Transcript Cellular Respiration - Hss-1.us

Introduction to Cells (Cytology Part II)
• Cell Processes
• BJ: Chapter 4 Cytology Part 2: Cellular
Processes pp 95 - 121 (BJ2 89)
• AP: Module #6 The Cell pp 176 -195
• Reading Assignments
• Homework Assignment
– Chap 4 Review Questions
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Cellular Processes BJ2 89
Involves the study of how energy is used for the basic life process.
Takes more energy to build an energy storing molecule than can be stored in the molecule
Also energy's lost when molecule is broken apart by the cell to access the energy.
Autotrophs: An autotroph [α] is an organism that produces complex organic compounds from simple
inorganic molecules using energy from light (by photosynthesis) or inorganic chemical reactions.
Autotrophs are the producers in a food chain, such as plants on land or algae in water. Bacteria which
derive energy from oxidizing inorganic compounds (such as hydrogen sulfide, ammonium and ferrous iron)
are chemoautotrophs, and include the lithotrophs.
Heterotroph (chemoorganotrophy: Greek ἕτερος heteros = another and τροφή trophe = nutrition) is an
organism that uses organic substrates to get its chemical energy for its life cycle. This contrasts with
autotrophs such as plants which are able to directly use sources of energy such as light to produce organic
substrates from inorganic carbon dioxide. The Cyanobacteria Synechocystis sp. PCC 6803 is an example
of an autotroph.
Heterotrophs are known as consumers in food chains and obtain organic carbon by eating other
heterotrophs or autotrophs. All animals are heterotrophic, as well as fungi and many bacteria. Some
animals, such as corals, form symbiotic relationships with autotrophs and obtain organic carbon in this
way. Furthermore, some parasitic plants have also turned fully or partially heterotrophic, while so-called
carnivorous plants consume animals to augment their nitrogen supply but are still autotrophic.
For a species to be termed a heterotroph, it must obtain its carbon from organic compounds. If it obtains
nitrogen from organic compounds, but not energy, it will be deemed an autotroph. If a species obtains
carbon from organic compounds then there are two possible subtypes of these heterotrophs:
* photoheterotroph — obtains energy from light but must still obtain carbon in an organic form
* chemoheterotroph — obtains energy from the consumption of organic or inorganic molecules, and
utilizes an organic source of carbon
Photosynthesis – see AP p 144 (BJ2 90)
• Basic balanced reaction:
• Water + CO2 + Light → Sugar and O2↑
• http://www.emc.maricopa.edu/faculty/farab
ee/BIOBK/BioBookPS.html
ATP - The Energy Currency in
Cells
• Adenosine-5'-triphosphate (ATP) is a multifunctional nucleotide, and
plays an important role in cell biology as a coenzyme that is the
"molecular unit of currency" of intracellular energy transfer.In this role,
ATP transports chemical energy within cells for metabolism. It is
produced as an energy source during the processes of
photosynthesis and cellular respiration and consumed by many
enzymes and a multitude of cellular processes including biosynthetic
reactions, motility and cell division. ATP is made from adenosine
diphosphate (ADP) or adenosine monophosphate (AMP), and its use
in metabolism converts it back into these precursors. ATP is therefore
continuously recycled in organisms, with the human body turning over
its own weight in ATP each day.
• The two reactions:
– ADP + P + energy → ATP (Energy Storage)
– ATP → ADP + P + energy (Energy Extraction)
Chlorophyll and Light
• Chlorophyll is the molecule that absorbs sunlight and uses
its energy to synthesize carbohydrates from CO2 and water.
This process is known as photosynthesis and is the basis
for sustaining the life processes of all plants. Since animals
and humans obtain their food supply by eating plants,
photosynthesis can be said to be the source of our life also.
• Types of chlorophyll:
– There are 4 different types of chlorophyll: Chlorophyll a, b, c and d
• Chlorophyll a - most common
• Chlorophyll b - in seedlings
• There are other pigment that absorb other wavelengths and
pass energy to Chlorophyll a
The molecular structure of
chlorophylls.
