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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