Biology 12
PLO
Cell Structure:
A1. Describe the following cell structures
and their functions:
•
Cell membrane- Also known as the plasma membrane. Controls passage of materials in
and out of the cell. It keeps the cytoplasm and all the organelles contains. It is a phospholipid
bilayer in which the hydrophilic “heads” point out and the hydrophobic “tails” point in. Protein
molecules can be found partially or completely attached to the membrane. The membrane has
a consistency of light oil, and the scattered protein on it's surface is called the fluid-mosaic
model of membrane structure.
•
Mitochondria- It processes energy through the breakdown of carbohydrates and stores
this energy in ATP (Adenosine triphosphate.) It is closely related to chloroplasts found in plant
cells. It is involved in cellular respiration. It looks like the imprint of a shoe, and is double
walled with many inner folds called cristae. In cells where active transport is performed
frequently, the mitochondria can usually be found near the plasma membrane where the
energy is needed. In this way it is considered the powerhouse of the cell.
•
Endoplasmic reticulum- Both Rough ER and Smooth ER are Membranous channels that
act as a transport system for the cell. The RER is covered in ribosomes and specializes in
protein synthesis. The Smooth ER produces different molecules depending on the cell. It
produces hormones in locations such as the testes and adrenal cortex, and helps break down
alcohol in liver cells. Small membrane bound sacs called transition or transport vesicles break
off the ER's in a process called “Blebbing.”
•
Ribosomes- Appear as small dense granules. Made of two unequal subunits which
consists of rRNA and protein. These are joined in the nucleolus, but don't form a ribosome
until they reach the cytoplasm. Ribosomes may attach to the RER or remain free in the
cytoplasm. Several ribosomes may together create one protein. This is called a polyribosome.
Ribosomes do not have a membrane, so they are not classified as an organelle.
•
Golgi Bodies- Named for the person who discovered it's existence the cell. Made of
about six saccules (flattened vacuoles) that look like a stack of pancakes. They receive, modify,
process, and package vesicles. Usually a carbohydrate group is added to the protein. This is
called a glycoprotein. Outgoing vesicles are called secretary vesicles, and they are sent to the
plasma membrane to be distributed. Vesicles sometimes remain in the cell and become
lysosomes.
•
Vesicles- Small membrane sacs that contain proteins or molecules. They are small
vacuoles. Transition (or transport) vesicles are created by blebbing from the ER. They are
destined for the Golgi body. Here they are modified and packaged further. Secretary vesicles
are then produced, which end up leaving the cell through the cell membrane to complete it's
task. A few stay in the cell.
•
Vacuoles- A large, membrane enclosed fluid sac. Found in both animal and plant cells,
but they are much bigger in plant cells, and are used to create support for the plant structure.
Vacuoles are used for the storage of molecules.
•
Lysosomes- They are vesicles created by the Golgi apparatus. When macromolecules
enter the cells in vesicles, the lysosome breaks them down to digest the contents into simpler
molecules. These are released into the cytoplasm. Lysosomes are also responsible for
autodigestion (self digestion), which is important when organelles cease to function properly
or the cell becomes old and ineffective. In order to digest molecules, lysosomes contain
hydrolytic enzymes. It uses water to break down polymers. They are sometimes called “suicide
sacs.” They are smaller than vacuoles and are granular in appearance.
•
Nuclear envelope- This is a double membrane that separates the nucleus from the
cytoplasm and the rest of the cell. This helps the nucleus keep it's shape and allows chromatin
attachment. Found throughout the nuclear envelope are nuclear pores which allows proteins to
enter and ribosomes to exit. Allows the cytoplasm and the nucleoplasm to remain somewhat
combined. It is very selective of which molecules it allows to enter the nucleus.
•
Nucleus- This is the control centre of the cell. The genetic material, chromatin, is made
of DNA and protein and remains suspended in the nucleoplasm. This chromatin becomes
chromosomes when it is coiled for cell division. While unraveled, small segments are copied in
RNA to allow for the manufacture of proteins in the cytoplasm. The creation of RNA requires
enzymes produces in ribosomes in the cytoplasm. Through this molecular communication the
nucleus controls all cell activity. It is the largest, most easiest identified organelle in the cell.
