Download IB Biology Topic 2 - Cells Revision Sheet What is understood by the

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IB Biology
What is understood by the term “cell theory”?
All living things are made of cells, All cells come from pre-existing cells, The
smallest unit of life is the cell.
Explain why striated muscle, giant algae, fungal hyphae don’t quite fit.
Striated muscle is multinucleate, extra large
Giant algae are too big, have super low SA:V ratio
Fungal Hyphae are multinucleate and super large
Is this enough evidence to falsify cell theory?
Briefly explain each of the following:
 Specialized tissues can develop by cell differentiation
Topic 2 - Cells
Revision Sheet
Explain why a small surface area to volume ratio limits cell size.
Materials that are essential to life have to be transported in via passive
transport. (due to the fact that they are needed all of the time, it is not
energy efficient to transport them via active transport)
For passive transport, you want lots of surface area (membrane area) to
passively transport things through. As you increase in size, your SA:V ratio
goes down, because volume goes up faster than area.
This leads to inefficiencies in passive transport as you increase the distance
materials have to travel via passive xport, and it ultimately means there is a
maximum cell size.
Name organelles A & B. Calculate the size of each.
Cells start out as stem cells, and are induced by chemical signals into
specific cell types by chemical signals.
Describe an example of an emergent property.
The living cells that make up your body are, in themselves, not special.
However, when they work together, they can have extra properties.
It works through the idea that cells - tissues  Organs  Organ Systems
 Organisms
At each of the levels, when they are combined, they create the next level,
and gain new abilities/properties.
Based on the fact that these new properties “emerge” at each subsequent
level, we call them “emergent properties”
Draw a simple labelled diagram of a Prokaryotic cell.
Draw a simple diagram of a Eukaryotic cell.
Stem cells can divide and differentiate along different pathways
Each stem cell can differentiate in to a wide variety of types of cells
from a single precursor
A Lysosome – 1 um B – Vacuole – 0.5 um
 Use of stem cells to treat one named disease
Leukemia – Harvest healthy Adult stem cells, chemotherapy kills off
cancerous tissue, reintroduce healthy stem cells back in to the body.
Explain how phospholipids form bilayers due to the amphipathic properties
Describe three locations & five functions of membrane proteins.
The head of a phospholipid is polar, while the tail is non polar. This means
that the heads of the molecules are attracted to each other and the tails are
attracted to each other. This contributes to the ability to form a bilayer.
The other factor in their ability to form a bilayer is how much they like
water. The polar parts will be outward facing the water environment, while
the tails will be facing inwards, away from the water.
Outside of the membrane
Signalling, receptors
Integrated through both
Integrated through one layer
Channels, Active transport proteins
Contributing to integrity of cell
Describe how molecules move across membranes by
simple diffusion,
High concentration to low concentration, through the plasma
facilitated diffusion,
High concentration to low concentration, through channel proteins
 osmosis
High concentration to low concentration, through aquaporins
Active transport.
Pay no attention to conc. Gradient, using active transport proteins
Explain how vesicles are used to transport materials within a cell
between the rough endoplasmic reticulum, golgi apparatus and plasma
Vesicles are formed from the membrane of the rough endoplasmic
reticulum around newly synthesized proteins. Vesicles then carry the
proteins to the golgi apparatus, which determines the end goal for the
proteins. The golgi then creates a new vesicle that moves the proteins to
the end destination. The plasma membrane allows all of this transport to
happen, due to the fact that it is resealable, and can allow vesicles to fuse
with it.
List the stages in cell division by mitosis? Give a detail about each stage.
Mitosis phase
Regular cell processes, DNA Synthesis, Cell gets
Nuclear membrane goes away, DNA condenses
Chromosomes line up in middle of cell, spindle
fibers reach out towards them
Chromosomes are pulled to opposite ends of the
New nuclear membrane begins to form, cells
begin dividing cytoplasm
What causes the cell cycle & division to go wrong and cause 1° and 2° tumors
in cancer? Use the terms cyclins, mutagens, oncogenes and metastasis
Cancer is caused by cells losing control of the cell cycle. Cyclins, which normally
can halt the cell cycle, can no longer do so, and for this reason, the cell cycle
proceeds when it shouldn’t. This occurs when oncogenes stop allowing the cell
to create p53. A primary tumor is a small formation of cells that have divided
from one cancerous cell. A secondary tumor is a tumor that has recruited
blood vessels because of its size. This leads to metastasis often.