Bio exam paper 1

The Cell

Plant Cell vs. Animal Cell

  • Plant Cell: Has a cell wall, chloroplasts, and a large central vacuole.

  • Animal Cell: Lacks a cell wall, has centrioles.

Key Organelles

  • Cell Wall: Rigid outer layer in plant cells; provides protection and support.

  • Cell Membrane: Semi-permeable membrane surrounding both plant and animal cells.

  • Nucleus: Contains genetic material; important for cell regulation.

  • Ribosomes: Sites of protein synthesis; can be free or attached to the endoplasmic reticulum.

  • Mitochondria: Powerhouse of the cell; site for ATP production.

  • Golgi Apparatus: Modifies, sorts, and packages proteins for secretion.

  • Vacuoles: Storage for nutrients, waste products, and maintains turgor pressure in plant cells.

  • Endoplasmic Reticulum:

    • Rough ER: Studded with ribosomes; synthesizes proteins.

    • Smooth ER: Lacks ribosomes; involved in lipid synthesis.

  • Chloroplasts: Site of photosynthesis in plant cells.

  • Lysosomes: Contain digestive enzymes for breakdown of waste materials.

Differences in Cell Structure

Flexibility and Shape

  • Plant Cells: Cell wall can be rigid or flexible, maintaining cell shape.

  • Animal Cells: More variable in shape and can change easily, not bound by a rigid wall.

Classification of Cells

Prokaryotic vs. Eukaryotic Cells

  • Prokaryotic Cells: Do not have a nucleus; genetic material is not membrane-bound.

    • Example: Bacteria.

  • Eukaryotic Cells: Contains a true nucleus; genetic material is membrane-bound.

    • Examples: Plant and animal cells.

Microscopy Techniques

  • Scanning Electron Microscope (SEM): Magnifies up to 80,000X; electrons bounce off the surface.

  • Transmission Electron Microscope (TEM): Magnifies up to 500,000X; electrons pass through the specimen.

Cell Membrane Structure

  • Phospholipid Bilayer: Composed of hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails.

  • Proteins and Carbohydrates: Integral to the membrane; carbohydrates form the glycocalyx, helping in cell recognition.

  • Fluid-Mosaic Model: Describes the flexible nature of the cell membrane with various components.

Cellular Transport Mechanisms

Diffusion

  • Process: Movement of molecules from high concentration to lower concentration; no energy required.

Facilitated Diffusion

  • Process: Utilizes specific transport proteins to move molecules across the cell membrane; does not require energy.

Active Transport

  • Process: Movement of ions or molecules against their concentration gradient; requires energy (ATP).

  • Carrier Proteins: Assist in the transport of substances.

Endocytosis

Phagocytosis and Pinocytosis

  • Phagocytosis: Engulfs solid particles, forming vesicles.

  • Pinocytosis: Engulfs fluids, forming vesicles.

Mitosis and Meiosis

Mitosis

  • Definition: Process where a somatic cell divides into two identical cells.

  • Purpose: Growth, repair, and replacement of cells.

  • Chromosome Count: Humans have 46 chromosomes.

Phases of Mitosis

  1. Prophase: Chromosomes condense, nucleolus disappears, nuclear membrane disintegrates.

  2. Metaphase: Chromosomes align at the equator, spindle fibers attach.

  3. Anaphase: Sister chromatids are pulled apart.

  4. Telophase: Chromosomes reach poles, nuclear envelope reforms.

Cytokinesis

  • Definition: Division of the cytoplasm after mitosis; results in two daughter cells.

Cancer

Types of Tumors

  • Benign: Non-cancerous; do not invade other tissues.

  • Malignant: Cancerous; invade surrounding tissues, can spread through metastasis.

Causes of Cancer

  • Environmental chemicals, radiation, viruses, and genetic mutations.

Circulatory System

Types

  • Open Circulatory System: Blood bathes organs directly; found in arthropods.

  • Closed Circulatory System: Blood remains enclosed in vessels; found in vertebrates.

Heart Structure

  • Chambers: Right atrium, right ventricle, left atrium, left ventricle.

  • Valves: Prevent backflow of blood (e.g., tricuspid and mitral valves).

Blood Vessels

  • Arteries: Carry oxygenated blood away from the heart (except pulmonary arteries).

  • Veins: Carry deoxygenated blood back to the heart.

  • Capillaries: Sites of gas exchange.

Plant Tissues

Types

  1. Meristematic Tissue: Cells that continuously divide.

  2. Epidermal Tissue: Protective outer layer.

  3. Ground Tissue: Fills spaces and stores substances.

  4. Vascular Tissue: Conducts water (xylem) and sugars (phloem).

Functions of Plant Roots

  • Anchor plants, absorb water, store nutrients, prevent erosion.

Photosynthesis

Process Overview

  • Definition: Conversion of light energy into chemical energy (glucose).

  • Equation: Sunlight + CO2 + H2O → C6H12O6 + O2

Two Phases

  1. Light-dependent Reactions: Occur in thylakoids; capture sunlight.

  2. Calvin Cycle (Light-independent Reactions): Occur in the stroma; synthesize glucose.