Human Biology,
Science and Society
What is Science? Johnson 2012,
2010, 2008 says that it is the study of the natural world, which includes all
matter and all energy.
What is Biology? Johnson 2012,
2010, 2008 says that it is the study of living organisms and life’s processes.
The study of life.
The
Characteristics of Life: (The difference between life and something that is
dead)
·
Living
things have a different molecular make-up than non-living things. Unlike
nonliving things, living organisms can combine elements creating certain
molecules. Such elements include proteins, carbohydrates, lipids, and nucleic acids.
·
Living
things require energy and raw material.
In order for living things to transform, molecules
require energy. Metabolism refers to the physical and chemical processes
involved in transforming molecules. All living things need raw materials and energy
from the environment to metabolize them into molecules and have the energy they
need to maintain life.
·
Living
things are composed of cells.
A cell is the smallest unit of life. All cells come
only from existing cells. Some organisms consist of just one cell-unicellular.
Some organisms contain many cells- multicellular.
·
Living
things maintain homeostasis.
Homeostasis is maintaining a
constant internal environment. All living organisms must maintain an internal
environment compatible with life. For ex., Single cell organisms are surrounded
by a membrane that allows the cell to maintain internal homeostasis by
providing a barrier to only allow certain substances to enter or exit that cell.
In multicellular organisms the tissues, organs and organ system work together
to maintain homeostasis of the fluid that surrounds all cells.
Ex. Maintain body temperature.
·
Living
things respond to their external environment.
If it is cold outside you move to somewhere it is
warm.
·
Living
things grow/reproduce
The ability to grow and reproduce is determined by
DNA, the genetic material in cells.
·
Populations
of living things evolve.
Classification
system places living things into groups according to characteristics and are placed
into three domains.
Domains: (Oellers,
Online Presentation)
1)
Archaea:
single-celled prokaryotes- are simple cells that contain no membrane.
Kingdom: archaebacteria
2)
Bacteria:
single-celled prodaryotes.
3)
Eukarya:
Single or multicellular. Addresses different kinds of bacteria.
Kingdoms that fall under this domain: Animals,
plants, fungi, protists.
The
criteria for classifying organisms is the presence of a nucleus, the number of
cells, and type of metabolism.
1)
Monera- All single-celled Prokaryotic
organisms. This group is comprised of bacteria.
2)
Animalia-multicellular organisms based on the organism’s
life cycle, structure, and mode of nutrition.
3)
Plantae-Same as above.
4)
Fungi-are decomposers. They obtain their
energy from decaying material.
5)
Protista- Comprises unicellular and relatively
simple multicellular eukaryotes such as protozoa, algae, slime molds.
The Domain Eukarya is organisms whose cells have nuclei.
Species is the smallest
unit of any classification system.
Humans belong to the kingdom Anamalia within the
domain Eukarya and our genus/species is Homo sapiens.
Genus is the second smallest unit.
Defining
features of humans
1)
Bipedalism-
Being able to stand upright and walk.
2)
Opposable
thumbs is having control over the thumb and fingers to work for your advantage.
3)
Large
brains compared to other species.
4)
Capacity
for complex language.
The Scientific
method is a five-step process where scientific knowledge is acquired.
Picture: (Johnson 2012,
2010, 2008 p.12)
1)Observe and generalize. Observe the world and make
a generalization about what you see. Ex. Water is cold.
1)
Formulate
a hypothesis. Have an idea of why the object you are observing is behaving in
that manner and consider all variables.
2)
Make
a testable prediction
Test under many different conditions. Testable predictions
should be based on the hypothesis and should be specific in order to be
testable.
3)
Experiment
or observe. Conduct experiments under controlled conditions and account for
variables. Have two groups a experimental group and a control group.
4)
Modify
hypothesis as necessary and repeat steps 3 and 4.
Learning to be a
Critical Thinker
1)
Be
a skeptic and question everything.
2)
Know
statistics. Scientists use statistics to determine how much confidence they
should place in information.
3)
Learn
how to read graphs
4)
Distinguish
anecdotes from scientific evidence. An anecdote is evidence that takes
the form of a testimony or an unverified report. Ex. Ads with stars on TV that
say this drug worked for them.
5)
Separate
fact from conclusion. Research and make sure you have more than one source that
says the same thing. I usually use three sources to verify a fact.
6)
Understand
the difference between correlation and causation. A correlation is a
close pattern or relationship between two or more things. Causation is
the action of causing or producing an effect.
References
Johnson, M. D. (2012, 2010, 2008).
Human Biology: concepts and current issues, sixth edition. Pearson Education,
inc.; Benjamin Cummings.
Oellers, J. (n.d). Online
Presentation: Ch1. Human Biology, Science, and Society. Retrieved February 2,
2012, from
http://lblackboard.yc.edu/webapps/portal/frameset.jsp?tab_tab_group_id=_2_1&url=%2Fwebapps%2Fblackboard%2Fexecute%2Flauncher%3Dcourse%26id%3D_43466_1
Ch. 2
The Chemistry of Living Things
All matter
consist of elements
·
The
natural world consists of matter and energy. Chemistry is the study of matter
and the energy that causes matter to combine, break apart, and recombine into
all substances both living and nonliving.
Johnson
2012, 2010, 2008 states that matter is anything that has mass and
occupies space.
·
All
matter is composed of elements (a pure form of matter that cannot be
broken down to a simpler form.) Ex. Aluminum, iron, oxygen and hydrogen.
There
is just over 100 known elements that together account for all matter on earth.
·
An
atom is the smallest unit of any element that keeps it’s physical and
chemical properties of that element. The atom itself equals neutrality.
·
The
nucleus is the center (core) of the atom.
·
The
nucleus is composed of protons- positively charged particles, a nearly
equal number of neutrons- neutral particles, all tightly bound together.
Atomic
mass
roughly equals the number of protons.
Neutrons
and protons equal mass.
Electrons
have no mass.
·
Electrons are smaller negative charged particles
that orbit around the nucleus called a shell.
Electrons
attract positive charged nucleus and repel each other.
Each
shell can hold a limited amount of electrons. The first shell can hold two; the
second and third shell can hold up to eight electrons.
Each
shell corresponds to a specific level of potential energy.
Each
shell further out represents higher potential energy level than the closer
shell.
When
an electron moves closer to the nucleus, it loses energy.
An
electrically neutral atom is the number of protons that equal the number
of electrons.
Elements
are also arranged in groups based on how many electrons are orbiting around the
nucleus, because electrons affect how an atom interacts with other elements.
Johnson
2012, 2010, 2008 states that isotopes are atoms with
more or less neutrons than the usual number for that element.
Isotopes
of an element have the same atomic number as the more common atoms, but
different atomic mass.
Isotopes
are always identified with a superscript mass number preceding the symbol. Ex.
Carbon-14 isotope is 14C.
Radioisotopes are unstable and
tend to give off energy in the form of radiation.
Atoms Combine to
form Molecules
Johnson
2012, 2010, 2008 states that a molecule consists of a stable relationship
between two or more atoms. Ex. Water H20 is two atoms of hydrogen and one atom
of oxygen.
·
There
are different kinds of energy that fuels life’s activities:
Energy is the capacity
to do work, a change in matter.
Potential
energy
stores energy that is not performing work.
Kinetic
energy
is doing work, work that is in motion.
·
When
chemical bonds of these energy-stored molecules are broken, potential energy
becomes kinetic energy. Ex. Water in a dam is potential energy; rushing water
is kinetic energy.
Johnson
2012, 2010, 2008 states that chemical bonds are attractive
forces that cause the atoms to be bound to each other.
1) Covalent Bonds- share
electrons with another atom. This happens when the outer shell is half-full.
Atoms are most stable when their outermost shell is completely full. This is
the strongest chemical bond.
Nonpolar covalent bonds happen when
electrons are shared equally. Ex. H2, O2 and CH4.
2)
Ionic Bonds- are another way that atoms can fill
their outer shell. This kind of bond forms between oppositely charged ions.
Such a loss or gain of electrons gives the atom a net charge.
A net charge occurs when there are fewer or
more electrons than protons in the nucleus. A net charge is positive for each
electron lost and negative for each electron gained.