•
Nucleolus- This is a visible region within the nucleoplasm, however it is not part of the
nucleus. This is where RNA and specific proteins join to form a ribosome.
•
Chromosomes- This is chromatin that has been coiled up in preparation for cell
division.
A2.
Identify the functional interrelationships of cell structures:
When vesicles enter the cell through endocytosis , recognition and communication must be
mad with the cell membrane in order for that vesicle to be accepted into the cell. The
mitochondria also relies on vesicles to supply it with macromolecules and polymers to break
down and create energy and ATP for cell activities. The ER relies on ribosomes to attach to
synthesize proteins. The transition vesicles emerge from the ER. The ribosomes rely on the
nucleus to supply the rRNA, the nucleolus a location where the subunits of protein and rRNA
can join, and the nuclear envelope to allow the large ribosome safe passage into the cytoplasm.
The golgi bodies receive transition vesicles from the ER and produce secretary vesicles bound
for the membrane. Some of the vesicles produced from the golgi body become lysosomes
because of the enzymes that are placed in the vesicles by the golgi body. Vesicles are classified
as small vacuoles. The nucleus holds the chromosomes, and acts as a control centre for all the
organelles and relations with other surrounding cells. The nucleolus allow for ribosomes to
emerge by combining proteins which entered through the nuclear envelope and rRNA, which
was copied from segments of chromosomes found in the nucleus.
Cell Compounds:
B1. Describe how the polarity of the water molecule results in hydrogen bonding:
Water is classified as a polar molecule because of the unequal sharing of electrons between the
hydrogen and oxygen ions. Because the oxygen ions are larger, they create a greater pull on
the orbiting electrons. This causes the electrons to orbit the oxygen ions more frequently,
granting the oxygen with a slightly negative charge. This leaves the hydrogen ions with a
slightly positive charge. Because of these charges, oxygen ions from one water molecule and
the hydrogen ions from another water molecule are attracted together. This bond between
water molecules is called a hydrogen bond. It is a weak bond, but is very important in giving
water some specific, unique characteristics. Water is attracted to itself by cohesion and by
adhesion to other molecules. This is why water creates a meniscus in a beaker- it is attracted to
the plastic material of the beaker and this pulls the water up on the
sides of the test tubes.
B2. Describe the role of water as a solvent, temperature regulator, and lubricant:
Water acts as a great solvent, temperature regulator, and lubricant. It is a chemical, and very
important for it's chemical properties. Water dissolves inorganic, polar materials (like dissolves
like.) Water is used to regulate temperature in many places, including our bodies. Because of
the thickness of water due to hydrogen bonding, water has a high heat capacity. This means it
requires a lot of energy in order for the temperature of water to raise. This allows us to
maintain a very precise body temperature, even with different temperatures around us. This is
vital because the proteins in our body will only function in a narrow temperature range.
Because water molecules have a fixed space in between themselves when they freeze, it makes
the density of frozen water less than the density of liquid water.
Water is also a lubricant.
In our eyes (tears)
in our joints (reduces friction) also around our lungs, heart
as saliva (swallowing),
in our skull (as a protective fluid) may result in a concussion
It is also used in our joints, our digestion, our organs, and even our
Another quality of water is it's surface tension. Because of hydrogen bonding, water is pulled
together to create the smallest surface area possible.
Water is a lubricant.
