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IB Biology Objectives
Topic 1: Cells

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Topic 1: Cells
Topic 2: The Chemistry of Life
Topic 3: Genetics
Topic 4: Ecology and Evolution
Topic 5: Human Health and Physiology
Topic 7: Cell Respiration and Photosynthesis
Topic 8: Genetics
Topic 9: Human Reproduction
Topic 10: Defense Against Infectious Disease
Topic 11: Nerves, Muscles, and Movement
Topic 12: Excretion
Topic 13: Plant Science
Option E: Neurobiology and Behaviour
Option H: Further Human Physiology

1.1 Cell Theory
1.1.1 Discuss the theory that living organisms are composed of cells. 
	All living things are made of cells, and that cells arise from other cells. 
It is important to note that all "rules" have exceptions. Skeletal muscles and
some fungal hyphae are not divided into cells but have a multinucleate
cytoplasm. Some biologists consider unicellular organisms to be acellular. 
 
1.1.2 State that a virus is a non-cellular structure consisting of DNA or RNA
surrounded by a protein coat. 
	A virus is a non-cellular structure consisting of DNA or RNA surrounded by a
protein coat. 
 
1.1.3 State that all cells are formed from other cells. 
	All cells are formed from other cells.
 
1.1.4 Explain three advantages of using light microscropes. 
	Advantages of using a light microscope include: color images instead of
monochrome images (one color), easily prepared sample material, the possibilty
of observing living material and movement, and a larger field of view.
 
1.1.5 Outline the advantages of using electron microscopes. 
	Since the resolution is higher in an electron microscope than a light
microscope, one can see more seperate particles and have a clearer picture of
those particles. Also, an electron microscope has a higher magnifaction than a
light microscope, so one would be able to see smaller objects.
 
1.1.6 Define organelle. 
	An organelle is a discrete structure within a cell that has a specific function,
it also needs to be covered by its own membrane.
 
1.1.7 Compare the relative sizes of molecules, cell membrane thickness, viruses,
bacteria, organelles and cells, using appropriate SI units. 
	1000 nm(nanometer) = 1 um, 1000 um = 1mm 
	Molecules are 1 nm while the thickness of a membrane is 10 nm. Viruses are 100
nm, bacteria are 1 um, organelles can be up to 10 um, and most cells can be up
to 100 um. The cell is much larger than all these when taken into consideration
the three-dimensional shape.
 
1.1.8 Calculate linear magnification of drawings. 
 
1.1.9 Explain the importance of the surface area to volume ratio as a factor
limiting cell size. 
	When a cell grows, the volume increases at a faster rate than the surface area.
Thus, as the cell grows the surface to volume ratio dereases. A cell needs
surface area in order to carry out metabolic functions (chemical reactions need
a surface), and as a cell grows it needs to carry out more and more reactions.
Therefore, since a cell must maintain a certain surface area to volume ratio,
its size is limited. 
 
1.1.10 State that unicellular organisms carry out all the functions of life. 
	Unicellular organisms carry out all the functions of life. 
 
1.1.11 Explain that cells in multicellular organisms differentiate to carry out
specialized functions by expressing some of their genes but not others. 
	In multicellular organisms, all the cells contain all the genes, but they do not
use all of them. The cells of a multicellular organism differentiate to carry
out specialized funcions by only expressing some of thier genes.
 
1.1.12 Define tissue, organ, and organ system. 
	A tissue is an integrated group of cells that have a common stucture and
function. An organ is a center of body function specialized for that one
function that is composed of several different types of tissue. An organ system
is a group of organs that specialize in a certain function together.
 
1.2 Prokaryotic Cells
1.2.1 Draw a generalized prokaryotic cell as seen in electron micrographs. 
 
1.2.2 State one function for each of the following: cell wall, plasma membrane,
mesosome, cytoplasm, ribosomes and naked DNA. 
	One function of the cell wall is that it maintains the shape of the cell. The
plasma membrane acts as a selective membrane that lets sufficient amounts of
oxygen and other nutrients to enter and leave the cell as needed. A mesosome
increases the cell's surface area for metabolic reactions to occur. The
cytoplasm holds and suspends the organelles of specialized function. Ribosomes
are the main site for protein synthesis and naked DNA contain genes which
controll the cell and contain its genotype.
 
