01. cell structure and function
TRANSCRIPT
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Introduction
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What is biochemistry?
Biochemistry can be defined as the scienceconcerned with the chemical basis of life (Gkbios life).
The cell is the structural unit of living systems.Thus, biochemistry can also be described asthe science concerned with the chemicalconstituents of living cells and with thereactions and processes they undergo.
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Biochemistry is a hybrid science: Biology is the science of living organisms and
chemistry is the science of atoms and
molecules, so biochemistry is the science of the atoms and molecules in living organisms.
Its domain encompasses all the living worldwith the unifying interest in the chemicalstructures and reactions that occur in livingsystems.
What is biochemistry?
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Biochemistry underlies ordinary life in unseen ways
For example, take a middle-aged man Takes a drug to lower his serum cholesterol. That drug
was developed by a pharmaceutical companysbiochemists to inhibit a key enzyme involved incholesterol biosynthesis
Shaves with a cream containing compounds thatsoften his beard. These active agents were developedafter studies of the physical properties of keratin, theprotein in hair.
Wears a shirt made from pest-resistant cotton. Thecotton plants were bioengineered by biochemists
through the transfer of genes from a bacterium intoplants.
All these everyday events depend on an understanding of thechemistry of living systems
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Aim of Biochemistry
The major objective of biochemistry is thecomplete understanding, at the molecularlevel, of all of the chemical processes
associated with living cells. To achieve this objective, biochemists have
sought to isolate the numerous moleculesfound in cells, determine their structures, andanalyze how they function.
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Most if not all diseases are manifestationsof abnormalities of molecules, chemical reactions,
or biochemical processes
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The major causes of diseases. All of the causes listed act by influencing thevarious biochemical mechanisms in the cell or in the body
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Some uses of biochemical investigations andlaboratory tests in relation to diseases.
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Distinguishing features of living organisms
A high degree of chemical complexity andmicroscopic organization.
Thousands of different molecules make up a cells
intricate internal structures Systems for extracting, transforming, and
using energy from the environment enabling organisms to build and maintain their
intricate structures and to do mechanical,chemical, osmotic, and electrical work
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Defined functions for each of their
components and regulated interactionsamong them The interplay among the chemical components of
a living organism is dynamic; changes in onecomponent cause coordinating or compensatingchanges in another, with the whole ensembledisplaying a character beyond that of its individualparts.
A history of evolutionary change.
Organisms change their inherited life strategies tosurvive in new circumstances
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Cellular Foundations
The smallest organisms consist of single cellsand are microscopic.
Larger, multicellular organisms contain many
different types of cells, which vary in size,shape, and specialized function. Despite these obvious differences, all cells of
the simplest and most complex organisms
share certain fundamental properties, whichcan be seen at the biochemical level.
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On the basis of their biochemicalcharacteristics, the diverse organisms of themodern world can be divided into three
fundamental groups called domains:1) Eukarya (eukaryotes),
2) Bacteria (formerly Eubacteria), and
3) Archaea (formerly Archaebacteria).prokaryotes
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Tree of life
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Eubacteria inhabit soils, surface waters, andthe tissues of other living or decayingorganisms.
Most of the well studied bacteria, includingEscherichia coli, are eubacteria.
The archaebacteria, more recently discovered,are less well characterized biochemically; most
inhabit extreme environmentssalt lakes, hotsprings, highly acidic bogs, and the oceandepths.
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Cells are the Structural and Functional Units of allLiving Organisms
Cells of all kinds share certain structural features The plasma membrane defines the periphery of the
cell, separating its contents from the surroundings. The internal volume bounded by the plasma
membrane, the cytoplasm , is composed of anaqueous solution, the cytosol, and a variety of suspended particles with specific functions
All cells have, for at least some part of their life, eithera nucleus or a nucleoid, in which the genome the
complete set of genes, composed of DNAis storedand replicated
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The nucleoid , in bacteria, is not separated from thecytoplasm by a membrane; the nucleus , in higherorganisms, consists of nuclear material enclosed withina double membrane, the nuclear envelope.
Cells with nuclear envelopes are called eukaryotes(Greek eu, true, and karyon, nucleus); thosewithout nuclear envelopesbacterial cellsareprokaryotes (Greek pro, before).
In comparison with the prokaryotes, eukaryotic cellshave greater specialization and complexity in theirstructure and functioning.
Eukaryotic cells are structured into compartments
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Structure of an animal cell The eukaryotic cell is subdivided by
membranes. On the outside, it is enclosed by a plasma
membrane. Inside the cell, there is a large space containing
numerous components in solutionthecytoplasm.
Additional membranes divide the internal spaceinto compartments (confined reaction spaces).
Well defined compartments of this type areknown as organelles.
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Organelles
Ribosomes are protein synthesizing machines Peroxisome destroys peroxides Cytoskeleton supports cell, aids in movement of
organelles Lysosome degrades intracellular debris Transport vesicle shuttles lipids and proteins
between ER, Golgi, and plasma membrane Golgi complex processes, packages, and targets
proteins to other organelles or for export Nucleus contains the genes (chromatin)
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Smooth endoplasmic reticulum (SER) is site of lipid synthesis and drug metabolism
Rough endoplasmic reticulum (RER) is site of much protein synthesis
Nucleolus is site of ribosomal RNA synthesis Nuclear envelope segregates chromatin (DNA
+ protein) from cytoplasm Plasma membrane separates cell from
environment, regulates movement of materials into and out of cell
Mitochondrion oxidizes fuels to produce ATP