CELL BIOLOGY:AN INTRODUCTION Department of Natural Sciences University of St. La Salle Bacolod City
1. Introduction to Cells2. Chemical Foundations - Biochemistry3. Methods of Studying Cells a. Investigating Cells b. Visualizing Biomolecules CELL BIOLOGY: c. Visualizing Nucleic Acids COURSE OUTLINE4. Genetic Mechanisms a. DNA and Chromosomes b. Anatomy of a Gene c. Replication, Transcription, Translation d. Regulating Gene Expression e. Genetic Techniques and Genomics - Biotechnology f. Molecular Basis of Inheritance - Genetics5. Cell Signaling6. Cell Membranes and Cell Architecture a. Plasma Membrane and Transport b. Organelles - Histology c. Cytoskeleton7. Energetics – Biochemistry8. Cellular Traffic9. Cell Birth, Lineage and Death10. Molecular Basis of Cancer
GRADING SYSTEM Quizzes/ Exams: 50% Seminar Presentation: 50%1. A long exam will be given after each seminar topic, with a 60% cut-off for the passing grade.2. Prelim, Midterm and Endterm exams will cover only the last topic covered for the period.3. The PP lessons prepared by the instructor will be the basis of the scope of the content material for the seminar topics. The use of such materials is allowed for all presentors.4. However, you are free to design the kind of presentations you will give your audience within 1-2 hours. The objective is they will understand the topic in accordance with the limits their intelligence genes would allow.
5. A copy of the presentation must be provided to the instructor at least 2 days before the scheduled event.6. No appearance during the scheduled presentation will automatically result to a grade of 60 for the presentor. No excuses will be entertained.7. Swapping of schedules is not allowed without previous notice.8. For additional points, invite at least one faculty of the Dept. of Natural Sciences/or a person of authority to evaluate your presentation. She/ He may attend during the final presentation and/or submit a written evaluation of the presentation on or before the scheduled event.9. Your presentation will be graded as follows: Comprehensiveness of content material – 20% Mastery of topic – 60% Audience impact- 10% Faculty Evaluation – 10%
Cell Biology in anutshell… (Basic Concepts)
All living organisms are constructed from cells.
All cells are prokaryotic or eukaryotic
General Structure Of The Cell1.Shape – depends upon: Functional adaptations Surface tension & viscosity of the protoplasm, e.g., leukocytes in circulating blood are spherical but emit pseudopods and become irregular in shape extravascularly. Mechanical action exerted by adjoining cells Rigidity of the cell membrane Presence of cytoplasmic microtubules2.Size – variations are due to: adaptations to perform a specific function withstand mechanical stresses & pressures environmental and genetic factors
All organisms from simple bacteria to complexmammals probably evolved from a common, single- celled progenitor.DNA and protein sequenceswere examined for assigning relationships, which agreewith fossil records. Although prokaryotes, Archaea are more similar to eukaryotes than to Eubacteria, e.g., archaean and eukaryotic genomesencode homologous histone proteins, which associate with DNA; bacteria lack histones. RNA and protein components of Archaean ribosomes are more like those in eukaryotes than those in bacteria.
MECHANISMS OF EVOLUTION Intragenic mutation: an existing gene can be modified by mutations in its DNA sequence. Gene duplication: an existing gene can be duplicated so as to create a pair of closely related genes within a single cell. Segment shuffling: two or more existing genes can be broken and rejoined to make a hybrid gene consisting of DNA segments that originally belonged to separate genes. Horizontal transfer: a piece of DNA can be transferred from the genome of one cell to that of another.
We develop from a single cell Fertilization of an egg by a sperm cell yields a zygote, a cell about 200 μm in diameter. A zygote houses all the necessary instructions for building the human body with 100 trillion (1014) cells. It generates hundreds of different kinds of cells that differ in contents, shape, size, color, mobility, and surface composition. Genes and signals control cell diversification Our current knowledge lead to stem cell, cloning, and related techniques that offer exciting possibilities but raise some concerns
The Molecules of a Cell 1. Small molecules carry energy, transmit signals, and are linked into macromolecules. Neurotransmitters Hor- mones Monomers to polymersAdenosine triphoshate (ATP)
2. Proteins give cells structure and perform most cellular tasks Each protein has a defined 3D conformation that is stabilized by numerous chemical interactions. Proteins below include enzymes, an antibody, a hormone, and the blood’s oxygen carrier. Models of a DNA segment and the lipid bilayer that forms cellular membranes demonstrate the relative width of these structures compared with typical proteins.
3. Nucleic acids carry coded information for making proteins at the right time and place. Step 1 : Transcription factors bind to the regulatory regions of the specific genes they control and activate them. Step 2 : Following assembly of a multiprotein initiation complex bound to the DNA, RNA polymerase begins transcription of an activated gene at a specific location, the start site. The polymerase moves along the DNA linking nucleotides into a single- stranded pre-mRNA transcript using one of the DNA strands as a template. Step 3: The transcript is processed to remove noncoding sequences. Step 4: In a eukaryotic cell, the mature messenger RNA (mRNA) moves to the cytoplasm, where it is bound by ribosomes that read its sequence and assemble a protein by chemically linking amino acids into a linear chain.
