Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Fundamentals of Anatomy & Physiology Frederic H. Martini Lecture 3: Chapter 3 An Introduction To The Cellular Level of organization Pages: Lecturer: Dr. Barjis Room: P313 / P307 Phone: (718)

Learning Objectives List the main points of the cell theory. Describe the chief structural features of the cell membrane. Describe the organelles of a typical cell, and give their specific functions. Summarize the process of protein synthesis. Describe the various transport mechanisms used by cells, and relate this to the transmembrane potential. Describe the cell life cycle, mitosis and cellular differentiation.

Cells are the building blocks of all plants and animals Cells are produced by the division of preexisting cells Cells are the smallest units that perform all vital physiological functions Each cell maintains homeostasis at the cellular level Homeostasis at higher levels reflects combined, coordinated action of many cells An Introduction to Cells The cell theory states:

The Diversity of Cells in the Human Body

Cytology, the study of the structure and function of cells The human body contains both somatic and sex cells Cell biology

The Anatomy of a Representative Cell

Is surrounded by extracellular fluid, which is the interstitial fluid of the tissue Has an outer boundary called the cell membrane or plasma membrane A typical cell

Physical isolation Regulation of exchange with the environment Structural support The Cell Membrane Cell membrane functions include:

The cell membrane is a phospholipid bilayer with proteins, lipids and carbohydrates. The Cell Membrane

Integral proteins Peripheral proteins Anchoring proteins Recognition proteins Receptor proteins Carrier proteins Channels Membrane proteins include:

Membrane proteins

Proteoglycans Glycolipids Glycoproteins Membrane carbohydrates form the glycocalyx

The fluid (cytosol) The organelles the cytosol surrounds The Cytoplasm The cytoplasm contains:

Nonmembranous organelles are not enclosed by a membrane and always in touch with the cytosol Cytoskeleton, microvilli, centrioles, cilia, ribosomes, proteasomes Membranous organelles are surrounded by lipid membranes Endoplasmic reticulum, Golgi apparatus, lysosomes, peroxisomes, mitochondria Organelles

The Anatomy of a Representative Cell

Microfilaments Intermediate filaments Microtubules Thick filaments Microvilli increase surface area Cytoskeleton provides strength and flexibility

The Cytoskeleton

Direct the movement of chromosomes during cell division Organize the cytoskeleton Cytoplasm surrounding the centrioles is the centrosome Centrioles

Is anchored by a basal body Beats rhythmically to move fluids across cell surface Cilia

Centrioles and Cilia

Are responsible for manufacturing proteins Are composed of a large and a small ribosomal subunit Contain ribosomal RNA (rRNA) Can be free or fixed ribosomes Ribosomes

Remove and break down damaged or abnormal proteins Require targeted proteins to be tagged with ubiquitin Proteasomes

Intracellular membranes involved in synthesis, storage, transportation and detoxification Forms cisternae Rough ER (RER) contains ribosomes Forms transport vesicles Smooth ER (SER) Involved in lipid synthesis Endoplasmic reticulum

The Endoplasmic Reticulum

Forms secretory vesicles Discharged by exocytosis Forms new membrane components Packages lysosomes Golgi Apparatus

The Golgi Apparatus

Functions of the Golgi Apparatus

Lysosomes are Filled with digestive enzymes Responsible for autolysis of injured cells Peroxisomes Carry enzymes that neutralize toxins Lysosomes and Peroxisomes

Lysosome Functions

Continuous movement and recycling of membranes ER Vesicles Golgi apparatus Cell membrane Membrane flow

Responsible for ATP production through aerobic respiration Matrix = fluid contents of mitochondria Cristae = folds in inner membrane Mitochondria

Surrounded by a nuclear envelope Perinuclear space Communicates with cytoplasm through nuclear pores The Nucleus The nucleus is the center of cellular operations

The Nucleus

A supportive nuclear matrix One or more nucleoli Chromosomes DNA bound to histones Chromatin Contents of the nucleus

Chromosome Structure

The cells information storage system Triplet code A gene contains all the triplets needed to code for a specific polypeptide The genetic code

Gene activation initiates with RNA polymerase binding to the gene Transcription is the formation of mRNA from DNA mRNA carries instructions from the nucleus to the cytoplasm Gene activation and protein synthesis

An overview of Protein Synthesis

A functional polypeptide is constructed using mRNA codons Sequence of codons determines the sequence of amino acids Complementary base pairing of anticodons (tRNA) provides the amino acids in sequence Translation is the formation of a protein

The Process of Translation

The ease with which substances can cross the cell membrane Nothing passes through an impermeable barrier Anything can pass through a freely permeable barrier Cell membranes are selectively permeable How Things Get Into and Out of Cells Permeability

Movement of a substance from an area of high concentration to low Continues until concentration gradient is eliminated How Things Get Into and Out of Cells Diffusion

Diffusion across the Cell Membrane

Diffusion of water across a semipermeable membrane in response to solute differences Osmotic pressure = force of water movement into a solution Hydrostatic pressure opposes osmotic pressure Water molecules undergo bulk flow How Things Get Into and Out of Cells Osmosis

The effects of osmotic solutions on cells Isotonic = no net gain or loss of water Hypotonic = net gain of water into cell Hemolysis Hypertonic = net water flow out of cell Crenation Tonicity

Osmotic flow across a cell membrane

Carrier mediated transport Binding and transporting specific ions by integral proteins Cotransport Counter-transport Facilitated diffusion Compounds to be transported bind to a receptor site on a carrier protein transport

Facilitated Diffusion

Active transport Consumes ATP Independent of concentration gradients Types of active transport include Ion pumps Secondary active transport Active transport

The Sodium Potassium Exchange Pump

Secondary Active Transport

Endocytosis is movement into the cell Receptor mediated endocytosis (coated vesicles) Pinocytosis Phagocytosis (pseudopodia) Exocytosis is ejection of materials from the cell Vesicular transport: material moves into or out of cells in membranous vesicles

Receptor-Mediated Endocytosis

Pinocytosis and Phagocytosis

Difference in electrical potential between inside and outside a cell Undisturbed cell has a resting potential The transmembrane potential

Cell division is the reproduction of cells Apoptosis is the genetically controlled death of cells Mitosis is the nuclear division of somatic cells Meiosis produces sex cells The Cell Life Cycle cell division

Most somatic cells spend the majority of their lives in this phase Interphase includes G1 S G2 The Cell Life Cycle Interphase

The Cell Life Cycle

DNA Replication

Prophase Metaphase Anaphase Telophase Mitosis, or nuclear division, has four phases During cytokinesis, the cytoplasm divides and cell division ends

Interphase, Mitosis, and Cytokinesis

Generally, the longer the life expectancy of the cell, the slower the mitotic rate Stem cells undergo frequent mitoses Growth factors can stimulate cell division Abnormal cell division produces tumors or neoplasms Benign Malignant (invasive, and cancerous) Spread via metastasis Oncogenes Mitotic rate and cancer

Process of specialization Results from inactivation of particular genes Produces populations of cells with limited capabilities Differentiated cells form tissues Differentiation

The main points of the cell theory. The chief structural features of the cell membrane. The organelles of a typical cell, and their specific functions. The process of protein synthesis. The various transport mechanisms used by cells, and how this relates to the transmembrane potential. The cell life cycle, mitosis and cellular differentiation. You should now be familiar with: