Copy of Ammar Siddiqui - Biology Unit 1 Notes [AS]- 2023 - 2024-5

Table of Contents

  • B1: Biological Molecules

  • B2: Cells & Cell Structure

  • B3: Biochemical Reactions in Cells

  • B4: Transport In & Out of Cells

  • B5: Gas Exchange & the Transport of O2

  • B6: Variation

  • B7: DNA, Genes & Chromosomes

  • B8: Protein Synthesis

  • B9: Meiosis & Genetic Variation

  • B10: Species & Taxonomy

  • B11: Biodiversity Within a Community

B1: Biological Molecules

Carbohydrates

  • Organic compounds made of carbon, hydrogen, and oxygen.

  • Basic monomer: Saccharide.

  • Key Definitions:

    • Monosaccharide: Single sugar monomer

    • Disaccharide: Two sugar units joined by glycosidic bond.

    • Polysaccharide: Long chain of sugar units joined by glycosidic bonds.

  • Important Saccharides:

    • Monosaccharides: Glucose, Fructose, Galactose, Ribose

    • Disaccharides: Maltose (glucose + glucose), Lactose (glucose + galactose), Sucrose (glucose + fructose)

    • Polysaccharides: Cellulose (β Glucose), Starch (α Glucose), Glycogen (α Glucose)

Reducing & Non-Reducing Sugars

  • Reducing sugars: Can donate electrons (e.g., all monosaccharides).

  • Non-reducing sugars: Cannot donate electrons.

Glycosidic Bonds

  • Representing a glycosidic bond between carbon 1, oxygen & carbon 4 can be shown as 1−4; present in amylose, amylopectin & glycogen.

Structures of Key Polysaccharides

  • Cellulose:

    • Made of β glucose, provides structural support in plants through hydrogen bonding between chains, creating microfibrils.

    • High tensile strength allows it to remain turgid.

  • Glycogen:

    • Made of α glucose, branched structure makes it compact for storage, allowing rapid condensation & hydrolysis reactions.

  • Starch:

    • Polysaccharide made of α glucose, consists of two polymers: amylose (1-4 bonds) and amylopectin (1-4 and 1-6 bonds).

    • Compact structure that allows for efficient energy storage and quick hydrolysis.

B4: Transport In & Out of Cells

Passive Transport

  • Simple Diffusion: Movement from high to low concentration, does not require energy.

  • Facilitated Diffusion: Uses channel proteins for hydrophilic molecules.

Active Transport

  • Movement against concentration gradient, requires energy in the form of ATP.

B5: Gas Exchange & the Transport of O2

Gas Exchange Systems

  • Importance of surface area to volume ratio in aiding gas exchange.

  • Different systems including lungs, gills in animals, and stomata in plants.

B6: Variation

Genetic Variation

  • Different forms of traits caused by alleles and mutations during asexual reproduction or meiosis.

  • Interspecific vs Intraspecific variations are classifications of variation.

B7: DNA, Genes & Chromosomes

DNA Structure

  • Made of nucleotides, has a double-helix structure.

Genes and Alleles

  • Genes are segments of DNA that code for proteins; alleles are variations of a gene.

B8: Protein Synthesis

Key Stages

  • Transcription: DNA to mRNA.

  • Translation: mRNA to Polypeptide.

B9: Meiosis

Process

  • Produces four haploid cells, involves multiple stages (PMAT). Meiosis contributes to genetic diversity through crossing over and independent assortment.

B10: Species & Taxonomy

Defining Species

  • A group of organisms capable of interbreeding.

Taxonomy Systems

  • Linnaean System: Taxa hierarchy from domain to species.

B11: Biodiversity Within a Community

Components of Biodiversity

  • Genetic, species, and ecosystem diversity.

  • Effects of human activities on biodiversity.

Investigating Biodiversity

  • Using sampling techniques and measuring species richness and index of diversity.