Download presentation
1
CHAPTER 6 SYSTEMS BIOLOGY OF CELL ORGANIZATION
Prepared by Brenda Leady, University of Toledo
2
Systems biology Researchers study living organisms in terms of their underlying network structure rather than their individual molecular components The goal is to understand how the organization of the cell arises by complex interactions between its various components and parts
3
All modern cells come from preexisting cell by division
All cells posses a genome Living cells require pre-existing molecules Cells require pre-existing organization
4
Cell’s genetic information produces proteome
Information in most genes is used to make mRNA molecules that encode amino acid sequences of proteins Study of individual proteins does not provide a broad integrated look at the dynamic nature of the cell
5
Genomes, proteomes and cell structure function and organization
The proteome is largely responsible for the structure and function of living cells Gene and protein regulation causes the proteome to be dynamic Proteins have sorting signals
7
Proteins often undergo protein-protein interactions
Cells must continually synthesize new molecules and break down unwanted components
9
Molecular machines A machine is an object that has moving parts and does useful work These machines provide structure and organization to cells and enable them to carry out complicated processes ATP synthase is a molecular machine that makes ATP Molecular recognition allows for complex assembly Subunits recognize each other and bind in a specific way
11
Other molecular machines
12
Cytoskeleton Key role in cell organization and many processes that maintain the cell Provides mechanical strength, cell shape, organization and direction to intracellular and cellular movements
15
Molecular recycling Large molecules, except DNA, have finite lifetimes
Half-life varies from 5 minutes for mRNA in prokaryotes to 30 minutes to several days for mRNA in eukaryotes Continual degradation of faulty or nonfunctional proteins and synthesis of new ones
16
Proteasome Molecular machine for protein degradation
4 stacked rings with caps in eukaryotes Ubiquitin directs unwanted proteins to proteasomes in eukaryotes Proteases degrade the unwanted protein into peptides and amino acids
18
Four systems work together
Interior of the nucleus Cytosol Endomembrane system Semiautonomous organelles Play a role in their own structure and in the structure and organization of the entire cell
20
Nucleus Genome produces the proteome that is responsible for the structure and function of the entire cell Gene regulation important in creating specific cell types and enabling response to environmental change Nucleus organizes itself with the nuclear matrix Collection of filamentous proteins
21
Cytosol Important coordination center
Compartment for metabolism- synthesis and breakdown Cytoskeleton found here
22
Endomembrane system Secretory pathway to move substances in and out of the cell Secretory and endocytic pathways Membranes are dynamic and change over time Nuclear membrane during cell division Lipids and proteins made and sorted Storage and recycling Vacuoles and lysosomes
23
Semiautonomous organelles
Tend to be independent Mitochondria make ATP Crucial for cell organization Chloroplasts capture light to store energy for later use
24
Endomembrane system Golgi apparatus, lysosomes, vacuoles, secretory vesicles, and plasma membrane Reside in cytosol Much of its activity related to transport between compartments Critical for lipid synthesis, protein synthesis and sorting, and the attachment of carbohydrates to lipids and proteins
25
Lipid synthesis Cytosol and endomembrane system work together to synthesize most lipids Building blocks of phospholipids made by enzymes in the cytosol or from the diet Phospholipids initially made in cytosolic leaflet but flipases in ER membrane transfer some to the other leaflet
27
Lipid transfer Lipids made in the ER membrane can be transferred to other membranes by… Lateral diffusion Vesicle transport Lipid exchange proteins
29
Studied pancreatic cells secreting proteins
Palade demonstrated that secreted proteins move sequentially through organelles of the endomembrane system Thousands of different proteins must be sorted to the correct locations George Palade’s team used pulse-chase experiments to determine where radioactive proteins were produced and the pathways they took Studied pancreatic cells secreting proteins Followed radioactive proteins from synthesis in the rough ER and movements through cellular compartments
31
Protein localization Sorting signals or traffic signals are short amino acid sequences that direct protein to correct cellular location Most eukaryotic proteins begin synthesis (translation) on ribosomes in the cytosol
32
Proteins that stay in the cytosol lack sorting signals so they stay in the cytosol
Proteins for the nucleus, mitochondria, chloroplasts, and peroxisomes occur after the protein is made Post-translational sorting Synthesis of other proteins destined for ER, Golgi, lysosome, vacuole, plasma membrane, or secretion halts until the ribosome is bound to the ER Cotranslational sorting
34
Proteins that stay in the ER have ER retention signals
Other proteins must be sorted Transported by vesicles Vesicles incorporate coat proteins Also incorporates v-snare indicative of cargo T-snare on target recognizes v-snare and vesicle fuses with target membrane
36
Glycosylation Attachment of a carbohydrate to a protein
Glycoprotein May aid in protein folding, extracellular protection, and protein sorting
37
2 forms of glycosylation
N-linked Carbohydrate attaches to nitrogen atom of asparagine in polypeptide chain in ER lumen Occurs in cell membrane surface proteins Role in cell-to-cell signaling O-linked String of sugars attaches to oxygen of serine or threonine in polypeptide Occurs only in the Golgi apparatus Important in extracellular matrix proteins
39
Semiautonomous organelles
Semiautonomous because they divide by fission to produce more of themselves Somewhat independent Genetic material, synthesize some proteins, divide independently of cell Do depend on the cell for raw materials and most of their proteins
40
Mitochondria and chloroplasts
2 traits similar to bacteria Contain DNA separate from the nuclear genome Mitochondrial and chloroplast genome Single small circular double stranded chromosome Similar to bacterial chromosomes Reproduce via binary fission Like bacteria
42
Genes of mitochondria and chloroplasts very similar to bacterial genes
Mitochondria and chloroplasts are derived from ancient symbiotic relationships Endosymbiosis- a smaller species lives symbiotically inside a larger species Beneficial for both species Genes of mitochondria and chloroplasts very similar to bacterial genes Endosymbiosis theory Modern mitochondria and chloroplasts have lost most of their genes through transfer to nucleus Origins of peroxisomes unclear but may be same path
44
Post-translational sorting
Most proteins for mitochondria, chloroplasts, and all proteins for peroxisomes sorted post-translation Must have sorting signal Example- protein destined for mitochondrial matrix
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.