02 cell structures 2015 ss
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PowerPoint Lecture prepared by Dr. Judi Roux,
University of Minnesota Duluth
Chapter 2
Cells & Their Structures
© 2016 Pearson Education, Inc.
Learning Outcomes
Compare and contrast
prokaryotic and eukaryotic cells.
© 2016 Pearson Education, Inc.
© 2015 Pearson Education, Inc.
Introduction
• In 1665, Hooke examined a piece of cork under a crude microscope and identified “little rooms” as cells.
• Leeuwenhoek, working at about the same time, used more refined lenses to describe living cells from blood, sperm, and pond water.
• Since the days of Hooke and Leeuwenhoek, improved microscopes have vastly expanded our view of the cell.
How small is small?
Most cells are microscopic
• Cells vary in size and shape; again Form = Function
• Think: What are the
largest cells?
Human height
Length of somenerve andmuscle cells
Chicken egg
Frog egg
Una
ided
eye
Ligh
t mic
rosc
ope
Ele
ctro
n m
icro
scop
e
10 m
1 m
100 mm(10 cm)
10 mm(1 cm)
1 mm
100 m
10 m
1 m
100 nm
10 nm
1 nm
0.1 nmAtoms
Proteins
Small molecules
Lipids
Viruses
Ribosome
Nucleus
Mycoplasmas(smallest bacteria)
Most plant andanimal cells
Most bacteria
Mitochondrion
All Cells are Contained within a -Plasma Membrane
- Holds the cell (metabolism & structures)
- Selectively permeable barrier between the cell and its environment
- Formed by molecules that are- water soluble at one end - lipid (water insoluble) at the other
Water
Water
Hydrophilicheads
Hydrophobictails
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH
CH
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
CH2
CH2
CH3
CH3
CH3N+
OO O–P
OCH2CHCH2
C O C O
O O
Phosphategroup
Symbol
Hydrophilic head
Hydrophobic tails
Phospholipids form Membranes
© 2015 Pearson Education, Inc.
The plasma membrane forms a flexible boundary between the living cell and its surroundings.
Phospholipids form a two-layer sheet called a phospholipid bilayer in which
• hydrophilic heads face outward, exposed to water, and
• hydrophobic tails point inward, shielded from water.
© 2015 Pearson Education, Inc.
The small size of cells relates to the need to exchange materials across the plasma membrane
• Membrane proteins are embedded in the lipid bilayer.
• Some proteins form channels (tunnels) that shield ions and other hydrophilic molecules as they pass through the hydrophobic center of the membrane.
• Other proteins serve as pumps, using energy to actively transport molecules into or out of the cell.
The membrane is a fluid mosaic of phospholipids and proteins
• With proteins and other molecules embedded in a phospholipid bilayer
Fibers of the extracellular matrix
Carbohydrate(of glycoprotein)
Glycoprotein
Microfilamentsof cytoskeleton
Phospholipid
CholesterolProteins
Plasmamembrane
Glycolipid
Cytoplasm
Prokaryotic and eukaryotic cells
All living things are made of cells.• Contain similar macromolecules and cell structures
© 2016 Pearson Education, Inc.
Prokaryotic cells are structurally simpler than Eukaryotic cells
• There are two kinds of cells
Prokaryotic cellNucleoidregion
Nucleus
Eukar yotic cell Organelles
Col
oriz
ed T
EM
15,
000
Prokaryotes
• Small; microscopic
• Simple
• Genetic material is “naked” DNA - not as protein-bound chromosomesNo nucleus
• No organelles
• Cell walls (Peptidoglycan)
Eukaryotes• Larger; single-celled or
multicellular
• Complex
• Genetic material is DNA as a complex with proteins = chromosomes
• Chromosomes contained in a nucleus
• Membrane-bound organelles
• Some with cell walls (Cellulose, Chitin)© 2016 Pearson Education, Inc.