4. The genome is packaged into chromosomes and replicated during cell division.A normal human has 23 pairs of morphologically distinct chromosomes; one member of each pair is inherited from the mother and the other member from the father. Chromosomes from the preparation on the left arranged inpairs in descending order of size, an array called a karyotype. The presence of X and Y chromosomes identifies the sex of the individual as male.
5. Mutations May Be Good, Bad, or Indifferent Mutations are mistakes that occasionally occur spontaneously during DNA replication, causing changes in the sequence of nucleotides. Such changes can arise from radiation, chemical poisons (e.g., cigarette smoke, alcohol). Mutations come in various forms: a simple swap of one nucleotide for another; the deletion, insertion, or inversion of one to millions of nucleotides in the DNA of one chromosome; and translocation of a stretch of DNA from one chromosome to another. “Indifferent” mutations in nonfunctional DNA have been a major player in evolution, leading to creation of new genes or new regulatory sequences for controlling already existing genes. Some of our own copies of genomes are genetic residues of infections acquired by our ancestors.
CELL FUNCTIONS1. Cells build and degrade numerous molecules and structures. ATP is formed from ADP and inorganic phosphate (Pi) by photosynthesis in plants and by the breakdown of sugars and fats in most cells. The energy released by the splitting (hydrolysis) of Pi from ATP drives many cellular processes.
2.Cells can be powered by a variety of free energy sources a. Organotrophic - animals, fungi, and the bacteria that live in the human gut, get it by feeding on other living things or the organic chemicals they produce. These organisms could not exist without primary energy converters: b. Phototrophic - those that harvest the energy of Living organisms at a hot hydrothermal vent sunlight At temperatures up to about 150°C, c. Lithotrophic - those that lithotrophic species of bacteria live, fuelled by geochemical energy. A little capture their energy from further away are the giant (2-m) tube worms, which live in symbiosis with energy-rich systems of huge numbers of symbiotic sulfur- inorganic chemicals in the oxidizing bacteria.
3. Animal cells produce their own external environment and glues.Animal cells produce and secrete an extracellular matrix that cushions, lubricates, and glue cells together for exchanging small molecules including nutrients and signals, and facilitating coordinated functioning of the cells. The cells of higher plants contain relatively few such molecules.
4. Cells change shape and move. Three types of protein filaments, organized into networks and bundles, form the cytoskeleton within animal cells. The cytoskeleton prevents the plasma membrane of animal cells from relaxing into a sphere; it also functions in cell locomotion and the intracellular transport of vesicles, chromosomes, and macromolecules . The cytoskeleton can be linked through the cell surface to the extracellular matrix or to other cells, helping to form tissues.A cultured fibroblast in a fluorescence microscope reveals the location of filaments bound to a particular dye-antibody preparation. All three fiber systems contribute to the shape and movements of cells.
5. Cells Sense and Send Information Binding of a hormone or other signaling molecule to its specific receptors can trigger an intracellular pathway that increases or decreases the activity of a preexisting protein. The hormone- receptor complexes activate transcription of specific target genes. Many signals that bind to receptors on the cell surface also act, by
6. Cells regulate their gene expression to meet changing needs. Cells often respond to changing circumstances and to signals from other cells by altering the amount or types of proteins they contain. Gene expression is commonly controlled to produce a particular mRNA only when the encoded protein is needed, thus minimizing wasted energy. Transcriptional activators, repressors and other mechanisms for controlling gene expression determine whether such could occur only in part of the brain, only during evening hours, only during a certain stage of
7. Cells Grow and Divide During growth, eukaryotic In animals, meiosis of diploid cells continually progress precursor cells forms gametes. through the four stages of The male parent produces two the cell cycle, generating types of sperm and new daughter cells. determines the sex of the zygote.
8. Cells die from aggravated assault or an internal program Left, normal WBC. Right, cell undergoing programmed cell death (apoptosis), form numerous surfaceblebs that eventually are released. Thecell is dying because it lacks certain Apoptosis is important to eliminate virus-infected cells, growth signals.remove cells where they are not needed (like the webbing thatdisappears as fingers develop), and to destroy immune system cells that would react with our own bodies.
9. Metabolic proteins, the genetic code, and organelle structures are nearly universal. (a) Hox genes serve to direct formation of the right structures in the right places. (b) Development of the large compound eyes in fruit flies requires a gene called eyeless. (c) Flies with inactivated eyeless genes lack eyes. (d) Normal human eyes require Pax6, that corresponds to eyeless. (e) People lacking adequate Pax6 function have the genetic disease aniridia, a lack of irises in the eyes. Pax6 and eyeless encode highly related proteins that regulate the activities of other genes, and are descended