Midterm 3 Study Guide - Fermentation, Cellular Respiration, and Photosynthesis

Fermentation and Cellular Respiration

• Fermentation

  • Occurs without oxygen or the electron transport chain

  • Inefficient compared to aerobic respiration

  • Utilizes glycolysis to produce 2 NADH and 2 ATP

  • Regenerates NAD+ by transferring electrons to alternate electron acceptors

  • Lactic Acid Fermentation

    • In human muscle cells when O2 is scarce, NADH transfers electrons to pyruvate, producing lactate.

  • Example: Muscle fatigue during intense exercise leads to lactate buildup.

  • Alcoholic Fermentation

    • Occurs in yeast, splits pyruvate into CO2 and a two-carbon molecule.

    • NADH donates electrons forming ethanol (alcohol).

  • Other fermentation pathways exist with variations across bacteria and archaea.

  • Some produce more ATP than fermentation but are less efficient than aerobic respiration.

• Catabolic Pathways

  • Breakdown molecules for energy; carbohydrates turn into glucose for cellular respiration.

  • Triglycerides and phospholipids break down into glycerol (enters glycolysis) and fatty acids (converted to acetyl CoA).

  • Proteins decompose into amino acids; amino groups are removed to enter cellular respiration.

• Anabolic Pathways

  • Construct molecules; intermediates from respiration assist in forming macromolecules including nucleic acids.

• Reactive Oxygen Species (ROS)

  • Damaging byproducts from cellular respiration when O2 captures electrons incorrectly.

Photosynthesis

• Location: Occurs in chloroplasts with three membranes defining various spaces.

  • Major processes occur in the thylakoid membrane (light reactions) and stroma (Calvin cycle).

• Photosynthetic Pigments

  • Found in the thylakoid membrane; they absorb specific light wavelengths.

  • Plants primarily absorb purple/blue and red light, appearing green due to unabsorbed wavelengths.

• Types of Pigments:

  • Chlorophylls: Absorb purple/blue and red light, appear green.

  • Carotenoids: Absorb blue/green, appear yellow/orange, act as antioxidants.

• Stages of Photosynthesis:

  • Light-Capturing Reactions: Convert light energy into ATP and NADPH.

  • Calvin Cycle: Uses ATP and NADPH to convert CO2 into carbohydrates.

  • Dependency of Stages: Disruption in one affects the other; Calvin cycle slows in the dark due to lack of ATP/NADPH.

• Photosystems:

  • Photosystem II: Utilizes an electron transport chain for ATP formation through photophosphorylation.

  • Water is split to release O2 and regenerate electrons lost from Photosystem II.

  • Photosystem I: Receives electrons from Photosystem II and converts them to NADPH.

• Calvin Cycle Details:

  • Produces G3P (3-carbon sugar), which can form sucrose or starch.

  • Key enzyme: Rubisco fixes CO2 to a 5-carbon sugar, leading to the formation of 6-carbon sugar which splits into two.

  • G3P exits for other pathways, while most continues in the cycle to regenerate the 5-carbon sugar.

  • Photorespiration may occur when O2 is fixed instead of CO2, leading to inefficiencies.

• Plant Adaptations:

  • C4 Plants: Separate carbon fixation and Calvin cycle spatially.

  • CAM Plants: Fix carbon at night, carry out the Calvin cycle during the day.

DNA Technology

• Hierarchical DNA Organization:

  • Genome: All genetic material in a cell.

  • Chromosome: Continuous DNA strand with associated proteins containing many genes.

  • Gene: DNA segment coding for a protein.

  • Allele: Different forms of a gene that produce variations in traits.

• Tools of DNA Technology:

  • Restriction Enzymes: Cut DNA at specific sequences; some produce sticky ends for recombination.

  • PCR: Amplifies DNA segments rapidly through temperature cycling.

  • Gel Electrophoresis: Sorts DNA by size using electric current.

• Applications:

  • DNA Profiling: Compares DNA samples for source identification; useful in forensics.

  • Transgenic Organisms: Created through recombinant DNA for agricultural and medical benefits.

• CRISPR/Cas9:

  • Advanced gene-editing tool; precise and efficient compared to older methods.

  • Can insert new genes or disrupt existing ones based on homologous sequences.

Mitosis and Cancer

• Types of Cell Division:

  • Mitosis: Produces identical daughter cells.

  • Meiosis: Produces gametes with half the DNA.

• Phases of Mitosis:

  • Prophase: Chromosomes condense and spindle apparatus forms.

  • Prometaphase: Nuclear membrane dissolves; microtubules attach to kinetochores.

  • Metaphase: Chromosomes align at the cell's equator.

  • Anaphase: Sister chromatids are pulled apart.

  • Telophase: Nuclei reform, and chromosomes decondense.

  • Cytokinesis: Cytoplasm divides; differs in plant and animal cells.

• Cell Cycle Control:

  • Checkpoints ensure proper DNA replication, chromosome alignment, and cell division.

  • Cancer Cells: Exhibit uncontrolled division and differentiation due to mutations in proto-oncogenes and tumor suppressor genes.

Meiosis and Chromosomal Inheritance

• Meiosis Overview:

  • Two rounds of division leading to haploid cells; increases genetic diversity.

  • Mechanisms: Independent assortment, crossing over during prophase, and random fertilization.

• Aneuploidy:

  • Abnormal number of chromosomes due to nondisjunction; can lead to conditions like Down syndrome (trisomy 21).

Genetics Introduction

• Genetic Variation:

  • Alleles determine traits; dominant and recessive interactions influence phenotypes.

  • Mendelian Genetics: Punnett squares predict inheritance based on allele segregation during meiosis.