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Lecture 3 4100 cell structure
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- 1Bacterial Cell what are the Fundamental features of Prokaryotes?Most Prokaryotes share Fundamental Traits. 1: Thick, Complex outer envelope Envelope structures provide protection from the environment and helps mediate exchange of small molecules and interactions with other cells.
2: Compact Genome - Prokaryotes have small genomes with little non coding DNA. Thus less resources are needed to replicate.
3: Tightly Coordinated cell function -
-Cellular process are tightly coordinated allowing the coupling of DNA, RNA and protein synthesis.This effects both the coordination of Gene expression and the efficiency of production. - 2Explain the Structure of Cell membrane and its membrane Protein function ?The Cell membrane is a semipermeable membrane.Membranes have equal parts of phospholipid and proteins. Proteins can be integrated into the membrane or loosely associated. Membrane Protein functions. 1: Structural support connecting the layers or anchor support for Flagella.
2: communication with the environment: secretion systems and sensors. 3: Transport of ions and nutrients and energy storage. - 3Whats the difference Between Eukaryotic, bacteria and Archae membrane Lipids?Archea membrane lipid differ from Eukarya and Bacteria in having branched chain Hydrocarbons attached to Glycerol by Ether links rather than Ester links like Eukarya and Bacteria.
- 4A Phospholipid consists of what ?A Phospholipid consists of Glycerol with ester links to two fatty acids and a phosphoryl head group.
- 5Explain transport across the cell membrane?The cell membrane acts a semipermeable membrane. 1:Passive diffusion: small uncharged molecules such as Oxygen and carbon dioxide. moving along the concentration gradient. 2: Osmosis: water diffuses across the membrane by osmosis, The resulting pressure is known as somatic pressure. 3: Facilitated diffusion: Transport of most Nutrients and ions requires specific transporters these may be passive transporters/facilitated diffusion moving along their concentration gradient. OR 4: Active Transport ( require energy to move against gradient)
- 6Name two organism for Gram + and G - cell explain how the cell envelope confers stability to environmental agents?Gram Positive: bacteria (Thick cell wall )
Bacillus anthracis (anthrax)
Gram Negative:Bacteria E.coli
(thin cell wall)
Found in the Gut can be pathogenic.
Gram negative bacteria also have an outer membrane.
Besides the cell wall another protective layer found in bacteria and Archea organism's is a surface layer made up of protein and Glycoprotein called the S-Layer. - 7What is the S-layer structure made up of and what is it's function ?S-Layer is a Crystalline layer of thick subunits consisting of proteins or Glycoproteins. Each subunit of the S-Layer contains a pore late enough to admit a wide range of molecules. The S-Layer may contribute to cell shape and help protect the cell from osmotic stress,but is often lost in culture.
- 8Define all structures of the Gram negative cell wall?Gram negative cell wall is thin. Most Gram-negative cell wall peptidoglycan lacks the peptide inter-bridge. The outer membrane lies outside the thin peptidoglycan layer.The outer membrane and peptidoglycan are connected in two way 1: The first is Braun’s lipoprotein, the most abundant protein in the outer-membrane. This small lipoprotein is covalently joined to the underlying peptidoglycan and is embedded in the outer membrane by its hydrophobic end. Possibly the most unusual constituents of the outer membrane are its Lipopolysaccharides (LPS) These large, complex molecules contain both Lipids and Carbohydrate, and consist of three parts
1: Lipid A 2: The core Polysaccharide and 3: O side chain
The lipid A region contains two glucosamine sugar derivatives, each with three Fatty acids and phosphate or pyrophosphate attached. The fatty acids attach the lipid A to the outer membrane, while the remainder of the LPS molecule projects from the surface. The Core Polysaccharide is joined to Lipid A . The O side chain or O antigen is a polysaccharide chain extending outward from the core. - 9Define all Structure of the Gram Positive Cell wall?Gram Positive bacteria normally have cell walls that are thick and composed primarily of peptidoglycan. Peptidoglycan in Gram Positive bacteria often contains a peptide inter-bridge. In addition gram-positive cell walls usually contain large amounts of Teichoic acids, polymers of glycerol or ribitol joined by phosphate groups (figure 3.24) Amino acids are covalently connected to either the peptidoglycan itself or to plasma membrane if connected to plasma membrane it’s called
Lipoteichoic acid. Teichoic acids, are extended to surface of the peptidoglycan and because they are negatively charged help give Gram – positive cell wall it’s negative charge. Teichoic acids, are not present in Gram Negative cell wall. - 10Explain why Mycobacterial cells have a complex Envelope name main components and function? also name an organism with such envelope?Organism: Mycobacterium tuberculosis have very complex cell envelopes. Their envelopes are characterized by the presence of unusual lipids Mycolic acid and unusual sugars, Arabinogalactans. Mycolic acids are attached to Arabinan. The thick waxy envelope offers protection from host defenses and excludes many antibiotics, contributing to the difficulties in in clearing Mycobacterium tuberculosis infection. The Capsule consist of Glycolipids and sugar mycolates.
- 11Explain Prokaryotic Nucleiod ?Prokaryotes have a nucleoid region that extends throughout the cytoplasm. Ribosome are excluded by the DNA and the nucleoid appears as a clear region in TEM. The DNA s organized in Loops called Domains and the central point, the origin of replication (ori) is attached to the cytoplasmic membrane at the midpoint of the cell. DNA is highly compacted by looping back on itself this is catalyzed by the enzyme gyrase, which supercoils the DNA. Bacteria and Archea have DNA binding proteins but lack the highly organized histones - mediated nucleosome found in eukarya cells.
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- Flashcards on Lecture 3 4100 cell structure , created by gurhan.3 on 17/09/2015.
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