AP Biology Test Review: Cell Structure, Function, and Transport (Perhaps a little about enzymes too!)
Topic #1: Flash Back Question
What are the special proteins which increase the rate of chemical reactions?
Enzymes
How do they increase the rate of chemical reactions?
Lower the required activation energy
Describe what is going on in this graph.
In line B there is no enzyme and the required activation
energy is much higher, line C is the same reaction with
an enzyme being used to decrease the necessary
activation energy making the reaction more efficient.
(This is an exergonic reaction because energy is lost
not gained)
Topic #2: cell Basics
If you had to be a cell would you rather be a larger or smaller cell? Smaller Cell
Why? If a cell gets too large it cannot attain enough nutrients and required resources to continue to
function efficiently and must either divide into two smaller cells or die.
What do the terms surface area and volume have to do with the size of a cell and its ability to function?
The more surface area you have for the amount of volume the more efficient you would be as a cell. In other
words a 6:1 surface area to volume ratio (6 times the surface area compared to volume) is much better than a
3:1 surface area to volume ratio.
What do prokaryotes and eukaryotes have in common? Both have DNA, ribosomes, and plasma membrane.
(Both can also have a cell wall or be unicellular)
What is their big difference? Big difference eukaryotic cells have membrane bound organelles
How do plant and animal cells differ in terms of organelles?
a) Plant cells have a central vacuole which services as a storage area and can also break down waste or
macro molecules. Plants also have chloroplasts to convert light energy into sugars, and a cell wall
which provides support for the plant.
b) Animal cells have lysosomes to break down macromolecules using hydrolytic molecules. Animal cells
also have centrosomes and may have flagella.
Topic #3: Eukaryotic Cell Organelles
How does the function of the rough and smooth ER differ?
The smooth ER is used by the cell to produce lipids (including steroids and phospholipids), metabolism of
carbohydrates, and detoxification of drugs and poisons (adding hydroxyl groups to make them soluble).
The rough ER produces, folds, and modifies proteins. These proteins are eventually sent to other organelles,
used to construct membranes, or sent out of the cell.
What is the basic function of a lysosome? Break down macromolecules using hydrolytic enzymes (in animal
cells).
What happens to most of the proteins made in the attached ribosomes? These proteins are eventually sent to
other organelles, used to construct membranes, or sent out of the cell.
What happens to most of the proteins freely floating in the cytosol? These proteins are synthesized to be
used in the cytosol, for processes such as helping to break down sugars.
Describe the pathway a protein might take on its way out of the cell. Initially produced in the attached
ribosomes, sent into and perhaps modified in the rough ER, then sent to the golgi apparatus, then finally sent
into a vesicle and out of the plasma membrane.
What organelles make up the endomembrane system? nuclear membrane, endoplasmic reticulum, golgi
apparatus, lysosomes, vacuoles, and plasma membrane.
What is the basic structure and function of the mitochondria, a chloroplast?
The mitochondria is a unique organelle which contains its own genetic information and ribosomes. It is the
major site of cellular energy production, with the ability to convert the sugar glucose to ATP, which the cell
can use for metabolic functions. THIS ORGANELLE IS FOUND IN BOTH PLANT AND ANIMAL CELLS.
The chloroplast is a unique organelle which is found in only producers, such as plants and some types of algae,
with the ability to complete the process of photosynthesis. It harnesses light energy and uses it to produce
glucose sugars which can be used in the mitochondria to make ATP.
Describe the function of a central vacuole, food vacuole, and contractile vacuole.
Central vacuole is used for storage of nutrients and break down of macromolecules
Tay-Sachs is a disorder which effects the human body in what way?
Individuals with Tay-Sachs lack the hydrolytic enzymes to break down lipids and so they accumulate in the
brain causing the destruction of nerve cells resulting in decreased motor skills.
