AP Bio Exam Review. Molecular Biology. Importance of molecules and bonding Bonds: Ionic – transfer of electrons, results in charged atoms or ions Covalent – sharing of electrons; most common in organic molecules. Types of covalent bonds.
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Molecular Biology • Importance of molecules and bonding Bonds: Ionic – transfer of electrons, results in charged atoms or ions Covalent – sharing of electrons; most common in organic molecules
Types of covalent bonds • Polar – results if one element is more “grabby” for the electrons (oxygen, nitrogen) ex – Oxygen in the H2O molecule • Nonpolar – electrons are shared equally, no areas of charge • Important in shape of molecules
Bonds between molecules • Hydrogen bonding- “attraction” between H of one molecule and an electronegative element in another molecule
Van der Waal forces: is the sum of the attractive or repulsive forces between molecules
Organic chemistry – the chemistry of Carbon compounds • Most biochemical macromolecules are polymers (units linked together) • For the exam, think about what elements are found in the various macromolecules.
Carbohydrates • Main energy source • Made of monosaccharides • many H and OH • In water, forms rings
Can link together to form disaccharides or polysaccharides (starches) with the loss of a water molecule (dehydration synthesis or condensation reaction)
When polysaccharides are taken apart, water has to be added back in: Hydrolysis
Important polysaccharidesThese are made of glucose units. • Glycogen – animal starch, stored in liver and muscles • Cellulose – plant starch (animal can’t digest) • Amylose – plant starch
Don’t forget when figuring out formula for the polysaccharides to subtract the water molecules! Linking 6 glucose (C6H12O6) units:
Proteins • Made of amino acids (20) • Used for structure, enzymes, hormones, transport molecules, etc. • Shape very important
R groups? • Make each amino acid unique • Can confer polarity to the protein • Can be hydrophobic or hydrophilic • Important in secondary and tertiary folding
Orientation is important – Carboxyl group joined to amino group Amino acids are linked by peptide bonds in a condensation (dehydration) reaction
Three levels of protein structure • Primary: chain of amino acids • Secondary: Beta pleats and alpha helix due to hydrogen bonding • Tertiary: interactions betweenR groups due to ionic attractions, polarity, disulfide bridges, etc. • Quaternary: attractions between chains
Lipids • Used for insulation, energy • Nonpolar (do not dissolve in water) • Contain fats, oils, waxes, steroids such as cholesterol
Structure of a fat – glycerol and 3 fatty acids unsaturated
Steroids, such as cholesterol,ring structure Also important in cell membranes
Nucleic Acids • DNA, RNA • Made of nucleotides • Each nucleotide has a sugar, phosphate, and a nitrogenous base (A,T,C,G) • Nucleotides also found in ATP and GTP, energy transfer molecules
Enzymes • Protein catalysts • Very specific • Affected by temp, pH, competing molecules • Rate can be altered by amount of substrate/enzyme • Usually named by what they work on
Enzyme Lab • Catalase – breaks down hydrogen peroxide into water and oxygen • Used sulfuric acid to stop reaction • Titration using KMnO4 to measure amt of H2 O2 left. • Measured rate
The rate can be defined as the amount of product formed in a period of time.
Allosteric Interactions • Another molecule can bind and cause the enzyme to change shape
Difference in Eukaryotic and Prokaryotic Cells • Prokaryotic cells do not have membrane-bound organelles such as nuclei, ER, Golgi, etc. • Their energy reactions are carried on in sections of their cell membrane. • They do have ribosomes , DNA and some have cell walls.
Developing the eukaryotic cell • Think about importance of an endomembrane system (endocytosis) and endosymbiosis.
Cell Organelles Nucleus – control via DNA making proteins Nucleolus – stores ribosomes ER – rough – site of ribosome attachment - smooth – lipid metabolism, toxin removal Lysosomes – digestive vacuoles Golgi – packages, modifies proteins Mitochondria – energy (ATP) via aerobic cell. resp Chloroplasts – photosynthesis Cytoskeletal elements – microtubules, microfilaments, support, make up other structures (centrioles, flagella, etc.) Centrioles – cell division (animal cells), anchor spindle fibers
Cell Membrane • Made of phospholipids and integral and peripheral proteins (act as carrier molecules, enzymes, gates etc) • Cholesterol – maintains fluidity • Have glycoproteins and glycolipids as surface markers (receptors, MHC’s etc) • Hydrophobic on inside, hydrophilic on outside
Differences in cells • Cell walls in plant, fungi, bacterial cells • Cell wall composition varies - fungi: chitin - plants: cellulose - bacteria: peptidoglycan • Chloroplasts in photosynthetic cells
Connections between cells Gap junctions – animals Plasmodesmata – plant cells
Movement of materials in and out of cells • Surface area to volume ratio important in determining the movement of materials Smaller cells better!
Types of transport • Diffusion (facilitated uses carrier molecules/channels) – passive • Osmosis – Water movement – passive • Active Transport: against conc gradient, - uses energy and carrier molecules, also includes endocytosis and exocytosis
Osmolarity • Direction of water flow depends on solute conc • WATER ALWAYS MOVES INTO A HYPERTONIC (HYPEROSMOTIC) SITUATION! • Look at solute concentration to gauge water movement.
Equation for water potential (osmotic potential) Ψ = ΨP + Ψs pressure potential + solute potential (+ or -) (always -) Ψ = 0 MPa for pure water As you add solute, the wp becomes more negative Water Potential
Our lab: Diffusion • Used bags of different molarities; weighed water gain • Determined the solute potential SP of potato cells • Where graph crossed line (no gain or loss of water) gave molar concentration - Use SP = -iCRT (to figure out solute potential; C = molar conc)
Mitosis • Keeps chromosome no. constant, no genetic diversity • 2 identical cells • Stages: PMAT • Think about what is happening to the DNA during the stages.
cytokinesis • Actual division of cytoplasm • Forms cell plate in plant cells • Cleavage furrow in animal cells
Meiosis • Purpose: to divide chromosome number in half (diploid – haploid) and to promote diversity. • Results in 4 NONIDENTICAL cells due to crossing over, different arrangement of chromosomes at Metaphase I. • Meiosis I: cuts chrom no in half • Meiosis II: divides chromatids
When does crossing- over occur? Tetrads
Meiosis is used to make gametes Some organisms such as fungi have complete bodies made of haploid cells
GeneticsRemember ratios. • One trait F2 3:1 (Aa x Aa) • Two trait – Remember each organisms has two alleles for each trait! ex: tall, green plant TtGg Each gamete gets ONE of each allele pair. Think of all possibilities. ex: TG, Tg, tG, tg F2 9:3:3:1 (AaBb x AaBb)
Be able to relate crosses to Mendel’s laws: Law of Segregation – alleles separate during formation of gametes
Law of Independent Assortment:each allele separates independently of other allele in pair (ie chromosomes in Metaphase I of meiosis)