1.2.3 State that prokaryotes show a wide range of metabolic activity including
fermentation, photosynthesis and nitrogen fixation. 
	Prokaryotes show a wide range of metabolic activity including fermentation,
photosynthesis and nitrogen fixation.
 
1.3 Eukaryotic Cells
1.3.1 Draw a diagram to show the ultrastructure of a generalized animal cell as
seen in electron micrographs. 
 
1.3.2 State one function of each of these organelles: ribosomes, rough
endoplasmic reticulum, lysosome, Golgi apparatus, mitochondion and nucleus. 
	The ribosomes are the main site for protein synthesis. The proteins made by
ribosomes can be used inside the cell, or be sent out of the cell. One function
of the rough endoplasmic reticulum is the portion of the endoplasmic reticulum
that is studded with ribosomes. The proteins made in these ribosomes are
packaged in the rough ER and are usually sent outside of the cell. A lysosome
uses hydrolytic enzymes to digest macromolecules. The Golgi apparatus recieves
many of the products of the rough endoplasmic reticulum and it modifies them.
Later these proteins are transported to other destinations in packages of
membrane. A mitochondrion is the site of cellular respiration. The nucleus
contains the DNA which controls and contains the genotype for the cell.
 
1.3.3 Compare prokaryotic and eukaryotic cells. 
	Both prokaryotic and eukaryotic cells have cell membranes and both carry out
functions of cells (metabolic functions, reproduction etc). 
In contrast to eukaryotes, prokaryotic cells have no organelles (no nucleus, no
mitochondria, etc.). Prokaryotes have one circular loop of DNA that is located
in the cytoplasm, whereas eukaryotic DNA is arranged in a very complex manner
with many proteins and is located inside a nuclear envelope. Because the
prokaryotic DNA is associated with very little protein, it is considered naked.
Also, eukaryotic cells are much larger than prokaryotic cells. In addition, the
ribosomes in prokaryotes and eukaryotes are structurally different. Prokaryotes
have 70S ribosomes, whereas eukaryotes have 80S ribosomes.
 
1.3.4 Describe three differences between plant and animal cells. 
	Plant cells contain a cell wall while animal cells do not. 
Plant cells have chloroplasts while animal cells do not. Animal cells contain
mitochondria and plant cells do not. 
Most animal cells do not contain large central vacuoles while most plant cells
do.
 
1.3.5 State the composition and function of the plant cell wall. 
	The plant cell wall contains cellulose microfibrils which help to maintain the
cell's shape.
 
1.4
1.4.1 Draw a diagram to show the fluid mosaic model of a biological membrane. 
 
 
 
1.4.2 Explain how the hydrophobic and hydrophilic properties of phospholipids
help to maintain the structure of the cell membrane. 
	The head of the phospholipid is polar and hydrophilic (water-loving), and these
heads make up the outside of the phospholipid bilayer. The tail of the
phospholipid that is located inside the membrane is nonpolar and
hydrophobic(water-fearing). Because one end of the phospholipid is hydrophobic
and the other is hydrophilic, phospholipids naturally form bilayers in which the
heads are facing outward (toward the water), and the tails are facing inward
(away from the water). Therefore, the characteristics of phospholipids enable
the phospholipids to form a stable structure.
 
1.4.3 List the functions of membrane proteins including hormone binding sites,
enzymes, electron carriers, channels for passive transport and pumps for active
transport. 
	Membrane proteins perform many taks which help the cell with its functions. They
act as hormone binding sites, enzymes, electron carriers, channels for passive
transport and pumps for active transport.
 
1.4.4 Define diffusion and osmosis. 
	Diffusion is the total movement of particles from a region of higher
concentration of that particle to a region of lower concentration of that
particle. The difference in concentration that drives diffusion is called a
concentration gradient. Osmosis is the passive movement of water molecules,
across a partially permeable membrane, from a region of lower solute
concentration to a region of higher solute concentration.
 
1.4.5 Explain passive transport across membranes in terms of diffusion. 
	Passive transport happens naturally (it requires no energy from the cell) if
there is a concentration gradient between one side of the membrane and the
other. This concentration gradient drives diffusion across the membrane.
 
