs due to **H-bonds** – it helps pull water up through the microscopic vessels of plants

Question 26

Adhesion & Cohesion

Answer 26

• Adhesion of water molecules *to plant cell walls* due to H-bonds helps transfer water upwards against gravity • Cohesion of water molecules helps them *stick together* during transfer

Question 27

Surface tension

Answer 27

- measure of how hard it is to break the surface of a liquid - Water has higher surface tension compared to other liquids due to **H-bonds**

Question 28

Temperature Moderation (2 ways)

Answer 28

– By absorbing heat from air that is **warmer** – By releasing the stored heat to air that is **cooler**

Question 29

specific heat of a substance

Answer 29

amount of heat that must be absorbed or lost for 1 gram of that substance to change its temperature by 1ºC

Question 30

What allows water to resist changes in temperature?

Answer 30

Water’s high specific heat = 1 cal/g/ºC

Question 31

Heat of vaporization -

Answer 31

quantity of heat a liquid must absorb for 1 gram of it to be converted to a gas

Question 32

Why does water have hight heat of vaporization and high specific heat?

Answer 32

due to H-bonding

Question 33

Evaporative cooling

Answer 33

- The ‘hottest’ molecules escape as gas and leave the ‘cooler’ molecules behind - Allows water to cool a surface ex: Organisms keep their body temperature constant by sweating (homeostasis)

Question 34

Life can exist under the frozen surfaces of lakes and polar seas b/c:

Answer 34

- ice less dense than liquid water and floats in it (H-bonds are more “ordered”) - insulates bodies of water underneath

Question 35

Water is a versatile solvent due to

Answer 35

its polarity

Question 36

Properties of water as solvent:

Answer 36

- forms hydrogen bonds easily - can form aqueous solutions - different regions of the polar water molecule can interact with ionic compounds called solutes and dissolve them solution = solvents + solute

Question 37

Due to covalent bond, water can easily interact w/

Answer 37

proteins & ionic compounds

Question 38

hydrophilic substance:

Answer 38

has an affinity for water ex: polar solutions, ionic molecules

Question 39

hydrophobic substance

Answer 39

Does not have an affinity for water ex: non-polar solutions, non-ionic molecules

Question 40

Molarity -

Answer 40

number of moles of solute per liter of solution (moles/L)

Question 41

acid -

Answer 41

– any substance that increases the hydrogen ion concentration [H+] of a solution by releasing H+ pH = 0-6

Question 42

base -

Answer 42

– any substance that reduces the hydrogen ion concentration of a solution by *accepting H+* or by *releasing OH-* pH = 8-14