Biology Flashcards
Metabolism
The sum of all chemical reactions that occur in the body. Can be divided into CATABOLIC REACTIONS and ANABOLIC REACTIONS
Catabolic Reactions
which break down large chemicals and release energy
Anabolic Reactions
Which build up large chemicals and require energy
Ingestion
The acquisition and consumption of food and other raw materials
Digestion
The process of converting food into a usable soluble form so it can pass through membranes in the digestive tract enter the body
Absorption
The passage of nutrient molecules through the lining of the digestive tract into the body proper. Absorbed molecules pass through cells lining the digestive tract by diffusion or active transport
Transport
The circulation of essential compounds required to nourish the tissues and the removal of waste products from the tissues
Assimilation
The building up of new tissues from digested food materials
Respiration
The consumption of oxygen by the body. Cells use oxygen to convert glucose into ATP, a ready source of energy for cellular activities
Excretion
The removal of waste products (such as carbon dioxide, water, and urea) produced during metabolic processes like respiration and assimilation
Synthesis
The creation of couple molecules from simple ones (anabolism)
Regulation
The control of physiological activities. The body’s metabolism functions to maintain its internal environment in a changing external environment.
Homeostasis
The steady state of the internal environment
-includes regulation by hormones and the nervous system
Irritability
the ability to respond to a stimulus and is part of regulation
Growth
An increase in size caused by cell division and synthesis of new materials
Reproduction
The generation of additional individuals of a species
External Respiration
refers to the entrance of air into the lungs and the gas exchange between the alveoli and the blood
Internal Respiration
Includes the exchange of gas between the blood and the cells and the intracellular processes of respiration.
What are the favored FUEL molecules in cells?
Carbohydrates and Fats
Dehydrogenation
oxidation reaction
-high-energy hydrogen atoms are removed from organic molecules
Glycolysis
1st stage of glucose catabolism
-is a series of reactions that leads to the oxidative breakdown of glucose into two molecules of pyrvuate, the production of ATP, and the reduction of NAD+ and NADH
Where does glycolysis occur?
cytoplasm
Substrate Level phosphorylation
ATP synthesis is directly coupled with the degradation of glucose without the participation of an intermediate molecule such as NAD+.
How many ATP’s are produced per glucose molecule in glycolysis
2 ATP per glucose molecule
How many NADH is produced per PGAL during glycolysis
One NADH is produced per PGAL.
- Since two PGAL are produced per glucose molecule there is a net production of two NADH
Under anaerobic conditions what happens to pyruvate after glycolysis?
pyruvate is reduced during the process of Fermentation
Under aerobic conditions what happens to pyruvate after glycolysis?
Pyruvate is oxidized during cellular respiration in the mitochonidria
Fermentation
-NAD+ must be regenerated for glycolysis to continue in the absence of oxygen. Accomplished by reducing pyruvate into ethanol or lactic acid.
What does fermentation produced?
Produced only 2 ATP per glucose Molecule
Alcohol Fermentation
- occurs in yeast and some bacteria.
- the glycolysis is converted to ethanol
- NAD+ is regenerated and glycolysis continues
Lactic Acid Fermentation
- occurs in certain fungi and bacteria and in human muscle cells during strenuous activity.
- When the oxygen supply to muscle cells lags behind the rate of glucose catabolism, the pyruvate is generated is reduced to lactic acid
- Also, like alcohol fermentation the NAD+ is regenerated when pyruvated is reduced so glycolysis can continue
Cellular Respiration
- most efficient catabolic pathway used by organisms to harvest the energy stored in glucose.
- Aerobic Process
What is the net production of ATP in cellular respiration?
can yield 36-38 ATP
What is the final accepter of electrons during the final stage of glucose oxidation in cellular respiration?
Oxygen acts as the final acceptor of electrons that are passed from carrier to carrier
Where do the metabolic reactions of cell respiration occur?
