Download AUS Biological Sciences 8: Science Unde

AN ACTIVE AUSTRALIAN SCIENCE 8 CURRICULUM MODULE
AUS BS8 SU STRAND: MODULE I: CELLULAR BIOLOGY
STUDENT’S NAME:
TUTORIAL:
TEACHER’S NAME:
DATE:
_______________________________________________________________________________________
AUS Biological Sciences 8: Science Understanding Strand Module 1: Key Conceptual Understandings
x
x
Students know that cells are the tiny living units that make up an organism.
Students compare and contrast the structure of a typical animal cell with the structure of a typical plant
cell.
x Students are aware that cells contain a cell nucleus (except red blood cells) and structures called
organelles that have particular functions.
x Students know that some organisms consist of one cell only (they are unicellular); while other organisms
consist of many cells (they are multicellular).
x Students are aware that all cells are formed from existing cells by cell division.
x Students understand that in order for the body of an organism to continue to function, cellular
replacement must occur, involving cell division to replace worn, damaged and dead cells. Are nerve cells
in the human brain replaced?
x Students know that cell division for growth and replacement is called mitosis.
_______________________________________________________________________________________
An Introduction to Cell Theory
Cell theory is as important in the study of Biology, as Atomic theory is important in the study of Chemistry.
x
Backward Reference: In the Biological Sciences 7 SU Strand Module 1, I introduced this Science
Concept: “Biologists refer to an individual living thing as an organism.”
x
Science Concept: Modern cell theory includes these science ideas: (1) All organisms are made up of
cells, (2) Cells are the structural and functional units of all organisms, (3) Cells come from pre-existing
cells by cell division, (4) All cells have basically the same chemical composition, (5) Metabolic energy
flows occur within cells, and (6) Cells contain hereditary information that is passed from cell to cell
during cell division.
x
In your study of the Biological Sciences, you will come across some organisms that are difficult to
classify. For example: Question: Are viruses alive? Answer: Viruses have both living and nonliving
characteristics.
x
Forward Reference: In the Biological Sciences Sub Strand at Year Level 9, you will study science
ideas (4) and (5); and in the Biological Sciences Sub Strand at Year Level 10, you will study science
idea (6) of modern Cell Theory.
ͺǣͳ̹ǤǤ…
ƒ””›ȋʹͲͳͳȌ
ƒ‰‡ͳ
x
Backward Reference: In the Biological Sciences 7 SU Strand Module 1, I introduced this Science
Concept: “Most biologists now subdivide living things into five (5) major kingdoms including the
Monera, the Protista, the Fungi, the Plantae, and the Animalia.” The prokaryotic kingdom Monera
includes the bacteria and the cyanobacteria. The protists, fungi, plants, and animals are all eukaryotes.
You will study the differences between prokaryotes and eukaryotes later in this AUS Science 8 SU module.
What are the similarities and differences between typical plant cells and typical animal cells?
Generalised Structure of typical Plant and Animal Cells
How are plant cells similar to animal cells? How are plant cells different from animal cells?
A cell organelle is a membranebound structure or compartment in a
cell that performs a special function.
Prokaryotes were believed, until very
recently, to have no organelles. Some
prokaryotes have now been described
as having organelles, e.g.,
carboxysome (a protein-shell
compartment for carbon fixation in
some bacteria); chlorosome (a light
harvesting structure in green sulfur
bacteria); magnetosome (found in
magnetotactic bacteria), and
thylakoid (in some cyanobacteria).
Can you now identify the cell organelles contained in a typical plant cell but not in a typical animal cell?
1. Which two cell organelles are found in a typical plant cell but not in a typical animal cell?
[2 marks]
2. What is the function of the mitochondria, i.e., what do mitochondria do?
[3 marks]
ͺǣͳ̹ǤǤ…
ƒ””›ȋʹͲͳͳȌ
ƒ‰‡ʹ
Functions of some Cell Organelles
TABLE 1: Functions of listed Cell Organelles
Cell Structure
Cell wall
Location
Found in bacteria, fungi,
and plant cells. Not
found in animal cells.
Cell membrane
Found in all cells.
Nucleus
Found in all cells except
prokaryotes.
Found in all cells
Cytoplasm
Description
Is rigid and strong.
Is made of cellulose.
Found inside cell
wall in plant cells.
Forms outer layer in
animal cells.
Holds nuclear DNA.
Mitochondria
Found in all cells except
prokaryotes.
Is a clear and
viscous jellylike
material (cytosol)
Are bean-shaped.
Contain m-DNA.
Vacuoles
Plant cells have a single,
large vacuole. Animal
cells have small
vacuoles.
Found in algae and green
plant cells. Not found in
animal cells.
Are fluid-filled sacs.
Largest organelle in
plant cells. Contains
cell sap in plants.
Are green, oval
shaped and contain
chlorophyll.
Chloroplasts
Function
Support and protection.
Allows H2O, CO2, and O2 to diffuse
in/out of cell.
Support and protection. Controls
movement of materials in/out of cell.
Barrier between cell and its
environment. Maintains homeostasis.
Controls cell activities.
Supports and protects cell organelles.
