AP Bio Exam Review:Biochemistry & Cells

Elements of Life

• 25 elements•96% : C, O, H, N•~ 4% : P, S, Ca, K & trace

elements (ex: Fe, I)

Hint: Remember CHNOPS

II. Atomic Structure

• Atom = smallest unit of matter that retains properties of an element

• Subatomic particles:

Mass(dalton or

AMU)

Location Charge

neutron 1 nucleus 0

proton 1 nucleus +1

electron negligible shell -1

BondsCovalent Ionic Hydrogen

All important to life

Form cell’s molecules

Quick reactions/ responses

H bonds to other electronegative

atoms

Strong bondWeaker bond (esp. in H2O) Even weaker

Made and broken by chemical reactions

Weaker Bonds:Van der Waals Interactions: slight, fleeting

attractions between atoms and molecules close together– Weakest bond– Eg. gecko toe hairs + wall surface

1. Polarity of H2O

• O- will bond with H+ on a different molecule of H2O = hydrogen bond

• H2O can form up to 4 bonds

H2O Property Chemical Explanation

Examples of Benefits to Life

Cohesion•polar•H-bond•like-like

↑gravity plants, treestranspiration

Adhesion•H-bond•unlike-unlike

plants xylembloodveins

Surface Tension•diff. in stretch•break surface•H-bond

bugswater

Specific Heat•Absorbs & retains E•H-bond

oceanmoderates temps protect marine life (under ice)

Evaporation•liquidgas•KE

CoolingHomeostasis

Universal Substance•Polarityionic•H-bond

Good dissolversolvent

4. Solvent of life

• “like dissolves like”

Hydrophilic Hydrophobic

Affinity for H2O Appears to repel

Polar, ions Nonpolar

Cellulose, sugar, salt Oils, lipids

Blood Cell membrane

Acids and Bases

Acid: adds H+ (protons); pH<7Bases: removes protons, adds OH-; pH>7Buffers = substances which minimize changes

in concentration of H+ and OH- in a solution (weak acids and bases)

• Buffers keep blood at pH ~7.4• Good buffer = bicarbonate

Figure 3.9 The pH of some aqueous solutions

Functional GroupsFunctional Group Molecular Formula Names & Characteristics Draw an Example

Hydroxyl -OH Alcohols Ethanol

Carbonyl >CO Ketones (inside skeleton)Aldehydes (at end)

AcetonePropanol

Carboxyl -COOH Carboxylic acids (organic acids) Acetic acid

Amino -NH2 Amines Glycine

Sulfhydryl -SH Thiols Ethanethiol

Phosphate -OPO32- / -OPO3H2 Organic phosphates Glycerol phosphate

Monomers Polymers Macromolecules•Small organic •Used for building blocks of polymers•Connects with condensation reaction (dehydration synthesis)

•Long molecules of monomers•With many identical or similar blocks linked by covalent bonds

•Giant molecules•2 or more polymers bonded together

ie. amino acid peptide polypeptide protein

smaller larger

Dehydration Synthesis(Condensation Reaction) Hydrolysis

Make polymers Breakdown polymers

Monomers Polymers Polymers Monomers

A + B AB AB A + B

+ H2O+ + H2O +

I. Carbohydrates

• Fuel and building• Sugars are the smallest carbs

Provide fuel and carbon• monosaccharide disaccharide

polysaccharide• Monosaccharides: simple sugars (ie. glucose)• Polysaccharides:

Storage (plants-starch, animals-glycogen) Structure (plant-cellulose, arthropod-chitin)

Differ in position &

orientation of glycosidic

linkage

II. Lipids

A.Fats: store large amounts of energy– saturated, unsaturated, polyunsaturated

B.Steroids: cholesterol and hormonesC.Phospholipids: cell membrane

– hydrophilic head, hydrophobic tail– creates bilayer between cell and external

environmentHydrophilic head

Hydrophobic tail

Four Levels of Protein Structure:1. Primary

– Amino acid sequence– 20 different amino acids– peptide bonds

2. Secondary– Gains 3-D shape (folds, coils) by H-bonding– α helix, β pleated sheet

3. Tertiary– Bonding between side chains (R groups) of amino acids– H & ionic bonds, disulfide bridges

4. Quaternary– 2+ polypeptides bond together

amino acids polypeptides protein

• Protein structure and function are sensitive to chemical and physical conditions

• Unfolds or denatures if pH and temperature are not optimal

IV. Nucleic AcidsNucleic Acids = Information

Monomer: nucleotide

DNA RNA•Double helix•Thymine•Carries genetic code•Longer/larger•Sugar = deoxyribose

•Single strand•Uracil•Messenger (copies), translator•tRNA, rRNA, mRNA, RNAi•Work to make protein•Sugar = ribose

Comparisons of ScopesLight

• Visible light passes through specimen

• Light refracts light so specimen is magnified

• Magnify up to 1000X• Specimen can be

alive/moving• color

Electron

• Focuses a beam of electrons through specimen

• Magnify up to 1,000,000 times

• Specimen non-living and in vacuum

• Black and white

Prokaryote Vs. Eukaryote• “before” “kernel”• No nucleus• DNA in a nucleoid• Cytosol• No organelles other

than ribosomes• Small size• Primitive• i.e. bacteria

• “true” “kernel”• Has nucleus and nuclear

membrane• Cytosol• Has organelles with

specialized structure and function

• Much larger in size• More complex• i.e. plant/animal cell

Parts of plant & animal cell p 108-109

• Cells must remain small to maintain a large surface area to volume ratio

• Large S.A. allows increased rates of chemical exchange between cell and environment

Animal cells have intercellular junctions:•Tight junction = prevent leakage•Desomosome = anchor cells together•Gap junction = allow passage of material

Cell Membrane

6 types of membrane proteins

Passive vs. Active Transport • Little or no Energy• Moves from high to low

concentrations• Moves down the

concentration gradient• i.e. diffusion, osmosis,

facilitated diffusion (with a transport protein)

• Requires Energy (ATP)• Moves from a low

concentration to high• Moves against the

concentration gradient• i.e. pumps,

exo/endocytosis

hypotonic / isotonic / hypertonic

Exocytosis and Endocytosis transport large molecules

3 Types of Endocytosis:

• Phagocytosis (“cell eating” - solids)

• Pinocytosis (“cell drinking” - fluids)

• Receptor-mediated endocytosis

• Very specific• Substances bind to

receptors on cell surface