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Cell TheoryVirchow, Schleiden and Schwann
1. Every organism is composed of one or more cells
2. Cells are the smallest units having properties of life
3. Continuity of life arises from growth and division of single cells
- Cells arise only from pre-existing cells.
How many cells in your body?
50 million million (trillion)
That’s 50,000,000,000,000 cells!!!!!!
And not only that, there are many different types.
Cells are diverse But only two basic types
Two Basic Cell Types
Prokaryote Eukaryote
NamePro = before
karyote = nucleusEu = true
karyote = nucleus
Relative size
very small large
True Nucleus present
No yes
Organelles Present
No Yes
DNA structure
loose, sometimes circular
packed into chromosomes
Examples Bacteria Plants, animals, protists
Prokaryotic Cell
Note the lack of nucleus, DNA free floating (nucleoid area)
DO HAVE plasma membrane, ribosomes, and cell wall (sometimes)
Endosymbiotic Theory
It is believed that eukaryotic cells arose from groups of prokaryotic cells living together.
Smaller ones inside larger ones.
EVIDENCE… For Endosymbiosis
Some eukaryotic organelles resemble bacteria
Mitochondria and Chloroplast – double membrane
Mitochondria and bacteria have similar size
Mitochondria and Chloroplast DNA circular like Bacteria
Mitochondria divide as bacteria do
Eukaryotic Cell
More Advanced, larger & have organelles
DO HAVE nucleus, ribosomes, mitochondria, chloroplasts (plants), cell wall (plants), endoplasmic reticulum, golgi complex, lysosomes, and vacuoles
Eukaryotic Cell
Lots of internal membrane-bound structures!
Why are cells so small?
Cells exchange all materials with their environment through the cell membrane.
Exchange is faster in a smaller cell.
Need a surface area proportional to their volume – Surface area to volume ratio decreases as cell gets larger.
Cells that are specialized for absorption have folds in plasma membrane to increase surface area
Plasma Membrane
Plasma Membrane
Both prokaryotic and eukaryotic cells have this “outer wall”
Holds the CYTOPLASM inside the cell
Gives cells their shape and flexibility
Helps to maintain HOMEOSTASIS by allowing substance to flow in and out of the cell – SELECTIVE PERMIABILITY
Structure of Plasma MembraneThe plasma membrane is a PHOSPHOLIPIID BILAYER
PHOSPHOLIPID BILAYER
Fluid Mosaic Model Phospholipids, cholesterol, and proteins all
flow like the surface of a wavy lake, moving and shifting.
Structure of Plasma Membrane
What are the structures and functions of the cell membrane?
Components of the Cell MembraneContains lipids, carbohydrates, and functional proteins
Phospholipid BilayerDouble layer of phospholipid molecules: hydrophilic heads—toward watery environment,
both sides hydrophobic fatty-acid tails—inside membrane
Membrane ProteinsIntegral proteins: within the membrane
Peripheral proteins: inner or outer surface of the membrane
CytoplasmAll materials inside the cell and outside the nucleus: cytosol (fluid):
dissolved materials: nutrients, ions, proteins, and waste products
organelles:
structures with specific functions
What are cell organelles & their functions?
