The basic thing to remember about cellular respiration and photosynthesis is that they are reverse reactions. In other words, the products of photosynthesis are the reactants in cellular respiration. You can easily see that in the following:

C6H12O6 + 6O2 6CO2 + 6H2O + Energy

6CO2 + 6H2O + Energy C6H12O6 + 6O2

Photosynthesis is the process that occurs within the chloroplasts (palisade mesophyll mostly), that uses the input of the sun’s energy to produce glucose, and oxygen.

Cellular respiration is the process that occurs within the cytoplasm and mitochondria, that uses oxygen and glucose to produce ATP, and the other byproducts, water and carbon dioxide.

Aerobic respiration requires oxygen. Aerobic respiration occurs in three phases:

• Gylcolysis

• Krebs Cycle (aka Citric acid cycle)

• Oxidative Phosphorylation (electron transport chain)

Anaerobic respiration does not require the presence of oxygen. It is also known as fermentation, and it allows glycolysis to continue when the lack of an electron acceptor shuts down oxidative phosphorylation.In eukaryotes, glycolysis takes place in the cytoplasm, while the Krebs Cycle takes place in the mitochondria, and oxidative phosphorylation (etc) proceeds in the inner membrane of the mitochondria, known as cristae.

Glycolysis and the Krebs cycle strip electrons from glucose and use them to reduce NAD+ and FAD. The resulting electron carriers – NADH, and FADH2 – then donate electrons to an electron transport chain, which gradually steps the electrons down in potential energy until they are finally accepted by oxygen, the final electron acceptor. This results in the formation of water in aerobic organisms.

Pathway Substrate Level Phosphorylation

Oxidative Phosphorylation

Total ATP

Glycolysis 2 ATP 2 NADH = 6 ATP 6

CoA 2 NADH = 6 ATP 6

Krebs Cycle

2 ATP 6 NADH = 18 ATP2 FADH2 = 4 ATP

24

Total 4 ATP 32 ATP 36

How Much ATP From Respiration?

Photosynthesis is the conversion of light energy to chemical energy, stored in the bonds of carbohydrates. The sugars generated by photosynthesis drives cellular respiration. Photosynthesis provides the energy that sustains most life on Earth.Photosynthesis consists of two distinct sets of reactions.

• The light dependent reactions occur in internal membranes of the chloroplast that are organized into structures called thylakoids in stacks known as grana.

• The light independent reactions, known as the Calvin cycle, take place in a fluid portion of the chloroplast called the stroma.ATP and the electron carrier NADPH are produced.

ATP and NADPH are used to reduce CO2 to carbohydrate. Energy is transformed from sunlight into chemical energy in the form of electrons with high potential energy. Excited electrons either are used to produce NADPH or are donated to an electron transport chain, which results in the production of ATP.

Some plants adapted to hot, arid regions have a different photosynthetic mechanism called CAM photosynthesis.

CAM (Crassulacean Acid Metabolism) photosynthesis is found in cacti and succulents, including the crassula family. During the hot daylight hours their stomata are tightly closed; however they still carry on vital photosynthesis as carbon dioxide gas is converted into simple sugars. How do they do it?

During the cooler hours of darkness their stomata are open and CO2 enters the leaf cells where it combines with PEP (phosphoenolpyruvate) to form 4-carbon organic acids (malic and isocitric acids). The 4-carbon acids are stored in the vacuoles of photosynthetic cells in the leaf. During the daylight hours the 4-carbon acids break down releasing CO2 for the dark reactions (Calvin cycle) of photosynthesis inside the stroma of chloroplasts.

The adaptive advantage of CAM photosynthesis is that plants in arid regions can keep their stomata closed during the daytime, thereby reducing water loss from the leaves through transpiration; however, they can still carry on photosynthesis with a reserve supply of CO2 that was trapped during the hours of darkness when the stomata were open.

The CO2 is converted into glucose through the Calvin-Benson cycle with the help of ATP and NADPH, which were synthesized during the light reactions of daylight in the grana of chloroplasts.

The tropical strangler Clusia rosea exhibits CAM photosynthesis. This unusual tree starts out as an epiphyte on other trees and then completely envelops and shades out its host.

C4 plants are so named because they form a four-carbon compound as the first product of the dark reactions of photosynthesis. Several thousand species in at least 19 families use the C4 pathway.