Site of aerobic cellular respiration.
Break down glucose sugar molecules
to release energy (ATP).
Store food, water, metabolic and toxic
wastes. Plants need to store large
amounts of food (glucose and starch).
Use sunlight energy to make food
(glucose) in green plants by the
chemical process of photosynthesis.
Source URL: http://www.schools.utah.gov/CURR/science/sciber00/7th/cells/sciber/orgtable.htm
Respiration in Animals and Plants
Respiration is a chemical reaction that occurs in both animal and plant cells. During respiration, the energy
released from glucose and oxygen is used by the cells to keep them living. Glucose and oxygen react in the
cells to produce carbon dioxide gas and water. The overall cellular reaction is called aerobic respiration as
oxygen from the air is needed for the reaction to occur.
The summary word equation for aerobic respiration can be shown as:
Glucose sugar + Oxygen gas
Carbon dioxide gas + Water + energy (ATP)
3. Can you now write a summary chemical symbol equation for aerobic respiration?
[5 marks]
ͺǣͳ̹ǤǤ…
ƒ””›ȋʹͲͳͳȌ
ƒ‰‡͵
x
Forward Reference: Year 8 students, as you have to know how to write balanced chemical symbol
equations in the Chemical Sciences Sub Strand at Year Levels 9, and 10; please do not worry too much
if you are unable to correctly answer Questions 3 and 4.
Photosynthesis in Plants
Green plants use chlorophyll in their leaves to trap light energy. The energy is used to chemically combine
carbon dioxide with water to make glucose. The glucose is used in plant respiration, or converted into starch
and stored in leaves. The overall process is called photosynthesis. Oxygen gas is produced as a by-product.
The summary word equation for photosynthesis can be shown as:
Light energy
Carbon dioxide gas + Water
Glucose sugar + Oxygen gas
Chlorophyll
4. Can you now write a summary chemical symbol equation for photosynthesis?
[5 marks]
The Green Sea Slug
The green sea slug Elysia chlorotica obtains chloroplasts, (cellular organelles that allow green plant cells to
carry out photosynthesis), from the algae it eats. It stores these chloroplasts in the cells that line its stomach.
x
Backward Reference: In the Biological Sciences 7 SU Strand Module 1, I introduced this Science
Concept: “Most biologists now subdivide living things into five (5) major kingdoms including the
Monera, the Protista, the Fungi, the Plantae, and the Animalia.” The prokaryotic kingdom Monera
includes the bacteria and the cyanobacteria. The protists, fungi, plants, and animals are all eukaryotes.
5. Would you classify the green sea slug as a plant or as an animal? You must give at least two reasons to
support your answer. To help you correctly answer Question 5, you could apply a “mini-key” to the five
kingdoms of living things.
[3 marks]
ͺǣͳ̹ǤǤ…
ƒ””›ȋʹͲͳͳȌ
ƒ‰‡Ͷ
Two main Classes of Cells
Cells are divided into two main classes on the basis of whether or not they contain a nucleus. Prokaryotic
cells do not have a nucleus; eukaryotic cells have a
nucleus in which the genetic material is separated
from the cytoplasm. Prokaryotic cells are generally
smaller and simpler than eukaryotic cells; and their
genomes are less complex, and they usually do not
contain membrane-bound organelles.
x
Science Concept: The major and significant differences between prokaryotic and eukaryotic cells are
that eukaryotic cells have a nucleus and membrane-bound organelles, while prokaryotic cells never have
a nucleus, and usually do not contain organelles. The DNA of a prokaryotic cell floats freely within the
cell; whereas the nDNA of a eukaryotic cell is held within its nucleus.
TABLE 2: Some primary Differences between Prokaryotes and Eukaryotes
Prokaryotes
Nucleus absent
Meiosis absent
1 basic genome
Mitochondria absent
Chloroplasts absent
Endoplasmic reticulum absent
Vacuoles absent
x
x
x
x
Eukaryotes
Nucleus present
Meiosis
Chromosome number 2-600
Mitochondria present
Chloroplasts may be present
Endoplasmic reticulum present
Vacuoles present
Science Concept: Meiosis is a two-part cell division process of those organisms that sexually reproduce.
Meiosis results in sex cells (or gametes) that contain half the number of chromosomes of the parent cell.
Forward Reference: In the Biological Sciences Sub Strand at Year Level 10, you will study the concept
of meiosis to a much greater depth of understanding.
Science Concept: The genome is the entire set of genetic instructions found within a cell. The human
genome contains 23 pairs of chromosomes, found in the cell nucleus, as well as the small mitochondrial
DNA found in cell organelles known as mitochondria.
Science Concept: The endoplasmic reticulum is a network of tube-like membranes within the cell
cytoplasm, which have either: a smooth surface (smooth endoplasmic reticulum), or a rough surface
containing ribosomes (rough endoplasmic reticulum).
6. Most biologists believe that eukaryotes evolved from prokaryotes. Eukaryotes contain mitochondria,
prokaryotes do not. By what theoretical, evolutionary process did eukaryotic cells acquire mitochondria?
