Cell Biology Overview Quiz

Bacterial Cell Envelope

• The outermost layer of the bacterial cell envelope is the glycocalyx.
• The bacterial cell wall is composed of peptidoglycan.
• Plasmid DNA functions to provide unique phenotypic characteristics to bacteria.

Ribosomes and Peroxisomes

• Ribosomes are involved in translating mRNA into proteins.
• A polysome refers to multiple ribosomes working on a single mRNA molecule.
• Peroxisomes are characterized by oxidative crystals.

Cells: Shape and Structure

• White blood cells have an irregular shape.
• Amoeboid movement refers to the ability of cells to change shape and move.
• The nucleus of a cell was discovered by Robert Brown.

Cell Cycle

• The cell cycle is a series of events that take place in a cell leading to its division and duplication.
• The cell cycle includes the following phases:
  • G1 Phase: Cell growth and preparation for DNA replication.
  • S Phase: DNA synthesis.
  • G2 Phase: Cell growth and preparation for mitosis.
  • M Phase: Mitosis (cell division).

Centrosome

• The centrosome is the major microtubule-organizing center (MTOC) in eukaryotic cells.
• It plays a role in various cellular processes, including sensory reception, locomotion, and embryogenesis.

Fluid Mosaic Model

• The Fluid Mosaic Model explains the structure of the cell membrane.
• The model emphasizes the quasi-fluid nature of lipids, enabling lateral movement of proteins within the bilayer.

Epithelial Cells

• Keratin is a protein that protects epithelial cells from damage.

Tissues

• A tissue is a group of similar cells that work together to perform a specific function.
• Tissues are essential for the division of labor in multicellular organisms.
• Tissues contribute to increased organization and efficiency within the organism.

Plant Tissues

• Plant tissues can be divided into two main categories:
  • Meristematic Tissue: Cells retain the ability to divide and are responsible for growth.
  • Permanent Tissue: Cells have lost the ability to divide and have taken on a specific function.

Meristematic Tissue

• Meristematic tissue is present in the growing regions of plants, such as roots, shoots, and stems.
• The cells are typically spherical, oval, or rectangular, with no intercellular spaces and absent vacuoles.
• They are actively dividing and have dense cytoplasm and prominent nuclei.

Permanent Tissue

• Permanent tissue forms when meristematic cells lose their ability to divide and differentiate into specialized cells.
• These cells have a defined shape, size, and function.
• Permanent tissues are characterized by large central vacuoles and thick/thin cell walls.

Functions of Permanent Tissue

• Permanent tissue serves various functions including:
  • Protection
  • Support
  • Storage
  • Photosynthesis

Types of Permanent Tissue

• Permanent tissue is classified as:
  • Simple Tissue: Composed of one type of cells.
  • Complex Tissue: Composed of more than one type of cells.

Simple Tissues

• Simple tissues include:
  • Collenchyma Tissue: Living cells with irregularly thickened walls, providing flexibility to plant parts.
  • Parenchyma Tissue: Living cells with thin walls, often specialized for storage or photosynthesis.
    • Aerenchyma: Loosely packed parenchyma tissue with air spaces, providing buoyancy.
    • Chlorenchyma: Parenchyma tissue containing chlorophyll, facilitating photosynthesis.
  • Sclerenchyma Tissue: Dead cells with thick walls, providing toughness and support.

Protective Tissues

• Protective tissues in plants include:
  • Epidermis: The outermost layer of plant parts, protecting from injury, infection, and water loss.
  • Cork: A protective layer forming on mature roots and shoots, regulating water and gas exchange.

Complex Permanent Tissue

• Complex tissues are composed of more than one type of cell and work together for a specific function.
• Ex: Vascular tissue is a complex tissue that transports water, minerals, and food throughout the plant.

Vascular Tissue

• Vascular tissue comprises two main types:
  • Xylem: Conducts water and minerals from roots to shoots.
    • Xylem Parenchyma: For food storage.
    • Tracheids and Vessels: For water conduction.
    • Xylem Fibers: For rigidity and support.
  • Phloem: Conducts food materials from leaves to other parts of the plant.
    • Sieve Tubes: For food conduction.
    • Companion Cells: For supporting and regulating sieve tubes.
    • Phloem Parenchyma: For food storage.
    • Phloem Fibers: For rigidity and support.

