Human Biology: Cells, Functions, and Exchange of Substances

Posted on May 23, 2024 in Biology

Chemical Composition and Life Functions

  • Chemical Composition: Organic and inorganic biomolecules
  • Cellular Structure: Trillions of eukaryotic cells, multicellular
  • Life Functions: Reproduction, interaction, nutrition

Types of Cells

  • Neuron: Transmits information (nervous system)
  • Osteocyte: Creates and produces bone (bone)
  • Keratinocyte: Produces hair, nails, scales, and horns (skin)
  • Cardiomyocyte: Contracts and relaxes to pump blood (heart)

Levels of Organization

  • Cell: Smallest component of a living thing
  • Tissue: Group of cells with a specific function
  • Organ: Group of tissues with a more complex function
  • Organ System: Group of organs that perform related functions

Nutrition Systems

  • Circulatory: Transports nutrients and oxygen to cells, removes waste
  • Respiratory: Exchanges gases, absorbs oxygen, removes carbon dioxide
  • Digestive: Breaks down food into nutrients, absorbs nutrients
  • Excretory: Removes waste products and carbon dioxide

Cell Respiration

Oxygen from the respiratory system combines with nutrients from the digestive system. The circulatory system carries these to the mitochondria in cells. Mitochondria produce energy and release carbon dioxide and waste. Waste is excreted through the excretory system, while carbon dioxide is expelled through the respiratory system.

Cell Structure and Function

Cell Membrane

  • Separates and communicates the cell with the environment
  • Protects and shapes the cell

Cytoplasm

  • Jelly-like substance containing organelles
  • Site of cell functions

Nucleus

  • Contains genetic material
  • Controls cell functions

Organelles

Endoplasmic Reticulum

  • Surrounds the nucleus
  • Rough ER: Contains ribosomes, synthesizes proteins
  • Smooth ER: Synthesizes lipids

Mitochondrion

  • Produces energy through cell respiration

Golgi Body

  • Processes and releases proteins, enzymes, and glucids

Ribosomes

  • Produce proteins
  • Attached to RER or free in cytoplasm

Lysosomes

  • Membranous sacs containing digestive enzymes
  • Participate in cell digestion

Vacuole

  • Stores reserve substances

Cytoskeleton

  • Network of protein filaments
  • Provides shape and support

Centrioles & Centrosomes

  • Control cilia and flagella movements
  • Build the skeleton and control cell division

GERL Complex

  1. Ribosomes produce proteins.
  2. RER stores and transports proteins.
  3. Golgi transforms proteins.
  4. Golgi releases proteins using lysosomes.

Exchange of Substances

  • Cells exchange nutrients and waste with the environment.
  • Plasma membrane regulates exchange.
  • Semipermeable membrane allows selective passage of substances.

Mechanisms of Exchange

Passive Diffusion

  • Small molecules cross the membrane from high to low concentration.
  • No energy required.

Active Transport

  • Moves molecules from low to high concentration.
  • Requires energy.

Endocytosis/Exocytosis

  • Endocytosis: Cell ingests particles.
  • Exocytosis: Cell expels waste or secretes substances.

Osmosis

  • Water moves from low to high concentration across a semipermeable membrane.
  • Regulates water balance in cells.

Osmotic Conditions

  • Hypertonic: Higher salinity outside the cell, causing dehydration (shrinking)
  • Isotonic: Balanced concentrations, maintaining cell shape
  • Hypotonic: Lower salinity outside the cell, causing swelling (lysis)