Diagram showing comparison of density of water and ice at the molecular level
B3. Distinguish among the acids, bases, and buffers, and indicate the importance of pH to
biological systems:
The pH scale ranges from 0-14. 7 is considered neutral because there is an equal number of H+
and OH- in the solution. 7 is the pH of pure water(H2O). An acid will donate H+'s when added
to an aqueous solution, and ranges in the pH from 0-6.9. A base breaks into OH- ions and
another compound when placed in an aqueous solution. A base's pH ranges from 7.1-14. A
buffer is a compound used to maintain a constant and steady pH within a system by releasing
or absorbing small amounts of H+ or OH-, depending on the make-up of that buffer. A buffer
itself is a weak acid or a weak base. (eg weak acid buffer releases small amounts of H+ ions to
lower a solution's pH if it is getting too high.) An example of a buffer is carbonic acid. A steady
pH is necessary in many body functions. The scale of 0-14 in a reflection of the concentration
of H+ ions. (eg pH of 2 has a hydrogen ion concentration of 1x10-2. This means that for every
100 molecules of water, 1 of them is a loose hydrogen ion. That is 1%.) A higher pH means a
smaller number of loose hydrogen ions because it is in negative scientific notation.
H2CO3
Carbonic acid
H+
+
HCO3-
bicarbonate ion
Biological Molecules:
C1. Demonstrate a knowledge of synthesis and hydrolysis as applied to organic polymers:
Synthesis and hydrolysis are procedures that occur when the body needs to either combine or
break up molecules. The four major types of macromolecules in living systems is
carbohydrates, lipids, proteins, and nucleic acids. All these are made of singular, joined
together monomers. When these monomers are joined together, they go through a process
called dehydration synthesis. Water is extracted from their molecular structure, and then they
are attached together to form a polymer. Monomers=H2O+Polymers. Hydrolysis is the
opposite process. A long polymer is broken apart by adding water. Polymers+H2O=Monomers.
C2. Distinguish among carbohydrates, lipids, proteins, and nucleic acids with their structures:
The four basic units of all biological molecules is glucose (carbohydrates), Amino acids
(polypeptides), fatty acids (lipids), and DNA (Nucleic acid). Glucose, the monomer of
carbohydrates, is a 6 carbon ringed structure with oxygen. Sucrose, maltose, fructose, and
lactose are other sugars that are all polymers of glucose. Glucose is the sugar that cells use to
function. It is an immediate source of energy.
There are 20 different amino acids that twist together differently at their tertiary structure to
create countless different proteins that carry out all cell functions. Amino acids are made of an
amide group, a carboxyl group, and an R (remainder) group. The R group is the only thing
that changes between each amino acid.
Lipids are made of 3 fatty acids and a glycerol. Glycerol forms the backbone (CH2OH) and the
three fatty acids are attached off the side. On the other end their is a carboxyl group. The circle
of black indicates where synthesis occurs and where water is taken out to bind glycerol to a
fatty acid.
DNA is made of nucleic acids which is a twisted double helix made up of a phosphate group, a
sugar, and 1 of 4 different nitrogenous bases.
C3. Recognize the empirical formula of a carbohydrate:
The empirical formula of a carbohydrate is CH2O. Carbon, Hydrogen, and Oxygen are in the
ratio of 1:2:1. This ratio is always true, however sometimes a water molecule is taken away
because the molecule underwent dehydration synthesis. For example, maltose's chemical
formula is C12H22O11 because 1 H2O has been taken out in synthesis.
C4. Differentiate among monosaccharides, disaccharides, and polysaccharides:
Carbohydrates are sugars and starches. Monosaccharides are monomers, single molecules of a
carbohydrates. Disaccharides are 2 monosaccharides joined together. Polysaccharides are
chains of sugars (glucose). Polysaccharides is plant and animal starch. Sugars are very water
soluble and starches are less water soluble. This is because starches are much longer.
Polysaccharide:
C5. Differentiate among starch, cellulose, and glycogen:
Plant starch is called starch. In the string of sugars, if the H's are all pointing the same way (up
or down) it means it is plant starch. Plants also make cellulose. In cellulose, the hydrogen ions
will be alternating. 1 up 1 down 1 up 1 down, or 2 up 2 down 2 up 2 down. Because of this
structural component, cellulose cannot be broken down by water. Animal starch is called
glycogen. It can be identified by it's long chain length and multiple complicated side chains.