Nonmembranous organelles: no membrane direct contact with cytosol
Membranous organelles: covered with plasma membrane isolated from cytosol
6 types of nonmembranous organelles: cytoskeleton microvilli centrioles
cilia ribosomes proteasomes
The CytoskeletonStructural proteins for shape and strength
Microfilaments Thin filaments composed of the
protein actin: provide additional mechanical strength interact with proteins for consistencyPairs with thick filaments of myosin for muscle movement
Intermediate Mid-sized between microfilaments
and thick filaments:durable (collagen)strengthen cell and maintain shapestabilize organellesstabilize cell position
Microtubules Large, hollow tubes of
tubulin protein:attach to centrosome
strengthen cell and anchor organelles
change cell shape
move vesicles within cell (kinesin and dynein)
form spindle apparatus
The Cytoskeleton
MicrovilliIncrease surface area for absorption
Attach to cytoskeleton
Centrioles in the Centrosome
Centrioles form spindle apparatus during cell division
Centrosome: cytoplasm surrounding centriole
Cilia PowerHair-like cilia move fluids across the cell surface
RibosomesBuild polypeptides in protein synthesis
Two types: free ribosomes in cytoplasm:
proteins for cell fixed ribosomes attached to
ER:proteins for secretion outside cell
ProteasomesContain enzymes (proteases)
Disassemble damaged proteins for recycling
Membranous Organelles5 types of membranous organelles: endoplasmic reticulum (ER) Golgi apparatus lysosomes peroxisomes mitochondria
Endoplasmic Reticulum (ER)endo = within
plasm = cytoplasm
reticulum = network
Cisternae are storage chambers within membranes
Functions of ERSynthesis of proteins, carbohydrates, and lipids
Storage of synthesized molecules and materials
Transport of materials within the ER
Detoxification of drugs or toxins
Smooth Endoplasmic Reticulum (SER)No ribosomes attached
Synthesizes lipids and carbohydrates: phospholipids and cholesterol (membranes) steroid hormones (reproductive system) glycerides (storage in liver and fat cells) glycogen (storage in muscles)
Rough Endoplasmic Reticulum (RER)Surface covered with ribosomes: active in protein and glycoprotein synthesis folds polypeptides protein structures encloses products in transport vesicles
Golgi ApparatusVesicles enter forming face and exit maturing face Secretory vesicles:
modify and package products for exocytosis
Membrane renewal vesicles:
add or remove membrane components
Transport vesicles:Carry materials to and from Golgi apparatus
Cis face, closer to ER
Trans face, closer to cell exit
LysosomesPowerful enzyme-containing vesicles:
lyso = dissolve, soma = body
Primary lysosome: formed by Golgi
and inactive enzymes
Secondary lysosome: lysosome fused
with damaged organelle
digestive enzymes activated
toxic chemicals isolated
Exocytosis Ejects secretory products and wastes
Lysosome Functions
Clean up inside cells: break down large molecules attack bacteria recycle damaged organelles ejects wastes by exocytosis
AutolysisSelf-destruction of damaged cells: auto = self, lysis = break lysosome membranes break down digestive enzymes released cell decomposes cellular materials recycle
PeroxisomesAre enzyme-containing vesicles: break down fatty acids, organic compounds produce hydrogen peroxide (H2O2) …TOXIC replicate by division
KEY CONCEPT
Cells: basic structural and functional units of life respond to their environment maintain homeostasis at the
cellular level modify structure and function
over time
Mitochondrion Structure
2 Membranes
Have smooth outer membrane and folded inner membrane (cristae)
Matrix: fluid around cristae
Mitochondrial FunctionMitochondrion takes chemical energy from food (glucose): produces energy molecule ATP
Nucleus
Nucleus
Control Center of the cell
Contain CHROMATIN (loose DNA) Bundles into CHROMOSOMES when cell is
ready to divide (it packs before moving)
Chromatin Chromosomes
Chromatin in the Nucleus
Directs PROTEIN SYNTHESIS (building proteins)
It contains the “blueprints” “Blueprints” are Called DNA DNA in loose coils called chromatin
How does the nucleus control the cell?
Nucleus: largest organelle
Nuclear envelope: double membrane
around the nucleus
Perinuclear space: between 2 layers of
nuclear envelope
Nuclear pores: communication
passages
Nucleus Controls Cell Structure and Function
Direct control through synthesis of: structural proteins secretions (environmental response)
Indirect control over metabolism through enzymes
Within the NucleusDNA: all information to build and run organisms
Nucleoplasm: fluid containing ions, enzymes, nucleotides,
and some RNA
Nuclear matrix: support filaments
Nucleoli in NucleusAre related to protein production
Are made of RNA, enzymes, and histones
Synthesize rRNA and ribosomal subunits
Organization of DNA
Figure 3–11
Nucleosomes: DNA coiled around
histones
Chromatin: loosely coiled DNA
(cells not dividing)
Chromosomes: tightly coiled DNA
(cells dividing)
DNA and GenesDNA: instructions for every protein in the body
Gene: DNA instructions for 1 protein
What is genetic code?
Genetic CodeThe chemical language of DNA instructions: sequence of bases (A, T, C, G) triplet code:
3 bases = 1 amino acid
KEY CONCEPT
The nucleus contains chromosomes
Chromosomes contain DNA
DNA stores genetic instructions for proteins
Proteins determine cell structure and function
Cell Walls
Outside of the plasma membrane
Can be made of thick fibers of cellulose (plants), chitin (fungi), or peptodoglycan (some bacteria)
Plant cells have openings in cell wall called GAP JUNCTIONS for cell to cell communication
Animal cells DO NOT have cell walls
Cell Wall of Plants
Is this a prokaryotic or eukaryotic cell?