Ion is an electrically charged atom
or molecule. Ex. Sodium (Na+), Chloride (Cl-).
Opposite charged ions are attracted to each other.
Ionic Bond is when two
oppositely charged ions come together. Ex. NaCl.
Ionic bonds are weaker than covalent bonds because
they tend to break easier.
Ions in aqueous (water) solution are called electrolytes
and are good conductors of electricity.
3)
Hydrogen Bonds- occur between molecules that do
not have a net charge, and occur between oppositely charged regions of polar
molecules.
This type of bonds form between polar molecules-
are molecules such as water that are electrically neutral overall, but still
have partially charged regions or poles (electrons are shared unequally).
Life Depends on Water
60% of our body
weight is comprised of water.
Water molecules
are polar because of polar covalent molecules.
Water can absorb
and hold heat energy.
Water is the
biological solvent.
Solvent is a liquid at
which other substances dissolve.
Solute is any
dissolved substance.
Hydrophilic molecules are polar
molecules that are attracted to water and interact with it easily.
Hydrophobic
molecules
are nonpolar neutral molecules such as cooking oils. Oils do not interact
easily with water and generally will not dissolve.
Water helps
regulate our body temperature when our bodies generate heat during metabolism.
Most biological
molecules dissolve readily in water because water is a polar molecule. The
liquid nature of water facilitates the transport of biological molecules. Water
absorbs, holds heat and can lower temperature through evaporation.
The Importance of Hydrogen Ions
Johnson 2012,
2010, 2008 states that one
of the most important ions in the body is the hydrogen ion (a single
proton without an electron).
When a covalent
bond is broken between hydrogen and oxygen in water the electron from one
hydrogen atom is transferred to the oxygen atom completely and the water
molecule breaks into two ions a hydrogen ion (H+) and a hydroxide ion (OH-).
An acid is any molecule
that can donate an H+ ion. When added to pure water acids produce an acidic
solution one with a higher H+ concentration than that of pure water.
A base
accepts Hydrogen ions and has a lower hydrogen ion concentration.
Acids and bases
neutralize one another.
pH scale expresses
hydrogen ion concentration of a solution. Indicates the acidity or alkalinity
of a solution.
Buffers minimize
changes in pH. They are essential to maintain homeostasis of pH in body fluids.
The Organic Molecules of Living
Organisms
Johnson 2012,
2010, 2008 states that organic molecules contain carbon and other
elements held together by covalent bonds.
Picture: (Johnson 2012,
2010, 2008 p.36)
Johnson 2012,
2010, 2008
carbon is the common building block for organic molecules because of the
many ways it can form strong covalent bonds with other atoms.
Macromolecules are built
within the cell in a process called dehydration synthesis (condensation
reaction) - when a subunit is added, the equivalent of water molecule is
removed.
Subunits needed
to synthesize macromolecules come from the foods we eat and from the
biochemical reactions in our body that break down other large molecules into
smaller ones.
Other
macromolecules are broken down by hydrolysis- a process where water is
added each time a covalent bond between single subunits in the chain is broken.
The breakdown of
macromolecules releases energy.
·
Living
organisms synthesize 4 classes of organic molecules:
1)
Carbohydrates are used for energy and structural
support.
Monosaccharides are simple
sugars. Ex. Glucose, Fructose, Galactose, Ribose and Deoxyribos.
Oligosaccharides are short
strings of monosaccharide linked together by the dehydration synthesis.
Diaccharides is two
monosaccharides linked together. Ex. Sucrose is Glucose + Fructose, Maltose is
Glucose + Glucose and Lactose is Glucose + Galactose.
Polysaccharides form when
thousands of monosaccharides are joined together into straight or branched
chains by dehydration synthesis. This is an easy way to stockpile energy by
locking it in the bonds of the polysaccharide molecule. Ex. Starch-made in
plants; stores energy, Glycogen is made in animals and stores energy and
cellulose is indigestible polysaccharide made in plants for structural support.
Glycogen is formed by
dehydration synthesis from glucose subunits and is stored in the liver and
muscles.
