Ch 6: Tour of the Cell
2016
Chapter 6: Cells
From Topic 1.1
From Topic 1.1
Nature of science: Looking for trends and discrepancies—although most organisms conform to cell
Applications & Skills:
theory, there are exceptions (3.1).
Skill: Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells.
Understandings:
Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown
• According to the cell theory, living organisms are composed of cells.
in drawings or micrographs (Practical 1).
Applications and skills:
Guidance:
• Application: Questioning the cell theory using atypical examples, including striated muscle, giant algae • Scale bars are useful as a way of indicating actual sizes in drawings and micrographs.
and aseptate fungal hyphae.
Guidance:
From Topic 1.2
• Students are expected to be able to name and briefly explain these functions of life: nutrition,
Nature of science: Developments in scientific research follow improvements in apparatus—the
metabolism, growth, response, excretion, homeostasis and reproduction.
invention of electron microscopes led to greater understanding of cell structure. (1.8)
Understandings:
From Topic 1.5
• Electron microscopes have a much higher resolution than light microscopes.
Essential idea: There is an unbroken chain of life from the first cells on Earth to all cells in organisms
Applications and skills:
alive today.
• Skill: Drawing of the ultrastructure of prokaryotic cells based on electron micrographs.
Nature of science: Testing the general principles that underlie the natural world—the principle that cells• Skill: Drawing of the ultrastructure of eukaryotic cells based on electron micrographs.
only come from pre-existing cells needs to be verified (1.9).
International-mindedness: Microscopes were invented simultaneously in different parts of the world at
Understandings:
a time when information travelled slowly. Modern-day communications have allowed for improvements
• Cells can only be formed by division of pre-existing cells.
in the ability to collaborate, enriching scientific endeavour.
• The first cells must have arisen from non-living material.
Aim 8: Developments in science, such as electron microscopy, can have economic benefits as they give
• The origin of eukaryotic cells can be explained by the endosymbiotic theory (introduced in HL 1,
commercial companies opportunities to make profits, but this can affect cooperation between
reinforced during HL 2).
scientists.
Applications and skills:
• Application: Evidence from Pasteur’s experiments that spontaneous generation of cells and organisms From Topic 1.1
does not now occur on Earth.
Essential idea: The evolution of multicellular organisms allowed cell specialization and cell replacement.
Guidance:
Understandings:
• Evidence for the endosymbiotic theory is expected. The origin of eukaryote cilia and flagella does not • Organisms consisting of only one cell carry out all functions of life in that cell.
need to be included (introduced in HL 1, reinforced during HL 2).
• Surface area to volume ratio is important in the limitation of cell size.
• Students should be aware that the 64 codons in the genetic code have the same meanings in nearly all• Multicellular organisms have properties that emerge from the interaction of their cellular
organisms, but that there are some minor variations that are likely to have accrued since the common components.
origin of life on Earth (introduced in HL 1, reinforced during HL 2).
Applications and skills:
Aim 6: Pasteur’s experiment can be repeated using modern apparatus.
• Application: Investigation of functions of life in Paramecium and one named photosynthetic unicellular
organism.
Chapter 6: Cells
From Topic 1.2
Essential idea: Eukaryotes have a much more complex cell structure than prokaryotes.
Understandings:
• Prokaryotes have a simple cell structure without compartmentalization.
• Eukaryotes have a compartmentalized cell structure.
Applications and skills:
• Application: Structure and function of organelles within exocrine gland cells of the pancreas and within palisade mesophyll cells of the leaf.
• Skill: Interpretation of electron micrographs to identify organelles and deduce the function of specialized cells.
Guidance:
• Drawings of prokaryotic cells should show the cell wall, pili and flagella, and plasma membrane enclosing cytoplasm that contains 70S ribosomes and a nucleoid with naked DNA.
• Drawings of eukaryotic cells should show a plasma membrane enclosing cytoplasm that contains 80S ribosomes and a nucleus, mitochondria and other membrane-bound organelles are
present in the cytoplasm. Some eukaryotic cells have a cell wall.
From Topic 3.2
Understandings:
• Prokaryotes have one chromosome consisting of a circular DNA molecule.
• Some prokaryotes also have plasmids but eukaryotes do not.
-Prep for 1.6 Cell Division, 1.3 Membranes Structure, 1.4 Membrane Transport, 2.8 and 8.2 Cellular Respiration, 2.9 and 8.3 Photosynthesis, Prep for 5.1 Evidence for Evolution (in HL 2)
Cell Theory
Nature of science: Looking for trends and discrepancies—although most organisms conform to cell theory, there
are exceptions (3.1).
• According to the cell theory, living organisms are composed of cells.
