Transcript Lecture 3 - Websupport1

Anatomy & Physiology
Lecture 3: Chapter 3
An Introduction To The Cellular Level of
organization
Pages: 62 - 105
Lecturer: Dr. Barjis
Room: P313 / P307
Phone: (718) 260-5285
E-Mail: [email protected]
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Frederic H. Martini
Fundamentals of
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.
An Introduction to Cells
The cell theory states:
• 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
The Diversity of Cells in the Human Body
Cell biology
• Cytology, the study of the structure and function
of cells
• The human body contains both somatic and
sex cells
The Anatomy of a Representative Cell
A typical 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
The Cell Membrane
Cell membrane functions include:
• Physical isolation
• Regulation of exchange with the environment
• Structural support
The Cell Membrane
• The cell membrane is a phospholipid bilayer with
proteins, lipids and carbohydrates.
Membrane proteins include:
• Integral proteins
• Peripheral proteins
• Anchoring proteins
• Recognition proteins
• Receptor proteins
• Carrier proteins
• Channels
Membrane proteins
Membrane carbohydrates form the glycocalyx
• Proteoglycans
• Glycolipids
• Glycoproteins
The Cytoplasm
The cytoplasm contains:
• The fluid (cytosol)
• The organelles the cytosol surrounds
Organelles
• 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
The Anatomy of a Representative Cell
Cytoskeleton provides strength and flexibility
• Microfilaments
• Intermediate filaments
• Microtubules
• Thick filaments
Microvilli increase surface area
The Cytoskeleton
Centrioles
• Direct the movement of chromosomes during cell
division
• Organize the cytoskeleton
• Cytoplasm surrounding the centrioles is the
centrosome
Cilia
• Is anchored by a basal body
• Beats rhythmically to move fluids across cell
surface
Centrioles and Cilia
Ribosomes
• 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
Proteasomes
• Remove and break down damaged or abnormal
proteins
• Require targeted proteins to be tagged with ubiquitin
Endoplasmic reticulum
• 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
The Endoplasmic Reticulum
Golgi Apparatus
• Forms secretory vesicles
• Discharged by exocytosis
• Forms new membrane components
• Packages lysosomes
The Golgi Apparatus
Functions of the Golgi Apparatus
Lysosomes and Peroxisomes
• Lysosomes are
• Filled with digestive enzymes
• Responsible for autolysis of injured cells
• Peroxisomes
• Carry enzymes that neutralize toxins
Lysosome Functions
Membrane flow
• Continuous movement and recycling of
membranes
• ER
• Vesicles
• Golgi apparatus
• Cell membrane
Mitochondria
• Responsible for ATP production through aerobic
respiration
• Matrix = fluid contents of mitochondria
• Cristae = folds in inner membrane
The Nucleus
The nucleus is the center of cellular operations
• Surrounded by a nuclear envelope
• Perinuclear space
• Communicates with cytoplasm through nuclear pores
The Nucleus
Contents of the nucleus
• A supportive nuclear matrix
• One or more nucleoli
• Chromosomes
• DNA bound to histones
• Chromatin
Chromosome Structure
The genetic code
• The cells information storage system
• Triplet code
• A gene contains all the triplets needed to code for
a specific polypeptide
Gene activation and protein synthesis
• 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
An overview of Protein Synthesis
Translation is the formation of a protein
• 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
The Process of Translation
The Process of Translation
How Things Get Into and Out of Cells
Permeability
• 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
Diffusion
• Movement of a substance from an area of high
concentration to low
• Continues until concentration gradient is
eliminated
Diffusion
Diffusion across the Cell Membrane
How Things Get Into and Out of Cells
Osmosis
• 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
Osmosis
Tonicity
• 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
Osmotic flow across a cell membrane
transport
• 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
Facilitated Diffusion
Active transport
• Active transport
• Consumes ATP
• Independent of concentration gradients
• Types of active transport include
• Ion pumps
• Secondary active transport
The Sodium Potassium Exchange Pump
Secondary Active Transport
Vesicular transport: material moves into or out
of cells in membranous vesicles
• Endocytosis is movement into the cell
• Receptor mediated endocytosis (coated vesicles)
• Pinocytosis
• Phagocytosis (pseudopodia)
• Exocytosis is ejection of materials from the cell
Receptor-Mediated Endocytosis
Pinocytosis and Phagocytosis
The transmembrane potential
• Difference in electrical potential between inside
and outside a cell
• Undisturbed cell has a resting potential
The Cell Life Cycle
cell division
• 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
Interphase
• Most somatic cells spend the majority of their
lives in this phase
• Interphase includes
• G1
• S
• G2
The Cell Life Cycle
DNA Replication
Mitosis, or nuclear division, has four phases
• Prophase
• Metaphase
• Anaphase
• Telophase
During cytokinesis, the cytoplasm divides and
cell division ends
Interphase, Mitosis, and Cytokinesis
Interphase, Mitosis, and Cytokinesis
Mitotic rate and cancer
• 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
Differentiation
• Process of specialization
• Results from inactivation of particular genes
• Produces populations of cells with limited
capabilities
• Differentiated cells form tissues
You should now be familiar with:
• 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.