The bigger the molecule the more energy stored.
Picture: (Johnson 2012,
2010, 2008 p.36)
2)
Lipids are insoluble in water meaning they are
polar.
There are 3 important classes of lipids:
·
Triglycerides: energy storage molecules.
Also known as fats and oils. Composed of Glycerol
and 2 fatty acids: Saturated (in fats), Unsaturated (in oils). Stored in adipose
tissue.
·
Phospholipids: the primary structural component of
cell membranes.
Is a modified
form of a lipid.
Phospholipids have a molecule of glycerol as the
backbone and two fatty acid tails one end of the molecule is polar (water
soluble; hydrophilic) and the other end is nonpolar (water insoluble;
hydrophobic)
·
Steroids: Composed of 4 carbon rings. Ex.
Cholesterol which increases stability of plasma membrane and hormones: estrogen
and testosterone.
3)
Proteins- are macromolecules constructed from
long chains (polymers) of subunits called amino acids.
20 different types of amino acids.
Johnson 2012, 2010, 2008 states that amino acids are joined by
peptide bonds (covalent bonds), which are produced by dehydration synthesis
reactions.
Johnson 2012, 2010, 2008 states that polypeptide is a single
string of three to 100 amino acids and is commonly referred to as a protein
when it is longer than 100 amino acids.
·
Protein
function depends on structure: (Oellers, Online Presentation)
Picture: (Johnson 2012,
2010, 2008 p.43)
Primary Structure is the sequence of amino acids
that are stabilized by peptide bonds.
Secondary Structure describes how
the chain of amino acids is oriented in space. Alpha helix is a common
secondary structure of proteins. Is a right-hand spiral that is stabilized by
hydrogen bonds between amino acids at regular intervals. Beta sheet is a flat
ribbon also stabilized by hydrogen bonds.
The Tertiary structure is the third
level, refers to how the protein twists, folds to form 3-D shape, and is
stabilized by disulfide and hydrogen bonds. Creates polar and nonpolar areas in
molecules.
Quaternary Structure the fourth
structure of proteins refers to how many polypeptide chains make up the protein
(if there is more than one) and how they associate with each other.
The human body has thousands of different proteins
each serving a different purpose.
High temperatures or changes in pH can damage
protein structure, sometimes permanently. Denaturation refers to
permanent disruption of protein structure, leading to a loss of biological
function.
Enzymes regulate the
rates of biochemical reactions within cells.
Enzymes are proteins that function as biological
catalysts.
A catalyst speeds up the rate of chemical
reactions without itself being altered or consumed by the reaction.
Without enzymes, many biochemical reactions would
not proceed quickly enough to sustain life.
The functional shape of an enzyme is dependent on
temperature, pH, ion concentration and presence of inhibitors.
Nucleic Acids store genetic information
(Another class of organic molecules)
Nucleic acids
are long chains containing subunits known as nucleotides.
2 types:
1)
DNA ( deoxyribonucleic acid) is the genetic
material in living things, directs everything the cell does. Contains the instructions
for producing RNA.
2)
RNA (ribonucleic acid) is responsible for
carrying out the instructions of the DNA. Contains the information for
producing proteins. Proteins direct most of life’s processes.
Both
DNA and RNA are composed of smaller molecular subunits called nucleotides.
Nucleotides
are the building blocks of nucleic acids. There are only eight different
nucleotides, four in DNA and four in RNA.
Structure
of DNA: (Oellers, Online Presentation)
·
Double-stranded
·
Nucleotides
contain
Deoxyribose (sugar)
Nitrogenous bases (adenine, Guanine, Cytosine and
Thymine
Pairing (Adenine and Thymine) and (Guanine and
Cytosine)
Structure of
RNA: (Oellers, Online Presentation)
·
Single-stranded
and shorter
·
Nucleotides
contain Ribose (sugar)
Nitrogenous bases (Adenine, Guanine, Cytosine, and
Uracil)
ATP (adenonsine triphosphate) is a related
nucleotide and is identical to the adenine-containing nucleotide in RNA except
that it has two additional phosphate groups (triphosphate).
