Chemical Basis of Life
Vocabulary
Polarity Hydrogen bond Adhesion Cohesion
Concentration Solution Solute Solvent
4 carbon compounds monomer polymer carbohydrate
monosaccharide polysaccharide amino acid protein
lipid fatty acid nucleic acid nucleotide
enzyme catalyst pH specific heat
Concepts to Know
WATER
Why so special and important?
Nearly 75% of our earth is covered in water.
Our bodies are 60-65% water. Our blood is 85% water.
None of the many reactions that occur in our bodies would occur
without water.
Composition of water: H2O
Properties of Water
· Water is POLAR.
The diagram shows that one side of the water molecule is positively charged and the other is negatively charged.
The molecule itself is neutral. These opposite charges make water a polar molecule.
· Water undergoes ADHESION and COHESION due to its polarity.
The negative oxygen of one water molecule is attracted to the positive hydrogen of another molecule forming a hydrogen bond. In other words water likes to stick to itself. Water sticking to water is called cohesion. Water’s polarity allows it to attract to other surfaces too (like glass). Water sticking to something else is called adhesion.
1. In the diagram to the right use dotted lines to draw in the bonds that form between water molecules.
Positives connect to negatives, up to four bonds per water molecule.
2. What is the name of this type of bond?
Hydrogen or “H” bond
3. What special property do the bonds give to water.
Several: cohesion first and foremost (water sticking to itself).
Creates surface tension on the water (water skipper can seemingly “walk” on water
· Water has a HIGH SPECIFIC HEAT.
Hydrogen bonds also give water a high specific heat . Water can absorb a great amount of heat. It takes a lot of energy input to change the temp. of water. This allows water to regulate temperature of the Earth and also our bodies.
Specific heat is the amount of energy required to raise one gram of water 1 degree Celsius.
8. Can you think of a reason why water can absorb so much heat? Hint – think bonds
Hint – think bonds
Before water boils or undergoes and extreme temperature change hydrogen bonds must be broken. Weak hydrogen bonds give water a high specific heat.
· Water EXPANDS WHEN IT FREEZES. Ice is therefore less dense than water. ICE FLOATS in water.
This is also due to hydrogen bonding. Molecules freeze in a rigid structure and expand.
9. Challenge yourself to think of two ways that specific heat and the freezing point of water help support life on earth.
Specific heat: keeps aquatic environments from experience extreme temperature fluctuations, changes are gradual.
Ice expands when frozen, floats on surface water bodies and insulates aquatic organisms from extreme cold.
CARBON
Use the diagrams below to fill in the blanks and describe why carbon is so important to life.
· Carbon has ______4______in the outer (valence) shell
o Valence shell enables easy formation of four covalent bonds
o Covalent bonds involve ____sharing_____ of ___electrons___ between two atoms
· Carbon has the ability to form ______long chains______by forming several bonds in a row
· Variety is created by the many partners that carbon can bond with
The 4 major Carbon Compounds: Carbohydrates, Lipids, Nucleic Acid, Protein
· Small carbon compounds called monomers link together to form large carbon compounds called polymers. Each of the 4 carbon compounds has a monomer that links together to make the macromolecule (polymer).
· Monomers bond together to make polymers by dehydration synthesis.
· Polymers can be broken down into monomers by hydrolysis.
MACROMOLECULES: STRUCTURE AND FUNCTION
Macromolecules and Their FunctionClass / Monomers / Functions
Carbohydrates / Monosaccharides / Energy, raw materials, energy storage, structural compounds
Lipids / Glycerol, fatty acids, steroids / Energy storage, membranes, steroids, hormones
Proteins / Amino acids / Enzymes, transport, movement, receptors, defense, structure
Nucleic acids / Nucleotides / Heredity, code for amino acid sequence
CARBOHYDRATES
· _Dehydration synthesis_ breaks down carbohydrates into monosaccharides like glucose.
· Glucose is used in ___mitochondria____ and converted to __ATP__ for energy.
· Excess glucose is bonded together to form a polymer called a _____polysaccharide______and stored in __cells______, ___organs (complex organisms)______and then ____used for energy______.
LIPIDS
· Lipids are nonpolar macromolecules made from long carbon chains
· Lipids can be fats, phospholipids, or steroids
· Fats act as storage of material that can be used for energy.
· ____Phospholipids________ compose cell membranes
· Lipids can be ___saturated______or _____unsaturated______
PROTEIN
· Protein is the main unit of structure and function in the body.
· Amino acids are made up of a carbon attached to _____Amino______and ____Carboxyl______groups. They are made unique by the “R” group that is attached to the carbon.
· There are __20__ amino acids.
· __DNA_____ codes for the amino acid sequence of each protein in the body.