1.4.6 Explain the role of protein pumps and ATP in active transport across
membranes. 
	During active transport across membranes, the substance being transported goes
against the gradient (it is going from where there is a lesser concentration to
a greater concentration), and so energy is required to transport it in the form
of ATP. Proton pumps in the cell membrane function in transporting particles
across a membrane against concentration membranes with energy from ATP.
 
1.4.7 Explain how vesicles are used to transport materials within a cell between
the rough endoplasmic reticulum, Golgi apparatus and plasma membrane. 
	Vesicles are membranous sacs in which materials are stored and transported
throughout the cell. In order for the materials within a vesicle to go through a
membrane (the membranes of organelles, or the cell's plasma membrane), the
membranous vesicle becomes part of the organell's membrane or the plasma
membrane, releasing the materials inside. The materials that were inside the
vesicle are now free on the opposite side of the membrane. 
 
1.4.8 Describe how the fluidity of the membrane allows it to change shape, break
and reform during endocytosis and exocytosis. 
	Endocytosis is the movement of material into a cell by a process in which the
plasma membrane engulfs extracellular material, forming membrane-bound sacs that
enter the cytoplasm. Exocytosis is the movement of material out of a cell by a
process in which intracellular material is enclosed within a vesicle that moves
to the plasma membrae and fuses with it, releasing the material outside the
cell. 
	The cell membrane is fluid in that it is constantly in motion. The movement of
the phospholipids changes the membrane's shape, and allows for temporary holes
in the membrane that let materials flow in and out of the cell. If the membrane
were not fluid in nature, it would not be able to fuse with vesicles in
endocytosis and exocytosis.
 
1.5 Cell Division
1.5.1 State that the cell-division cycle involves interphase, mitosis and
cytokinesis. 
	The cell-division cycle involves interphase, mitosis and cytokinesis.
 
1.5.2 State that interphase is an active period in the life of a cell when many
biochemical reactions occur, as well as DNA transcription and DNA replication. 
	Interphase is an active period in the life of a cell when many biochemical
reactions occur, as well as DNA transcription and DNA replication.
 
1.5.3 Describe the events that occur in the four phases of mitosis (prophase,
metaphase, anaphase and telophase). 
	Mitosis contains four phases which are prophase, metaphase, anaphase, and
telophase. During mitosis, chromatin fibers become tightly coiled and can be
seen as chrmosomes. The chromosomes appear as two identical sister chromatids
joined at the centromere. The mitotic spindle begins to from in the cytoplasm.
Some of the microtubules that make up the spindle attach to the chromosomes. In
metaphase the chromosomes line up on the cell equator, with each sister
chromatid facing a different pole of the cell. During anaphase, the centromere
replicates and the sister chromatids separate. These news chromosomes move to
opposite poles, so that each pole of the cell contains a complete set of
chromosomes. During telophase, the microtubules elongate the cell, further
separating the two poles. Then the parent cell's nuclear encelope is broken down
and fragments are used to form new nuclear envelopes.
 
1.5.4 Explain how mitosis produces two genetically identical nuclei. 
	During mitosis, pairs of two identical chromosomes are pulled to opposite ends
of the cell. These identical chromosomes contain the same genetic information as
the chromosomes of the parent cell, so they are genetically identical. The two
identical sets of chromsomes become the nuclei of the two daughter cells.
 
1.5.5 Outline the differences in mitosis and cytokinesis between animal and
plant cells. 
	The differences in plant and animal cell mitosis exist because the plant cell
has a cell wall. Mitosis in plant cells involves the formation of a cell plate
that separates the two daughter cells, while animal cells use a cleavage furrow
to separate the two new cells. Also, plant cells lack the centrioles involved in
animal cell mitosis.
 
1.5.6 State that growth, tissue repair and asexual reproduction involve mitosis. 
	Growth, tissue repair and asexual reproduction involve mitosis.
1.5.7 State that tumours (cancers) are the result of uncontrolled cell division
and that these can occur in any organ. 
	Tumours (cancers) are the result of uncontrolled cell division and these can
occur in any organ.