ATP is the universal energy source for cells because
the bonds between the phosphate groups contain a great deal of potential
energy.
ATP ADP + Pi + energy
The breakdown of
ATP produces ADP (adenosine diphosphate) plus an inorganic phosphate group (p1).
References
Johnson, M. D. (2012, 2010, 2008).
Human Biology: concepts and current issues, sixth edition. Pearson Education,
inc.; Benjamin Cummings.
Oellers, J. (n.d). Online
Presentation: Ch1. Human Biology, Science, and Society. Retrieved February 2,
2012, from http://lblackboard.yc.edu/webapps/portal/frameset.jsp?tab_tab_group_id=_2_1&url=%2Fwebapps%2Fblackboard%2Fexecute%2Flauncher%3Dcourse%26id%3D_43466_1
Ch. 3
Structure and Function of Cells
The Cell
Doctrine- consists of 3 Principals: (Johnson 2012, 2010, 2008)
1)
All
living things are made of cells.
2)
A
cell is the smallest unit that exhibits all the characteristics of life.
3)
All
cells are made from existing cells.
Cell
Classification (Oellers, Online Presentation)
2
basic cell types classified by Internal Organization:
Picture: (Johnson 2012, 2010, 2008 p.53)
Eukaryotic Cells Prokaryotic Cells
Plasma Membrane
Plasma
membrane (No Nucleus)
Nucleus:
Information Center Cytoplasm: fluid within the membrane
Cytoplasm No
True Organelles
Organelles
(Structure with specialized functions)
All
human cells are Eukaryotic
Organelles are in the
cytoplasm and includes everything inside the cell except the nucleus. They
carry out specialized functions such as digesting nutrients or packaging
cellular products.
Cell Size
Picture: (Johnson 2012,
2010, 2008 p.55)
Cell
size and plasma membrane shape affect the surface area and volume.
The
surface of any cell can be increased by microvilli.
Small
cells have a higher surface to volume ratio.
A
high surface to volume ratio promotes efficiency in requiring nutrients and
disposal of wastes through diffusion.
Plasma Membrane
Picture: (Johnson 2012,
2010, 2008 p.56)
Johnson
2012, 2010, 2008 states that human cells are surrounded by a plasma membrane,
which serves to contain cellular structures within the cell and to regulate the
kinds and quantities of molecules that can enter and exit the cell.
The
plasma membrane is made up of phospholipids, cholesterol, and proteins.
Phospholipids are a
particular type of lipid with a polar head (has a charge) and a neutral
nonpolar tail (no charge) that is pointed to the inside of the lipid bilayer
due to the nonpolar tail being hydrophobic (does not like water).
Cholesterol is what makes
the membrane rigid. It increases the strength of the membrane by preventing it
from becoming too flexible. Also prevents the phospholipids from moving around
too much and helps anchor the proteins within the membrane.
Proteins provide a way
for transporting molecules and information across the plasma membrane.
Molecules cross
the plasma membrane by passive transport (diffusion or osmosis), active
transport and endocytosis or exocytosis.
Passive
transport
does not need molecules to pass through a channel. The molecules attach to a
membrane protein that triggers a change in the protein’s shape, transfers the
molecule to the other side of the membrane, and releases it. Direction of
movement is always from a higher concentration to a lower concentration and
does not require the cell to expend energy.
Picture: (Johnson 2012, 2010, 2008 p.59)
Diffusion is molecules in
a gas or liquid that move about randomly and collides into other molecules
causing them to change direction.
Osmosis is the net
diffusion of water across the membrane. Net diffusion requires that there is a
difference in concentration between two points. Once the concentration of
molecules is the same, a state of equilibrium exists and the molecules are able
to diffuse randomly in all directions.
Picture: (Johnson 2012,
2010, 2008 p.59)
Active
transport
moves from lower concentration to a higher concentration and requires energy.
In order to move molecules against the concentration gradient ATP must be used.
ATP breaks down to ADP and the energy is transferred to the protein and the
protein changes shape. This energy is the used to transport one or more
molecules across the plasma membrane.
