BISC-225 TEST 2 Flashcards
Enzyme - pace of each reaction is controlled by a special type of protein
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metabolism - sum total of all reactions occurring within a cell
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anabolism - Larger molecules are constructed from smaller ones, requiring an input of energy
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anabolism provides all the substances required for cellular growth and repair.
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Dehydration synthesis is within Anabolism
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dehydration synthesis joins many simple sugar molecules to form larger molecules of glycogen.
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dehydration synthesis - an –OH ( hydroxyl group ) from one monosaccharide molecule and an-H ( hydrogen atom ) from a hydroxyl group of another monosaccharide are removed, forming a water molecule
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dehydration synthesis allows fat molecules and proteins to form.
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Dehydration synthesis - three hydrogen atoms are removed from a glycerol molecule, and an –OH group is removed from three fatty acid molecules to form a fat molecule
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Peptide bond or Dehydration synthesis - an –OH from one amino acid and an –H from the –NH2 of another amino acid are removed, resulting in a bond forming between a carbon atom and a nitrogen atom – this is a Peptide bond and holds the two amino acids together
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Catabolism - Larger molecules are broken down into smaller ones, releasing energy
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Hydrolysis - an example of catabolism in which a water molecule is used to split the large substances into two parts
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hydrolysis - reverse of dehydration synthesis
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Hydrolysis -requires the help of specific enzymes to occur
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Hydrolysis - disaccharides monosaccharides; lipids glycerol and fatty acids;proteins amino acids; nucleic acids nucleotides
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Enzymes - the reactions within cells include hundreds of very specific chemical changes that occur in a particular sequence
- the rates of these reactions are controlled
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Enzymes - Reactions require energy ( activation energy ) before they can proceed. The temperature within the cell is usually too mild to start these reactions – Enzymes
make the reactions possible.
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enzymes - usually globular proteins which function by lowering the activation energy required to start the reactions.
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enzymes - can speed up reactions by a factor of a million or more
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enzymes - very small quantities are needed since they are not consumed in the reaction
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each enzyme has specificity
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subtrate - each enzyme acts only on a particular substance
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catalase - found in peroxisomes of kidney and liver – has hydrogen peroxide as its substrate – breaks down H2O2 into water and oxygen
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different chemical reactions make up Cellular Metabolism with each reaction controlled by a specific enzyme.
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Chemical reactions make up metabolic pathways
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hundreds of enzymes in each cell and each enzyme must be able to recognize its specific substrate
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Enzyme molecule shape - identifying a substrate
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the Enzyme Shape fits the special shape of its substrate molecule
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Active sites of the enzyme temporarily combine with portions of substrate
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Active sites - Interaction strains chemical bonds in substrate so that a particular reaction is more likely to occur - active sites
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Active sites - the enzyme is released to its original form – able to bind another substrate
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enzymes and substrate molecules - the speed of the reaction depends on the number
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enzyme names are often derived from the substrate by adding –ase
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lipase is lipid splitting enzyme
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A regulatory enzyme often determines the rate at which a metabolic pathway functions.
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regulatory enzyme often present in limited quantity – can become saturated when the substrate concentration exceeds a certain level
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This rate-limiting enzyme is often the first enzyme in a series.
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rate-limiting enzyme - often the product of a metabolic pathway inhibits this enzyme-negative feedback
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cofactors and coenzymes are nonprotein components that are often necessary for an enzyme to work.
They may help the active site reach an appropriate shape or help bind the enzyme to the substrate.
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Cofactors may be the ion of an element, such as copper, iron, or zinc.
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Coenzymes are small organic molecules – often composed of vitamin molecules or incorporate altered forms of vitamin molecules into their structures.
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vitamins are essential organic substances that human cells cannot synthesize( or may not synthesize in sufficient quantities ) and therefore must come from the diet
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Since enzymes are usually proteins, they can be denatured by heat, radiation, electricity, certain chemicals, and extreme pH values
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ATP Molecules ( adenosine triphosphate )
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Each ATP molecule consists of an adenine, a ribose, and three phosphates in a chain – the last phosphate attached by a high-energy bond
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ATP molecule the chemical energy can be quickly transferred to another molecule in a metabolic reaction
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An ATP that loses its terminal phosphate becomes ADP ( adenosine diphosphate ).
