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Cell Structure and
Function
Chapter 3
Part A
Introduction
• In the image of a wall, what is the basic
building block?
• If you look closely enough at living
organisms you can see that the basic
building block is cells
o There are many kinds of cells with specific
purposes
• Just like a house is made with a variety of
building materials
Microscopy
•
Because cells are so small microscopes are needed to view
them
o
Light microscopes
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Use a beam of light
Used for viewing
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Small, thin or translucent specimens
Living organisms
Stained cells (ususally dead)
Images are inverted
Up to about 400X magnification
Microscopy
•
Because cells are so small microscopes are needed to view
them
o
Dissecting microscopes
•
Used for viewing
o
o
o
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Larger, thick specimen
Tissue structure and overall anatomy
Living organisms
Images are three dimensional
Up to about 40X magnification
Microscopy
•
Because cells are so small microscopes are needed to view
them
o
Transmission electron microscopes
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Use a beam of electrons transmitted through the cell
Higher magnification
More internal detail
No live cells
Scanning electron microscopes
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Use a beam of electrons reflecting off the specimens’ surfaces
Details of surface characteristics
Scanning Electron Microscopy
• Tip of a straight pin with rodshaped bacteria
Robert Hooke saw “cells” in
thin sections of cork
Cell Theory
1.
2.
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4.
All organisms consist of one or more cells
The cell is the basic unit of life
All cells arise from pre-existing cells
Cells contain hereditary material which they pass to their
offspring
Comparing Prokaryotic and Eukaryotic Cells
• All cells share four common components
o Plasma membrane
• Separates cell from surroundings
• Communicates with surroundings
o DNA
• Free-floating (nucleoid)
• Membrane bound (nucleus)
o Cytoplasm
• Semifluid mixture filling the cell
o Ribosomes
• Protein synthesis
Comparing Prokaryotic and Eukaryotic Cells
• Prokaryotes
o No nucleus
• Prokaryotes have a nucleoid region where
DNA is located (not enclosed in a
membrane)
o No membrane bound organelles
o Small (1-10 micrometers)
o Most have a cell wall around their cell
membrane
o Many produce a capsule
• Slime layer for protection
o Some have flagella, pili, or fimbriae
Comparing Prokaryotic and Eukaryotic Cells
• Prokaryotes include organisms from
o Domain Bacteria
• Kingdom Eubacteria
o Domain Archae
• Kingdom Archaebacteria
Comparing Prokaryotic and Eukaryotic Cells
• Eukaryotes
o Contain a nucleus
• Membrane surrounding the DNA
• Keeps the DNA separated from the cytoplasm
o Contain many organelles
• Structures that have specific metabolic functions
• Often surrounded by phospholipid membrane
o Larger size (0.1-1 millimeter)
Comparing Prokaryotic and Eukaryotic Cells
• Eukaryotes Include organisms from
o Domain Eukarya
• Kingdoms Protista, Plantae, Fungi, and Animalia
Comparing Prokaryotic and Eukaryotic Cells
• Cell size and shape
o When a cell grows, the volume increases faster than the surface area
• The cell membrane becomes too small relative to the volume
o Can’t move enough nutrients into the cell or wastes out of the cell
• Surface-to-volume ratio
• Limits growth
o Alternate shapes can result in larger cells
• Long and thin (neuron) or frilly surfaced (intestinal villi)
Questions
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What is one of the four tenets of the cell theory?
Why are most cells very small?
What is one type of microscope?
If you found a cell that was very small what type of cell would you
expect it to be? Would you expect it to have a nucleus?
• Which type has a nucleus?
• Which kingdoms have prokaryotic cells?
Eukaryotic Cells
• The following slides will discuss the different cells structures,
organelles, and components of eukaryotic cells
Plasma Membrane
• Phospholipid bilayer
o With embedded proteins
• All cells have a plasma membrane
o Distinct identity
o Communicates with surroundings
o Controls what enters or exits the cell
Cytoplasm
• Metabolic activities occur and organelles are suspended in the
cytoplasm
• Contents of a cell between the plasma membrane and the nucleus
• Consists of
o Cytosol: A semi-fluid gel-like matrix
o Nutrients, enzymes, and organelles
Cytoplasm
Dynamic Cytoskeleton
• System of interconnected protein fibers
o Maintain shape
o Secure certain organelles in specific positions
o Movement
• Intracellular: cytoplasm, vesicles, organelles
• Extracellular: flagella and cilia
• Unicellular organisms move independently
Dynamic Cytoskeleton
• Components of the cytoskeleton
o Microtubules
• Long hollow cylinders made of tubulin subunits
• Temporary scaffolding for many processes
o Rapidly assembling and disassembling as needed
• Mitosis and Flagella/cilia
• Centrosomes made up of two centrioles direct assembly
Microtubules
Centrioles
Dynamic Cytoskeleton
• Components of the cytoskeleton
o Microfilaments
• Fibers consisting of actin subunits
• Strengthen and affect shape
• Myosin and actin filaments produce muscle contractions
o Intermediate filaments
• Mechanical strength
• Underlie and reinforce membranes
Dynamic Cytoskeleton
• Components of the cytoskeleton
o Motor proteins (kinesin and dynein)
• Drag cellular structures along microtubules and microfilaments
• Requires ATP
Dynamic Cytoskeleton
• Components of the cytoskeleton
o Motor proteins (kinesin and dynein)
• Flagella and cilia
o Microtubules are arranged lengthwise in a 9 + 2 array
• A basal body (a specialized centriole) controls microtubule lengths
o Dynein “walks” along the microtubules causing them to bend back and
forth
Flagella and cilia
Flagella and Cilia 2
Dynamic Cytoskeleton
• Components of the cytoskeleton
o Motor proteins (kinesin and dynein)
• Flagella and Cilia
o Flagella: long, few/cell
o Cilia: short, many/cell
Dynamic Cytoskeleton
• Components of the cytoskeleton
o Pseudopods or “false feet”
• Microfilaments build scaffolding which support temporary, irregular membrane lobes
• Motor proteins drag the plasma membrane along with them
Dynamic Cytoskeleton
• Components of the cytoskeleton
o Pseudopods or “false feet”
• Pseudopodal movement
o Amoeba creeping along
• Phagocytosis
o White blood cell engulfing a bacterium
o White blood cell engulfing bacteria
Endomembrane System
• A series of membranous compartments that work together to
modify, package, label, and ship proteins and lipids
• Consists of
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Nuclear envelope
Lysosomes
Vesicles
Endoplasmic reticulum
Golgi apparatus
Endomembrane System
• The nucleus
o Contains DNA in the form of chromatin
o Directs the synthesis of ribosomes and proteins
Nucleus
Endomembrane System
• Nuclear envelope
o Two phospholipid bilayers
o Pores control the passage of ions, molecules, and
RNA
• Chromosomes
o Double-stranded DNA molecule with attached
proteins
o Codes for the genetic/hereditary material
o Chromatin is the name for all of the chromosomal
DNA and associated proteins
• Nucleolus
o A region where ribosome subunits are assembled
Endomembrane System
• Endoplasmic Reticulum (ER)
o Series of interconnected membranous
tubules
• Continuous with the nuclear envelope
• Two types of ER