4. THE CHEMICAL BASIS OF LIFE

Question 1

1. What are organisms composed of?

Answer 1

• matter

Question 2

2. What is the definition of matter?

Answer 2

• anything that takes up space and has mass

Question 3

3. What is matter made up of?

Answer 3

• elements

Question 4

4. What is the definition of elements?

Answer 4

• substances that cannot be broken down into other substances through chemical reactions

Question 5

5. How many elements exist in nature, and where are they listed?

Answer 5

• 92 elements exist in nature
• they are listed in the Periodic Table

Question 6

6. What are compounds?

Answer 6

• a substance consisting of 2 or more elements
• that are combined in a fixed ratio
• compounds have different characteristics from elements

Question 7

7. What elements make up 96% of living matter?

Answer 7

• carbon (C)
• hydrogen (H)
• oxygen (O)
• nitrogen (N)

Question 8

8. Which elements make up most of the remaining 4% of living matter?

Answer 8

• Calcium (C)
• Potassium (K)
• Sodium (Na)
• Phosphorous (P)

Question 9

9. Which elements are only required by the organism in minute quantities?
   They make up 0.01% of living matter

Answer 9

• Iron (Fe)
• Iodine (I)
• Selenium (Se)
• Zinc (Zn)
• THEY ARE CALLED TRACE ELEMENTS

Question 10

10. What is the name given to the condition of iodine deficiency in the body?

Answer 10

• hypothyroidism is when there is an iodine deficiency in the body
• it leads to Goitre (an enlargement of the thyroid gland)

Question 11

11. What is Iodine?

Answer 11

• it is an essential trace element for the production of thyroid hormones
• thyroxine and triiodothyronine are examples of thyroid hormones

Question 12

12. What is the name given to a condition caused by an Iron Deficiency?

Answer 12

• Anaemia
• Iron (Fe) is a part of the haemoglobin structure
• it holds oxygen in the haemoglobin molecule

Question 13

13. What does each element consist of?

Answer 13

• a specific atom

Question 14

14. What is an atom?

Answer 14

• it is the smallest unit of matter that still retains the properties of an element
• an element and it’s atom have the same symbol

Question 15

15. What are atoms composed of?

Answer 15

• smaller parts called subatomic particles

Question 16

16. What are the three types of Subatomic Particles?

Answer 16

1. Neutrons: no electrical charge (0)
2. Protons: positively charged (+1)
3. Electrons: negatively charged (-1)

Question 17

17. Which two subatomic particles are identical in mass

What is their mass?

Answer 17

• protons and neutrons are identical in mass
• their mass is 1.7x10-24g
• this is equal to 1 Dalton

Question 18

18. Why is the mass of electrons considered negligible?

Answer 18

• it is 1/2000 of the mass of a proton or a neutron

Question 19

19.Where are protons and neutrons found?
What are they surrounded by?

Answer 19

• in an atomic nucleus
• they are surrounded by an electron cloud

Question 20

20.What is the atomic number of an atom?
Why does it exist?

Answer 20

• the atomic number is equal to the number of protons in the element
• it is equal to the number of electrons
• it is unique to each element
• it is written as a subscript to the left of the symbol
• it exists because various elements differ in their number of subatomic particles

Question 21

21. What is the Mass Number of an element?

Answer 21

• it is the sum of the protons and the neutrons in the nucleus of an atom
• it is an approximation of the atomic mass of an atom
• it is given in Daltons
• the atomic mass is the approximation of the mass number
• it is written as a superscript to the left of the symbol

Question 22

22. How do we work out the number of neutrons in an element?

Answer 22

mass number (number of protons+neutrons)
MINUS the atomic number (number of protons)

Question 23

23. What is the Atomic Mass?

Answer 23

• it is the atom’s total mass
• it is equal to the mass number (in Daltons)
• it is equal to the sum of the protons and the neutrons

Question 24

24. What are Isotopes?

Answer 24

• they are different forms that atoms of a given element may occur in
• they have a different number of neutrons in the atomic nucleus
• this means they have a different mass number from one another
• they have the same number of protons
• this means they have the same atomic number

Question 25

25. What are Radioisotopes?

Answer 25

• they are radioactive isotopes
• they are unstable
• they spontaneously decay to give off particles and energy
• they are used in nuclear medicine and imaging

EG: C14, H3

Question 26

26. Name some Clinical Applications of Radioisotopes?

Answer 26

• disease diagnosis (imaging)
• disease treatment (I131 is used for thyroid cancer treatment and for treating hypothyroidism)
• this radioisotope needs to release radioactive energy into the thyroid gland that it enters
• assessment of degree of disease severity
• treatment monitoring

Question 27

27. What is Nuclear Medicine Imaging?

Answer 27

• it is based on the use of radioactive isotopes
• a PET scan is an example
• this scan is more accurate than a CT scan
• it can pick up medical abnormalities in their earlier stages
• a PET scan is an imaging technique that produces a 3D image of the functional processes occurring in the body
• it is the detection of the y-rays that are emitted by a radioisotope
• this is known as a tracer
• these y-rays are introduced into the body as part of a biologically active molecule (Fluoro deoxy glucose)
• the reason this is effective is because cancer cells eat glucose
• they eat much more glucose than regular cells
• this is because they are reproducing much quicker
• they multiply in the form of a tumour (an indistinguishable single cell)

Question 28

28. What is the chemical behaviour of an atom defined by?

Answer 28

• its electron configuration

Question 29

29. What is the definition for Electron Configuration?

Answer 29

• it is the distribution of an atom’s electrons in shells

Question 30

30. What table shows the electron distribution for all the elements?

Answer 30

• the Periodic Table