Eukaryotic Mitochondrion and are catalyzed by reaction-specific enzymes
What are the stages of cellular Respiration?
1) Pyruvate Decarboxylation
2) Citric Acid Cycle
3) Electron Transport Chain
Pyruvate Decarboxylation
The pyruvate formed during glycolysis is transported from the cytoplasm into the mitochondrial matrix where it is decarboxylated(LOSES a CO2)
- The acetyl group that remains is transferred to coenzyme A to form acetyl-CoA
- NAD+ is reduced to NADH
Citric Acid Cycle/ Krebs Cycle
The cycle begins when the acetyl group (2 C’s) from the acetyl-CoA combines with oxaloacetate (4 C’s) to for the 6-carbon CITRATE.
-Through the reactions, 2 CO2 are released, and oxaloacetate is regenerated for use in another turn of the cycle.
How much ATP is produced for each turn of the citric acid cycle?
One ATP is produced by substrate level phosphorlation via GTP intermediate
What is the net production of the citric acid Cycle?
6 NADH
2 FADH2
2 ATP
Electron Transport Chain
-complex carrier mechanism located on the inside of the INNER MITOCHONDRIAL MEMBRANE.
-ATP is produced when high-energy potential electrons are transferred from NADH and FADH2 to oxygen by a series of carrier molecules located in the inner mitochondrial membrane.
As the electrons are passed from carrier to carrier-free energy is released- which is used to form ATP
-Most molecules are CYTOCHROMES
-redox reactions continue to occur as the electrons are transferred from one carrier to the next
-The last carrier of the ETC passes its electrons to the final electron accepter O2.
What is the function of O2 in the Electron transport chain?
is the final electron acceptor. also picks up a pair of hydrogen ions from the surrounding medium, forming water
Net production of substrate phosphorylation?
degradation of one glucose molecule yields a net of two ATP from glycolysis and one ATP for each turn of the Citric Acid Cycle.
–A total of 4 ATP are produced!!
Oxidative Phosphorylation
- process that produces more than 90 percent of the ATP used by the cells in our body
- major steps occur within the ETC or respiratory chain of the mitochondria
Steps at the end of the ETC chain
Steps at the end of ETC chain, where ATP are generated:
- The respiratory enzymes continually pum hyrdogen ions from the matrix of the mitochondria to the inter membrane space, which creates a large concentration gradient
- Hydrogen ions pass thorough channels in the respiratory enzymes along the concentration gradient at the end of the ETC.
- As the hydrogen ions pass through these enzymes, the energy released is used to convert ADP to ATP.
Oxidative Phosphorylation Yields
>
What is the tool amount of ATP produced during Eukaryotic Glucose Catabolism?
4 via substrate-level phosphorylation
32 via oxidative phosphorlation
36 TOTAL ATp
What is the tool amount of ATP produced for Prokaryotes
38 ATP because the two NADH of glycolysis doesn’t have any mitochondrial membranes to cross and therefore don’t lose energy
What is the preferential order of alternate energy sources when glucose is running low?
1) other carbohydrates
2) Fats
3) proteins
Alternate Energy sources
-are first converted to either glucose or glucose intermediates, which can then be degraded in they glycolytic pathway and the citric acid cycle
Cytochromes
electron carriers that resemble hemoglobin in the structure of their active site.
- the functional unit contains a central iron atom that is capable of undergoing a reversible redox reaction
- MOST MOLECULES OF THE ETC ARE CYTOCHROMES
Carbohydrates as an alternative energy source
Disaccharides are hydrolyzed into monosaccharides, which can be converted into glucose or glycolytic intermediated
-Glycogen stored in the liver can be converted, when needed, into a glycolytic intermediate
Fat as an alternative energy source
Fat molecules are stored in adipose tissue in the form of triglycerides.
-They are hydrolyzed by LIPASES to FATTY ACIDS and GLYCEROL and are carried by the blood to other tissues for oxidation when needed.
