Unit 2 (Biochemistry) Notes, Part 2: Properties of Water

Why do we study water properties in biology class?

• About 2/3 of the mass of a cell is water!

• Most life-sustaining reactions occur in water solutions (mixtures of water and dissolved substances)

Water Molecule

• 2 atoms of hydrogen linked by covalent bonds to 1 atom oxygen (H2O)

• Polar Molecule: has positive hydrogen end and negative oxygen end

Water is Polar Polarity: The electrons are unevenly distributed between

the Oxygen and the two Hydrogen atoms.

– Oxygen has 8 protons. Each hydrogen has 1.

Water is PolarThe atom with more protons (Oxygen) pulls shared

electrons towards itself this atom ends up with a slight negative charge. The other atom ends up with a slight positive charge.

Water forms Hydrogen Bonds

Hydrogen Bonds: Form due to attraction between different water molecules (because opposites attract).– Not as strong as

ionic/covalent bonds

Water can form up to 4 hydrogen bonds at once– A diagram of what’s going on:

Water forms Hydrogen Bonds

Water is CohesiveCohesion: Water molecules are drawn tightly together

(due to hydrogen bonding)

Water molecules on the surface of a lake or pond attract (through cohesion) and form a film that requires force to break through (this is called surface tension)

• Explains why:– Water beads on a surface (like the lab table)– Insects can walk on water

Cohesion Surface Tension

Water is Adhesive = Adhesion = Water adheres (sticks) to

different surfaces– Ex: Measuring water in a graduated cylinder

• Water adheres (sticks) to the glass more than it sticks to itself

• That’s why there is a dip (aka meniscus) in the water when you read the volume

Cohesion Adhesion

Ex: Water Bubble Ex: Water and Paper Towels

Water can undergo Capillary Action

Capillary Action= Water can flow up a tube, against gravity– Ex: Plants absorbing water through their

roots and up their stems

Capillary Action (Draw this!)

Water is an Excellent Solvent

• Water often found as part of a mixture called a solution

• Solution: one substance (solute) dissolves into another (solvent); water is called the “universal solvent”

Salt (NaCl) in Water

Why is this important in

humans?

Water as a Solvent

Water Has a Neutral pH

• pH: measure of how acidic or basic a solution is

• scale is 0 to 14• If pH = 7, then

substance is neutral (not acid or base)

Water is less dense in its solid form

• Water is less dense in its solid form than it is in its liquid form (Ice floats!)… as water cools, more hydrogen bonds form and push water molecules farther apart from one another

• Why might it be a bad thing for ice to sink in a pond?

What does ice look like at the molecular level?

Water has a High Heat Capacity• Water absorbs a lot of heat

from the air without having a large temperature change because it takes a lot of energy to break bonds between water molecules before the water can increase in temperature!

• So…lakes and oceans often stabilize air temperatures

• Water absorbs heat when it evaporates; this is why sweating helps us cool down!

High Heat Capacity of Water

Unit 2 (Biochemistry) Notes, Part 3: Macromolecules

What elements are most common in our cells?

• Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and Sulfur.

• Remember CHNOPS!

What have we already talked about?

• Water…which elements are found in water?

Carbon CompoundsA carbon atom can form four covalent

bonds with other atoms

Carbon Compounds• Organic chemistry is the study of all

compounds that contain bonds between carbon atoms.

Carbohydrates

Nucleic Acids (DNA)

Lipids (Fats)

Proteins

Carbon Compounds

• macromolecules: large molecules formed by process called polymerization

• polymer: forms when many smaller molecules (called monomers) bond together, usually in long chains

Macromolecules in Living Things

• 4 Types

1) Carbohydrates

2) Lipids

3) Nucleic Acids

4) Proteins

1) Carbohydrates

• Functions: source of short-term energy; also used in plant cell walls

• Made of: Carbon, Hydrogen, Oxygen (1 C: 2H: 1O)

Glucose

1. Carbohydrates (Sugars)

• monosaccharide: carbohydrate monomer, simple sugars

Example: glucose and fructose

• disaccharide: 2 monosaccharides form 2-sugar carbohydrate

Example: sucrose

1. Carbohydrates• polysaccharide: carbohydrate polymer

(forms when monosaccharides join together in a long chain)

Examples:1) starch: plant energy storage2) glycogen: animal energy storage3) cellulose: cell walls in plants

2. Lipids (Fats)

• Made of: Carbon and Hydrogen (with a few Oxygens)

• Functions: long-term energy storage, insulation, cell membranes

• Examples: fats, oils, and waxes

2. Lipids

• Structure: Usually 3 fatty acids (carbon-hydrogen chains) bonded to 1 glycerol molecule

2. Lipids• Saturated vs. Unsaturated Fat…which is

“worse” for you and why?

Saturated Fat (Butter)

Unsaturated Fat (Oil)

3. Nucleic Acids

• Functions: store & transmit information in cells in form of a code

• Made of: C, H, O, N, and P

• Nucleotide: monomer of a nucleic acid

• DNA or RNA: polymers made by linking nucleotides in a chain

3. Nucleic Acids

• Nucleotide

• DNA

3. Nucleic Acids

• DNA : deoxyribonucleic acid; master copy of organism's genetic code

• RNA: ribonucleic acid; forms copy of DNA; used to make proteins (protein synthesis)

4. Proteins

• Made of: C,H,N,O and sometimes S

• Functions: 1) Structure (proteins in hair and nails)2) Transport (hemoglobin in blood)3) Movement (proteins in muscle)4) Defense (antibodies)5) Controlling signals between cells and reactions inside cells (hormones and

enzymes)

4. Proteins• Amino Acids : Monomers of proteins; 20

common amino acids ; Consists of a central Carbon atom bonded to 4 groups

• 4 Groups

1) Hydrogen Atom

2) Amino Group

3) Carboxyl Group

4) R group (changes in each Amino Acid!)

4. Proteins• Polypeptide: polymer; one chain of amino

acids

• Proteins: several polypeptides folded around each other (shape function)

Unit 2 (Biochemistry) Notes, Part 4: Enzymes

Why do we study chemical reactions in biology?

• Chemistry isn’t just what life is made of, chemistry is also what life does

• Everything that happens in an organism is based on chemical reactions (growth, response to environment, etc.)

Chemical Reaction

• A process that changes reactants into products.

• Slow Reactions vs. Fast Reactions

• Chemical reactions breaking bonds in reactants and forming bonds in products

Energy Changes• Some reactions release energy and some

absorb energy

• Activation Energy: the energy required to start a reaction

Speeding up Reactions

• Slow reactions or reactions with high activation energies need a catalyst

• Catalyst = any substance that lowers the activation energy of a reaction to “speed it up”

• Enzymes are catalysts that are protein molecules.

Enzymes• Enzymes provide a site

where reactants can be brought together to react.

• In an enzyme-catalyzed reaction, the reactants are called substrates.

• Each enzyme has a specific shape and a specific portion called the active site, where substrates bind.

• The substrates must fit exactly into the active site. This is called the lock and key model.

• Once the reaction is complete, the enzyme releases the products of the reaction.

• Enzymes can join or break substrates into products.

Breaking 1 Substrate into 2 Products

G:\Teacher Resources\Downloaded Videos\Enzyme Action.avi

Joining 2 Substrates into 1 Product

• Enzymes can break or join substrates into products.

• Enzymes work best at a certain pH and temperature.

• Roles of Enzymes:1) regulating chemical pathways2) making materials3) releasing energy4) transferring info