C6. The main functions of Carbohydrates are:
Giving energy to the metabolism; cell structural components; cell-to-cell contact and
recognition; and elimination of wastes.
C7. Compare and contrast saturated and unsaturated fats in terms of molecular structure:
A saturated fat have no double bonds because it is attached to the maximum number of
hydrogen ions. Unsaturated fats have double bonds because more hydrogen ions could be
attached to the carbon molecules.
C8.
Location and importance of neutral fats, steroids, and phospholipids in the human body:
Neutral fats store energy for later use. They form deposits around the body and are usually
considered “body fat.” Steroids increase protein synthesis, which increases muscle and growth
development. Phospholipids form the main component of every cell membrane. They are a
special type of lipid with a phosphate group. Because of it's chemical properties, it creates a
double-sided sheet with hydrophilic (water friendly) heads facing out and hydrophobic (water
repelling) tails facing in. This creates a boundary to contain cell organelles. It also allows the
membrane to be partially permeable to some molecules. Also used for insulation and
protection of organs and bones e.g. long bones, hips. Ribs
C9. Below is the common amino acid Alanine. The yellow CH3 group is the remainder R
group.
C10. Differentiate among the primary, secondary, tertiary, and quaternary structure of
proteins:
The primary, linear structure of a protein is when a sequence of amino acids are formed. The
secondary structure of a protein is when the amino acids twist together to form an alpha helix
due to peptide bonding. A peptide bond is when the carboxyl group of one amino acid attaches
to the amide group of another amino acid. There are also hydrogen bonds between every
fourth amino acid. It also forms a wavy sheet, called a beta pleated sheet. A protein's tertiary
structure is when the helix of amino acids are spiralled and all twisted together. More
ionic/covalent/hydrogen bonds have formed as a result. The quaternary structure of a protein
is when different tertiary structures associate together and function as one unit. Hemoglobin is
an example of a quaternary protein.
C11. List the major functions of proteins:
The job of every cell is to create protein. These proteins are used for many different things.
They are enzymes, which are used to speed up chemical reactions. They transport substances
to the correct sites. They make up antibodies critical to good health, and are a critical
component of all body tissues. They are also hormones which trigger specific body functions.
Structural
e.g. keratin I collagen
Physiological
e.g. hormones, antibodies
Metabolic
Enzymes
C12. Relate the general structure of the ATP molecule to its role as the “energy currency” of
cells:
ATP stands for adenosine triphosphate. Its structure is the nitrogenous base adenine with a
sugar and three phosphates. The bonds between the phosphate groups allow for large energy
storage. Large amounts of energy are released when these bonds are broken, and energy is
added to create this bond. It is the energy currency of the cell because When the cell needs
energy, ATP undergoes hydrolysis, breaking off one of the phosphates to create ADP. When
enough energy is available, it reforms into ATP to store that energy instead of losing it as heat.
DNA:
D1. Name the 4 bases of DNA and describe the structure of DNA using the following terms:
The four bases in DNA are Thymine, Cytosine, Guanine, and Adenosine.
•
A nucleotide is one segment of one side of a DNA strand. It is composed of a phosphate
group, shown as a circle, connected to a sugar group, shown as a pentagon, connected to one
of the above named nitrogenous bases.
•
Complementary base pairing occurs between the four bases. The purines, Adenosine
and Guanine, will always bond to Thymine and Cytosine. In this way assumptions can be made
about the percentages of each base because A=T and C=G. The consistency of the bonding pair
is extremely important to the stability of DNA replication.
•
The DNA strand is a parallel, double helix, spiral staircase. This allows it to hold the
most information possible.
•
Hydrogen bonding is present between the complementary base pairs. They keep the
bases connected, but are also easily broken when replication or transcription is being
performed.