Glycerol (FAT) as a alternative energy source
can be converted to PGAL, a glycolytic intermediate
Fatty Acid (FAT)
- Fatty Acid-must first be “activated” in the cytoplasm; this process requires TWO ATP. Once activated the fatty acid is transported into the mitochondrion and taken through a series of Beta-oxidation cycles that convert it into 2-carbon fragments, which are converted into Acetyl-CoA. Acetyl-CoA then enters the Citric Acid cycle.
- With each round of B-oxidation of a saturated fatty acid, one NADH and one FADH2 are generated
What compound in cellular respiration yields the greatest number of ATP per gram?
FATS, which makes them extremely efficient energy storage molecules.
Proteins as a alternative energy source
- most amino acids undergo a TRANSMINATION REACTION-in which they lose an amino group to form an alpha-keto acid
- The carbon atoms of most amino acids are converted into Acetyl-CoA, pyruvate, or one of the intermediates of the citric acid cycle.
- These intermediates enter their respectable metabolic pathway allowing cells to produce fatty acids, glucose, or energy in the form of ATP
Oxidative Deamination
Removes an ammonia molecule directly from the amino acid
Ammonia
is a toxic substance in vertebrates
- fish can excrete ammonia
- insects and birds convert it to uric acid
- mammals convert it to urea for excretion
Catalyst
are any substance that affects the rate of a chemical reaction without itself being changed
Enzymes
- are crucial to all living things because all living systems must have continuously controlled chemical activity.
- They regulate metabolism by speeding up certain chemical reactions
- They affect the reaction rate by decreasing the activation energy
- they are proteins thus thousands of different enzymes can be formed
- many are conjugated proteins and thus have a nonprotein coenzyme (both must be present for the enzyme to function)
- selective
- DO NOT alter equilibrium constants
- Are NOT consumed in the reaction. They will appear in both the reactants and the products
- PH and temperature dependent, with optimal activity at specific pH and temp ranges
- most enzyme catalyzed reactions are reversible
- the produce synthesized by an enzyme can be decomposed by the same enzyme
- an enzyme that synthesizes maltose from glucose can also hydrolyze maltose back to glucose
substrate
the molecule that the enzyme acts upon
active site
area on each enzyme to which the substrate binds
Lock and Key Theory
The spatial structure on an enzymes active site is exactly complementary to the spatial structure of its substrate.
-the two fit together like a lock and key
OR
-Receptors are large proteins that contain a recognition site (lock) that is directly linked to transduction systems. When a drug or endogenous substance (key) binds to the receptor, a sequence of events is started
Induced Fit Theory
More accepted
- the active site is flexible when it comes to its shape
- when the appropriate substrate comes in contact with the active site, the conformation of the active site changes to fit the substrate
Temperatures effect on enzymes
- As temperature increases the rate of the enzyme action increases until an optimal temp is reached (usually around 40 C)
- beyond optimal T, heat alters the shape of the active site of the enzyme molecule and deactivated it, leading to a rapid drop in the rate of active site
pH affect on enzymes
-for each enzyme there is an optimal pH, above an below that pH enzymatic activity declines.
What is the maximal pH of most human enzymes?
7.2 since this is the pH of most body fluids.
-exception is PEPSIN, which works best in highly acidic conditions of the stomach (pH=2)
-pancreatic enzymes work optimally in the alkaline conditions of the small intestine (pH=8.5)
-
How does the concentration of the enzyme and substrate affect the reaction rate
When the concentration of both enzyme and substrate are low, many of the active sites on the enzyme are unoccupied, and the reaction rate is low
increasing the substrate concentration will increase the reaction rate until all of the active sites are occupied. After this point in substrate concentration will not increase the reaction rate, and the reaction is said to have read the maximum velocity, Vmax
Competitive Inhibition
If a similar molecule that is similar to the substrate is present it may be able to bind to the active site of the enzyme. If the substrate and the similar molecule are equal in concentration then they will compete with each other for binding sites on the enzyme and interfere with the enzyme activity.