Agriculturally important C4 plants are sugarcane, corn, and members of the grass family.

• In C4 plants, such as sugarcane, these two steps are separated spatially; the two steps take place in two cell types. (Mesophyll, and bundle sheath cells)

• In CAM plants, such as pineapple, the two steps are separated temporally (time); carbon fixation occurs at night, and the Calvin cycle functions during the day.

Both C4 and CAM are two evolutionary solutions to the problem of maintaining photosynthesis with stomata partially or completely closed on hot, dry days. However, it should be noted, that in all plants, the Calvin cycle is used to make sugar from carbon dioxide.

Typical, or C3 photosynthesis is carried out by most plants growing in areas with sufficient water.  In this type of photosynthesis, an enzyme called RuBP carboxylase grabs CO2 in one of the first steps of photosynthesis.  This works fine as long as there is plenty of carbon dioxide and relatively little oxygen.  If there is too much oxygen, RuBP carboxylase will grab that instead of the CO2, and a process called photorespiration will occur.  Photorespiration does not help build up any sugars, so if photorespiration occurs, growth stops. 

Normally, oxygen (produced in photosynthesis) exits the plant through the stomata; however, if there isn't enough water available (as would happen under bright, hot, sunny conditions), excess oxygen may build up and trigger photorespiration, because the stomata close to conserve water. If water is present, however, this process is very efficient because both the light reactions and Calvin Cycle can occur simultaneously in the same cell, and almost all of the cells in the leaf will be producing sugars.

C4 photosynthesis differs from C3 in 2 key ways.  First, instead of RuBP carboxylase, a different enzyme, PEP carboxylase, is used to grab CO2.  The PEP carboxylase is less likely to bind to oxygen, thus photorespiration is less likely to occur, a decided advantage under hot, dry conditions where water may be scarce and the stomata remain closed for long periods, trapping oxygen in the plant.  This process is relatively inefficient, but if water is in short supply the inefficient C4 route is still better than the C3 route with photorespiration.  Also, since there are fewer cells involved in making sugars, fewer sugars can be made.Thus desert plants can survive the dry conditions, but at the cost of rapid growth.  Desert plants are often very slow to grow, and this is one of the reasons they invest so much energy in defensive structures (spines) and chemicals C3  is best under moist conditions, C4 under warm, sunny, dry conditions, CAM under desert conditions  

Photosynthesis Cellular Respiration

Food synthesized Food broken down

Energy from sun stored in glucose

Energy of glucose released

Carbon dioxide taken up Carbon dioxide given off

Produces sugars from PGAL Produces CO2 and H2O

Oxygen given off Oxygen taken in

Requires light Does not require light

Occurs only in presence of chlorophyll

Occurs in all living cells

Prokaryotes divide through binary fission. In a nutshell, binary fission is a simplistic form of mitosis. There are two processes through which eukaryotic cells can divide: • Mitosis

• Meiosis

Mitosis is responsible for:

• growth of tissue

• repair of tissue

• cell replacements in multicellular eukaryotes

Cell Death

Includes: Interphase, and

Mitosis. A great deal goes on during interphase, and while we used to call this the “resting” phase, the cell is hardly at rest. After interphase, an even more active part of the cell cycles progresses. It is known as Mitosis. Mitosis has four stages:

• Chromosomes are visible threads.

• Some fibers cross the cell to form the mitotic spindle.

• Nuclear envelope breaks down•Microtubules from spindle at each pole push apart.

• Microtubules attach to one of two sister chromatids of each chromosome pair

• Centrioles begin moving to opposite ends of the cell and fibers extend from the centromeres. All chromosomes have

become aligned at the spindle equatorAt this stage of mitosis, the chromosomes are most tightly condensed.

In animals

The sister chromatids of each chromosome pair separate from each other and move to opposite spindle poles.Once these sister chromatids are separated, we recognize them as chromosomes

As soon as the two clusters of chromosomes get to the poles of the cells, telophase gets under way.

Once the nuclear membranes are synthesized, and the chromosomes are separated from the cytoplasm, mitosis is complete.

• In animal cells, a cleavage furrow forms

• In plant cells, a cell plate forms because of the cell wall

In Plants

•Meiosis results in the Meiosis results in the formation of haploid (n) cells.formation of haploid (n) cells.