These
proteins are known as pumps. Some pumps can transport several different
molecules at once and in both directions at the same time. One of the pumps is
known as the sodium-potassium pump. This pump uses energy to transport sodium
out of the cell and potassium into the cell. This pump is essential for the
regulation of cell volume. When the sodium leaves so does water. By decreasing
pumping, the cell volume increases and so does water in the cytoplasm.
Picture: (Johnson 2012,
2010, 2008 p.60)
Endocytosis moves materials
into the cell. Also known as bulk support.
Exocytosis moves materials
out of the cell. Also known as bulk support.
·
Information
is transferred across the plasma membrane using receptors.
Receptors use protein to
span the membrane required for transmission of information to and from the
cell.
Receptor
sites
(on receptor proteins) interact with signal molecules. A change is triggered
within the cell as a result of binding of signal molecule to receptor site
(Oellers, Online Presentation).
·
Different
cell types have different receptor proteins.
Isotonic
Extracellular fluid maintains cell volume.
The
sodium potassium pump keeps homeostatic regulatory processes that keep the
tonicity of the extracellular fluid relatively constant.
Johnson
2012, 2010, 2008 states that tonicity is the relative
concentration of solutes in two fluids. Water can diffuse across the cell
membrane easily so for the cell to control its volume also depends on the
tonicity of the extracellular fluid.
Variations
in Tonicity.
Hypertonic is
extracellular ionic concentration higher than intracellular. Water will diffuse
out of the cell and the cell will shrink and die.
Hypotonic is
extracellular ionic concentration lower than intracellular concentration. Water
will diffuse into the cell and the cell may swell and burst.
Some
extracellular fluid is isotonic this is the fluid concentration inside and
outside of the cell.
Extracellular
and intracellular ionic concentrations are equal.
Cell
maintains a normal volume in isotonic extracellular fluids.
Regulatory
mechanisms maintain extracellular fluid that is isotonic with intracellular
fluid.
Internal
structures carry out specific functions
Inside
the cell is membrane-bound and non-membrane bound structures.
The
membrane-bound structures are called organelles. Organelles are like
tiny organs that have a specific function to perform.
The
nucleus controls the cell (organelle). This is the information center of
the cell and contains most of the cell’s genetic material (DNA).
The
nuclear membrane is the outer surface of the nucleus that consists of a
double-layered membrane. This keeps the DNA within the nucleus.
The
nucleolus is within the nucleus where the ribosomes are formed.
Ribosomes
are
small structures of RNA and certain proteins responsible for making specific
proteins.
There
are 2 styles of ribosomes:
Free
floating in cytoplasm and bound- attached to the outer surface of the ER
(endoplasmic reticulum).
Picture: (Johnson 2012,
2010, 2008 p.65)
The
ER manufactures most other cellular production in the rough ER.
The
rough ER contains ribosomes
The
smooth ER does not contain ribosomes and is responsible for packaging
the proteins and other productions of the ER and prepares them for shipment to
the Golgi apparatus in vesicles.
The
Golgi apparatus receives substances from the ER, refines them into final
products and packages them into vesicles for their final destination.
·
There
are different types of vesicles: (Oeller’s, Online Presentation)
Some
store and ship, others are secretory vesicles (sweat glands), endocytic
vesicles- come into the cell, peroxisomes (metabolism) breaks down free
radicals to water and contains enzymes that detoxify, lysosomes contains
digestive enzymes that engulf bacteria and spits them out through the process
of endocytosis.
Johnson
2012, 2010, 2008 states that enzymes are any various
proteins that are capable of producing certain chemical changes in organic
substances by catalytic action as in digestion.
·
Energy
Sources for the cell
Picture: (Johnson 2012,
2010, 2008 p.68)
The
mitochondria provide energy. They are organelles that manufacture ATP
for the cell and are surrounded by a double membrane. Utilizes oxygen (cellular
respiration) and produces carbon dioxide (ATP).
Fats
and Glycogen are sources of energy as well.
Fats
include triglycerides. They have twice the energy of carbohydrates.
Glycogen
stores carbohydrates. This energy is used first then when expended moves into
the fat cells for energy.
Cells have
structures for support and movement
Structural
elements for support and movement include the cytoskeleton, cilia and flagella
and centrioles.
