MBIO 1220 Unit 2: Chemical Properties

Atom

Smallest chemical unit of matter

Element

Matter composed of one type of atom

Molecule

Two or more atoms of the same type combined together (e.g., C, N, O, Na).

Compound

Two or more different atoms combined together (e.g. NaCl)

What particles make up the nucleus of an atom?

Protons (+) and Neutrons (neutral)

Do protons and neutrons participate in chemical reactions?

No, the nucleus is stable and does not participate.

Where are electrons found and what is their charge?

Orbiting the nucleus in shells, negatively charged (e-)

Proton

Positively charged particle in the nucleus

Neutron

Neutrally charged particle in the nucleus

Nucleus (in chemistry)

Dense center of an atom containing protons and neutrons

Electron shell

Energy levels around the nucleus where electrons orbit

Ion

Atom(s) that have lost or gained an electron

Cation

Positively charged ion (lost electrons)

Anion

Negatively charged ion (gained electrons)

Bonding capacity

The number of covalent bonds an atom can form (based on unfilled outer shell electrons)

Electronegativity

An atom’s ability to attract electrons in a chemical bond

Polypeptide

A chain of amino acids linked by peptide bonds.

Peptide bond

Covalent bond linking amino acids in a protein

Purine

Double-ring nitrogenous base (Adenine, Guanine)

Pyrimidine

Single-ring nitrogenous base (Cytosine, Thymine, Uracil)

Sugar-phosphate backbone

The alternating sugar and phosphate structure forming the structural framework of DNA/RNA strands

Complementary base pairs

Specific hydrogen bonding between nitrogenous bases: A–T (or A–U in RNA), G–C

An ionic bond is formed by…

Attraction between oppositely charged ions (cation + anion)

Usually between metal + non metals

Strength of ionic bonds

Strong in dry environments, weaker in aqueous solutions

Example of ionic bond in biology

NaCl (sodium chloride)

Covalent bonds are formed by…

Sharing pairs of electrons between atoms.

Usually between non metal + non metal

Strength of covalent bonds

Very strong

Example of covalent bond in biology

CH₄, organic molecules like glucose

Commonly found is compounds containing Carbon & Hydrogen

hydrogen bond is formed by…

Hydrogen bonds form when the hydrogen atom (that is covalently bonded to an electronegative atom) is attracted to another electronegative atom in the same compound or different compound. It is a weak attraction between a slightly positive H and a slightly negative atom (like O or N)

Strength of hydrogen bonds

Weak individually, but strong collectively

Example of hydrogen bond in biology

Between water molecules, or between DNA base pairs

Which type of bond is formed by sharing electrons?

Covalent bonds

Which bond is weak and helps bridge separate molecules?

Hydrogen bond

What defines an organic molecule?

Contains both carbon and hydrogen

What are the four major classes of organic molecules?

Carbohydrates, lipids, proteins, nucleic acids

What is the ratio of C:H:O in carbohydrates?

1:2:1

monosaccharides, disaccharides, and polysaccharides

Mono = one sugar, Di = two sugars, Poly = many sugars

Main function of carbohydrates

Provide quick energy and structural support

Monosaccharide example

Glucose (C₆H₁₂O₆)

fructose (from fruits)

galactose (from milk)

ribose & deoxyribose (components of DNA & RNA, respectively)

Disaccharide example

Sucrose (glucose + fructose)

Lactose (glucose + galactose)

Maltose — malt sugar (glucose + glucose)

Polysaccharide example

Glycogen, Starch (energy storage)

Cellulose (structural component in plant cell wall)

lipids are made of…

Glycerol + fatty acids (sometimes phosphate or steroid rings)

Main function of lipids

1. Energy storage

2. Membrane structure

3. Signaling

phospholipids are made of…

Glycerol, 2 fatty acids, and a phosphate group

What structure do phospholipids form in water?

Bilayer (biological membrane)

What makes phospholipids unique?

Amphipathic (hydrophilic head + hydrophobic tails)

Example of a steroid

Cholesterol, vitamin D

What makes steroids different from other lipids?

4-ring hydrophobic structure

proteins are made of…

Amino acids linked together by peptide bonds

Function of proteins

Enzymes, structure, transport, regulation.

nucleic acids are made of…

Nucleotides (sugar, phosphate, nitrogen base)

DNA’s function

Stores genetic information

RNA’s function

Carries instructions from DNA and helps build proteins

Why do chemical bonds form?

To achieve chemical stability by filling outer electron shells

How many electrons can be found in each electron shell (1st, 2nd, 3rd)?

1st = 2, 2nd = 8, 3rd = 8

What gives water its unique properties like high boiling point?

Ability to form up to 4 hydrogen bonds

How does water moderate temperature and why does it have a high boiling point?

Hydrogen bonds absorb heat before breaking, slowing temperature changes and giving water a high boiling point

How does water act as a solvent and why is that important?

Its polarity allows it to surround and separate ions/polar molecules, making it essential for chemical reactions and transport in cells

How is water used in digestion and synthesis of molecules?

Hydrolysis uses water to break molecules apart; dehydration synthesis removes water to build larger molecules

What is the difference between saturated and unsaturated fatty acids?

Saturated = no double bonds, solid; Unsaturated = double bonds, fluid

What role do saturated vs. unsaturated fatty acids play in membranes?

Saturated = rigid membranes; Unsaturated = fluid membrane

What does it mean that membranes are semi-fluid?

Lipids and proteins can move laterally, allowing flexibility while maintaining structure

How many hydrogen bonds are formed between complementary DNA bases?

A–T = 2 hydrogen bonds; G–C = 3 hydrogen bonds

What does the pH scale measure?

Concentration of H+ ions (acidity)

pH values – what is neutral, acidic, and basic?

Neutral = 7, Acidic < 7, Basic > 7