Chapter 2 - The Molecules of Life

What are Atoms?

• The smallest unit of matter

What is an element?

• Matter composed of one type of atom

What is a molecule?

• Formed by two or more atoms

  • Same type of atom or different

What is a compound?

• A molecule made with different types of atoms

What is the nucleus made out of? (2.1)

• Protons (+)

• Neutrons

  • Therefore a net positive charge and stable

What are electrons? (1.2)

• Particles that orbit the nucleus in shells

  • Negatively charged

    • Stabilize the positive charge of the nucleus

What are chemical bonds?

• Formed between atoms through interactions of electrons in their outer shells

How does an atom obtain an overall positive charge?

• By losing an electron (Cation)

How does an atom obtain an overall negative charge?

• Gaining an electron (Anion)

What is an ion?

• An atom or group of atoms that has a positive or negative charge

What are the types of bonds found in living organisms? (3)

• Ionic

• Covalent

• Hydrogen

What are ionic bonds?

• The result from attraction between ions of opposite charges

What are covalent bonds? (1.2)

• Formed when atoms share pairs of electrons

  • They’re strong bonds

• Found in many compounds, especially ones containing carbon

What are hydrogen bonds? (2.1)

• Occur between covalently bonded molecules that display polarity

• Loose attraction between oppositely charged regions of different molecules

  • Weaker than ionic and covalent bonds

What is polarity? (2.2)

• An unequal distribution of electric charges

• Creates regions of:

  • Partial negative charges

  • Partial positive charges

What are the characteristics as water as the solvent of life? (4.1)

• Water is approx. 75% cell weight

• High boiling point (100°C)

• Resistant to rapid changes in temperature 

• Water has an unequal charge distribution

  • Each water molecule can form up to 4 hydrogen bonds w/ other water molecules = unique properties

What does water’s unequal charge distribution result in? (1.2.1)

• Allows it to dissolve many ionic compounds (as a polar solvent)

  • Positive regions surround negative ions

  • Negative regions surround positive ions

    • → Holds ions in solution

What are the characteristics of water due to it’s polar nature? (1 + 1.1 + 1.1 + 1.1 + 1)

• Strong attraction between water molecules

• Polarity = Disassociation

  • Positive area attracts O^-, negative area attracts H⁺

• Key for digestive processes:

  • Large molecules → smaller

• Key for synthetic reactions:

  • Source of H + O atoms → organic compounds in cells

• Heat absorption increases kinetic energy + rate of motion

What is the relation between water’s polarity and ions?

• Facilitates the splitting + joining of hydrogen ions + hydroxide ions

What is the pH scale? (1.3)

• Describes concentration of H+ ions in a solution

  • pH 7 → netural

  • pH <7 → acidic

  • pH >7 → basic/alkaline

What are organic molecules?

• Any molecule that contains both hydrogen + carbon

What are the 4 major classes of organic molecules? (4)

• Carbohydrates

• Lipids

• Proteins

• Nucleic Acids

What are carbohydrates?

• Large group of compounds incl. sugars + starches

What are the characteristics of carbohydrates? (3)

• Contains C, H, O

• Generally polar

• Ready source of energy for cells

What are the types of carbohydrates? (2)

• Monosaccharides

• Disaccharides

What are monosaccharides? (2)

• Simple sugars - one saccharide

• Basic building blocks of other carbs

What are disaccharides?

• Two saccharides

What are polysaccharides + characteristic? (1.1)

• Many monosaccharides joined together

  • Often not soluble in water

What are lipids?

• Fats, complex lipids, steroids

What are the functions of lipids + characteristic? (3)

• Essential to structure + function of membranes

• Used for energy storage

• Non-polar molecules (hydrophobic)

What are fats composed of? (2)

• A glycerol backbone

• Fatty acids

What are the types of fats? (3)

• Monoglyceride - one fatty acid

• Diglyceride - two fatty acids

• Triglyceride - three fatty acis

What are saturated fats + the relation to membranes? (1.1)

• Fats with no double bonds

  • creates more solid membranes

What are unsaturated fats + the relation to membranes?

• Fats with double bonds 

  • creates more fluid membranes

What are the components of phospholipids? (3)

• Glycerol backbone

• 2 Fatty acids - non-polar (hydrophobic)

• Phosphate group head - polar (hydrophilic)

What are the characteristics of biological membranes + function? (1.1 + 1)

• Made from a phospholipid bilayer

  • semi-fluid (unsaturated + saturated fats)

• Separates ICF + ECF of cell

What are the characteristics of steroids? (3)

• Structurally different from other lipids

• Built on a hydrophobic 4 ring structure

• Found in eukaryotes + not prokaryotes

What are amino acids?

• Building blocks for proteins

What elements are proteins made of?

• C, H, O, N, S

What is the function of proteins? (1.1)

• Required in all aspects of cell structure + function

  • Most act as enzymes 

What are enzymes?

• Proteins that act as biological catalysts

What is the structure of proteins? (1 + 1.2 + 1)

• Contain 20 different amino acids

• Have at least:

  • One amino group (-NH2)

  • One carboxyl ground (-COOH)

• Side groups determine properties

What are covalent peptide bonds?

• Bonds that join amino acids together → proteins

What is a polypeptide? (1.1)

• A chain of amino acids

  • makes up proteins

How is the shape + function of a protein determined?

• The sequence of amino acids

What are nucleotides?

• Building blocks of nucleic acids

  • Covalently bonded → a strand of nucleic acid

What are nucleic acids? (2)

• Deoxyribonucleic acid

• Ribonucleic acid

What are the parts of a nucleotide? (3)

• Nitrogenous base

• Pentose sugar

• Phosphate group

What are nitrogenous bases? (2)

• Purines - Adenine, Guanine

• Pyrimidines - Cytosine, Thymine, Uracil

What are pentose sugars? (1.2)

• Five carbon sugars

  • Ribose

  • Deoxyribose

What are the components of DNA? (3)

• Nitrogenous bases - A, T, C, G

• Sugar - Deoxyribose

• Phosphate group 

What are the components of RNA? (3)

• Nitrogenous bases - A, U, C, G

• Sugar - Ribose

• Phosphate group 

What is the function of DNA?

• Stores genetic info of all cellular organisms

What is the function of RNA?

• Involved in communicating the instructions stored in DNA

What is the structure of DNA? (2)

• Strands build from a sugar phosphate backbone

• Two strands held together by hydrogen bonds between nitrogenous bases = double helix