• Application: Questioning the cell theory using atypical examples, including striated muscle, giant algae and
aseptate fungal hyphae.
• Students are expected to be able to name and briefly explain these functions of life: nutrition, metabolism,
growth, response, excretion, homeostasis and reproduction (at the beginning of the year).
Essential idea: There is an unbroken chain of life from the first cells on Earth to all cells in organisms alive today.
• Living things are made of cells
• Cells are the smallest unit of life
• Cells come from pre-existing
cells
Evidence for Cell Theory
Nature of science: Testing the general principles that underlie the natural world—the principle that cells only come from pre-existing cells needs to be verified (1.9).
• Cells can only be formed by division of pre-existing cells.
• The first cells must have arisen from non-living material.
• Application: Evidence from Pasteur’s experiments that spontaneous generation of cells and organisms does not now occur on Earth.
Aim 6: Pasteur’s experiment can be repeated using modern apparatus.
•
•
•
•
•
•
Robert Hooke- in 1665, first to coin the word “cell”
Anton Von Leeuwenhoek- in 1680’s, first to see microbes using pond water
Matthias Schleiden- in 1838, proposed that all plants are made of cells
Theodor Schwann- in 1839, proposed that all animals are made of cells
Rudolf Virchow- in 1855,proposed that cells come from pre-existing cells
Louis Pasteur- in 1859, disproved Spontaneous Generation
Pasteur experiment: http://bcs.whfreeman.com/thelifewire/content/chp03/0302003.html
Cell theory: : http://ed.ted.com/lessons/the-wacky-history-of-cell-theory
Microscopes
Skill: Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and
ultrastructures shown in drawings or micrographs (Practical 1).
• Scale bars are useful as a way of indicating actual sizes in drawings and micrographs.
Nature of science: Developments in scientific research follow improvements in apparatus—the invention of electron microscopes led to greater understanding of cell structure. (1.8)
• Electron microscopes have a much higher resolution than light microscopes.
• Skill: Drawing of the ultrastructure of prokaryotic cells based on electron micrographs.
• Skill: Drawing of the ultrastructure of eukaryotic cells based on electron micrographs.
International-mindedness: Microscopes were invented simultaneously in different parts of the world at a time when information travelled slowly. Modern-day communications have allowed for
improvements in the ability to collaborate, enriching scientific endeavor.
Aim 8: Developments in science, such as electron microscopy, can have economic benefits as they give commercial companies opportunities to make profits, but this can affect cooperation
between scientists.
• How to Calculate Magnification Power
- Eyepiece times Objective
• Resolving power vs magnification (there’s a difference)
• Limits – pro’s and con’s on each type of microscopes
• Selection of proper scope to use based on the limits
Types of Microscopes
Skill: Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of
structures and ultrastructures shown in drawings or micrographs (Practical 1).
• Scale bars are useful as a way of indicating actual sizes in drawings and micrographs.
Nature of science: Developments in scientific research follow improvements in apparatus—the invention of electron microscopes led to greater understanding of cell
structure. (1.8)
• Electron microscopes have a much higher resolution than light microscopes.
• Skill: Drawing of the ultrastructure of prokaryotic cells based on electron micrographs.
• Skill: Drawing of the ultrastructure of eukaryotic cells based on electron micrographs.
International-mindedness: Microscopes were invented simultaneously in different parts of the world at a time when information travelled slowly. Modern-day
communications have allowed for improvements in the ability to collaborate, enriching scientific endeavor.
Aim 8: Developments in science, such as electron microscopy, can have economic benefits as they give commercial companies opportunities to make profits, but this can
affect cooperation between scientists.
• Light microscope: uses light
• Electron microscope: uses beams of
electrons
- Scanning electron microscope:
specimen is coated with metal and
scanned with electrons.
- Transmission electron microscope:
specimen is sliced thin and stained;
bombarded with electrons.
Light vs. Electron Microscopes
•
•
•
•
•
Uses light
Lower magnification power
For viewing living and dead specimen
Can be viewed in color
Tend to be smaller in size
From Topic 1.2
Nature of science: Developments in scientific research follow improvements in apparatus—the
invention of electron microscopes led to greater understanding of cell structure. (1.8)
Understandings:
• Electron microscopes have a much higher resolution than light microscopes.
Applications and skills:
• Skill: Drawing of the ultrastructure of prokaryotic cells based on electron micrographs.
• Skill: Drawing of the ultrastructure of eukaryotic cells based on electron micrographs.
International-mindedness: Microscopes were invented simultaneously in different parts of the
world at a time when information travelled slowly. Modern-day communications have allowed
for improvements in the ability to collaborate, enriching scientific endeavour.
Aim 8: Developments in science, such as electron microscopy, can have economic benefits as
they give commercial companies opportunities to make profits, but this can affect cooperation
between scientists.