- known as competitive inhibition because the enzyme is inhibited by the inactive substrate.
- If sufficient quantities of the substrate are introduced then the substrate can over compete the competitor molecule
Non-competitive inhibition
- noncompetitive inhibitor is a substance that forms strong covalent bonds with an enzyme making it unable to bind with its substrate. Thus the noncompetitive inhibitor cannot be replaced
- Addition of excess substrate will not affect the rate of the reaction and the reaction site will never reach Vmax.
- the noncompetitive inhibitor may be bound at , near, or far from the active site.
Allosteric inhibition
when the inhibitation takes place at a site other then the active site.
-the interaction changes the structure of the enzyme so that the active site is also changed
Hydrolysis reactions
function to digest large molecules into smaller components.
Lactase
hydrolyzes lactose to the monosaccharide glucose and galactose
Proteases
degrade proteins to amino acids
Lipases
breakdown lipids to fatty acids and glycerol
Synthesis reactions
can be catalyzed by the same enzymes as hydrolysis sections but the directions of the reactions are reversed
protein synthesis
occurs in the ribosomes and involved dehydration reactions between amino acids
Cofactors
enzymes require the incorporation of these cofactors which is a nonprotein molecule-this is how they become active
-can be metal cations such as Zn2+ and Fe2+ or small organic groups called coenzymes
Prosthetic groups
cofactors that bind to the enzyme by strong covalent bonds
Genes
-are composed of DNA(Deoxyribose bonded to a phosphate group and one of the four nitrogenous bases) and are located on chromosomes
alleles
when a gene exists in more than one form
genotype
the genetic makeup of an individual
Phenotype
the physical manifestations of the genetic makeup
Mendel’s four principles of inheritance
- genes exist in alternative forms (alleles). A gene controls a specific trait in an organism
- An organism has two alleles for each inherited trait, one inherited from each parent
- the two alleles segregate during meiosis, resulting in gametes that carry only one allele for any given inherited trait.
- If two alleles in an individual are different, only one will be fully expressed, and the other will be silent. The expressed allele is said to be dominant while the silent allele is said to be recessive.
Mendel’s Law of Dominance
The dominant allele is expressed in the phenotype
Monohybrid cross
when only one trait is being studied in a cross of two parents
Parental or Pgeneration
the individuals being crossed in a punnet square
F generations or filial
are the progeny generations and are labeled F1,F2, F3, etc.
What are the genotypic and phenotypic ratios produced during a monohybrid cross?
Genotype: 1:2:1
Phenotype: 3:1
Testcross
is a diagnostic tool used to determine the genotype of an organism.
- Only with a recessive phenotype can genotype be predicted with 100 percent accuracy.
- the appearance of the recessive phenotype in the progeny indicates that the phenotypically dominant parent is genotypical heterozygous
Mendels Law of Independent Assortment
-postulated that the inheritance of one such trait is completely independent of any other as long as the genes are on separate chromosomes and assort independently of any other.
Non medelian genetics argument against law of independent assortment
genes on the same chromosome will not follow this rule and instead will stay together unless CROSSING OVER occurs.
Crossing Over
exchanges information between chromosomes and may break the linkage of certain patterns.
-Generally the closer the genes are on the chromosome the more likely they are to be inherited together
What is the typical ratio of inheritance for a cross between two heterozygotes
9:3:3:1 with independently assorting traits
Drosophila Melanogaster and its advantages with genetic research
Fruit Fly
-helped to provide explanations for mendelian genetic patterns.
- it reproduces often (short life cycle)
- it reproduces in large numbers (large sample size)
- its chromosomes (especially in salivary glands) are large and easily recognizable in size and shape
- Its chromosomes are few (4 pairs, 2N=8)
- Mutations occur relatively frequently
-through the research scientists have found a pattern of embryological development, discovered how genes expressed in development can affect the adult organism
Incomplete dominance
NonMendelian Inheritance Patterns
-some progeny phenotypes are apparently BLENDS of the parental phenotypes (heterozygotes)
Ex: red and white flower crossed and produces some pink flowers
-an allele is incomplete dominant if the phenotype of the heterozygote is an intermediate of the phenotypes of the homozygotes
Codominance
occurs when MULTIPLE alleles exist for a given gene and more than one of them is DOMINANT.
