CELL STRUCTURE & FUNCTION
Professor Andrea GarrisonBiology 11
Illustrations ©2010 Pearson Education, Inc.
Cell Theory
• Cells :– Most basic unit of living system– Arise by cell division from existing cell– Make up all living organisms
• All living things composed of one or more cells & cell products
Cell Structure and Function 2
Basic cell structure
NucleusContains genetic material; controls cell activities
Cell membraneSeparates cell from environment and regulates passage in/out of cell
Cytoplasm 80% water, organelles
Cell Structure and Function 3
Electron Microscope
• Used to see things smaller than 0.1 mm (= 100 μm)
• Uses beam of electrons to “see” structures
• Scanning EM used to study surface of object
• Transmission EM used to internal structure
Cell Structure and Function 7
Categories of Cells
• Based on how they feed– Autotrophs vs. Heterotrophs
• Based on cell structure– Prokaryotes vs. Eukaryotes
Cell Structure and Function 9
Categories of Cells
Autotrophs make their own food
Heterotrophs eat another organism
Cell Structure and Function 10
Categories of Cells
Prokaryotes lack organelles
Eukaryotes have organelles
Cell Structure and Function 11
• Organelles– Internal membrane-bound structures
• For example, nucleus & chloroplasts
Cell Structure and Function 12
• Organelles– Internal membrane-bound structures
• For example, nucleus & chloroplasts
– Perform specific functions• Nucleus contains DNA, transcribes genetic code into
messages that control cell activities• Chloroplasts site of photosynthesis
Cell Structure and Function 13
Eukaryotic Cell Structure
• Variety of organelles present• Cell structure related to cell function
– Not all organelles present in all cells– Abundance of organelles differs between cells
Cell Structure and Function 16
Plant vs. Animal Cells
• Plant cells– Cell wall– Chloroplasts for P/S
• Animal cells– None– None
Cell Structure and Function 19
Plant vs. Animal Cells
• Plant cells– Cell wall– Chloroplasts for P/S– Central vacuole
• Animal cells– None– None– None
Cell Structure and Function 20
Plant vs. Animal Cells
• Plant cells– Cell wall– Chloroplasts for P/S– Central vacuole– None
• Animal cells– None– None– None– Lysosomes
Cell Structure and Function 21
Plant vs. Animal Cells
• Plant cells– Cell wall– Chloroplasts for P/S– Central vacuole– None– None
• Animal cells– None– None– None– Lysosomes– Centrioles to assist with
cell division
Cell Structure and Function 22
Nucleus
Functions: • Holds genetic
material (DNA)• Controls cell
activities
Cell Structure and Function 25
Nucleus
Nuclear Envelope:• 2-layered membrane• Pores allow chemical
communicationInside Nucleus:• Chromatin =
DNA + protein• Nucleolus
– makes ribosomal RNA (rRNA)
Cell Structure and Function 26
Nucleus
Ribosomes:• Made of rRNA• Not organelles• Present in cytoplasm
& on membrane outside nucleus
• Function in makingproteins
Cell Structure and Function 27
Nucleus
Inside nucleus:• DNA messenger RNAOutside nucleus:• Ribosomes use mRNA
to make proteinsto be used in cell functions
Cell Structure and Function 28
Endomembrane System
• Membrane made around nucleus• Membrane moves from nucleus to outer
plasma membrane– Moves through various organelles on the way– Different function with each new organelle
Cell Structure and Function 31
Organelles of Endomembrane System: Nuclear Envelope
• Membrane made around the nucleus
• Moves into Endoplasmic Reticulum
Cell Structure and Function 40
Organelles of Endomembrane System: Endoplasmic Reticulum
Rough ER:• Has ribosomes• Surface area • Makes proteins
Cell Structure and Function 41
Organelles of Endomembrane System: Endoplasmic Reticulum
Rough ER:• Has ribosomes• Surface area • Makes proteins
Smooth ER:• No ribosomes, has enzymes• Surface area• Makes lipids• Breaks down drugs, etc.
