Introduction To Cells - Lecture notes, lecture 1 PDF

Preview

Summary

Download Introduction To Cells - Lecture notes, lecture 1 PDF

Description

Cell biology and genetics (24/03/16) Three major scientists creating cell theory  Mathias schleiden  Theodor schwann  Rudolf Virchow Cell theory 1. all organisms are composed of cells 2. cells are the smallest living things 3. cells arise only from pre-existing cells

All cells have certain structure in common 1. Genetic material- in nucleoid or nucleus 2. Cytoplasm- a semifluid matrix 3. Plasma membrane- a phospholipid bilayer Cell size is limited. E.g. Logistics of carrying out cellular metabolism sets limits on the size of cells. Grouping species Taxonomy



The branch of biology that names and classifies species into groups of increasing breadth. Carl Linnaeous (1707-1778) known as father of taxonomy.

 

Followed by kingdoms are broadest units of classification. 3 domains (domain bacteria, domain archaea, domain eukarya.)

 Domains

In common  Plasma membrane  Cytosol  Chromosomes Procaryotic cells  Are relatively simple.  No nucleus  DNA in an unbound region (nucleoid.)  Most are microscopic  Thrive almost everywhere (acidic, salty, cold, hot environments)  Most are unicellular.  Most are 0.5-5 um.  Have a variety of shapes  Two types- bacteria and archaea  Often have a cell wall to protect (material capsule external to sell allowing support.  Cell wall maintains cell shape, provides physical protection, prevents cell from bursting in a hypotonic environment.  Bacterial cell walls contain peptidoglycan.  Archaea contain polysaccharides and proteins but lack peptidoglycan.

  

        

Bacterial cell walls may be differentiated through GRAM-STEIN. They will be either Gram positive (thick cell wall) or Gram negative (thin cell wall.) Prokaryotes reproduce quickly by binary fission and can divide every 1-3 hours. Many prokaryotes form metabolically inactive endospores (hard outer shell) (remain viable in harsh conditions for centuries) basically waiting till the environmental conditions improve before passing on DNA (reproducing.) CELL SURFACE STRUCTURES- Some have fimbriae (allow them to stick to a substrate in a colony.) They DO have sex. Sex pili are longer than fimbriae and allow the exchanging of DNA. Most motile bacteria propel themselves by flagella. Usually lack compartmentalization. Some have specialized membranes but in general they are very simple. The prokaryotic genome has less DNA than a Eukaryotic genome. Some species of bacteria also have smaller rings of DNA called plasmids. Bacteria live in colonies (biofilms.) Meaning they live together not they are multicellular. Most are unicellular cells.

Eukaryote cells  Cell walls are made of cellulose or chitin.  Complex  Compartmentalize many cellular functions (organelles separate one set of functions within a cell to the others) Also use of an endomembrane system.  Posses a cytoskeleton for support and to maintain cellular structure.  Possess a membrane-bound nucleus.  Much bigger than prokaryotic cells and hence cytoskeleton acts to provide a skeletal structure within the cell and to hold things in place.  Cytosol functions o Location of specific chemical reactions o Storage of fat and carbohydrates. o Storage of secretory vesicles.  Cell is full of organelles.  Plant cells have a cell wall (typically a large vacuole.) Vacuole much more present and visible in plant cells than in animal cells. Plasma membrane    

Surrounds the cytoplasm, acting as a physical barrier. Plasma membrane is selectively permeable. Allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell. Fluid mosaic model- used to show structure of the plasma membrane.

Nucleus  Double membrane (2 layers)  Contains most of the genes and is usually the most conspicuous organelle in the cell.  Shape is maintained by the nuclear lamina, (composed of proteins.) DNA- Transmission and expression of genetic information.  DNA transcribed into RNA (mRNA) necessary to express the code.

Ribosomes  Site of protein synthesis.  Particles made of ribosomal RNA and protein.  They carry out protein synthesis in the cytosol (free ribosomes) and the outside of the ER (Endoplasmic reticulum.) Endomembrane system  Series of membranes throughout the cytoplasm. o ER o Golgi apparatus o Lysosomes Endoplasmic reticulum (ER) o Two distinct regions. o Smooth ER and rough ER. Golgi apparatus o Flattened stacks of interconnected membranes. o Packaging and distribution of materials to different parts of the cell. o Synthesis of cell wall components (plants and fungi) o Functions- Modification of ER products. Manufacture of certain macromolecules. Packaging materials into transport vesicles. Lyosomes o o

Membrane-bound vesicles containing digestive (hydrolytic) enzymes to break down macromolecules. Destroy cells or foreign matter the cell has engulfed by phagocytosis.

Vacuoles   

Central vacuole (in plants used for storage) Food vacuoles (formed by phagocytosis.) Contractile vacuoles (hold organic compounds and water.)

Mitochondria  Present in all eukaryotic cells.  Contain oxidative metabolism enzymes for transferring the energy within macromolecules to ATP.  2 membrane layers  Smooth outer membrane  Folded inner membrane with layers called cristae  Matrix within the inner membrane  Intermembrane space is located between the two membranes.  Contain their own DNA. Chloroplasts  Surrounded by 2 membranes.  Contain chlorophyll (Site of photosynthesis.)  Contain grana, stacks of thylakoids.

Cytoskeleton  Network of proten fibres found in eukaryotic cells.  Supports cell shape.  Keeps organelles in fixed locations.  Helps move materials within cell.  Functions o Mechanical support o Suspension of organelles o Contraction o Cell motility  3 FILAMENTS o Microfilaments (smallest diameter)  Used in muscle contraction.  Amoeboid-like movements.  Seperation of cytoplasm during cell devsion. o Intermediate filaments  Contain vimentin and keratin.  Support cellular membranes and keep organelles in fixed place. o Microtubules (largest diameter.)  Contain hollow tubes called tubulin.  Provide strength to cytoskeleton.  Determine overall shape of cell and distribution of organelles.  Major components of cilia and flagella. Extracellular structures  Cell walls of plants, fungi and some protists.  Extracellular matrix surrounding animal cells.  Intercellular junctions....