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Transcript
Lecture no.3 An Introductory Overview of Cells 1 22/05/2017 Lecture no.3 What We Will Be Covering-I? What is a Cell? The Two Types of Cells ? The Exception? The Organelles and Their Functions. 2 22/05/2017 Life begins with cells Lecture no.3 Cell came from Latin word mean small room. A cell is the functional and structural unit of all living organism. The Cell Theory --1839 by the German botanist Matthias Jakob Schleiden and German physiologist Theodore Schwann. 3 22/05/2017 Cell Theory Lecture no.3 All living things are made up of cells. Cells are the smallest working units of all living things. All cells come from preexisting cells through cell division. 4 22/05/2017 Lecture no.3 Plant Stem Amoeba Proteus Examples of Cells Bacteria Nerve Cell 5 22/05/2017 Red Blood Cell Types of Cells Lecture no.3 1. Prokaryotic • Bacteria • Archaea 2. Eukaryotic Unicellular • Protists Multi-cellular • Fungi • Plants • Animals 6 22/05/2017 Prokaryotic Cells Lecture no.3 • Characteristics Unicellular (some multi-cellular). Lacks a membrane bound nucleus. Lacks membrane bound organelles. Has a cell membrane and cell wall. Has ribosomes (protein production). Circular DNA. 7 22/05/2017 Eukaryotes Lecture no.3 • Characteristics Unicellular (Protists). Multicellular (fungi, plants, animals). Membrane bound Nucleus. Contains Organelles. Linear DNA. 8 Typical animal cell Typical plant cell 22/05/2017 Types of Eukaryotic Cells Lecture no.3 1. Somatic Greek for “body’’ All cells in the body except the sex cells. Found in the bones, skin, organs, tissues, blood. Reproduce by Mitosis. All somatic cells in a human body have the same genetic information (except RBC) 2. Germ 9 The Sex Cells. Sperm and Ova. Reproduce by Meiosis. Are haploid e.g. in humans: 23 chromosomes 22/05/2017 Lecture no.3 Is there any exception ? 10 22/05/2017 The Exception: Viruses Lecture no.3 • Characteristics Latin for “poison”. Does not meet all the criteria of “Life” Viruses are not cells; they are supramacromolecules made of two types of macromolecules i.e. proteins and nucleic acids Outer coat is made of proteins and inner core is nucleic acid, which may be either DNA or RNA, but not usually both. Require a host to replicate. 11 22/05/2017 Lecture no.3 Cell Parts Organelles 12 22/05/2017 I- Surrounding the Cell Lecture no.3 - Cell Membrane - Cell wall Outer membrane of cell that controls movement in and out of the cell. Made of phospholipid bilayer with embedded proteins (enzymes, receptors, channels etc). Place of communication with the environment and other cells. 13 “Gate of the Cell”. Most commonly found in plant cells & bacteria. Made of mucopolysaccharides (yeast, procaryotes) or cellulose (plants) “Supports & protects cells”. 22/05/2017 Lecture no.3 II- Inside the Cell - Nucleus First described by Robert Brown in 1831. Largest organelle. Separated from cytoplasm by nuclear membrane in eucaryotes. Contains genetic material – DNA. “Control Center” 14 - Nuclear membrane Double membrane envelop that surrounds nucleus. Contains nuclear pores which is place of selective transport between cytoplasm and inside of nucleus (proteins, mRNA) “Gate of the Nucleus” 22/05/2017 Lecture no.3 Continue… - Chromosomes In nucleus. Present in the form of strings of DNA and histones. Contain instructions for traits & characteristics . “Director of the Cell” 15 - Nucleolus Inside nucleus. The nucleolus plays an indirect role in protein synthesis by producing ribosomes. Nucleolus is not a structure!!! Just a visible region. 22/05/2017 Lecture no.3 Chromosomes in eukaryotes & prokaryotes are different PROKARYOTES EUKARYOTES • single chromosome plus plasmids many chromosomes • circular chromosome linear chromosomes • made only of DNA made of chromatin, a nucleoprotein (DNA coiled around histone proteins) • found in cytoplasm found in a nucleus • copies its chromosome and divides immediately afterwards copies chromosomes, then the cell grows, then goes through mitosis to organise chromosomes in two equal groups © 2007 Paul Billiet ODWS Numbers of chromosomes Lecture no.3 • Constant for each cell in the body (except sex cells which only have half sets). • Constant throughout the life of an individual. • Chrosomes are of two types: autosomes (same in males and females) and sex (X and Y) chromosomes • Constant for all members of a species. Lecture no.3 Human Genome Basics • Most human somatic cells are diploid, having 2 copies of each chromosome, one from each parent. • The gametes, sperm & egg, are haploid, with 1 copy of each chromosome. • Humans have a haploid number n of 23, meaning that there are 23 chromosomes in a complete haploid set. Thus, gametes have 23 chromosomes and diploid cells have 46. The pairs of chromosome in a diploid cell are called homologues. • The X and Y chromosomes are sex chromosomes, and the other 22 chromosomes are called autosomes. • Normal males are XY and normal females are XX. Thus, sperm cells either contain an X or a Y. Eggs always contain an X chromosome. Conti… • In somatic cells: diploid (2n) cell: 23 x2= 46 chromosomes : 22 pair of autosomes + XY chromosomes : 22 pairs of autosomes + XX chromosomes • In germ cells: • Sperms are of two types: 22 autosomes + Y chromosome 22 autosomes + X chromosome • 19 Ova has: 22 autosomes + X chromosome 22/05/2017 Lecture no.3 Chromosomes and reproduction 20 22/05/2017 Lecture no.3 Continue… - Cytoplasm -Endoplasmic Reticulum Gel-like material. The portion of the cell enclosed by the cell membrane but not part of any organelle It stores the organelles, water, and the chemicals in it. “Area of Movement”. The transportation center for the cell. Smooth and rough types. SER Site of fatty acid and phospholipid synthesis, While RER place of extracellular proteins synthesis 21 22/05/2017 Lecture no.3 Continue… - Ribosomes Found in the cytoplasm and on the ER. Their job is to make proteins. The nucleus makes the ribosomes. 22 - Mitochondria Place of oxidative metabolism and ATP production. Contains its own DNA and ribosomes. “Powerhouse of the Cell” 22/05/2017 Lecture no.3 Continue… - Golgi Bodies Package and to move protein to the out side of the cell. They also process proteins from ribosomes that are located on the ER. 23 - Lysosome Digest the wastes and unwanted organelles. Acidic organelles - low pH due to proton pump (pH=5) in the membrane. Contain many degradative enzymes such as acid hydrolases. 22/05/2017 Tay-Sachs disease : is a genetic defect in one of specific lysosomal hydrolases 24 22/05/2017 Lecture no.3 Continue… - Vacuoles The vacuole in the plant cell is larger than the vacuole in the animal cell. Membrane-bound sacs for storage, digestion, and waste removal. “Storage Tanks” . 25 - Chloroplast Contains green chlorophyll. Where photosynthesis takes place. “Food Producers” . 22/05/2017 Summary 26 Lecture no.3 22/05/2017 Lecture no.3 See you later to continue with the The structure and properties of Nucleotides 27 22/05/2017