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ATP can be resynthesized from an ADP by using energy released from cellular respiration to reattach a phosphate, a process called phosphorylation
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The energy used in metabolic reactions is chemical energy which is held in the bonds that link atoms into molecules – energy is released when the bonds are broken.
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Burning releases the chemical energy in these bonds as heat and light.
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Cells “burn” glucose molecules in a process called oxidation to release energy used to promote cellular metabolism.
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Burning in nonliving systems requires a relatively large amount of energy to begin, and most of the energy released escapes as heat and light.
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In cells, where oxidation occurs, enzymes lower the activation energy needed to start the reactions, and cells capture almost half of the energy released by
transferring it to special energy-carrying molecules.
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the rest of the energy escapes as heat which helps maintains body temperature
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Cellular respiration is the process that releases energy from molecules such as glucose and transfers it to other molecules.
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cellular respiration the chemical reactions occur in a particular sequence, each one controlled by a different enzyme
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some enzymes are in the cytosol, and others in the mitochondria
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cellular respiration occurs in three distinct, yet interconnected series of reactions whose products include CO2, water, and energy
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cellular respiration includes aerobic reactions and anaerobic reactions
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Glycolysis ( “breaking of sugar” ) is a series of 10 enzyme-catalyzed reactions that break the 6-carbon glucose into two 3-carbon pyruvic acid molecules.
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Glycolysis occurs in the cytosol
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Glycolysis does not require oxygen
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Glycolysis is the anaerobic phase of cellular respiration
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Three main events: In Glycolysis
a. glucose is phosphorylated by the addition of two phosphate groups – requires ATP – it “primes” the molecule for the rest of the steps
b. the 6-carbon glucose is split into two 3-carbon molecules
c. NADH is produced, ATP is synthesized, and two 3-carbon pyruvic acid molecules result.
1) hydrogen atoms are released and their electrons contain much of the energy in the original glucose molecule
2) the electrons are passed in pairs to molecules of the hydrogen carrier NAD+( nicotinamide adenine dinucleotide ): NAD+ + 2H NADH + H+
3) NADH delivers these high-energy electrons to the electron transport chain in the mitochondria, where most of the ATP will be synthesized
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glycolysis - ATP is synthesized directly – substrate level phosphorylation.
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Anaerobic Reactions - In the absence of oxygen ( which acts as the final electron acceptor ), NADH + H+ can give its electrons and hydrogens back to pyruvic acid in a reaction that forms lactic acid. This regenerates the NAD+ but the buildup of lactic acid eventually inhibits glycolysis and ATP production declines.
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Aerobic Reactions - Aerobic pathways include the synthesis of acetyl coenzyme A, the citric acid cycle, and the electron transport chain – yielding water, carbon dioxide, and up to 36 ATP molecules.
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Aerobic Reactions have three main events: formation of acetyl CoA, citric acid cycle, electron transport chain
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FIRST: Formation of acetyl CoA
1) pyruvic acid moves into the mitochondrion
2) enzymes remove two hydrogen atoms, a carbon atom, and two oxygen atoms generating NADH and CO2, and leaving a 2-carbon acetic acid
3) the acetic acid combines with a molecule of coenzyme A to form acetyl CoA which carries the acetic acid into the citric acid cycle
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SECOND: .citric acid cycle
1) begins when a 2-carbon acetyl CoA molecule combines with a 4-carbon oxaloacetic acid molecule to form the 6-carbon citric acid molecule
a) CoA is released and can be used again to form acetyl CoA from pyruvic acid
2) the citric acid is changed through a series of reactions back to oxaloacetic acid
3) three important consequences of this cycle:
a) one ATP is produced for each citric acid molecule that goes through cycle
b) eight hydrogen atoms with high-energy electrons are transferred to NAD+and FAD ( flavine adenine dinucleotide ) for each citric acid molecule
NAD+ + 2H NADH + H+
FAD + 2H FADH2
c) two carbon dioxide molecules are produced for each citric acid molecule
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THIRD: electron transport chain
1) the high-energy electrons in NADH and FADH2 are handed off to the electron transport chain, which is a series of enzyme complexes that carry and pass electrons along from one to another
a) on the folds of the inner mitochondrial membranes
2) the energy is transferred to ATP synthase, an enzyme complex that uses this energy to phosphorylate ADP to form ATP
3) these reactions are known as oxidation/reduction reactions
4) the final enzyme in the chain gives up a pair of electrons that combine with two hydrogen ions and an atom of oxygen to form a water molecule:
2 e- + 2 H+ + ½ O2 H2O
a) thus oxygen is the final electron “carrier”
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Carbohydrate Storage
a. metabolic pathways are interconnected so that certain molecules are able to enter more than one pathway
b. glucose molecules may enter catabolic pathways and used to supply energy or may enter anabolic pathways and be stored or be converted to nonessential amino acids
c. excess glucose in cells can be linked together forming glycogen for storage – about 400 – 450 grams – ¼ in the liver, ¾ in skeletal muscles, small amount in cardiac muscle
d. glucose can be converted to fat and stored in adipose tissue – if more carbohydrates are taken in than can be stored as glycogen or required for normal activities
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Genetic Information passes to a child from its parents in the form of DNA.
