introduction to cell biology
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Introduction to Cell Biology. Structure and Function Craig Simpson. Resources. Molecular Biology of the Cell, 4th edition Bruce Alberts , Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walter. New York: Garland Science; 2002. - PowerPoint PPT PresentationTRANSCRIPT
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Introduction to Cell Biology
Structure and FunctionCraig Simpson
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Resources
Molecular Biology of the Cell, 4th edition
Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walter.
New York: Garland Science; 2002.ISBN-10: 0-8153-3218-1ISBN-10: 0-8153-4072-9
Open Source at: http://www.ncbi.nlm.nih.gov/books/NBK21054/
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A human body consists of:
1. Watera. 75% of total mass
2. Organsa. Brain, bones, muscles,
lungs, liver, etc3. Small Molecules
a. DNA, RNA, Proteins, sugars, fats, etc
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Organs contain specialized cell types
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All species originate from a single cell
• Embryonic Stem Cell– Fusion of sperm and ovum
• Human body estimated 1013 cells• Each cell has a specified function• From 1 to 1013…– Cells divide and differentiate
Figure 1-1
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Cellular Differentiation
• Defn: when a less specialized cells divides into cells of more defined cellular species
• Best example: Hematopoiesis
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Take home message
• Human body is complex – made up of multiple organ systems
• Organs are specialized collections of cells that have a set physiological role in the body
• All this complexity came from 1 cell– All cells contain the same genetic information…
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What is a cell?
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Plasma Membrane Function
• Gives cell its structure• Segregates the extracellular environment from
the cytosol (inside cell)• Gives structure to organelles• Contains molecules (lipids and proteins)
important for cellular signaling
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Plasma Membrane Structure
• Lipid bilayer– Consists of phospholipids, cholesterol and
glycolipids– Hydrophilic and hydrophobic regions
• Membrane bound proteins
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Phospholipids are amphiphylic
Figure 10-2
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Four types of phospholipids in plasma membrane
Figure 10-12
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Amphiphylic nature of phospholipids allow for formation of lipid bilayer
Figure 10-4
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Cholesterol helps maintain bilayer structure
• In Eukaryotes 1 molecule cholesterol for every 4 phospholipids
• Makes bilayer more rigid• Decreases permeability of bilayer to small
water-soluble molecules• Prevents hydrocarbon chains from closely
packing and forming a solid
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Cholesterol orientation amongst phospholipids
Figure 10-11
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Glycolipids
• Modified through addition of sugar groups to the phosphate groups of the phospholipid
• Found exclusively on the extracellular side of the cell
• Important for interaction of the cell with its environment
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Glycolipid Structure
Figure 10-16
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Membrane Proteins
• 50% of mass of plasma membrane• Multiple types of interactions with lipid bilayer• Highly glycosylated• Work horse of the plasma membrane– Transport of molecules across membrane– Transport of signals from extracellular
environment/other cells (receptors)– Enzymatic reactions– Energy production
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Membrane Protein IntegrationTransmembrane
a-Helix b-barrel
Figure 10-17
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The Cell
Figure 12-1
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Figure 12-2
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Cytoplasm
• Contains:– Cytosol (aqueous environment)– All organelles
• Half the volume of the cell• Location of large amount of bioorganic
reactions– Protein synthesis and degradation– Intermediary metabolism (building and breakdown
of small molecules)
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Nucleus
• Contains the Chromosome (genomic DNA)• Site of DNA replication• Site of RNA transcription
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Nucleus Structure
• Two concentric membranes– Nuclear pores
• Inner membrane contains proteins that give structure to nucleus and support for chromatin
• Outer membrane is connected to the ER
Figure 12-9
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Nuclear Pores
• Allow for transport of proteins into the nucleus and RNA out of the nucleus
• Multi protein complexes, highly regulated
Figure 12-10
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Ribosomes• Protein synthesizing
machines– Add 2 amino acids to peptide
sequence each second• Consist of 2 subunits (50
different proteins)– 2/3 RNA, 1/3 protein
• Located in cytosol, on ER– Ie protein synthesis happens
in both ER and cytosol– Functionally and structurally
identical
Figure 6-62
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Endoplasmic Reticulum (ER)
• Extends throughout the cell• Complex structure of continuous tube and
flatten sacs– Double membrane surrounding the ER lumen
(aqueous environment)• Two types– Rough ER (contains ribosomes)– Smooth ER
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Endoplasmic Reticulum
Figure 12-36
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Rough ER
• Protein and lipid biosynthesis– Site of protein glycosylation
• Contain ribosomes• Membrane is the site of production for all
transmembrane proteins, and lipids for the plasma membrane and other organelles
• Also produces all proteins used in intermembrane spaces (lumens of different organelles)
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Smooth ER
• Don’t contain ribosomes• Exit site of synthesized proteins being
exported to the Golgi apparatus• Important in lipid synthesis• Important in steroid synthesis from
choloesterol
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Golgi Apparatus
• Consists of stacks of membrane bound cisternae
• Pancake like shape
Figure 13-22
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Function of Golgi
• Further modification of proteins and lipids– N and O glycosylation (important for function)
• Transport of finished proteins and lipids to plasma membrane, lysosomes and secretory vesicles (ie out of the cell)
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Lysosomes and Peroxisomes
• Membrane bound vesicles• Contain enzymes• Some have lower pH• Lysosomes aid in the breakdown of proteins• Peroxisomes aid in the oxidation of small
molecules
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Mitochondria
• Two highly specialized membranes that create two compartments– Internal matrix– Intermembrane space
• Inner membrane forms cristae
Figure 14-8
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Mitochondria produce ATP
• The source of all energy for the cell
• Site of the citric acid cycle where glucose is broken down to NADH and ATP
• NADH is converted to ATP through the electron transport chain
Figure 14-10
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Summary
• Nucleus contains information to make proteins
• Ribosome read information from nucleus to make protein
• ER and Golgi sites of protein synthesis and modification
• Mitochondria supply all the engery