D2. Describe DNA replication in three basic steps:
DNA replication occurs when the cell is preparing for division and must make an entire copy
of it's complete genetic code. DNA replication is semi-conservative, and ensures that the
genetic information is passed from cell to cell. The enzyme helicase is used to unzip the DNA
strand for replication. This enzyme breaks the hydrogen bonds between the repeating
nucleotide bases. Then, complementary base pairs are brought in to attach themselves to each
side of the parent strand. This is “pro freed” by DNA polymerase. This leaves two complete
strands of DNA, each with a parent strand and a daughter strand. In this way the original
parent DNA strand is “semi-conserved” in both new strands.
D3. Define recombinant DNA:
Recombinant DNA is combining DNA from two different sources. By identifying a specific
gene, this portion of nucleotide sequences can be extracted and synthetically mass produced
for specific purposes. Insulin is one of the first mass produced uses of recombinant DNA.
D4. Describe three uses for recombinant DNA:
1.
Extracting the human gene for making insulin and splicing it into a bacteria to be mass
produced for people with diabetes who cannot produce their own insulin.
2.
Plasminogen (hPTA) manufactured and taken by haemophiliacs to allow their blood to
clot.
3.
Plant vaccines such as a vaccine for Tobacco Mosaic Virus(TMV).
4.
Growth hormones.
D5. Compare and contrast DNA and RNA
DNA
Has deoxyribose
Double stranded
Contains thymine
In-the nucleus
Permanent
One form
Long ( 100000 bases)
Protein Synthesis:
RNA
Has ribose
Single stranded
Contains uracil
In nucleus and cytoplasm
Temporary
Three forms ( mRNA, tRNA, rRNA)
Short ( 100-500 bases)
E1. Demonstrate a knowledge of the basic steps of protein synthesis, identifying, the roles of
DNA, mRNA, tRNA, and ribosomes in the processes of transcription and translation:
The only product a cell ever makes is protein. Because of this, protein synthesis is always
occurring. The first step of protein synthesis is Transcription:
1.
The DNA is unwound in a specific place. This is done by using DNA Helicase.
2.
Then, free mRNA nucleotides are brought into the nucleus and matched up to
complementary DNA bases using RNA polymerase. However, because RNA doesn't have
Thymine, Uracil bases are attached to Adenine in the DNA.
3.
Lastly, the mRNA moves out of the nucleus. The purpose of mRNA is to copy
nucleotide sequences from the DNA template and move it out into the cytoplasm to instruct
for the synthesis of proteins.
The next step in protein synthesis is Translation, which is conducted in the cytoplasm.
1.
Imitation: The mRNA moves to a ribosome, where rRNA lines up the nucleotides and
assembles them, like a factory line. A ribosome is made of 2 parts. The large subunit has 2
active sites, where mRNA codons are shuffled down. Each triplet of bases in the mRNA strand
is called a codon. Each codon is the instructions for the production of one amino acid.
2.
Elongation: tRNA brings amino acids to the ribosome. It's anticodons on one end are
complementary to the mRNA's codon. The codons and anticodons temporarily attach. On the
other end of the tRNA structure is an amino acid. As the ribosome moves along the mRNA
strand and each tRNA molecule is gathered, the amino acids on the end of the tRNA molecule
are joined together with peptide bonds. The tRNA molecule then leaves, leaving behind a
polypeptide that corresponds to the mRNA codons. This is why the mRNA codons are used to
identify what amino acid has been formed. The polypeptide will then become a protein. The
original DNA base sequences are similar to the tRNA anticodons, except tRNA molecules have
Uracil instead of Thymine.
3.
Termination: After the right amount of amino acids has been formed, a stop codon is
reached in the mRNA strand. This codon still attracts a specific anticodon of tRNA, but this
tRNA anticodon does not have an attached amino acid. In this way protein synthesis is
terminated.
E2. Determine the sequence of amino acids coded for by a specific DNA sequence, given a
table of mRNA codons:
A sequence of triplets in the DNA that codes for a complete protein is called a gene. One gene
can have a thousand bases in it. Because there are only 4 bases, combinations of 3 bases make
one codon (amino acid). Because 4 bases make 64 combinations of 3 and there are only 20
amino acids, some codons code for the same amino acid. Also, there are a few stop codons that
don't code for any amino acid and are used to stop protein synthesis.