•
•
•
•
Uses electrons
Higher magnification power
Viewing dead specimen
Can only be viewed on black and
white
• Tend to be bigger in size
Scanning EM
• Uses scattered
electrons
• Focuses on the
sample’s surface or
composition
• 3D image
• Up to 2 million times
in magnification
Transmission EM
• Uses transmitted
electrons
• Focuses on what’s
inside or beyond the
surface
• 2D image
• Up to 50 million
times in
magnification
Cell Size
• Surface area to volume ratio is important in the limitation of cell size.
What limit cell size?
• SA/V ratio: the smaller the cell,
the greater its SA/V ratio.
Cells must be small enough to
accommodate the rate at which
wastes must be disposed out of the
cell and nutrients must enter inside
the cell.
Prokaryotic Cells
Essential idea: Eukaryotes have a much more complex cell structure than prokaryotes.
Understandings:
• Prokaryotes have a simple cell structure without compartmentalization.
Guidance:
• Drawings of prokaryotic cells should show the cell wall, pili and flagella, and plasma membrane enclosing cytoplasm that contains 70S ribosomes and a nucleoid with naked DNA.
Understandings:
• Prokaryotes have one chromosome consisting of a circular DNA molecule.
• Some prokaryotes also have plasmids but eukaryotes do not.
• Bacteria and
Arachaea
• Size
• 2-8 um
• No Nucleus
• Nucleoid
• Ribosomes (70s)
• Plasma membrane
• Cell Wall
• Capsule
• Pili
• Flagella
• Circular DNA
(plasmid)
Eukaryotic Cells
From Topic 1.2
Essential idea: Eukaryotes have a much more complex cell
structure than prokaryotes.
Understandings:
• Prokaryotes have a simple cell structure without
compartmentalization.
• Eukaryotes have a compartmentalized cell structure.
• Larger
• 10-100 um
• Membranous organelles
•
•
•
•
•
•
Nucleus
Endoplasmic Reticulum
Golgi
Mitochondria / Plastids
Lysosomes
Peroxisomes
Eukaryotic Cells: Plant vs. Animal Cells
• Non-membranous
Organelles
• Animal Cells: no cell wall but contains lysosomes
and centrioles, and some have flagella
• Ribosomes (80s)
• Plant cells: remember the 5 C’s:
• Microtubules
-cell wall
• Centrioles
-central vacuole
• Flagella
• Cytoskeleton
-central vacuole
-chloroplast
Essential idea: Eukaryotes have a much more complex cell
structure than prokaryotes.
-no centriole
BONUS: tonoplast and plasmodesmata; few with
flagella
Prokaryotes Vs. Eukaryotes
Essential idea: Eukaryotes have a much more complex cell structure than prokaryotes.
Understandings:
• Prokaryotes have a simple cell structure without compartmentalization.
• Eukaryotes have a compartmentalized cell structure.
Applications and skills:
• Application: Structure and function of organelles within exocrine gland cells of the pancreas and within palisade mesophyll cells of the leaf.
• Skill: Interpretation of electron micrographs to identify organelles and deduce the function of specialized cells.
Guidance:
• Drawings of prokaryotic cells should show the cell wall, pili and flagella, and plasma membrane enclosing cytoplasm that contains 70S ribosomes and a nucleoid with naked DNA.
• Drawings of eukaryotic cells should show a plasma membrane enclosing cytoplasm that contains 80S ribosomes and a nucleus, mitochondria and other membrane-bound
organelles are present in the cytoplasm. Some eukaryotic cells have a cell wall.
Understandings:
• Prokaryotes have one chromosome consisting of a circular DNA molecule.
• Some prokaryotes also have plasmids but eukaryotes do not.
• Prokaryote
•
•
•
•
•
• Eukaryote
Naked DNA
DNA in Cytoplasm
No Mitochondria
70s Ribosomes
No internal membranes
Make sure you know
how to compare all
three.
• DNA with Associated
Proteins (Histones)
• DNA in Nucleus
• Mitochondria
• 80s Ribosomes
• Membrane bound
organelles
Mitochondria and Chloroplast: Endosymbiotic Theory
• Evidence for the endosymbiotic theory is expected. The origin of eukaryote cilia and flagella does not need to be included (introduced in HL 1, reinforced during HL 2).
Endosymbiotic Theory: the theory that explains the origin of the mitochondrion and the chloroplast
- Each organelle were initially a prokaryote (bacteria) absorbed by a eukaryote (most likely algae)
through endocytosis.
-This is supported by the fact that both organelles contain their own set of DNA with their own set of 70s
ribosomes as well a double membrane.