–In Humans, these are the Ova (egg) and In Humans, these are the Ova (egg) and sperm.sperm.–Ova are produced in the ovaries in Ova are produced in the ovaries in femalesfemales–Sperm are produced in the testes of Sperm are produced in the testes of males.males.

Meiosis II

Meiosis I

Most important phases in meiosis:

Chiasma

Crossing over occurs and form chiasma. An actual blending of parental chromosomes occurs during this phase. It accounts for great genetic diversity among filial generations.

Chiasmata separate. Chromosomes, each with two chromatids, move to separate poles. Many genetic chromosomal abnormalities occur during this stage due to improper separation.

Meiosis II proceeds directly after Telophase I, and is similar to mitosis. It is the stage at which the reduction in the number of chromosomes occurs.

The structure of DNA was worked out by James Watson and Francis Crick in 1953. They were awarded the Nobel Prize in 1962 for this work. Single-ringed pyrimidines:

Double-ringed purines:

Which one is deoxyribose, and why?

What type of bond joins the nitrogenous bases together?

Deoxyribose Ribose

Semiconservative Model:Semiconservative Model:Watson and Crick showed:Watson and Crick showed: the two

strands of the parental molecule separate, and each functions as a template for synthesis of a new complementary strand.

• The replication fork opens with the help of the enzyme helicase.

• DNA polymerase adds nucleotides at the free 3’ end, forming new DNA strands in the 5’ to 3’ direction only in a continuous fashion, while checking for errors.• On the other strand, assembly is discontinuous because the exposed –OH group is the only place where nucleotides can be joined together.• DNA ligase then helps to wind the new strands together into a double helix.

Occurs inside the nucleus when DNA is copied by mRNA. Remember Uracil replaces Thymine in RNA.

Transcription is initiated at a “promoter, and ended at a terminator, and it only occurs on the DNA strand situated in the 3’-5’ direction.

A promoter and terminator are specific sequences in the DNA that code for the “beginning” and the “end”.Only the segment that codes for a specific protein needed by the cell

(a gene), will unwind and create the mRNA transcript.

There are coding and non-coding sections found within DNA. They are exons, and introns.

These non-coding sections are also copied by the complementary pre-mRNA, but must be “clipped” from the molecule before it can leave the nucleus for translation.The free transcript is not completed yet. Before it can leave the nucleus it must be modified. First the introns must be lysed out, and then a protein cap and a polyA tail must be added.

Finally we have a mature mRNA molecule, fully functional, and able to leave the nucleus.

The mRNA moves through the cytoplasm to the ribosomal subunit (rRNA). Once there, the triplet code (codons) message is read by the tRNA, as anticodons are brought to the ribosome where polypeptides are assembled. This is called “translation”. So…translation occurs at the ribosome, while transcription occurs in the nucleus.

The DNA’s original message is now carried on the mRNA (messenger RNA), and is read in three-letter sequences known as codons.

The tRNA (transfer RNA) interprets those codon “words”, and carries in appropriate amino acids corresponding to the codon. While it does this, it is assembling a protein (polypeptide chain of amino acids.) The three letter sequence on the tRNA is the “anti-codon”

Each codon of mRNA

codes for a different

amino acid which is

associated with a

specific tRNA’s

anticodon.Know how to determine possible sequences using the codon chart!

Enzymes are globular proteins that act as catalysis (activators or accelerators) for metabolic reactions.

Enzyme Characteristics:• The substrate is the substance or substances upon which the enzyme acts. For example, amylase catalyzes the breakdown of the substrate amylose (starch)

• Enzymes are substrate specific. The enzyme amylase, for example, catalyzes the reaction that breaks the α-glycosidic linkage in starch but cannot break the β-glycosidic linkage in cellulose.

• The induced-fit model describes how enzymes work. Within the enzyme, there is an active site with which the reactants readily interact because of the shape, polarity, or other characteristics. The interaction of the substrate and the enzyme causes the enzyme to change shape. Once the reaction takes place, the product is released.

• An enzyme is unchanged as a result of a reaction. It can perform its enzymatic function repeatedly.