Prokaryotic cells are small, relatively simple cells that do not have a membrane-bound nucleus
Prokar yoticflagella
Ribosomes
Capsule
Cell wall
Plasmamembrane
Nucleoid region (DNA)
Pili
There is a size limitation on cells
The interior cytoplasm of a large cell cannot interact quickly enough with the cell’s environment to:
- Take up nutrients & oxygen - Release wastes & carbon dioxide
Solution: Bring the border with the environment inside the cell
• A small cell has a greater ratio of sur face area to volume
• Than a large cell of the same shape
30 m 10 m
30 m 10 m
Surface areaof one large cube 5,400 m2
Total surface areaof 27 small cubes 16,200 m2Figure 4.2B
Eukaryotic cells are compartmentalized• Distinguished by the presence of a true nucleus• Have internal membranes to contain and control
chemical reactions• Eukaryotic cells can form
• Single-celled organisms
• Colonial organisms
• Multicellular organisms
FUNCTIONAL CATEGORIES OF ORGANELLES
Eukaryotic organelles comprise four functional categories
• Eukar yotic organelles fall into four functional groups• Manufacturing• Breakdown • Energy processing• Support, movement, and communication between
cells
• Eukar yotic organelles and their functions
Roughendoplasmicreticulum
Smoothendoplasmicreticulum
Golgi apparatus
LysosomeMitochondrion
Centrosomewith pair ofcentrioles
Plasmamembrane
Peroxisome
Intermediatefilament
MicrofilamentMicrotubule
CYTOSKELETON
NUCLEUSNuclear envelopeNucleolusChromatin
Ribosomes
© 2015 Pearson Education, Inc.
Eukaryotic cells are partitioned into functional compartments
Plant but not animal cells have• a rigid cell wall that contains cellulose,• plasmodesmata, cytoplasmic channels through cell
walls that connect adjacent cells,• chloroplasts, where photosynthesis occurs, and• a central vacuole, a compartment that stores water
and a variety of chemicals.
Roughendoplasmicreticulum
Smoothendoplasmicreticulum
NUCLEUSNuclear envelopeNucleolusChromatin
Ribosomes
Plasmamembrane
Peroxisome
Mitochondrion
MicrofilamentMicrotubule
CYTOSKELETON
Cell wall ofadjacent cell Golgi
apparatus
PlasmodesmaCell wall
Chloroplast
Centralvacuole
© 2016 Pearson Education, Inc.
Cell StructurePlasma membrane
• Encloses all cells
• Defines outer boundary of cells
• Isolates cell contents from environment
© 2016 Pearson Education, Inc.
Cell StructureCytoplasm: includes cytosol and organelles
• Organelles: perform specific jobs required by the cell and work with other organelles
• Cytosol: watery matrix with salts and enzymes; houses the organelles
© 2016 Pearson Education, Inc.
3 Cell StructureCell structure
© 2016 Pearson Education, Inc.
3.2 Cell StructureSubcellular structures
• Cell wall: helps protect certain cells (plants, fungi, bacteria) and maintains shape
• Nucleus: holds chromatin (DNA and proteins) in eukaryotic cells
• Nucleolus: synthesizes ribosomes; inside nucleus
© 2016 Pearson Education, Inc.
3.2 Cell StructureSubcellular structures
• Mitochondrion: produces energy for the cell through cellular respiration
• Chloroplast: produces sugars through photosynthesis in plant cells
• Lysosome: contains digestive enzymes to recycle molecules
© 2016 Pearson Education, Inc.
3.2 Cell StructureSubcellular structures
• Ribosomes: assemble proteins; free floating or attached to ER
• Rough endoplasmic reticulum (rough ER): membrane network with ribosomes attached for protein synthesis
• Smooth endoplasmic reticulum (smooth ER):involved in lipid synthesis; lacks ribosomes
• Golgi apparatus: modifies, sorts, and packages proteins
© 2016 Pearson Education, Inc.
3.2 Cell StructureSubcellular structures
• Centrioles: move chromosomes during animal cell division
• Cytoskeletal elements: form cytoskeleton for maintaining shape and structural support
• Central vacuole: stores water, starch, and pigments in plant cells
Animation: A Comparison of Prokaryotic and Eukaryotic Cells
© 2016 Pearson Education, Inc.
This animation may be available in our ebook, but not viewable on SlideShare.
2.5 An Introduction to Evolutionary Theory
The tree of life
Common ancestor(4 billion years ago)
• Led to 10 millionorganisms of today
• Diversity due tonatural selection
© 2016 Pearson Education, Inc.
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