Photosynthesis

Overview of Photosynthesis

Photosynthesis is the process by which plants, algae, and some bacteria capture light energy from the sun and convert it into chemical energy stored in sugars and other organic molecules.

• Photosynthesis Equation: Water, carbon dioxide, and light energy are converted to glucose and oxygen.

• General Equation:

• Water Entry: Water enters plants through roots.

• CO2 Entry: Carbon dioxide enters through leaf pores called stomata.

Structure of the Chloroplast

Photosynthesis occurs in the chloroplast, an organelle found in plant cells.

• Stroma: Fluid-filled space inside the chloroplast.

• Thylakoid Membrane: Contains chlorophyll and other pigments.

• Grana: Stacks of thylakoids.

• Inner and Outer Membranes: Enclose the chloroplast.

Plant Pigments and Light Absorption

Chlorophyll molecules are embedded in the thylakoid membrane. Their primary function is to absorb solar energy.

• Absorption: Chlorophyll absorbs violet-blue and red light, reflects/transmits green-yellow light, making leaves appear green.

Light Dependent Reactions vs. Calvin Cycle

Photosynthesis consists of two main stages: light dependent reactions and the Calvin cycle (light independent reactions).

• Light Dependent Reactions: Use sunlight to produce ATP and NADPH.

• Calvin Cycle: Uses ATP and NADPH to produce G3P, which can be used to make glucose.

Comparison Table

• Process of Light Reactions: Chlorophyll absorbs solar energy, ejects an electron, electron passed down electron transport chain, water split to release O2.

• Calvin Cycle: Carbon dioxide is fixed; product is G3P.

C3 vs. C4 Photosynthesis

• C3 Photosynthesis: Traditional pathway; most plants.

• C4 Photosynthesis: Adaptation for hot, dry climates; example: sugar cane, corn.

Relationship to Cellular Respiration

• Photosynthesis: Stores energy in glucose.

• Cellular Respiration: Releases energy from glucose.

Cellular Respiration

Overview of Cellular Respiration

Cellular respiration is the process by which cells extract energy from glucose, producing ATP.

• Oxidation: Loss of electrons.

• Reduction: Gain of electrons.

• General Equation:

• Aerobic Respiration: Requires oxygen; electron transport chain is oxygen-dependent.

• Anaerobic Respiration: Does not require oxygen; fermentation.

Structure of the Mitochondrion

• Outer Membrane

• Inner Membrane

• Matrix: Site of citric acid cycle.

• Cristae: Folds of inner membrane; site of electron transport chain.

Stages of Cellular Respiration

• Glycolysis: Splits glucose into two pyruvate molecules; produces ATP and NADH; occurs in cytoplasm.

• Citric Acid Cycle (Krebs Cycle): Completes breakdown of glucose; produces ATP, NADH, FADH2; occurs in mitochondrial matrix.

• Electron Transport Chain: NADH and FADH2 deliver electrons; produces most ATP and H2O; occurs in inner mitochondrial membrane.

Comparison Table

Fermentation

• Occurs without oxygen (anaerobic).

• Produces: Ethanol (yeast), lactic acid (muscle cells).

Cell Reproduction

Functions of Cell Reproduction

Cell reproduction is essential for reproduction, growth, development, repair, and renewal.

• Chromatin: DNA combined with proteins; forms chromosomes.

The Cell Cycle

The cell cycle is the life of a cell from formation to division. It consists of interphase and mitosis.

• Interphase: G1 (growth), S (DNA synthesis), G2 (preparation for division).

• Mitosis: Division of nucleus.

• Cytokinesis: Division of cytoplasm.

Chromosome Structure

• Duplicated Chromosome: Two sister chromatids joined at centromere.

Spindle Formation and Function

• Spindle: Microtubules assembled by centrosome; attaches to centromere; separates chromatids.

Stages of Mitosis

• Prophase: Chromosomes condense, spindle forms.

• Metaphase: Chromosomes align at cell equator.

• Anaphase: Sister chromatids separate to opposite poles.

• Telophase: Nuclear envelope reforms, chromosomes decondense.

Cell Cycle Regulation

• Checkpoints: G1, G2, M; prevent division if errors are detected.

• Cancer: Uncontrolled division due to checkpoint failure; forms tumors.

Types of Cells

• Gametes: Reproductive cells (sperm, egg).

• Somatic Cells: All other body cells.

Chromosome Types

• Homologous Chromosomes: Pair, one from each parent; same characteristics.

• Sex Chromosomes: X and Y; determine sex.

• Autosomes: Other chromosomes.

Haploid vs. Diploid

• Haploid (n): One set of 23 chromosomes.

• Diploid (2n): Two sets of 23 chromosomes.

Human Life Cycle

• Gametes: Produced by meiosis; fuse during fertilization to form diploid zygote.

• Mitosis: Develops multicellular diploid adult.

Meiosis

• Occurs in testes (males) and ovaries (females).

• Reduces chromosome number from diploid to haploid.

• Two divisions: Meiosis I (separates homologous chromosomes), Meiosis II (separates sister chromatids).

Stages of Meiosis

• DNA replicates before Meiosis I, not before Meiosis II.

• Meiosis I: Separates homologous chromosomes.

• Meiosis II: Separates sister chromatids.

Mitosis vs. Meiosis

• Mitosis: Produces 2 diploid cells; no crossing over.

• Meiosis: Produces 4 haploid cells; crossing over, synapsis, tetrads, separation of homologues.

Genetic Variation

• Origins: Independent assortment, crossing over, random fertilization.

• Advantage: Increases genetic diversity.

Patterns of Inheritance

Mendel's Experiments and Terminology

Gregor Mendel studied inheritance in pea plants, introducing key concepts.

• Trait: Characteristic (e.g., flower color).

• True-breeding: Organisms that produce offspring identical to themselves.

• Hybridization: Crossing different true-breeding varieties.

• Alleles: Alternative versions of a gene.

• Dominant: Allele that determines phenotype.

• Recessive: Allele masked by dominant.

Mendel's Techniques and Generations

• Testcross: Used to determine genotype.

• P Generation: Parental.

• F1 Generation: First filial; hybrids.

• F2 Generation: Second filial; shows 3:1 ratio in traits.

Mendel's Model

1. Alternative versions of genes (alleles) account for variation.

2. Each trait: two alleles, one from each parent.

3. If alleles differ, dominant determines appearance; recessive has no effect.

4. Law of Segregation: Two alleles separate during gamete formation.

Genotype vs. Phenotype

• Homozygous: Two identical alleles.

• Heterozygous: Two different alleles.

• Genotype: Genetic makeup.

• Phenotype: Physical appearance.

Punnett Squares

Punnett squares are used to predict offspring genotypes and phenotypes from parental crosses.

Law of Independent Assortment

• Each pair of alleles segregates independently during gamete formation.

Multiple Alleles, Incomplete Dominance, Codominance

• Multiple Alleles: More than two allelic forms exist in a population.

• Incomplete Dominance: Offspring have intermediate phenotype.

• Codominance: Offspring display two dominant phenotypes simultaneously.

ABO Blood Group Example

• Controlled by multiple alleles (IA, IB, i).

• Punnett squares can predict child’s blood type based on parents.

Sex-linked Inheritance

• Traits linked to sex chromosomes (e.g., colorblindness).

• More common in males due to single X chromosome.

Additional info: Academic context and explanations have been expanded for clarity and completeness. Tables have been recreated and summarized for comparison and classification purposes.