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Cell Structure and FunctionChapter 4
xenophilius.wordpress.com/2008/09/21/commons.wikimedia.org/wiki/File:SEM_blood_cel...
What is a Cell?• The smallest unit of matter
that can carry all processes of life.
• Structure directly related to Function
• ≈ 10-100 trillion cell in the human body
• All cells are not created equal• cell diversity-cells differ
in shape, size, and organization• Limited in size by surface
area to volume ratio• Shape indicates function
• At least 200 cell types in your body!
www.tutorvista.com/.../structure-cell.php
Background CheckCell Discovery:
◦ Possible by development of microscope
◦ Robert Hooke-examined cork
◦ Anton van Leeuwenhoek-1st to observe living cells
• Cell Theory:1. All living things are
composed of one or more cells
2. Cells are the basic units of structure and function in an organism
3. Cells come only from the reproduction of existing cells
www.microbeworld.org/index.php?option=com_con...
askabiologist.asu.edu/.../rhooke.html
Eukaryotes Vs. ProkaryotesEukaryotes:
◦ Membrane-bound nucleus and organelles
◦ Example(s): YOU, animals, plants, fungi, protists
Prokaryotes:◦ Lack nucleus and
membrane-bound organelles
◦ Example(s): bacteria
www.uoregon.edu/~bsl/astronomy/
Cell Membrane
Surrounds entire cell Selectively
permeable – some substances pass with ease while others cannot pass at all
Made of:-- Lipids and proteins
Fluid Mosaic Model
commons.wikimedia.org/wiki/File:Cell_membrane...
Membrane Lipids and ProteinsPhospholipids
◦ Polar head: hydrophilic
◦ Nonpolar tails: hydrophobic
◦ Forms lipid bilayer
Steroids◦ Cholesterol main
steroid in animal cells
◦ Stabilize membrane/maintain fluidity
Proteins◦ Peripheral proteins: on
exterior or interior surface of cell membrane
◦ Integral proteins: embedded in lipid bilayer Carbohydrates:
involved with self recognition and attachment
Transport of molecules through bilayer (channels or pores)
Cytoplasm/CytosolCytoplasm:
◦ Area between cell membrane and nucleus contains organelles
• Cytosol: Gelatin-like
aqueous in cytoplasm
Salts, minerals, organic molecules
Mitochondria
Site of chemical reactions producing ATP – “power house”
Own DNA and grow and divide on own
2 membranes◦ Smooth outer:
boundary◦ Inner: cristae
(folds)- enlarge surface area for reactions
www.yellowtang.org/cells.php
RibosomesNo membraneTwo compounds-
proteins and RNAAssembled in
nucleusFree or attached to
Endoplasmic reticulum
Role: protein synthesis
www.biologie.uni-hamburg.de/b-online/library/...
Endoplasmic Reticulum (ER)
System of membranous tubules and sacs
Function: intracellular highway
2 types:◦ Rough- has ribosomes
cells with high rate of proteins being exported out or inserted into membrane
◦ Smooth- no ribosomes calcium regulation in
muscle cells Breaks down toxic materials
www.yellowtang.org/cells.php
Golgi ApparatusThe UPS of the cell
◦ Packaging, processing, and secreting proteins
System of membranes/sacs◦ Works closely with ER
www.yellowtang.org/cells.php
LysosomesSmall and spherical
◦ Enclose hydrolytic enzymes
Enzyme use:◦ Digest- proteins,
carbohydrates, lipids, RNA, DNA
◦ Digest- old organelles, viruses, and bacteria
Common in: ◦ Animals, fungi, and
protists ◦ RARE in plants
CytoskeletonLong protein strands in
cytosol ◦ maintain cell shape and size◦ support and movement◦ No membrane
2 Components:◦ Microfilaments-
Actin polymer chains Smallest Contribute to movement and
contraction of muscle
◦ Microtubules- hollow tubes Largest Active role in cell division-
spindle fibers
Cilia and FlagellaCilia
◦ Hair-like organelles ◦ Numerous on cell ◦ Crawling motion
Help unicellular bacteria search for food/escape
On surface of respiratory tract
Flagella◦ Hair-like organelles◦ Long, less
numerous◦ Swimming/
whipping motion Quick movement for
unicellular organisms
Nucleus- “the brain”Nuclear matrix
◦ Protein skeleton◦ Maintains shape
Nuclear envelope◦ Double membrane◦ Chromatin within
DNA and protein combination Coil for cell division forming
chromosomes
Nuclear Pores-visible◦ Holes in envelope
Nucleolus-visible◦ Ribosome
synthesis/partially assembled
www.cartage.org.lb/.../Nucleus/Nucleus.htm
Cell Wall- Plant cellsOutside cell membraneRigid- support and
protection◦ Long chains of cellulose◦ Pores-allow passage of
ions and molecules2 types
◦ Primary- when cell being formed
◦ Secondary- when cell reaches full size Between primary wall and
membrane Tough and woody
www.microscopy-uk.org.uk/.../fixation.html
Vacuoles- Plant cellsFluid-filledOften large can
occupy up to 90% of cell volume
Storage:◦ Store enzymes and
metabolic waste◦ Some waste toxic-
can be a defense
www.yellowtang.org/cells.php
Plastids- Plant cellsDouble membrane and contains DNAStore:
◦ Starch, fats, or pigmentsChloroplast- most common
◦ Chlorophyll- green pigment◦ Thylakoids: system of flattened, membranous sacs
Sunlight converted to chemical energy- PhotosynthesisOther plastids contian pigments that give fruit
and flowers color
www.yellowtang.org/cells.php