Food molecules and tests

• Chemical elements in carbohydrates are carbon, hydrogen, and oxygen.

• Fats consist of carbon, hydrogen, and oxygen.

• Proteins contain carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.

• Proteins have primary, secondary, tertiary, and quaternary structures.

• Carbohydrates provide an immediate source of energy.

• Fats insulate against heat loss and provide long-term energy storage.

• Proteins synthesize new protoplasm for growth and repair.

Tests

• Starch test: iodine in potassium iodide solution turns blue-black if positive.

• Negative starch test: The mixture remains yellowish-orange.

• Reducing sugars test: Benedict's solution turns brick red (large amount), orange (moderate), yellow (low), or green (trace) if positive.

• Negative reducing sugars test: The mixture remains blue.

• Protein test: Biuret solution turns violet/lilac if positive.

• Negative protein test: The mixture remains blue.

• Fats test: Ethanol creates a white emulsion when water is added if positive.

• Negative fats test: The mixture remains clear when water is added.

• Large molecules like cellulose, glycogen, and starch are synthesized from glucose.

• Polypeptides and proteins are synthesized from amino acids.

• Lipids are synthesized from glycerol and fatty acids.

DNA Structure and Function

• Genes are segments of DNA, and chromosomes are long DNA strands containing many genes.
• DNA is a double helix of two nucleotide strands, each nucleotide contains a sugar, a phosphate group, and a base (A, G, C, or T).
• Condensation reactions join nucleotides, forming di- and polynucleotides, linked by phosphodiester bonds.
• Complementary base pairing: guanine to cytosine, and adenine to thymine.

Semi-Conservative DNA Replication

• Begins at the origin of replication.
• Helicase unwinds the helix by breaking hydrogen bonds between base pairs of parental strands.
• Each parental strand serves as a template for a new DNA strand.
• Primase synthesizes an RNA primer, providing free 3' OH ends for DNA polymerase III.
• DNA polymerase III elongates the new strand in the 5' to 3' direction, forming phosphodiester bonds.
• Deoxyribonucleotides are incorporated by base pairing: adenine to thymine, guanine to cytosine.
• The leading strand synthesizes continuously, while the lagging strand forms Okazaki fragments discontinuously.
• DNA polymerase I replaces RNA primers with deoxyribonucleotides.
• DNA ligase seals gaps in Okazaki fragments by forming phosphodiester bonds.

Gel Electrophoresis

• DNA's negative charge causes it to migrate toward the anode under electric current within an agarose gel.
• The agarose gel acts as a molecular sieve separating DNA by size.
• Larger DNA fragments migrate slower and travel a shorter distance while smaller fragments travel further.
• Loading dye marks DNA migration in the gel.
• One dye runs faster than most fragments.
• Another dye migrates with very large fragments.
• DNA sample migrates in between the dyes.
• Glycerol makes DNA samples denser than the running buffer, causing them to sink into the well.
• Dye stains the agarose gel and nucleic acid dyes bind to DNA to visualize DNA under UV or blue light

Cell Cycle, Mitosis & Meiosis

• Mitosis is asexual reproduction that produces genetically identical cells and maintains chromosome number.

• Mitosis is important for growth, repair, and asexual reproduction.

• Mitosis & Meiosis II are very similar

• Nuclear division divides the nucleus, cytokinesis divides the cytoplasm during the last stage of cell division.

• Cancer development involves accumulated mutations, angiogenesis, and metastasis.

• Mutation accumulation results in uncontrolled cell division and tumor formation.

• Angiogenesis is when malignant tumors promote new blood vessel growth for oxygen and nutrients.

• Metastasis: tumors spread and establish in other body locations.

• Haploid cells have one set of chromosomes.

• Diploid cells have two sets of chromosomes, one from each parent.

• Reduction division process (meiosis) halves chromosome number for correct chromosome number after egg and sperm fusion.

• Homologous chromosomes: matching pairs with same genes/alleles.

• One member of the pair from each parent.

• They share the same size, shape and sequence of genes.

• Meiosis yields genetically dissimilar cells with halved chromosome number by separating homologous chromosomes.

• Meiosis is used in gamete formation.

• Meiosis and fertilization can lead to genetic variation.

• Independent assortment: chromosome pairs line up randomly during meiosis I.

• Which chromosome of a given pair goes to which pole is independent of the behavior of the chromosomes in other pairs

• Crossing over of segments results in new allele combinations on chromosomes in the haploid cells so produces almost unimaginable variation.

• Both generate high degree of variation

• Random fusion of male and female gametes in sexual reproduction.