Cell Structure and Function 42
Organelles of Endomembrane System: Transport Vesicles
• Flattened sacs pinched off ER or other organelles
• Transport– to Golgi apparatus– to other areas of cell– to outside of cell
Cell Structure and Function 44
Organelles of Endomembrane System: Transport Vesicles
• Flattened sacs pinched off ER or other organelles
• Transport– to Golgi apparatus– to other areas of cell– to outside of cell
Cell Structure and Function 45
Organelles of Endomembrane System: Golgi Apparatus
• Flattened sacs pinched off Rough ER
• Receives proteins from rough ER via transport vesicles
• Modifies proteins• Packages proteins for
transport
Cell Structure and Function 46
Organelles of Endomembrane System: Transport Vesicles
• Flattened sacs pinched off ER or other organelles
• Transport– to Golgi apparatus– to other areas of cell– to outside of cell
Cell Structure and Function 48
Organelles of Endomembrane System: Lysosomes
• Sac pinched off from Golgi membrane
• Contains digestive enzymes
• Intracellular digestion– Food vacuoles to digest
food– Damaged organelles– Cell destruction after
death
Cell Structure and Function 49
Organelles of Endomembrane System: Vacuoles
• Sacs pinched off from internal membrane or plasma membrane
• Variety of types with different functions– Contractile vacuoles in Protista – Central vacuole in plants
Cell Structure and Function 51
Organelles of Endomembrane System: Vacuoles
Contractile vacuole• Absorbs excess
water in cytoplasm
• Contracts to expel excess water
Cell Structure and Function 52
Organelles of Endomembrane System: Vacuoles
Central vacuole• Storage
– Water– Nutrients– Wastes – Toxins – Pigments
Cell Structure and Function 53
Other Organelles & Structures Not Associated with Endomembrane
System
Cell Structure and Function 54
Organelles associated with energy
• Chloroplasts and mitochondria– Provide cellular energy– Contain their own DNA
• Feature not found in other organelles• Encodes some of their proteins• Still require nuclear DNA for full function• Considered evidence that these organelles evolved
form free-living prokaryotes
Cell Structure and Function 55
Organelles associated with energyChloroplasts• Found in
photosynthetic cells – plants and
some protistans
• Site of P/S
Cell Structure and Function 56
Chloroplasts
• Grana– Surface area
to trap light– Contains
chlorophyll
• Stroma– fluid– Site of sugar
production
Cell Structure and Function 57
Organelles associated with energyMitochondria• Found in all
eukaryotes• Site of ATP
production
Cell Structure and Function 58
Mitochondrion
• Cristae– Surface area
for ATP production
• Matrix– Fluid– Site of sugar
breakdown
Cell Structure and Function 59
Non-membrane bound structures
• Found in prokaryotes or eukaryotes• May or may not be found in all cells
Cell Structure and Function 60
Non-membrane bound structuresCytoskeleton• Network of fibers
– Microtubules• Associated with
cell movement
– Intermediate filaments
– Microfilaments
• Function– Support – Movement
Cell Structure and Function 61
Non-membrane bound structuresCytoskeleton• Support
– Maintains cell shape– Holds organelles in
place
Cell Structure and Function 62
Non-membrane bound structuresCytoskeleton• Movement
– Network of fibers constantly dissolving and reforming in new arrangements
• Allows cell to change shapes
• Pulls chromosomes apart during cell division
Cell Structure and Function 63
Non-membrane bound structuresFlagella & Cilia• Hair-like structures
that aid in movement• Core of microtubules
creates beating motion
• Move cells through liquid
• Create currents past non-moving cells
Cell Structure and Function 64
Non-membrane bound structuresFlagella• Long whipping “tails”• Usually 1-3 per cell• Propel cell forward• Found in many
protists• Found in human
sperm
Cell Structure and Function 65
Non-membrane bound structuresCilia• Short hair-like
structures• Usually many on cell
surface• Beat in synchrony• Found in many
protists• Found in human
tissues
Cell Structure and Function 66
Non-membrane bound structuresCell Wall• Found in variety of
cells– Bacteria– Protistans– Plants– Fungus
• Protective structure outside plasma membrane
• Porous to water, salts
Cell Structure and Function
Cell wall
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Cell Junctions
Cell Structure and Function
• Connections between cells– Proteins tie cells together
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Cell Junctions
Cell Structure and Function
• Types– Tight junctions
• Seal cells together so molecules cannot slip between cells
– i.e., cells lining intestine
– Adhering junctions (desmosomes)• Strengthen attachment so cells won’t tear apart
– i.e., skin
– Gap junctions• Channels allow movement of molecules between cell
– i.e., heart muscle
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Cell Junctions
Cell Structure and Function
• http://www.biology.arizona.edu/cell_bio/problem_sets/membranes/junctions.html
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