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Genetic Information DNA contains the information for construction of the proteins in the cells
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gene ( about 20,325 of these ) -the portion of the DNA molecule containing the genetic information for making a particular protein
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Genome - All of the DNA in a cell
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exom is a small part of the genome encodes protein
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nucleotides are the building blocks of nucleic acids (DNA, RNA)-a nucleotide consists of a 5-carbon sugar, phosphate group, and an organic, nitrogen-containing base.
a. in DNA, the bases are adenine, thymine, guanine, and cytosine
b. the DNA molecules form long strands (polynucleotide chains) by alternately joining their sugar and phosphate portions – providing a “backbone” to which the bases are attached
c. DNA consists of 2 polynucleotide chains with the nitrogenous bases projecting from the backbone of one strand binding to the bases of the second strand
1) the two strands are antiparallel
d. the bases pair in a particular manner, due to their shape – complementary base pairs
1) adenine pairs with thymine, guanine pairs with cytosine
e. the sequence of bases in one of the strands encodes the information of a protein
f. the double-stranded DNA molecule twists to form a double helix which may be several million base pairs long
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DNA Replication
- Each newly formed cell from mitosis must have an identical copy of DNA; therefore DNA must replicate, before mitosis can occur. This replication occurs during interphase.
- Hydrogen bonds holding the two strands together break, the helix unwinds and pulls apart, exposing unpaired nucleotide bases.
- DNA polymerase catalyzes the base pairing of new nucleotides to the exposed nucleotides of the strand.
a. enzymes knit together the sugar-phosphate backbone - The resulting two DNA molecules are exactly like the original DNA molecule and during mitosis one DNA molecule goes to each new cell.
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Genetic Code
- Each of the twenty different amino acids in a polypeptide chain is represented in a DNA molecule by a triplet code, consisting of sequences of three nucleotides.
a. e.g. CGA represents one kind of amino acid; GCA represents another amino acid - The sequence of nucleotides in a DNA molecule dictates the sequence of amino acids in a particular protein molecule.
- DNA is in the nucleus and protein synthesis occurs in the cytoplasm – RNA is used to get the genetic information from the nucleus to the cytoplasm
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RNA molecules have single stranded, have ribose sugar, and the bases are adenine, uracil, cytosine, and guanine.
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Messenger RNA will carry the information from the nucleus to the cytoplasm and must be synthesized from the DNA strand.
