Life at the cellular level 1- molecules

Question 1

Define the major elements used to construct human biomolecules?

Answer 1

H, C, N, O. 99% of our bodies are this

Question 2

What seven elements are required in large amounts for human biomolecules?

Answer 2

Na, Mg, K, Ca, P, S, Cl.

Question 3

What 12 other elements are required in small amounts?

Answer 3

Mn, Fe, Co, Ni, Cu, Zn, Mo, Se, I.
(Usually form critical interactions in proteins, e.g. Fe in haemoglobin)

Question 4

How many bonds do H, O, N , C make?

Answer 4

1,2,3,4

Question 5

How is a molecule formed?

Answer 5

When atoms share electrons (or lose or gain electrons) and they stick together (covalent bond) they form molecules. Two or more elements bonded together = molecule.

Question 6

What are the important functional groups?

Answer 6

Amino- NH3
Carboxyl-COOH
Hydroxyl-OH
Phosphate-H2PO4

Question 6

Why can’t biomolecules have many different configurations?

Answer 6

Many biomolecules contain a double bond between carbon atoms (C=C) which is rigid (no freedom of rotation). They can therefore only interconvert between the two by breaking and re-forming bonds (energetically expensive!)

Question 6

Functional groups and their effect on molecules?

Answer 6

Groups of elements that attach to these carbon structures are called “functional groups” and confer specific chemical properties to the molecule. Biomolecules can contain more than one functional group.

Question 7

What configurations do biomolecules take?

Answer 7

cis/trans
Cis- Groups on the same side of the double bond
Trans-Groups on opposite sides of the double bond.

Question 8

Why is configuration of biomolecules important? Rhodopsin example

Answer 8

Rhodopsin is a protein embedded in the (rods of the) retina of the eye that is bound to retinal. On exposure to light the configuration of retinal alters (from cis-retinal to trans-retinal) and this alteration stimulates nerves cells in the optic nerve to send messages to the brain where we “see”.

Question 9

What is configuration?

Answer 9

the fixed arrangement of atoms in a molecule

Question 10

What is conformation?

Answer 10

the spatial arrangement of groups that can have different positions in space due to the freedom of rotation of single bonds

Question 11

What are the 5 chemical reactions of life?

Answer 11

Redox reactions
Making and breaking C-C bonds
Internal rearrangements
Group transfers
Condensation and hydrolysis reactions

Question 12

OILRIG?

Answer 12

Oxidation Is Loss (of electrons)
Reduction Is Gain (of electrons)

Question 13

What is oxidising agent and what is reducing agent?

Answer 13

The oxidising agent is what becomes reduced itself and a reducing agent becomes oxidised itself.

Question 14

Redox in the context of NAD+ AND NADH?

Answer 14

NADH a reducing agent (which becomes oxidised itself to NAD+ as it reduces other compounds)

NAD+ is an oxidising agent (which becomes reduced itself as it oxidises other compounds)

Question 15

Condensation?

Answer 15

two smaller molecules combine to form a larger molecule and in doing so release water

Question 16

Hydrolysis?

Answer 16

breaking a large molecule into smaller units using water

Question 17

Describe protein structure?

Answer 17

Proteins are long chains of amino acids (polypeptides are chains of amino acids as well but shorter than proteins).
The amino group of one amino acid reacts with the carboxyl group of another to form a peptide bond.
A molecule of water is lost (condensation) as each bond is form.

Question 18

Describe structure of nucleic acid?

Answer 18

These form the core structure of DNA and RNA.
Nucleic acids are polymers of nucleotide (phosphate group attached to a sugar and a nitrogenous base) monomers linked by 3’,5’-phosphodiester bonds.

Question 19

What sugar is in RNA compared to DNA?

Answer 19

RNA- ribose
DNA- deoxyribose

Question 20

What are the nitrogenous bases?

Answer 20

Pyrimidines- Cytosine, Thymine (in DNA) , Uracil ( in RNA)
Purines- Adenine and Guanine

Question 21

Difference between RNA and DNA?

Answer 21

RNA is single stranded nucleic acid
DNA is double stranded nucleic acid

Question 22

Describe structure of lipids (fats and oils)?

Answer 22

Lipids (fats and oils) consist mainly of repeating units of fatty acids (FAs), which are long chains of C and H.

Question 23

Saturated, monosaturated, unsaturated fatty acids?

Answer 23

Saturated-ALL bonds are single
Monosaturated- ONE double bond
Polyunsaturated-more than one double bond

Question 24

How do double bonds affect fatty acid structure?

Answer 24

The more unsaturated the fatty acid (the more double bonds in the chain) the more fluid the fatty acid.

This has important implications for cell membranes, which are largely composed of fatty acids.

Question 25

Describe structure of Triacylglycerides ?

Answer 25

Also called triglycerides or fats.
Glycerol + 3 fatty acid chains.
The fatty acid chains can be the same (simple triacylglycerides) or mixed (2 or more different fatty acids).

Question 26

Describe structure of phospholipids?

Answer 26

Glycerol + 2 fatty acid chains + phosphate group.

Question 27

Describe structure of sterols?

Answer 27

Sterols are structural lipids present in cell membranes.
They have an steroid nucleus – 4 fused rings

Question 28

Explain how cholesterol is important sterol?

Answer 28

Essential component of cell membranes (role in membrane fluidity and reduces the permeability of the cell membrane).
Precursor to steroid hormones and fat soluble vitamins (A, D, E).