Process of Photosynthesis
• Basic balanced reaction:
• More complete reaction: later studies that
water is a by product or photosynthesis so a
more complete description of the reaction is:
Conditions Necessary for
Photosynthesis
• A supply of certain wavelengths of light (see Figure 4A-4 page 93 BJ2)
– Need enough energy to energize the
chlorophyll molecule - need daylight
– Sufficient CO2 - not generally a problem
– Proper temperatures - varies with plant - too
hot stops and below freezing stops
– Sufficient H2O - too dry stops
Photosynthesis occurs in two
phases: Photo and Dark
• Photo phases - occurs in light - energy
absorbed an energizes chlorophyll
– Photo phases - occurs in light - energy absorbed an
energizes chlorophyll. Two things happen during
this phase
• Photolysis - breaking apart of water molecule
• From ATP form ATP and P
– (ADP + P + energy → ATP)
Dark Phase
• Name not related to time of day, but refer
to the fact need the product of the photo
phase to occurs
– ATP→ ADP + P + energy reaction occurs
during this phase
– See diagrams on page 94
Phases of Photosynthesis
Light and Photosynthesis
Absorption spectrum of several plant pigments (left) and action spectrum of elodea
(right), a common aquarium plant used in lab experiments about photosynthesis. I
Cellular Respiration
• Cellular respiration is the set of the metabolic reactions and processes that
take place in organisms' cells to convert biochemical energy from nutrients
into adenosine triphosphate (ATP), and then release waste products. The
reactions involved in respiration are catabolic reactions that involve the
oxidation of one molecule and the reduction of another.
• Nutrients commonly used by animal and plant cells in respiration include
glucose, amino acids and fatty acids, and a common oxidizing agent
(electron acceptor) is molecular oxygen (O2). Bacteria and archaea can also
be lithotrophs and these organisms may respire using a broad range of
inorganic molecules as electron donors and acceptors, such as sulfur, metal
ions, methane or hydrogen. Organisms that use oxygen as a final electron
acceptor in respiration are described as aerobic, while those that do not are
referred to as anaerobic.
• The energy released in respiration is used to synthesize ATP to store this
energy. The energy stored in ATP can then be used to drive processes
requiring energy, including biosynthesis, locomotion or transportation of
molecules across cell membranes. Because of its ubiquity in nature, ATP is
also known as the "universal energy currency".
Aerobic respiration:
• Aerobic respiration requires oxygen in order to
generate energy (ATP). It is the preferred method
of pyruvate breakdown from glycolysis and requires
that pyruvate enter the mitochondrion in order to be
fully oxidized by the Krebs cycle. The product of
this process is energy in the form of ATP
(Adenosine Triphosphate), by substrate-level
phosphorylation, NADH and FADH2.
• Basic reactions
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– (Resp) C6H12O6 (aq) + 6 O2 (g) → 6 CO2 (g) + 6 H2O (l)
Anaerobic Respiration
See Figure 4A-8 p 101
• Without oxygen, pyruvate is not metabolized by cellular respiration but
undergoes a process of fermentation. The pyruvate is not transported into
the mitochondrion, but remains in the cytoplasm, where it is converted to
waste products that may be removed from the cell. This serves the purpose
of oxidizing the hydrogen carriers so that they can perform glycolysis again
and removing the excess pyruvate. This waste product varies depending on
the organism. In skeletal muscles, the waste product is lactic acid. This type
of fermentation is called lactic acid fermentation.
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In yeast, the waste products are ethanol and carbon dioxide. This type of
fermentation is known as alcoholic or ethanol fermentation. The ATP
generated in this process is made by substrate phosphorylation, which is
phosphorylation that does not involve oxygen.
• Anaerobic respiration is less efficient at using the energy from glucose since
2 ATP are produced during anaerobic respiration per glucose, compared to
the 38 ATP per glucose produced by aerobic respiration. This is because the
waste products of anaerobic respiration still contain plenty of energy.
Ethanol, for example, can be used in gasoline (petrol) solutions.
Cellular Fermentation:
• The process by which anaerobic respiration
takes place. Cellular fermentation supplies no
ATP energy beyond that obtained form
glycolysis.