Origin of Organelles: http://www.sumanasinc.com/webcontent/animations/content/organelles.html
Ultrastructures in Micrographs: Prokaryote
From Topic 1.2
Nature of science: Developments in scientific research follow improvements in apparatus—the invention of electron microscopes led to greater understanding of cell structure. (1.8)
Understandings:
• Electron microscopes have a much higher resolution than light microscopes.
Applications and skills:
• Skill: Drawing of the ultrastructure of prokaryotic cells based on electron micrographs.
Applications and skills:
• Skill: Interpretation of electron micrographs to
identify organelles and deduce the function of
specialized cells.
Guidance:
• Drawings of prokaryotic cells should show the cell
wall, pili and flagella, and plasma membrane
enclosing cytoplasm that contains 70S ribosomes and
a nucleoid with naked DNA.
From Topic 3.2
Understandings:
• Prokaryotes have one chromosome consisting of a
circular DNA molecule.
• Some prokaryotes also have plasmids but
eukaryotes do not.
Ultrastructures in Micrographs: Eukaryotic-plant cell
From Topic 1.2
Nature of science: Developments in scientific research follow improvements in apparatus—the invention of electron microscopes led to greater understanding of cell structure. (1.8)
Understandings:
• Electron microscopes have a much higher resolution than light microscopes.
Applications and skills:
• Skill: Drawing of the ultrastructure of prokaryotic cells based on electron micrographs.
• Skill: Drawing of the ultrastructure of eukaryotic cells based on electron micrographs.
Applications and skills:
• Skill: Interpretation of electron micrographs
to identify organelles and deduce the function
of specialized cells.
Guidance:
• Drawings of eukaryotic cells should show a
plasma membrane enclosing cytoplasm that
contains 80S ribosomes and a nucleus,
mitochondria and other membrane-bound
organelles are present in the cytoplasm. Some
eukaryotic cells have a cell wall.
Electron Micrographs: https://www.youtube.com/watch?v=k0YqEpA-62A
Drawing Micrographs: https://www.youtube.com/watch?v=vLORO1KKY74
Ultrastructures in Micrographs: Eukaryotic- Animal Cell
From Topic 1.2
Nature of science: Developments in scientific
research follow improvements in apparatus—the
invention of electron microscopes led to greater
understanding of cell structure. (1.8)
Understandings:
• Electron microscopes have a much higher
resolution than light microscopes.
Applications and skills:
• Skill: Drawing of the ultrastructure of
prokaryotic cells based on electron micrographs.
• Skill: Drawing of the ultrastructure of eukaryotic
cells based on electron micrographs.
Major Functions of Organelles
From Topic 1.1
Essential idea: The evolution of multicellular organisms allowed cell specialization and cell replacement.
Understandings:
• Organisms consisting of only one cell carry out all functions of life in that cell.
• Surface area to volume ratio is important in the limitation of cell size.
• Multicellular organisms have properties that emerge from the interaction of their cellular components.
Can you categorize what major function(s) each organelle performs?
• Nucleus
• Centrosome (full
Categories:
function ?)
• Nucleolus
• Manufacture
• Cilia/ Flagellum
• Plasma membrane
• Breakdown
• Rough ER
• Ribosomes
• Energy
• Smooth ER
•
Golgi
apparatus
Processing
• Central Vacuole
• Lysosomes
• tonoplast
• Support and
• Mitochondrion
Movement
• Chloroplasts
• Peroxisomes
• Cell wall
• Other- specify!
• Cytoskeleton
(microfilaments –AKA
actin, intermediate
filaments, microtubules
• Plasmodesmata
• Gap junctions
• Desomosomes
• Students should be aware that the 64 codons in the genetic code have the same meanings in nearly all organisms, but that there are some minor variations
that are likely to have accrued since the common origin of life on Earth (introduced in HL 1, reinforced during HL 2).
Aim 6: Pasteur’s experiment can be repeated using modern apparatus.
International-mindedness: Microscopes were invented simultaneously in different parts of the world at a time when information travelled slowly. Modern-day
communications have allowed for improvements in the ability to collaborate, enriching scientific endeavour.
Aim 8: Developments in science, such as electron microscopy, can have economic benefits as they give commercial companies opportunities to make profits,
but this can affect cooperation between scientists.
From Topic 3.2
Understandings:
• Prokaryotes have one chromosome consisting of a circular DNA molecule.
• Some prokaryotes also have plasmids but eukaryotes do not.
-Prep for 1.6 Cell Division, 1.3 Membranes Structure, 1.4 Membrane Transport, 2.8 and 8.2 Cellular Respiration, 2.9 and 8.3 Photosynthesis, Prep
for 5.1 Evidence for Evolution (in HL 2)