[5 marks]
ͺǣͳ̹ǤǤ…
ƒ””›ȋʹͲͳͳȌ
ƒ‰‡ͷ
x
Backward Reference: On Page 1 of this AUS Biological Sciences 8 SU Strand Module 1, I stated this
Cell Theory science concept: Number (3) “Cells come from pre-existing cells by cell division”.
How do new cells come from pre-existing cells?
The Cell Cycle
x
Science Concept: Living cells go through a series of stages known as the cell cycle. The cells grow, copy
their chromosomes, and then divide to form new cells.
Stages within the Cell Cycle:
In the G0 stage, the cell is resting
and not undergoing cell division.
The G1 stage is the period prior to
the synthesis of DNA. In the G1
stage, the cell increases in mass in
preparation for cell division.
The S stage is the period in which
the chromosomes are replicated by
DNA synthesis.
The G2 stage is the period after
DNA synthesis has occurred, but
prior to the start of prophase. In the
G2 stage, the cell makes proteins
and continues to increase in mass.
Source of Image URL: http://www2.le.ac.uk/departments/genetics/vgec/education/under18/topics/cellcycle-mitosis-meiosis
x
Science Concept: The cell cycle is the process by which a single-celled fertilized egg (or zygote),
develops into a mature organism. Also, the cell cycle is the process by which hair, skin, blood cells, and
some internal organs are replaced.
x
Science Concept: Mitosis is the process whereby a single cell divides resulting, normally, in two
identical cells, each containing the same number of chromosomes and genetic content as that of the
original cell.
x
The process of mitosis within the cell cycle is illustrated by the schematic diagram displayed on Page 7.
x
Science Concept: Prophase is the early stage of nuclear division during which chromosomes condense
and become visible. Prophase is the initial stage of mitosis or meiosis in which chromosomes become
visible and the cell spindles begin to form.
x
Science Concept: Cytokinesis is the division of the cytoplasm and the plasma membrane following the
division of the nucleus resulting in two cells, each having its own nucleus and cytoplasm surrounded by
a plasma membrane.
ͺǣͳ̹ǤǤ…
ƒ””›ȋʹͲͳͳȌ
ƒ‰‡͸
A Schematic Diagram of Mitosis
The following schematic diagram locates and illustrates the process of mitosis within the cell cycle.
Source of Image URL: http://en.wikipedia.org/wiki/Mitosis
x
Science Concept: The M stage of the cell cycle includes the processes of mitosis and cytokinesis.
7. Why must DNA replication occur as an essential step in the cell cycle?
[3 marks]
If you badly scrape your hand, your skin cells undergo mitosis to make new skin cells to repair the abrasion.
x
Science Concept: Wound repair is a complex process in which the skin (or another organ-tissue) repairs
itself after injury.
The healing of most wounds occurs by the processes of regeneration and repair. In regeneration, the wound
heals as the lost tissue is replaced by cells from adjacent healthy tissue. Mitosis occurs in these adjacent cells
to replace the cells lost as a result of the injury. In the repair process, lost tissue is replaced with fibrous scar
tissue.
Source of Images: http://en.wikipedia.org/wiki/Wound_healing
ͺǣͳ̹ǤǤ…
ƒ””›ȋʹͲͳͳȌ
ƒ‰‡͹
Extension and Challenge Questions
Questions about Red Blood Cells
8. What is one advantage of red blood cells having no cell nucleus?
[1 mark]
9. What is one disadvantage of red blood cells having no cell nucleus?
[1 mark]
Questions about Nerve cells in the Human Brain
10. Are nerve cells in the human brain replaced?
[2 marks]
Extra Online Resources
You may like to access these extra URL’s to learn more about cellular biology?
URL 1: http://micro.magnet.fsu.edu/cells/index.html
URL 2: http://history.nasa.gov/CP-2156/contents.htm
URL 3: http://www.cellsalive.com/cells/cell_model.htm
URL 4: http://www.ncbi.nlm.nih.gov/About/primer/genetics_cell.html
URL 5: http://www2.nau.edu/~gaud/bio372/class/readings/giard.htm
URL 6: http://bugs.bio.usyd.edu.au/learning/resources/CAL/Microconcepts/index.html
URL 7: http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html
URL 8: http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__control_of_the_cell_cycle.html
URL 9: http://www.wiley.com/college/boyer/0470003790/animations/cell_structure/cell_structure.htm
ͺǣͳ̹ǤǤ…
ƒ””›ȋʹͲͳͳȌ
ƒ‰‡ͺ
What new science ideas have you now learned about cellular biology by studying this AUS
BS8 SU Strand Module 1? List your newly learned key Science Concepts, as dot-points, in
the textbox given below.
_______________________________________________________________________________________
A Self-Check Summative Assessment Table
Now complete this assessment table by adding the ‘self-check’ mark achieved for your answer to each focus
question. Your teacher will provide his/her ‘model’ answer to each question, via ‘whole of class’ discussion.
Total Mark Possible = 30
Mark Achieved =
Percent (%) Score Achieved =
ͺǣͳ̹ǤǤ…
ƒ””›ȋʹͲͳͳȌ
ƒ‰‡ͻ