Example:
DNA base sequence is
mRNA codons would be
TAC GTG CAA ACT
AUG CAC GUU UGA
tRNA anticodons would be UAC GUG CAA ACU
The amino acids would be Methionine (AUG) Histidine(CAC) Valine (GUU) and stop codon
with no attached amino acid(UGA)
E3. Two examples of environmental mutagens that can cause mutations in humans:
Two environmental mutagens that can cause mutations in humans are heavy metals such as
copper, radiation, and chemicals found in cigarette smoke and certain pesticides.
E4. Examples to explain how mutations in DNA affect protein synthesis and may lead to
genetic disorder:
There are three main mutations that can occur in DNA sequences that can effect protein
synthesis. Because each codon is a specific amino acid in a specific order, changing or altering
even one of the bases can change the entire protein that is being created, not be noticeable at
all, or be anywhere in between. It depended on where the mutation occurs. Many agree that
the third base in a triplet is not as important as the first two.
1.
Deletion is when part of all of a codon is not properly copied into mRNA. eg. CATTAG
changes to CATAG.
2.
Substitution occurs when a base is changed to another. This has the least probability of
creating a noticeable mutation as only 1 amino acid is affected in the sequence. eg. CATTAG
changes to CATGAG.
3.
Addition is when bases are added to the sequence. CATTAG changes to CATTAGG.
Sickle cell disease in humans occurs when the sixth amino acid in the protein chain of 146
amino acids for hemoglobin is changed from glutamate to valine. This has a dramatic effect
because glutamate has a polar R group and valine has a non polar R group. This causes the
sickled cell to be less soluble and to precipitate out of solution, distorting the red blood cell
into a sickle shape.
Transport Across Cell Members:
G1. Apply knowledge of organic molecules to explain the structure and function of the fluidmosaic membrane model:
The fluid mosaic membrane model is a demonstration of the different molecular components
in the cell membrane. Phospholipids align themselves with their non-polar “tails” facing in and
their polar “heads” facing out. Also embedded in the membrane are polysaccharides, lipids,
and proteins. The phospholipid is a special lipid that contains a phosphate group in the place
of a CH4 group. This causes the attached fatty acid (NH4) on the end to attract to the PO4.
This creates the characteristic polar head and non-polar tail of each phospholipid.
G2. Explain why the cell membrane is described as “selectively permeable”:
One of the main functions of the cell membrane is to contain organelles and to carefully
regulate what materials enter and exit the cell. The cell will “select” what materials to will
permit into the cells. The proteins attached to the cell membrane are very specialized as to
what materials they will allow into the cell.
G3. Compare and contrast diffusion, facilitated transport, osmosis, and active transport:
•
Diffusion: Diffusion is the movement of particles from an area of high concentration to
an area of low concentration. It doesn't require energy, and occurs via random kinetic energy.
Diffusion is slow and constant, occurring extremely slowly when solute concentrations on
either side of a membrane are equal. Diffusion of one compound is independent of diffusion of
another compound. CO2, O2, and H2O all move easily through the cell membrane.
•
Osmosis: This is the diffusion of water. The plasma membrane is permeable to water,
but not to the solutes water carries. Because of this, water will move from an area of low solute
concentration to an area of high solute concentration. This is an attempt to equalize the
concentration of solutes on both sides by equaling the percentage of water to solute on both
sides. This could also be presented as the water moving from an area of high water
concentration to an area of low water concentration.
•
Facilitated Diffusion: This is where proteins on the membrane surface allow large
molecules to pass through their channels to allow for faster diffusion. This movement,
however, is still passive, so it requires no ATP energy. Proteins embedded in the membrane
that allow molecules to enter and exit the cell are called channel proteins.
•
Active Transport: This is where a molecule is moved across a membrane into an area of
higher concentration. This requires ATP. These transport proteins are called carrier proteins.