– Glycolysis (from glycose, an older term for glucose +
-lysis degradation) is the metabolic pathway that
converts glucose, C6H12O6, into pyruvate, C3H3O3-.
The free energy released in this process is used to
form the high energy compounds, ATP (adenosine
triphosphate) and NADH (reduced nicotinamide
adenine dinucleotide)
Glycolysis
Two types:
• Alcoholic Fermentation: Ethanol fermentation is a biological
process in which sugars such as glucose, fructose, and sucrose
are converted into cellular energy and thereby produce ethanol
and carbon dioxide as metabolic waste products. Because
yeasts perform this process in the absence of oxygen, ethanol
fermentation is classified as anaerobic.
• C6H12O6 → 2C2H5OH + 2CO2
• Lactic Acid Fermentation: Lactic acid fermentation is a
biological process by which sugars such as glucose, fructose,
and sucrose, are converted into cellular energy and the
metabolic product fermental acid. It is the anaerobic form of
respiration that occurs in some bacteria and animal cells in the
absence of oxygen
• C6H12O6 → 2C3H6O3 + 2ATP
Cellular Metabolism and Protein
Synthesis BJ2 4B p 102 - 109
• Metabolism: Metabolism is the set of chemical
reactions that occur in living organisms to
maintain life. These processes allow organisms
to grow and reproduce, maintain their structures,
and respond to their environments. Metabolism
is usually divided into two categories.
Catabolism breaks down organic matter, for
example to harvest energy in cellular respiration.
Anabolism, on the other hand, uses energy to
construct components of cells such as proteins
and nucleic acids.
Protein Synthesis:
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The process in which cells build proteins. . For synthesis of protein, a succession of
tRNA molecules charged with appropriate amino acids have to be brought together with an
mRNA molecule and matched up by base-pairing through their anti-codons with each of its
successive codons. The amino acids then have to be linked together to extend the growing
protein chain, and the tRNAs, relieved of their burdens, have to be released. This whole
complex of processes is carried out by a giant multimolecular machine, the ribosome,
formed of two main chains of RNA, called ribosomal RNA (rRNA), and more than 50
different proteins. This molecular juggernaut latches onto the end of an mRNA molecule
and then trundles along it, capturing loaded tRNA molecules and stitching together the
amino acids they carry to form a new protein chain. Protein biosynthesis, although very
similar, is different for prokaryotes and eukaryotes.
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Structural Protein: Structural proteins are fibrous proteins. The most familiar of the
fibrous proteins are probably the keratins, which form the protective covering of all land
vertebrates: skin, fur, hair, wool, claws, nails, hooves, horns, scales, beaks and feathers.
Equally widespread, if less visible, are the actin and myosin proteins of muscle tissue.
Another group of fibrous structural proteins are the silks and insect fibers. In addition,
there are the collagens of tendons and hides, which form connective ligaments within the
body and give extra support to the skin where needed.
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Polypeptide Chain: A polypeptide is a single linear chain of amino acids.
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Functional Proteins: No formal definition - but proteins that combine with lipids,
carbohydrates or inorganic material for some specific function.
DNA
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DNA The Code of Life: Deoxyribonucleic acid (DNA) is a nucleic acid that contains the
genetic instructions used in the development and functioning of all known living organisms
and some viruses. The main role of DNA molecules is the long-term storage of information.