The
cytoskeleton forms a supportive framework for the cell inside the
cytoplasm.
Made
of proteins 2types:
1)
Microtubules
are tiny hollow tubes
2)
Microfilaments
are thin solid fibers.
Cilia
and flagella
are specialized for movement. Cilia are short and are found on cells lining
airways. Cilia move materials along the surface of a cell with a brushing
motion.
Flagella are long and extend from the
surface. They move the entire sperm cell from one place to another in a whip
like movement.
Centrioles are short, rod
like microtubular structures located near the nucleus. They are essential to
cell division by aligning and dividing the genetic material of the cell.
Cells use and
transform matter and energy
Living
cells can release energy stored in the chemical bonds of molecules and use it
to build, store and break down other molecules.
Metabolism refers to all
of a cell’s chemical processes.
Metabolic
pathways
are where the chemical reactions in an organism take place, where one reaction follows
another in order. They either create molecules and use energy or break them
down and liberate energy.
Some
metabolic pathways are linear where the product (end material) from one
chemical reaction becomes the substrate (starting material) for the next.
There
are 2 basic metabolic pathways:
1)
Anabolism molecules are assembled
into larger molecules that contain more energy achieved through the dehydration
synthesis. This process requires energy and stores energy.
2)
Catabolism is larger molecules that are broken
down. This process releases energy.
Requires enzymes used to break down nutrients and
recycle cell components.
The primary source of energy for a cell is ATP,
produced within the mitochondria by the complete breakdown of glucose to carbon
dioxide and water.
Mitochondria are the organelles responsible for
providing most of this useable energy; they are also known as the cells power
plants.
·
Glucose
provides the cell with energy. Energy is glucose used to generate ATP. In the
absence of glucose, other carbohydrates, fats and proteins can be catabolized
to generate ATP.
The production of ATP from glucose requires four
consecutive stages (Oeller’s, Online Presentation)
Picture: (Johnson 2012,
2010, 2008 p.75)
1)
Glycosis- occurs in cytoplasm. Series of 10
reactions that split glucose into 2 molecules of pyruvic acid. 2 ATP are
produced (net). High-energy electrons and hydrogen ions are removed and picked
up by a coenzyme NAD+ forming NADH.
NAD+
gets stuck on hydrogen and molecules and forms NADH.
2)
Preparatory step for Citric Acid Cycle- Production of
carbon dioxide and NADH leads into the citric acid cycle. Pyruvate enters
mitochondria and is converted to acetyl group and carbon dioxide. High-energy
electrons and hydrogen ions are removed and picked up by a conenzyme NAD+,
forming NADH. The acetyl group joins to a coenzyme (A) to form acetyl CoA. Acetyl
CoA will enter the citric acid cycle.
3)
Citric Acid Cycle produces ATP, more NADH and
FADH2 occurs in the mitochondria. Extracts high-energy electrons to form NADH
and FADH2. Produces 2 ATP and carbon dioxide.
4)
Electron Transport System generates ATP
in the mitochondria. Properties of hydrogen and electrons make a lot of ATP.
Uses oxygen to make water. Takes electrons from NADH and FADH2. The movement of
electrons from one electron carrier to the next releases energy that is
harvested to generate ATP. When ATP is done going through the system it
attaches to oxygen. Final electron acceptor is Oxygen, which forms water upon
receiving electrons and hydrogen ions. ATP generated by ADP forms enzyme.
·
Anaerobic pathways make energy available without
oxygen. Cellular response cannot continue in the absence of oxygen. Glycolysis
will continue and pyruvate will build up. Pyruvate will be converted to lactic
acid and will cause muscles to have a burning sensations if there is a buildup
of lactic acid. 2 ATP produces per molecule of glucose. When oxygen is available,
lactic acid will be metabolized aerobically.
References
Johnson, M. D. (2012, 2010, 2008).
Human Biology: concepts and current issues, sixth edition. Pearson Education,
inc.; Benjamin Cummings.
Oellers, J. (n.d). Online
Presentation: Ch1. Human Biology, Science, and Society. Retrieved February 2,
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