Topic #4: Cellular Plasma Membrane
What is the cell membrane composed of? Phospholipids and Proteins which are amphipathic molecules (Have
hydrophobic and hydrophilic portion to these molecules). It also contains cholesterol and may contain
carbohydrate chains and glycolipid molecules.
What are the characteristics which determine if a molecule will move through the membrane?
Size of the molecules, polar or nonpolar (hydrophobic or hydrophilic), and charge (ions)
How does the presence of cholesterol impact a cell membrane? Keeps the membrane less fluid at human body
temperature however ensures that the phospholipids do not become too closely packed together. (Considered
a temperature buffer)
Differentiate between an integral and peripheral protein. Integral proteins go into the hydrophobic core, not
always all the way through the entire membrane. Peripheral proteins are on the surface of the membrane
either attached to the phospholipids or other proteins.
Topic #5: Movement through the Membrane
What does the term osmoregulation mean? The ability to regulate water movement into or out of the cell,
found in unicellular organisms which live in solution.
How do paramecium control the amount of water which moves into their bodies? Paramecium have a
contractile vacuole which pumps out excess water to ensure that the organism does not swell too much and
burst (lysis).
Would a cell with a cell wall be able to move materials into the cell through the process of phagocytosis? No,
the cell wall would not permit large amount of material to move from cell to cell because it acts as a barrier
the membrane is not accessible for vacuoles or vesicles to pinch off or enclose materials.
Differentiate between passive and active transport. Passive transport moves materials from high to low
concentration, which is considered with the concentration gradient, meaning it requires no input of energy.
Active transport moves materials from low to high concentration, which is considered against the
concentration gradient, which will require the input of cellular energy (ATP).
Provide examples of both passive and active transport.
Examples of passive transport are diffusion, osmosis, and facilitated diffusion.
Examples of active transport are the sodium potassium pump, which is an electrogenic pump found in animals
or the proton pump which is an electrogenic pump found in plants, fungi, and bacteria.
Cotransport, which requires two transport proteins, and bulk transport (like endocytosis and exocytosis) are
all examples of active transport as well.
How are diffusion and osmosis related to each other yet different? Diffusion is the movement of particles
from high to low concentration, osmosis is a particular type of diffusion which is only the movement of water
from high to low concentration.
In other words the general term diffusion can be used to describe movement of any particle, including water.
If a cell is placed in a hypotonic solution what will happen to the cell (describe plant and animal)?
In a hypotonic solution water will move from outside the cell, where there is more water, into the cell
attempting to dilute the larger amount of solute found in the cell. In an animal cell this could cause the cell
to burst or (lyse) and in a plant cell this will increase the amount of turgor pressure which will ensure that
they plant is stiff and rigid.
What happens to a cell placed in a isotonic solution? Cells in isotonic solutions should remain the same, water
will continue to move however it should move in and out at the same rate keeping it at equilibrium.
What happened to the celery placed in fresh water? It was very rigid and stiff, snapped when attempting to
break it into two pieces. Salt water? The celery was very flexible and bent easy, it was difficult to snap into
two pieces because it just bent each way you tried to break it.
Describe what is going on in each step of the sodium potassium pump diagram provided below:
Step One: Sodium molecules from inside the cell are moving
into the protein structure and ATP is then attaching to the
protein as well, but at a different location.
Step Two: A bond between two of the phosphate molecules
is broken releasing energy to fuel the pump and it changes
shapes.
Step Three: The sodium molecules are released out of
the cell and the potassium molecules are attached to the
protein pump.
Step Four: The potassium molecules move through the
pump and are released into the cell and the inorganic
phosphate is released from the pump.
There are lots of graphs on this test, make sure you are comfortable reading graphs and can determine the
slope of a line.
Make sure you study tonight and good luck! I will be wishing you all the best
Do not forget to bring your water writing on Wednesday to class and try to make sure you have finished the
lab write ups for part one and two by Thursday so we can complete part three of the lab on Thursday and
Friday.