They are designed to combine with a very specific type of molecule. For example, the carrier
protein for glucose will not combine with other sugars, even if they are the same size. Proteins
in active transport can also be called pumps. The sodium-potassium pump moves Na (sodium)
into the cell and K (potassium) out of the cell.
Active/Passive What moves Direction
Energy?
Protein?
Diffusion
Passive
Small,
hydrophobic
Towards low
concentration
no
no
Osmosis
Passive
water
Towards high
no
concentration of
solutes
no
Facilitated
diffusion
Passive
Any with
specific
transporter
Towards low
concentration
no
yes
Active
transport
Active
Any with
specific
transporter
In or out,
depends on the
transporter
yes
yes
G4.Explain factors that affect the rate of diffusion across a cell membrane:
The rate of diffusion depends on the following factors:
•
Steepness of concentration gradient- the larger the concentration difference, the faster
the diffusion.
•
The higher the temperature the faster the diffusion because there is more energy
available.
•
The larger the surface area the faster the diffusion.
•
The type of molecule being diffused- smaller molecules diffuse faster.
The type of molecule being diffused will move more easily through the membrane if it has the
following properties:
•
Small
•
Gaseous
•
Non-polar (hydrophobic)
•
•
Non-charged
Lipid soluble
G5. Describe endocytosis, including phagocytosis and pinocytosis, and contrast it with
exocytosis:
Endocytosis is how large food particles and large molecules are absorbed by the cell. It uses
ATP. These molecules are encased inside a vesicle for absorption through the membrane.
Vesicles are made of the plasma membrane bilayer. After passing through the membrane, the
vesicle pinches off to reform an intracellular vesicle. The type of endocytosis used for large
molecules, and in some cases bacteria cell envelopment by white blood cells, is called
phagocytosis. The vesicles allow the molecules to be contained and isolated from the
cytoplasm before they are broken down. Small particles or liquids that need vesicles for
transport come into the cell by way of pinocytosis.
Exocytosis begins when a vesicle pinches off of the Golgi body, connects with the cell
membrane, and “pinches” out. It is used to excrete cell wastes and products. During cell
growth, exocytosis is used for elongation of the cell membrane.
-Exocytosis
ATP- Cytosis
-Endocytosis - Pinocytosis
- Phagocytosis
G6. Predict the effects of hypotonic, isotonic, and hypertonic environments on animal cells:
Animal cells in different solutions:
In a hypotonic solution, there is a higher concentration of solute in the cell than in the
surrounding environment. This causes water to rush into the cells in an attempt to equalize
the concentration. This will cause the cell to swell and become turgid. It may also burst, called
lysis.
In an isotonic solution, the cell and surrounding environment have the same concentration
gradient. This is the goal of all cells, allowing them to remain a normal shape with no fast
movement in or out of the cell membrane.
In a hypertonic solution, there is a higher concentration of solute outside the cell than in it.
This will cause water to leave the cell in an attempt to equalize the concentration. This causes
the cell to shrivel, called crenation.
G8. Demonstrate an understanding of the relationship and significance of surface area to
volume, with reference to cell size:
The most important job of the body is to get nutrients to all the cells and to carry wastes away
from all the cells. If we were one giant cell, the surface area would be very small compared to
the volume of our body. Having many tiny cells allows for the ratio between surface area and
volume to be much closer. This allows adequate surface area for the cell to be reached and
provided with nutrients ect.
Enzymes:
H1. Explain metabolism, enzyme, substrate, coenzyme, activation energy:
Human metabolism is a set of chemical reactions and processes that keep the body running.
The production of protein is essential for cell metabolism. Each protein has a function based
on it's specific shape. These functions include:
1)
Enzymatic
2)
Hormonal
3)
Structural
4)
Other
Enzymes are proteins that speed up chemical reactions that would normally occur very
slowly or not at all. An enzyme is a type of catalyst. A catalyst is a substance that will increase
the rate of reaction between substrates without becoming part of the reaction itself. It is also
not self regulating. Enzymes break apart things or put them back together. Enzymes deform
slightly when they attach with a substrate. When the substrate is released, the enzyme resumes
it's original shape and is reused to bind with other substrates. An enzyme-substrate complex is
formed when they are temporarily bonded together. Many enzymes may work on a single
substrate in order for it to form the desired product. The meeting between the enzyme and the
substrate are random. Chemical reactions are driven by heat (energy), concentration, and pH
levels.