DNA is often compared to a set of blueprints or a recipe, or a code, since it contains the
instructions needed to construct other components of cells, such as proteins and RNA
molecules. The DNA segments that carry this genetic information are called genes, but
other DNA sequences have structural purposes, or are involved in regulating the use of
this genetic information. Chemically, DNA consists of two long polymers of simple units
called nucleotides, with backbones made of sugars and phosphate groups joined by ester
bonds. These two strands run in opposite directions to each other and are therefore antiparallel. Attached to each sugar is one of four types of molecules called bases. It is the
sequence of these four bases along the backbone that encodes information. This
information is read using the genetic code, which specifies the sequence of the amino
acids within proteins. The code is read by copying stretches of DNA into the related nucleic
acid RNA, in a process called transcription. Within cells, DNA is organized into X-shaped
structures called chromosomes. These chromosomes are duplicated before cells divide, in
a process called DNA replication. Eukaryotic organisms (animals, plants, fungi, and
protists) store most of their DNA inside the cell nucleus and some of their DNA in the
mitochondria (animals and plants) and chloroplasts (plants only) Prokaryotes (bacteria and
archaea) however, store their DNA in the cell's cytoplasm. Within the chromosomes,
chromatin proteins such as histones compact and organize DNA. These compact
structures guide the interactions between DNA and other proteins, helping control which
parts of the DNA are transcribed.
RNA
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RNA: Ribonucleic acid (RNA) is a biologically important type of molecule that consists of a
long chain of nucleotide units. Each nucleotide consists of a nitrogenous base, a ribose
sugar, and a phosphate. RNA is very similar to DNA, but differs in a few important
structural details: in the cell, RNA is usually single-stranded, while DNA is usually doublestranded; RNA nucleotides contain ribose while DNA contains deoxyribose (a type of
ribose that lacks one oxygen atom); and RNA has the base uracil rather than thymine that
is present in DNA. RNA is transcribed from DNA by enzymes called RNA polymerases and
is generally further processed by other enzymes. RNA is central to the synthesis of
proteins. Here, a type of RNA called messenger RNA carries information from DNA to
structures called ribosomes. These ribosomes are made from proteins and ribosomal
RNAs, which come together to form a molecular machine that can read messenger RNAs
and translate the information they carry into proteins. There are many RNAs with other
roles – in particular regulating which genes are expressed, but also as the genomes of
most viruses.
Three types of RNA:
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Messenger RNA: Messenger ribonucleic acid (mRNA) is a molecule of RNA encoding a chemical
"blueprint" for a protein product. mRNA is transcribed from a DNA template, and carries coding
information to the sites of protein synthesis: the ribosomes.
Transfer RNA: Transfer RNA (abbreviated tRNA) is a small RNA molecule (usually about 74-95
nucleotides) that transfers a specific active amino acid to a growing polypeptide chain at the
ribosomal site of protein synthesis during translation.
Ribosomal RNA: Ribosomal RNA (rRNA) is the central component of the ribosome, the protein
manufacturing machinery of all living cells. The function of the rRNA is to provide a mechanism for
decoding mRNA into amino acids and to interact with the tRNAs during translation by providing
peptidyl transferase activity. The tRNA then brings the necessary amino acids corresponding to the
appropriate mRNA codon.
For a diagram that illustrates all of the metabolic process form Photosynthesis to
protein synthesis see See Figures on p 106.
DNA
RNA
Manufacture of an Amino Acid Chain
• mRNA leaves nucleolus with DNA triplet code passing
through a pore in the nucleolus.
• Ribosome lines up on one end of the mRNA so tRNA
anticodon can line up with mRNA codon.
• One codon and anticodon mathce up, ribosome
moves down the mRNA to next codon.
• Ribosomal enzymes cause amino acids that have
been formed, to form the peptide bond, thus
eventually forming the polypeptide amino acid chain.
• For diagram of manufacture of a polypeptide chain
of amino acids see Fig 4B3 on page 107 BJ2
Metabolism and Homeostasis
• Metabolism - function processes of the organism.
• Homeostasis - a condition where the organism is stable - metabolism is
critical to maintaining homeostasis
• Metabolic Rate: the amount of energy expended at any given time to
maintain life. The rate is dependent on:
• - The organism
• - The environment different
• Basal metabolic rate (BMR) is the amount of energy expended while at rest
in a neutrally temperate environment, in the post-absorptive state (meaning
that the digestive system is inactive, which requires about twelve hours of
fasting in humans). The release of energy in this state is sufficient only for
the functioning of the vital organs, such as the heart, lungs, brain and the
rest of the nervous system, liver, kidneys, muscles and skin.
• Anabolism: The process that build molecules and store energy.
• Catabolism: Process that break down molecules and release energy.