NPB 101: Lecture 2 - Physiology Basics 1: Cell Physiology

Learning Objectives: Explain how the plasma membrane's structure supports compartmentalization, transport, and cell communication. Trace the flow of information from DNA to protein, identifying the roles of mRNA, tRNA, and ribosomes. Relate the functions of the major organelles and the cytosol to the activities of a cell. Trace the route of a secreted protein from synthesis through the rough ER and Golgi to release from the cell. Compare the reoles of microfilaments, intermediate filaments, and microtubules in cell structure, movement, and transport. Predict which organelles and cellular structures would be especially abundant or developed in a cell with a particular specialized function.

Physiology

The study of body function.

Anatomy

The study of the structure of the body and how these structures relate and interact with each other.

Cell

The basic unit of life. It’s functions include:

• obtaining nutrients

• exchanging materials

• intracellular transport

• metabolism

• synthesis

• reproduction

Cell membrane

Cell membranes create functional compartments within cells. They are associated with transport, signaling, metabolism, etc.

Plasma Membrane (Phospholipid Bilayer)

Made of:

• Phosphate head: a polar, hydrophilic (water-loving), outward-facing group

• Fatty acid tails: two non-polar, hydrophobic (water-fearing) chains that point inward, away from water

Contains:

• Glycoproteins

• Membrane Proteins

  • Channels and carriers to transport molecules and ions

  • Receptors to signal responses

  • Form adhesion and junctions

    • in order for cells to work together, they want to stick together

Nucleus

Membrane-bound organelle containing genetic material:

• DNA (Deoxyribonucleic Acid)

  • Genes are blueprint for protein synthesis

  • DNA is replicated during cell division

• RNA (Ribonucleic Acid)

  • Messenger RNA (mRNA)

    • DNA code transcribed in message to leave nucleus

  • Ribosomal RNA (rRNA)

    • participates in reading and translating the mRNA

  • Transfer RNA (tRNA)

    • transfers the appropriate amino acids to the protein being synthesized

Endoplasmic Reticulum (ER)

Network of interconnected membrane tubes (continuous with the nuclear envelope).

• Functions:

  • synthesis, storage, and transport of biomolecules

• Rough ER

  • membrane covered with ribosomes

• Smooth ER

  • membranes lack ribosomes

Golgi Complex

Series of hollow curve sacs stacked on top of one another and surrounded by vesicles.

• Function:

  • modifies molecules from the rough ER and packages them into vesicles to direct destination

  • sorts proteins to:

    • Plasma Membrane

    • Secreted into extracellular space (e.g. hormones)

    • lysosomes

Lysosomes

Membrane-enclosed sacs containing hydrolytic enzymes.

• Function: Intracellular digestive system

  • Pinocytosis

    • invagination of the membrane to form a pouch and internalize extracellular fluid

  • Receptor-mediated endocytosis

  • Phagocytosis

    • invagination of the plasma membrane to form a large vesicle and internalize large particles

      • bacteria or tissue debris

    
    

Peroxisomes

Small spherical vesicles involved in oxidation (important in cell homeostasis).

• Function: Detoxification with reactions involving hydrogen peroxide

  • Detoxify reactive oxygen species

  • Catalase to degrade hydrogen peroxide

  • Lipid metabolism

Mitochondria

Double-membrane structure creates inter-membrane space and matrix.

• Function: Responsible for aerobic metabolism and production of cellular energy.

  • Chemical energy stored in the form of ATP

  • Requires oxygen (aerobic)

  • Citric acid cycle

  • Electron transport chain

Cytosol

Semi-liquid portion of the cytoplasm.

• Functions:

  • Enzymatic regulation of intermediate metabolism

  • Ribosomal protein synthesis

  • Storage of fat and glycogen

Cytoskeleton

Protein network for structural support, transport, and movement.

• Includes:

  • Microfilaments

  • Microtubules

  • Intermediate filaments

Microfilaments (Cytoskeleton)

Made up of globular actin proteins.

• Functions:

  • Associates with myosin for cellular contraction.

  • Specialized actin filaments are essential for muscle contractions

Intermediate filaments (Cytoskeleton)

Filamentous proteins. Keratin is the major intermediate filament protein of epithelial cells.

• Function:

  • Provides mechanical strength and stability

Microtubules (Cytoskeleton)

Long, hollow tubes formed by tubulin proteins

• Functions:

  • Maintain cell shape

  • Control axonal transport

  • Movement of cilia, flagella, and chromosomes

Cilia (Microtubules)

Motile protrusions on cell surface to move fluid.

• Present in:

  • Respiratory pathway, oviduct, etc.

Flagella (Microtubules)

Motile appendage enabling cell movement.

• Present in:

  • Sperm