A substrate is the chemical or compound that an enzyme is acting upon. Enzymes are
used on substrates when the structure of a substrate needs to be changed.
Co-enzymes are smaller, “side” enzymes that are needed by the main enzyme in order
for a substrate to properly fit. Some vitamins are co-enzymes.
Activation energy is the input energy that is needed for a substrate to undergo a
chemical change. Enzymes work by decreasing the amount of activation energy that is needed
to make the reactions proceed.
H2. Source gland for thyroxin and it's function in relation to metabolism:
Thyroxine is produced in the thyroid gland in the throat. It is a hormone that helps regulate
growth and metabolism.
H3. Explain the “lock and key” model of enzymatic reactions:
An enzymatic reaction is routinely related to a “lock and key” model. The enzyme acts as the
door and the substrate acts as the key. The door will only open if the key is the right size and
shape and if it is placed in the right spot on the door, the active site of the enzyme. The
differently shaped key holes will only react with specific substrates. Also, a wrong key will still
fit into a door lock, however it will not work (inhibitors).
H4. The role of vitamins in biochemical reactions:
Vitamins are important in biochemical reactions because they act as co-factors and coenzymes. They transport hydrogen ions to and from a reaction. They are known as hydrogen
carriers. Different minerals and vitamins help to regulate other aspects of enzymatic reactions
such as adding stability when the electron distribution shifts.
H5. Differentiate between the roles of enzymes and co-enzymes in reactions:
Enzymes and co-enzymes are both needed to make a chemical reaction proceed properly.
However, enzymes are usually quite large, and usually have only 1 active site for substrates to
bind too. They are uncontrollable, and their activity levels must be strictly regulated. They will
continue to catalyze a reaction until all the substrate has been consumed. Co-enzymes are
much smaller, and are not as hazardous. They simply help the enzyme work even more
efficiently and add support and stability.
H6. Explain what effects enzyme activity:
Enzymes, which are all proteins, are very sensitive to their environment. All enzymes require
specific conditions in order for them to work properly. In this way, the body is able to regulate
where and when enzymes should work by manipulating the surrounding environment.
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Temperature:
The optimal temperature for our enzymes to work is at 37 degrees, the temperature of the
human body. Because the hydrogen bonds are weak within the protein, they become broken
and permanently denatured if the temperature rises much past 37 degrees. If the temperature
is lowered, the reaction also slows. However, if the temperature is raised again the enzyme will
be able to regain proper function. The rate of enzymatic reaction will increase rapidly up to 37
degrees, then plunge sharply.
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pH:
Changing the pH is one of the main ways the body uses to regulate enzyme activity. Many
enzymes have only a narrow pH window that they will function within.
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Enzyme Concentration:
If more enzyme is added, the reaction will continue to increase as long as the substrate doesn't
run out. The reaction will increase steadily, then flatten out slightly until more enzymes are
added, then will increase again.
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Substrate concentration:
If substrate is continually added, the reaction will increase until all active sites on the enzymes
are being used up. Then it will level out flat. This means the reaction is occurring at it's
maximum rate.
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Competitive inhibitors:
Competitive inhibitors compete with the substrate for occupancy of the active site. They
inhibit enzymes from binding with the right substrate to form an enzyme substrate complex.
These inhibitors block the active sites of the enzyme and restrict the enzyme's ability to
catalyze a reaction.
Competitive inhibition Allows a mechanism for controlling rate of product formed (metabolic
pathways)
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Heavy Metals:
Heavy metals disrupt the distribution of elections within an enzyme. When this happens, the
shape of the enzyme is changed. This decreases the likelihood of an enzyme-substrate complex
forming. Heavy metals can also denature enzymes.