The domains and kingdoms of life
• Three domains• Bacteria
• Archaea
• Eukarya
• Six kingdoms• Bacteria
• Archaea
• Protista
• Plantae
• Fungi
• Animalia
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Types of microscopes
• Light• Simple
• Compound
• Electron• Scanning electron
microscope (SEM)
• Transmission electron microscope (TEM)
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What is cell theory?
• The cell theory states that cells are the basic units of life
• Proposed by botanist Matthias Schleiden and zoologist Theodor Schwann in 1830
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What is cell theory?
• Three principles comprise the cell theory1. Every living organism is made of one or more cells
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What is cell theory?
• Three principles comprise the cell theory2. The smallest organisms are single cells, and cells are the functional units of multicellular organisms
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What is cell theory?
• Three principles comprise the cell theory3. All cells arise from preexisting cells
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Main two types of cells
• Main two types of cells:• Prokaryotic (meaning “before nucleus”) cells
• Eukaryotic (meaning “true nucleus”) cells
cytoplasmic fluid
cytoplasm
cell wall plasmamembrane
free ribosome
nucleus chromosome(DNA)
ribosomes
cell wall
plasma membrane
cytoplasm
plasmid (DNA)
lysosome
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Prokaryotes
• Unicellular
• All cells identical – no specialized function
• Lack nucleus, other membrane-bound organelles
• Possess specialized surface features and fewer specialized structures within their cytoplasm
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Prokaryotic cells
• Most have a stiff cell wall (peptidoglycan wall)
• Prokaryotic cells can take several shapes• Rod-shaped bacilli
• Spiral-shaped spirilla
• Spherical cocci
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Prokaryotic cells
• Prokaryotic cells have no nuclear membrane or membrane-bound organelles present
• In the central region of the cell is an area called the nucleoid• Within the nucleoid is a single, circular
chromosome of DNA
• Small rings of DNA (plasmids) are located in the cytoplasm
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Prokaryotic cells
• Some bacteria have pili (meaning hairs) • Attachment pili or fimbriae are short and
abundant; they help bacteria adhere to structures
• Sex pili are few in number and long
• Some bacteria have a flagellum• Locomotion
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Eukaryotic Cells
• Differ greatly in appearance and function
• Four basic components in common
1. Plasma membrane• Isolation
• Protection
• Sensitivity
• Support
• Gatekeeper
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Eukaryotic Cells
• Differ greatly in appearance and function
• Four basic components in common
2. Cytoplasm• Material inside the cell but
outside the nucleus
• Contains the cytosol and organelles
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Eukaryotic Cells
• Differ greatly in appearance and function
• Four basic components in common
3. The nucleus• Control center – the “brain of the
cell”
• Contains the DNA
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Eukaryotic Cells
• Differ greatly in appearance and function
• Four basic components in common
4. Organelles• “Organs” of the cell
• Perform specific functions
• Some bound by membranes
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Cytoplasm
• Everything inside the membrane, except the nucleus
• A LOT more on the membrane later
• Includes…• Cytosol = liquid portion
• Organelles
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Organelles
Non-membranous
• Cell wall
• Cytoskeleton
• Cellular extensions
• Microvilli
• Cilia
• Flagella
• Ribosomes
Membranous
• Endomembrane system
• Vacuoles
Double Membrane
• Nucleus
• Mitochondria
• Plastids
• Chloroplasts
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Cell membrane
• All cells are surrounded by a cell membrane
• Also called a plasma membrane
• Consists of a bilayer made of mostly phospholipids
• Critical to cell function
• Discussed in great detail later
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Cell Wall
• Plants, fungi, and bacteria are also have cell walls• Animal cells do not
• All have a cell membrane
Cell membrane
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Cell wall
• Made of polysaccharides secreted through plasma membrane• Non-living
• Exterior to cell
• Cell walls of adjacent plant cells stuck together with pectin
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Cell wall
• Adds strength and integrity to cells• Plants, fungi don’t have bones
• Allows them to withstand gravity and wind and grow upright
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Cytoskeleton
• Internal protein network of cells
• Stabilize cell’s 3D shape
• Guide vesicles
Cytoskeleton
intermediatefilaments
Light micrograph showing the cytoskeleton
microtubules
microfilaments
microtubules (red)
microfilaments (blue)
nucleus
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Cytoskeleton
• The cytoskeleton is composed of three types of protein fibers• Thin microfilaments
• Medium-sized intermediate filaments
• Thick microtubules
Cytoskeleton
intermediatefilaments
Light micrograph showing the cytoskeleton
microtubules
microfilaments
microtubules (red)
microfilaments (blue)
nucleus
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Cytoskeleton
• The cytoskeleton regulates the following cell properties:• Cell shape
• Cell movement
• Organelle movement
• Cell division
Cytoskeleton
intermediatefilaments
microtubules
microfilaments
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Cellular extensions
• Cilia and flagella • Hair-like structures that propel cells through fluids
or move fluids past cells
• Arise from a basal body, which anchors them to the plasma membrane
• Basal bodies are derived from centrioles, which are identical in structure to basal bodies
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plasma membrane
section of cilium
ciliumParamecium
protein sidearms
0.1 micrometer
centralpair of microtubules
fusedmicrotubulepair
basal body(extends intocytoplasm)
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Cellular extensions - Cilia
• Example: trachea, Fallopian tubes
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mucus-secreting cells
Cilium power stroke
propulsion of fluid
plasma membranereturn stroke
cilia liningtrachea
Cellular extensions - Flagella
• Substantially longer than cilia• Only example in human body: sperm
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propulsion of fluiddirection of locomotion
continuous propulsionFlagellum
flagellum ofhuman sperm
Cellular extensions - microvilli
• Very small, highly numerous finger-like projections
• Increase absorptive surface area
• Example: small intestine
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Ribosomes
• Site of protein synthesis
• Abundant in cells that produce a lot of protein• Example: human liver cells have on average 13
million ribosomes in each cell!