-when two dominant alleles are present, the phenotype is the result of the expression of both dominant alleles simultaneously
-condominance differs from incomplete dominance because in incomplete dominance the phenotype is expressed is a blend of both genotypes. While in codominance both alleles int he genotypes are expressed at the same time NO BLENDING
ABO blood groups
CODOMINANCE
- Bood type is determined by three different alleles I^A, I^B, and i.
- only two alleles are present in any single individual, but the population contains all three alleles
- I^A and I^B are both dominant to i.
What are the different genotypes that result in blood type A
I^A homozygous
I^Ai heterozgyous
What are the different genotypes that result in blood type B
I^B homozygous
I^Bi Heterozygous
What genotypes result in blood type O
ii
What genotypes result in blood type AB
I^AI^B
How many autosomes do all humans have?
22
Sex Chromosomes
-the sex chromosomes pair during meiosis and segregate during the first meiotic division.
Sex Linkage
Recessive genes carried on the X chromosome will produce the recessive phenotypes whenever they occur in men because no dominant allele is present to mask them.
- Femals have 2 X chromosomes while men only have one
- The recessive phenotype will be made much more frequently in men
What are some examples of sex-linked recessives in humans
hemophilia
color blindness
Nondisjunction
is the failure of the homologous chromosomes to separate properly during meiosis I or the failure of sister chromatids to separate properly during meiosis II
- the resulting zygote might have three copies of the chromosome called a TRISOMY or a single copy of that chromosome called MONOSOMY
- most monosomies and trisomies are lethal, causing the embryo to spontaneously abort early in the pregnancy
What is an example of a trisomy?
the birth defect Down Syndrome, which is caused by trisomy of chromosome 21
Mutations
are changes in the genetic information coded in the DNA of a cell.
- most mutations occur in regions of DNA that do not code for proteins and are silent (not expressed in the phenotype)
- Mutations that do change the sequence of amino acids in proteins are most often recessive and deleterious
What do mutations in somatic cells result in?
lead to tumors in individuals
What do mutations in sex cells (gametes) result in?
the mutations will be passed down to the offspring
Mutagenic agents
- induce mutations
- include cosmic rays, X-rays, ultraviolet rays, and radioactivity as well as chemical compounds such as colchicine or mustard gas
-they can also be carcinogenic
What does colchicine result in?
inhibits spindle formation
What does mustard gas result in?
alkylates guanine in DNA
Point Mutation
a nucleic acid is replaced by another nucleic acid.
-The number of nucleic acids substituted may vary, but generally point mutations involve between one and three nucleotides
Codon
the sequence of three nucleotides that determines the identity of the amino acids
Silent mutation
the new codon may code for the same amino acid and no change in the resulting protein is seen
Missense Mutation
the new codon may code for a different amino acid
-this may or may not lead to a problem with the resulting protein, depending on the role of that amino acid in determining the protein structure
Nonsense Mutation
the new codon may be a stop codon
-are often lethal or severely inhabit the functioning of the protein, which can lead to many different problems depending on the role of that protein in organism function
Frameshift Mutation
nucleic acids are deleted or inserted into the genome sequence.
- this frequently is lethal
- the insertion or deletion of nucleic acids throws off the entire sequence of codons from that point on because the genome is “read” in routs of three nucleic acids
- the length of the genome changes
Phenylketonuria (PKU)
molecular disease caused by the inability to produce the proper enzyme for the metabolism of phenylalanine
- a degradative produce (phenylpyruvic acid) accumulates as a result
- administration of any product that contains phenylalanine (such as aspartame) to an individual with this condition could be detrimental to their health.