NUCLEIC ACID
· Nucleic acids are polymers of nucleotides
· Nucleotides are monomers that consist of pentose sugar (the hexagon shape in the diagram) attached to a phosphate group (in red on diagram) and nitrogen base (in blue on diagram)
· The sugar can be deoxyribose (as in DNA or__deoxyribose nucleic acid__) or ribose (as in RNA or __ribose nucleic acid__)
· DNA and RNA are central to heredity and are made unique by the nitrogenous ___base____ that is attached
· Nitogenous bases can be cytosine (C), thymine (T), uracil (U), adenine (A), or guanine (G)
ENZYMES
· Enzymes are proteins that act as biological catalysts
· Catalysts increase the rate of a reaction without being changed by the reaction
· Substrates are the reactants on which enzymes work
· Rate of reaction in both directions (oxidation or reduction) is increased by the presence of specific enzymes.
· __Active______Site___ refers to the part of an enzyme that interacts with a substrate, where the substrate fits
· Enzyme reaction rates are impacted by temperature, pH & substrate concentration
· Temperature is a measure of kinetic energy
o Kinetic energy is the energy of motion. Higher temperature means __faster_____ moving particles.
o The number of collisions between enzymes and substrates is increased if the particles move around __faster__ (higher temperature)
o Our enzymes do not function well above or below the ___optimal (best)______temperature
o The enzyme denatures, or breaks down, if the enzyme gets too ___hot or cold___
· pH measures acidity
o Each enzyme has a specific pH at which it functions best
o If the conditions are too acidic (low pH) or too basic (high pH), the enzyme may denature
· Concentration is a measure of how many substrate molecules are present in a given volume.
o Higher concentration of substrate means more substrate finding the active site.
o Production speeds up.
Practice Questions:
1. Which statement correctly describes how carbon’s ability to form four bonds makes it uniquely suited to form macromolecules?
A. It forms short, simple carbon chains.
B. It forms large, complex, diverse molecules.
C. It forms covalent bonds with other carbon atoms.
D. It forms covalent bonds that can exist in a single plane.
2. What reaction or process forms a polymer from 2 monomers?
A. glycolysis
B. hydrolysis
C. photosynthesis
D. dehydration synthesis
3. Carbohydrates and proteins are two types of macromolecules. Which functional characteristic of proteins distinguishes them from carbohydrates?
A. large amount of stored information
B. ability to catalyze biochemical reactions
C. efficient storage of usable chemical energy
D. tendency to make cell membranes hydrophobic
4. Substance A is converted to substance B in a metabolic reaction. Which statement best describes the role of an enzyme during this reaction?
A. It adjusts the pH of the reaction medium.
B. It provides energy to carry out the reaction.
C. It dissolves substance A in the reaction medium.
D. It speeds up the reaction without being consumed.
5. A scientist observes that, when the pH of the environment surrounding an enzyme is changed, the rate the enzyme catalyzes a reaction greatly decreases. Which statement best describes how a change in pH can affect an enzyme?
A. A pH change can cause the enzyme to change its shape.
B. A pH change can remove energy necessary to activate an enzyme.
C. A pH change can add new molecules to the structure of the enzyme.
D. A pH change can cause an enzyme to react with a different substrate.
6. Whenever biological organic compounds, such as proteins and carbohydrates, are broken down or synthesized...
a. a phase change of matter results.
b. thermal expansion occurs.
c. sunlight is required.
d. energy is absorbed or released.
7. Why does an enzyme function as a catalyst in a reaction?
a. It creates the right pH needed for the reaction.
b. It decreases the amount of energy needed for the reaction.
c. It provides the extra energy needed for the reaction.
d. It maintains the proper temperature needed for the reaction.
Examine the structural formula below.
8. Which of the following macromolecules is best represented by this formula?
a. nucleic acid c. protein
b. carbohydrate d. lipid (remember lipids are made of one glycerol (red) and three long chain fatty acids (blue)
Open-ended Question:
9. Proteins are a major part of every living cell and have many different functions within each cell. Carbohydrates also perform numerous roles in living things.
Part A: Describe the general composition of a protein molecule.
_____Proteins are made from carbon, oxygen, hydrogen, nitrogen and some have sulfur. These elements form amino acids. Amino acids form proteins.
______
Part B: Describe how the structures of proteins differ from the structures of carbohydrates.
______Carbohydrates are in long chains formed by sugars that have bonded together. Proteins can be in sheets or folded shapes. Carbohydrates only have carbon, hydrogen and oxygen in them. ______
Part C: Describe how the functions of proteins differ from the functions of carbohydrates
______Proteins make up the reactions that speed up reactions in living things. Proteins also make antibodies. Carbohydrates give us energy (starch, glycogen) and make up plant cell walls (cellulose)
______