Animal Tissues

• Animal tissues are categorized into four main types:
  • Epithelial Tissue: Covers and protects the body, forming linings for organs.
  • Muscular Tissue: Responsible for movement and contraction.
  • Connective Tissue: Provides support, structure, and connects tissues.
  • Nervous Tissue: Transmits signals and coordinates body functions.

Epithelial Tissue

• Epithelial tissue is tightly packed and forms a continuous sheet.
• It serves as a protective barrier against injury and infection, and plays a role in absorption and excretion.
• Epithelial tissue is classified based on cell shape and arrangement:
  • Squamous Epithelium: Flattened cells
    • Simple Squamous: Single layer, found in lining of mouth.
    • Stratified Squamous: Multiple layers, found in skin.
  • Cuboidal Epithelium: Cube-shaped cells, found in lining of glands.
  • Columnar Epithelium: Column-shaped cells, found in lining of intestines.
  • Ciliated Epithelium: Cuboidal or columnar cells with cilia on their surface, found in the respiratory tract.

Connective Tissue

• Connective tissue is characterized by cells embedded in a matrix.
• The matrix can be jelly-like, fluid, dense, or rigid.
• Connective tissue provides support, structure, and connects tissues.
• It is classified into several types including:
  • Areolar Connective Tissue: Loose tissue found between skin and muscles, supporting internal organs.
  • Adipose Connective Tissue: Stores fat, providing insulation and energy reserves.
  • Cartilage: Strong and flexible tissue found in joints, ears, and nose.
  • Blood: Fluid connective tissue composed of red blood cells, white blood cells, and platelets.
  • Bone: Hard and rigid tissue providing support and protection to the body.
  • Tendons: Dense fibrous tissue connecting muscles to bones.
  • Ligaments: Dense fibrous tissue connecting bones to bones.

Adipose Connective Tissue

• Aggregation of fat cells
• Cells are rounded/oval and contain large fat droplets
• Located below the skin and between internal organs
• Functions:
  • Prevents body from mechanical shocks
  • Fat reservation
  • Acts as insulation
  • Temperature regulation

Skeletal Connective Tissue

• Types:
  • Cartilage
  • Bones
• Bones:
  • 300 bones in a child
  • 206 bones in an adult
  • Longest bone: Femur (thighs)
  • Shortest bone: Stapes (ear)

Cartilage

• Widely spaced out cells
• Matrix is gel-like and slightly elastic
• Flexible
• Occurrence:
  • Ear pinna, nose tip, trachea, larynx
  • Smoothens bone surfaces at joints
• Function:
  • Support and flexibility to body parts

Bones

• Strong, non-flexible, hard and rigid
• Matrix is hard and composed of calcium and phosphorus compounds
• Functions:
  • Forms a framework
  • Supports the body
  • Provides shape to body
  • Protects vital body organs like brain, lungs, etc.
  • Layers:
    • Meninges
    • 22 bones in the brain (8 cranial & 14 facial)

Fluid Connective Tissue

• Connects different parts of the body
• Maintains continuity
• Types:
  • Blood
  • Lymph

Blood

• Function: transports gases, digested food, hormones, waste materials
• Composition:
  • Plasma (55%):
    • 90% water
    • Proteins, glucose, salts, hormones, fats, vitamins
  • Solid (45%):
    • Red Blood Cells (RBCs)
    • White Blood Cells (WBCs)
    • Platelets

Red Blood Cells (RBCs)

• Red in colour due to the presence of heme (Fe)
• Heme has a high affinity towards oxygen, transporting it throughout the body for respiration and energy production

White Blood Cells (WBCs)

• Also known as leukocytes
• Prevent infection and provide a defense mechanism for the body

Platelets

• Also known as thrombocytes
• Help in blood clotting
• Reduced in dengue

Lymph

• Yellow fluid
• Function:
  • Transports digested fat from small intestine to blood
  • Drains excess fluid from intercellular spaces and returns it to blood
  • Filters microbes and destroys them