Exam 3 Study Guide: Photosynthesis, Cell Cycle, Meiosis, and Animal Development

Ch. 10: Photosynthesis

Overview of Photosynthesis

Photosynthesis is the process by which autotrophic organisms convert light energy into chemical energy, producing glucose and oxygen from carbon dioxide and water. This process is fundamental to life on Earth, providing the primary energy source for most ecosystems.

• Photosynthesis vs. Cellular Respiration: Photosynthesis stores energy in glucose molecules, while cellular respiration releases energy by breaking down glucose.

• Organisms: Plants, algae, and some bacteria perform photosynthesis.

Structure and Function of Plant/Cell Parts

• Chloroplasts: Organelles where photosynthesis occurs; contain thylakoids (site of light reactions) and stroma (site of Calvin cycle).

• Thylakoid Membrane: Contains chlorophyll and other pigments; location of the electron transport chain.

Autotrophs vs. Heterotrophs

• Autotrophs: Organisms that produce their own food from inorganic substances (e.g., plants).

• Heterotrophs: Organisms that obtain energy by consuming other organisms.

Stages of Photosynthesis

• Light Reactions: Occur in the thylakoid membranes; convert light energy to chemical energy (ATP and NADPH); oxygen is produced as a byproduct.

• Calvin Cycle: Occurs in the stroma; uses ATP and NADPH to convert CO2 into glucose.

Electron Flow and Redox Reactions

• Flow of Electrons: Electrons move from water to NADP+ via photosystems II and I.

• Oxidation/Reduction: Water is oxidized (loses electrons), NADP+ is reduced (gains electrons).

Pigments and Light Absorption

• Chlorophyll a and b: Main pigments absorbing light for photosynthesis.

• Accessory Pigments: Carotenoids broaden the spectrum of absorbed light.

Electron Flow Pathways

• Linear Electron Flow: Produces ATP and NADPH; involves both photosystems.

• Cyclic Electron Flow: Produces ATP only; involves photosystem I.

C3, C4, and CAM Plants

• C3 Plants: Use the Calvin cycle directly; most common type.

• C4 Plants: Minimize photorespiration by separating carbon fixation and the Calvin cycle spatially.

• CAM Plants: Open stomata at night to reduce water loss; separate processes temporally.

Ch. 12: The Cell Cycle

Phases of the Cell Cycle

The cell cycle is the series of events that cells go through as they grow and divide.

• Interphase: Consists of G1 (cell growth), S (DNA synthesis), and G2 (preparation for mitosis).

• M Phase: Includes mitosis (nuclear division) and cytokinesis (cytoplasmic division).

Key Structures

• Centrioles: Organize microtubules in animal cells.

• Centrosomes: Microtubule-organizing centers; duplicate during interphase.

• Centromeres: Region where sister chromatids are joined.

• Kinetochores: Protein complexes on centromeres where spindle fibers attach.

Mitotic Spindle and Regulation

• Mitotic Spindle: Structure made of microtubules that separates chromosomes during mitosis.

• Density-dependent Inhibition: Cells stop dividing when crowded.

• Anchorage Dependence: Cells must be attached to a substrate to divide.

Stages of Mitosis

• Prophase: Chromosomes condense, spindle forms.

• Metaphase: Chromosomes align at the metaphase plate.

• Anaphase: Sister chromatids separate.

• Telophase: Nuclear envelopes reform, chromosomes decondense.

Ch. 13: Meiosis and Sexual Reproduction

Function and Phases of Meiosis

Meiosis reduces the chromosome number by half, producing four genetically unique gametes. It is essential for sexual reproduction.

• Meiosis vs. Mitosis: Meiosis produces haploid cells; mitosis produces diploid cells.

• Phases: Meiosis I (homologous chromosomes separate), Meiosis II (sister chromatids separate).

Genetic Variation

• Gametes: Reproductive cells (sperm and egg).

• Homologous Chromosomes: Chromosome pairs, one from each parent.

• Crossing Over: Exchange of genetic material between homologous chromosomes during prophase I.

• Random Fertilization: Any sperm can fertilize any egg, increasing genetic diversity.

Ch. 47: Animal Development

Phases of Embryonic Development

Animal development involves a series of stages from fertilization to the formation of a multicellular organism.

• Fertilization: Fusion of sperm and egg to form a zygote.

• Cleavage: Rapid cell divisions without growth, forming a blastula.

• Blastula: Hollow ball of cells; contains the blastocoel (fluid-filled cavity).

• Gastrulation: Formation of germ layers (ectoderm, mesoderm, endoderm).

• Neurulation: Formation of the neural tube, precursor to the nervous system.

Cell Fate and Differentiation

• Determination: Process by which cells become committed to a specific fate.

• Differentiation: Process by which cells become specialized in structure and function.

Sequence of Development

• Fertilization → Cleavage → Blastula → Gastrula → Neurula