- these individuals are thus unable to consume products containing aspartame
- PKU may result from an impaired conversion of phenylalanine to tyrosine.
- **characterized by an increased concentration of phenyalanine in blood, increased concentration of phenylalanine and its by-products in urine, and mental retardation
**PKU is caused by deficiency of phenyalanine hydrolase
Sickle Cell Anemia
a disease in which red blood cells become crescent shaped because they contain defective hemoglobin.
- The sickle Cell Hemoglobin carries less oxygen
- the disease is caused by a substitution of valine for gluatmic acid because of a single base pair substitution in the gene coding for hemoglobin
-These individuals do have less severe symptoms of malaria if they are infected, indicating a possible evolutionary advantage in regions where malaria infection is common
Bacterial Genome
consists of a singular chromosome located in the nucleoid region of the cell.
-many bacteria also contain smaller circular rings of DNA called PLASMIDS which contain accessory genes
What do Plasmids contain
accessory genes
Episomes
are plasmids that are capable of integration into the bacterial chromosome
Replication in a bacterial chromosome
UNIQUE origin of replication and proceeds in both directions simultaneously.
-DNA is synthesized in the 5’ to 3’ direction
What three mechanisms do bacteria utilize to increase their genetic variance
Transformation
Conjugation
Transduction
Transformation
is the process by which a foreign chromosome fragment(PLASMID) is incorporated into the bacterial chromosome via recombination, creating new inheritable genetic combinations
Conjugation
can be described as SEXUAL MATING in bacteria
- it is the transfer of genetic material between two bacteria that are temporarily joined
- a cytoplasmic conjugation bridge is formed between the two cells and the genetic material is transferred from the donor male (+) type to the recipient female (-) type.
- only bacteria containing plasmids called sex factors are capable of conjugating
Conjugation in E. Coli
F Factor in E. Coli, bacteria that possess this are called F+ cells and replicate its F factor and donates the copy to the recipient-> which converts it to a F+ cell.
Hfr cells
during conjugation, the entire bacterial chromosome replicates and begins to move from the donor cell into the recipient cell. The conjugation bride usually breaks before the entire chromosome is transferred, but the bacterial genes that enter the recipient cell can easily recombine with the genes already present to form NOVEL genetic combinations
HFR means high frequency of recombination
Transduction
occurs when fragments of the bacterial chromosome become packaged into the viral progeny produced during a viral infection by a bacteriophage.
- These visions may infect other bacteria and introduce new genetic arrangements through recombination with the new host cell’s DNA
- the closer the two genes are to one another on a chromosome, the more likely they will be to transduce together
Recombination
occurs when linked genes are separated.
-it occurs by breakage and rearrangement of adjacent regions of DNA when organisms carrying different genes or alleles for the same traits are crossed.
Prokaryotic regulation of transcription
- enables prokaryotes to regulate their metabolism
- based on the ability of RNA polymerase to gain access to the genes being transcribed and is directed by an operon
What does the operon consist of?
consists of structural genes, an operator region, and a promoter region on the DNA before the protein coding genes
What do structural genes contain
sequences of DNA that code for proteins
Operator
is the sequence of non transcribable DNA that is the REPRESSOR binding site
Promoter
is the noncoding sequence of DNA that services as the initial binding site for RNA polymerase
Regulator Region
codes for the synthesis of a repressor molecule and binds to the operator and blocks RNA polymerase from transcribing the structural genes
RNA polymerase function
must be able to move past the operator to transcribe the structural genes
Inducible Systems
require the presence of a substance called the INDUCER for transcription to occur
–the repressor binds to the operator, forming a barrier that prevents RNA polymerase from transcribing the structural genes
Repressible Systems
are in a constant state of transcription unless a COREPRESSOR is present to inhibit transcription
- the repressor is inactive until it combines with the corepressor
- Corepressors are often the end products of the biosynthetic pathways they control