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Ribosomes
• Made from rRNA (2 units) and proteins
• Polypeptide chain constructed using information provided by mRNA
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mRNA
• Final destination of protein somewhere else = mRNA/ribosome complex associates with endomembrane system
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Endomembrane System
• Elaborate system of membranes used to make and move proteins in a cell
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Organelles Used
• Rough ER
• Vesicles
• Golgi apparatus
• Cell membrane
• Lysosome
Final Destination of Protein
• Outside cell
• Within cell membrane
• Lysosome
Endoplasmic Reticulum
• Collection of membranous tubes and envelopes
• Two forms• Smooth endoplasmic reticulum (sER)
• Site of lipid synthesis, detoxification, calcium storage
• Abundant in liver, kidney, endocrine glands
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Rough Endoplasmic Reticulum
• Gateway to endomembrane system
• Studded with ribosomes
• Proteins made by ribosomes enter rERthrough pore
• Portion of rER pinches off to encapsulate protein in a transport vesicle
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Movement of vesicles
• Vesicles are membranous sacs transporting molecules to the various regions of the membrane system
• Exocytosis1. Vesicles fuse with the plasma membrane2. Export their contents outside the cell
• Endocytosis 1. Plasma membrane extends 2. Surrounds material outside the cell3. Fuses and pinches off to form a vesicle inside the
cell
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Protein-carryingvesicles from the ERmerge with the Golgiapparatus
Vesicles carryingmodified protein leave the Golgi apparatus
Golgiapparatus
Golgi apparatus
• Proteins are modified and/or combined in the Golgi, encapsulated and transported to…
1. Secretory vesicles• Proteins for discharge from cell
• Examples: insulin, antibodies
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Antibody protein is
synthesized on ribosomes
and is transported into
channels of the rough ER
The protein is
packaged into vesicles
and travels to the Golgi
apparatus
Vesicles fuse with the
Golgi apparatus, and
carbohydrates are added
as the protein passes
through the compartments
Completed glycoprotein
antibodies are packaged
into vesicles on the opposite
side of the Golgi apparatus
Vesicles merge with the
plasma membrane and
release antibodies into the
interstitial fluid
Golgi apparatus
forming vesicle
vesicles
(interstitial fluid)
(cytosol)
Golgi apparatus
• Proteins are modified and/or combined in the Golgi, encapsulated and transported to…
2. Cell membrane components• Example: glycoproteins
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Golgi apparatus
• Proteins are modified and/or combined in the Golgi, encapsulated and transported to…
3. Lysosomes• Cytosolically-active vesicles
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Lysosomes
• Contain more than 50 enzymes
• pH of ~4.5
• Break down almost any biomolecule
• Cell’s “garbage disposal”
• Can fuse with other membrane-defined structures and release contents• Fuses with a food vacuole and digests food into
basic nutrients
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Digestiveenzymes aresynthesized onribosomes andtravel throughthe rough ER
The enzymesare packaged into vesicles and travel to the Golgi apparatus
The Golgi apparatus modifiesthe enzymes forexport to thelysosomes
The enzymesare delivered tothe lysosome invesicles
A lysosome fuseswith a food vacuole,and the enzymesdigest the food
Golgi apparatus
digestiveenzymes
lysosome
(interstitial fluid)
(cytosol) foodvacuoles
food
Vacuoles
• Membranous, fluid-filled sacks
• Most cells contain one or more• Animal cells have small ones
• Plant cells typically have one large, central one (may have other, small ones as well)
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Animal Cell Plant Cell
Vacuoles
• Play a role in maintaining cell integrity
• Regulate cell’s water content• Example: Paramecia have contractile vacuoles that
expel water that leaks in through cell membrane
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Vacuoles
• Storage site in plants
• Waste that can’t be excreted
• Poisonous compounds
• Amino acids, sugars
• Pigment (flowers)
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Mitochondria
• Site of ATP synthesis – “powerhouse of cell”
• Double membrane (inner and outer)• Outer membrane is smooth
• Inner membrane has deep folds called cristae
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outermembrane
innermembrane
intermembranespace
matrix
cristae
0.1 micrometer
Mitochondria
• Carry own DNA
• Make some of their own proteins (contain ribosomes)
• Only cellular site to use molecular oxygen
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outermembrane
innermembrane
intermembranespace
matrix
cristae
0.1 micrometer
Mitochondria
• Provide energy = most abundant in cells that need a lot of energy
• Compare: sperm vs cartilage
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Plastids• Contained ONLY by plants and photosynthetic
protists
• Primarily used for storage• Pigments (fruit)
• Starch
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Chloroplasts
• Highly specialized plastid
• Site of photosynthesis
• Contains• Stroma (fluid)• Thylakoids (membranous sacks)
• A stack is called a granum
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Chloroplasts
• Thylakoids contain a pigment called chlorophyll• Gives plants green color
• Captures energy from sunlight
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Nucleus
• Covered with pores
• Water/ions pass through freely
• Ribosomes stud outer membrane
• Continuous with endomembrane system
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• Control center of cell
• Surrounded by nuclear envelope
• Double membrane
Nucleus
• Contains chromatin• Unwound protein-chromosome complexes
• DNA and associated proteins
• Contains all instructions for building cell’s proteins
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Nucleus
• mRNA made in nucleus
• Exits through nuclear pores
• Finds ribosomes
• Translated into protein in the cytoplasm
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