The Chemistry of LifeIB Biology
Biochemistry Elements of lifeMost common elements of living things: (3.1.1)• Carbon (C)• Hydrogen (H)• Oxygen (O)Other elements both plants and animals have:
(3.1.2 & 3.1.3)• Nitrogen (N)
DNA and RNA
Amino acids (proteins)
• Calcium (Ca)
Component of cell walls
Component of bones and teeth
• Phosphorus (P)
ATP• Adenosine triphosphate stores energy in both plants and
animals
DNA and RNA
• Iron (Fe)
In hemoglobin (animals)
In cytochromes• Molecules in the electron transport chain (ETC) of:
– Photosynthesis (in plants)
– Cellular respiration (in plants and animals)
• Sodium (Na)
Ion used for osmosis – “salty roots”
Ion used for nerve transmission in animals
Atom vs. Ion
Ex: Hydrogen• Atom
• Ion – charged particle
1 p+
1 n0
1e-
1 p+1 n0
(no electron orbiting)
H
H+
Water (3.1.4)
1. Structure
-O H+
water is polar (has a positive and +H negative end)
Hydrogen BondO H 1. alone they are weak
2. together they are strong
H ex: slide on a desk
O H
H
Oxygen is very electronegative, which means it has an affinity for the electrons it is “sharing” in the covalent bond with hydrogen.
The hydrogen bond is the attraction between the slightly positive H and the slightly negative O
2. Thermal Properties of Water
(3.1.5, 3.1.6)
a) Water has a high heat of vaporization
• Takes a lot of heat to change the state of water from a liquid to a gas
• 60 times more energy to vaporize water than alcohol
• Because energy (heat) is required to vaporize water (even when it’s at its boiling point), evaporation of water cools down surfaces (SKIN, LEAVES)
a)
b) Water has a high specific heat• 2X that of alcohol• 4X that of air• 1 calorie raises 1 gram of water 1o C• Keeps temperature of water constant
c) Water changes density as it freezes
10oC 4oC 0oC
Less dense Most dense Least dense
(sinks) (ice floats)
3. Cohesive properties of water (3.1.5, 3.1.6)
• Molecules stick together (hydrogen bonds)• Due to polarity• Water moves up the xylem in plant stems
– Capillary action– Cohesion and adhesion
» Adhesion occurs when water clings to xylem tissue during plant transpiration
1.
2.
4. Solvent properties of water (3.1.5, 3.1.6)• Salt (ionic-ally bonded) is dissolved in water (because
it’s polar) and carried by blood
Na+ -O H+
+H
Cl-
Hydrophilic – has an affinity for water; “water-loving”
ex: glucose in blood
sucrose in plants
Hydrophobic – water fearing
ex: oil, grease
Question: When is it beneficial to have lipids be hydrophobic?
5. Significance of water to living organisms (3.1.6)
PLANTSANIMALS
A. Coolant evaporation evaporation-use of heat for on leaf causes of sweat causesevaporation cooling cooling(high heat ofVaporization)
B. Transport carries carries medium sucrose glucose-because itspolarity causesit to be a goodsolvent
PLANTSANIMALS
C. Good
habitat -water stays at a constant
-due to temperature high specific
heat
1. Keeps
temperature
constant
2. Transparency -photosynthesis -see prey
Organic – contains carbon (and usually hydrogen), and is found in a living organism
-ex: C6H12O6 glucose
• Exceptions:• Hydrogencarbonates – (a.k.a. bicarbonate) the anion
HCO3-
• Carbonates – the anion CO3-
• Oxides of carbon – carbon monoxide (CO), carbon dioxide (CO2)
(3.2.1)
(continuing… NOT talking about water anymore!)
4 Biological Molecules: 1. Carbohydrates (sugars)
• Monosaccharides – major nutrients for cells
glucose, galactose, fructose, ribose
Glucose circulates in animal blood and is used by cells for energy (3.2.4)
Fructose is the sugar in the fruit of plants
• Disaccharidesglucose + glucose maltose
glucose + fructose sucrose
glucose + galactose lactose
Lactose is the sugar in milk – gives energy (3.2.4)
Sugar is transported as sucrose through the vascular tissue of plants (3.2.4)
(3.2.3)
• Polysaccharides (3.2.3.& 3.2.4)
Energy-storing in plants: starch
Energy-storing in animals: glycogen
Structural in plants: cellulose
Structural in animals: chitin
All of these are made of chains of glucose molecules
2. Proteins (structure, enzymes)
Amino acids are the building blocks
2 amino acids – a dipeptide
Peptide Bonds
R R R R
H2N – C – C – N – C – C – N – C – C – N – C – C – OH || || || ||
H O H H O H H O H H OAmino
CarboxylThis is a ‘polypeptide’
3.2.5 Condensation & Hydrolysis Reactions
• When are joining subunits (monomers) of molecules together to make polymers, a water molecule is given off.
• This is a condensation synthesis.• When a polymer is broken into monomers, a water
molecule is used.• This is hydrolysis.
NH2 -–C—COOH + NH2—C—COOH NH2—C—CO—NH—C—COOH + H2O
R R R R
H H H H
Mono Mono Polymer Water
3. Lipids (fats; mainly for energy storage, thermal insulation, and structure)H GLYCEROL O 3 FATTY ACIDS | ||
H C OH HO C (CH2)n CH3
O ||
H C OH HO C (CH2)n CH3
O ||
H C OH HO C (CH2)n CH3 |
H
Hydrolysis vs. Condensation Synthesis (3.2.5, 3.2.6)
H O | ||
H C O C (CH2)n CH3
O ||
H C O C (CH2)n CH3
O ||
H C O C (CH2)n CH3 |
H +3 H2O Lipid + Water
Phospholipid
O-
|
R – O – P – O – CH2
|| |
O H – C – O – C – (CH2)n – CH3
|
H – C – O – C – (CH2)n – CH3
|
H
POLAR HEAD
(hydrophilic)
NON-POLAR TAIL
(hydrophobic)
O
O
This negative oxygen makes
this part of the molecule
hydrophilic
Energy Storage (3.2.7)
Carbohydrates vs. Lipids
Soluble in water, Insoluble in water, do not
easily transported in blood cause problems with osmosis
Broken down quickly Broken down for energy
for energy more slowly
Less energy per gram Twice as much energy
per gram
4. Nucleic Acids (DNA & RNA) (3.3.1, 3.3.2)
• Made of nucleotides (these are the monomers)
Phosphate
Sugar Nitrogen
Base
Nitrogen Bases• Adenine• Guanine• Cytosine• Thymine (*DNA only)
• Uracil (*RNA only)
Ribose or Deoxyribose sugar
• DNA (3.3.3, 3.3.4, 3.3.5)
P P
D A T D
P P
D G C D
P P
D C G D
P P
D G C D
-double stranded
-Helix (twisted)
-A-T and G-C are complementary
(weak) hydrogen
bond
One nucleotide
Covalent
bond
• RNA
P
R U
P
R A
P
R C
P -single strand
R G -U instead of T
You MUST be able to recognize the following molecules from diagrams showing their structure: (3.2.2)
• Amino acids
• Glucose
• Ribose
• Fatty acids