• The efficiency of an enzyme is affected by temperature and pH. Optimal temperature for most human enzymes is 98.6°. Above 104°, these enzymes begin to lose their ability to catalyze reactions as they become denatured. The enzyme pepsinogen becomes active only at very low pH, as it works on digestion of proteins in the stomach.

• The standard suffix for enzymes is “ase”, so it is easy to identify enzymes that use this ending (although some do not).

• Noncompetitive inhibitor binds to an enzyme at locations other than an active site. The inhibitor changes the shape of the enzyme which disables its enzymatic activity.

• Competitive inhibition is where a substance mimics the substrate, inhibiting an enzyme by occupying the active site. The mimic displaces the substrate and prevents the enzyme from catalyzing the substrate.

The Hardy-Weinberg principle is a tool we can use to calculate the frequency of particular alleles in a population. The Hardy-Weinberg model enables us to compare a population's actual genetic structure over time with the genetic structure we would expect if the population were in Hardy-Weinberg equilibrium (or not evolving) If the parent generation had 92% B and 8% b and their offspring collectively had 90% B and 10% b, it would be evident that evolution had occurred between the generations. There are five basic assumptions that must be occurring in a population in order to be in Hardy-Weinberg equilibrium. They are:

3.  mutation is not occurring

5.  natural selection is not occurring

1.  the population is infinitely large, and that genetic drift is not an issue within the population.

4. all mating is totally random

2.  there is no gene flow, or migration in or out of the population

Hardy Weinberg shows us that microevolution is inevitable because the chance that all these assumptions can occur is impossible!

p² + 2pq + q² = 1

p is defined as the frequency of the dominant allele q is the frequency of the recessive allele for a trait controlled by a pair of alleles (A and a)

p + q = 1

In this equation, p² is the predicted frequency of homozygous dominant (AA) organisms in a population, 2pq is the predicted frequency of heterozygous (Aa) organisms, and q² is the predicted frequency of homozygous recessive (aa) ones!

1. You have sampled a population in which you know that the percentage of the homozygous recessive genotype (aa) is 36%. Using that 36%, calculate the following: A. The frequency of the "aa" genotype.

B. The frequency of the "a" allele. C. The frequency of the "A" allele. D. The frequencies of the genotypes "AA" and

"Aa."

Given: .36

.6

.4

.16; .48

A species is usually defined as a group of individuals capable of interbreeding. Speciation, the formation of new species, occurs by the following processes, as illustrated below: Allopatric speciation begins

when a population is divided by a geographic barrier so that interbreeding between the two is prevented. Once reproductively isolated by the barrier, gene frequencies in the two populations can diverge due to natural selection, mutation, or genetic drift.

If the gene pools sufficiently diverge, then interbreeding between the populations will not occur if the barrier is removed. As a result, new species have formed.

Sympatric speciation is the formation of new species without the presence of a geographic barrier. This may happen in several different ways:

Balanced Polymorphism among subpopulations may lead to speciation. Suppose a population of insects possess a polymorphism (many genes code) for color. Each color provides a camouflage to a different substrate. And if not camouflaged, the insect is eaten. Under these circumstances, only insects with the same color can associate and mate. Similarly colored insects are reproductively isolated from other subpopulations, and their gene pools diverge as in allopatric speciation.

Polyploidy is another form of sympatric speciation. When a population is in possession of more than the normal two sets of chromosomes found in diploid (2n) cells. Polyploidy often occurs in plants (and occasionally animals) where triploid (3n), tetraploid (4n), and higher ploidy chromosome numbers are found.

Polyploidy occurs as a result of nondisjunction of all chromosomes during meiosis, producing two viable diploid gametes and two sterile gametes with no chromosomes. A tetraploid zygote can be established when a diploid sperm fertilizes a diploid egg. Since normal meiosis in the tetraploid individual will continue to produce diploid gametes, reproductive isolation with other individuals in the population (and thus speciation) occurs immediately in a single generation.

Adaptive radiation is the relatively rapid evolution of many species from a single ancestor. It occurs when the ancestral species colonizes an area where diverse geographic or ecological conditions are available for colonization. Variants of the ancestral species diverge as populations specialize for each set of conditions.

• the marsupials of Australia began with the colonization and subsequent adaptive radiation of a single ancestral species.

• the fourteen species of Darwin’s finches on the Galapagos Islands evolved from a single ancestral South American mainland species.