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Messenger RNA nucleotides form complementary base pairs with a section of the strand of DNA that encodes a particular protein – the strand of DNA must be “read” in the correct direction; and only one of the antiparallel strands contains the genetic information
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an enzyme called RNA polymerase determines the correct DNA strand and the correct direction for RNA synthesis
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the RNA polymerase binds to a promoter ( a region of DNA that begins a gene ) - this causes the DNA molecule to unwind at this region, exposing the gene
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RNA polymerase moves along the strand, exposing more of the gene, while RNA nucleotides are binding complementarily to the DNA nucleotides forming a mRNA strand ( messenger RNA )
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when the RNA polymerase reaches a termination signal ( a specific DNA base sequence ), the newly formed mRNA is released from the RNA polymerase and it leaves the DNA
1) the DNA rewinds
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Transcription is process of copying DNA information into the structure of an mRNA molecule
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translation is protein synthesis: the mRNA molecule leaves the nucleus through pores and enters the cytosol where it becomes associated with ribosomes and act as templates, or patterns, for synthesizing proteins
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Codon is the complementary set of three nucleotides in the RNA molecule
1) there are 64 possible RNA base triplets encoding for twenty different amino acids more than one codon can specify the same amino acid
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In Protein Synthesis the correct amino acids must be present in the cytoplasm and they must align in the proper sequence along a strand of mRNA in order to synthesize
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transfer RNA is a type of RNA that aligns the amino acids along the mRNA
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Transfer RNA consists of 70-80 nucleotides and has a complex 3-D shape – its two ends have unique shapes important for its “connector” function
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One end of transfer RNA has a specific binding site for a particular amino acid – at least one tRNA molecule for each of the twenty amino acids – ATP provides the energy to form the bond between amino acid and tRNA
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the other end of transfer RNA includes a region, called the anticodon
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Anticodon contains three nucleotides in a particular sequence unique to that tRNA – the anticodon bonds only to a specific complementary codon of the mRNA
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There are 64 different codons but 3 of these do not code for an amino acid, they are “stop” signals; signaling the end of protein synthesis.
a. there are 61 different tRNAs, specific for the 61 codons – more than one type of tRNA can correspond to the same amino acid ( there are only 20 amino acids)
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Binding of tRNA and mRNA occurs in close association with a ribosome.
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ribosomes are small particles consisting of two subunits – composed of proteins and ribosomal RNA
b. the smaller subunit binds to mRNA near a beginning codon and then tRNA brings its amino acid into position and temporarily joins to the ribosome
1) a second tRNA brings its amino acid and binds to mRNA – the first tRNA releases its amino acid, providing energy for a peptide bond to form between the two amino acids
c. this process continues as the ribosome moves along the mRNA
1) a mRNA strand is usually associated with several ribosomes at the same time
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Proteins called chaperones fold the developing protein into its unique shape – and when the process is completed, the protein is released from the mRNA into the cytoplasm as a functional molecule
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ATP provides the energy for protein synthesis – 3 ATP molecules are required to link each amino acid to the growing chain.-
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Proteins called transcription factors activate certain genes, thereby controlling which proteins a cell produces and how many copies form.
a. extracellular signals such as hormones and growth factors activate transcription factors
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Mutations are changes in the DNA – due to an error during replication or to some sort of damage.
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Some mutations cause devastating medical conditions; others can be beneficial.
a. up to 1% of individuals in some populations have mutations that render their cells unable to become infected with HIV
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During mutation replication, a base may pair incorrectly with the newly forming strand, extra bases may be added, bases may be deleted, bases may move another region of the strand, or even move to another chromosome.
a. all of these result in a changed DNA strand – the genetic information is changed
1) if a protein is constructed from this information, its molecular structure may be faulty and the function altered or absent
b. e.g. sickle cell anemia
1) the change of one base leads to this disorder
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cells detect the damage in their DNA molecules and use repair enzymes to clip out the defective nucleotides and fill the resulting gap with complementary bases – thus restoring the original structure of the DNA.
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61 codons specify the 20 amino acids – therefore some amino acids are represented by more than one codon – usually the codons for the same amino acid differ only in the 3rd base of the codon
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a mutation in the 3rd base, may result in a codon for the same amino acid
1) e.g. GGA and GGG each specify proline
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if a mutation occurs in the 2nd base, the substituted amino acid is often very similar in structure as the normal one, and the protein may not be changed enough to affect its function
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people have two copies of every chromosome, and therefore each gene.
a. if one is mutated, the other may provide enough of the gene’s normal function so that this is not a harmful mutation
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A mutation occurring in an adult cell may not be noticed because of all the normal cells surrounding it – in a developing embryo, the abnormal cell will give rise to
many more abnormal cells and this can be very destructive
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Mutations may occur spontaneously if a chemical quirk causes a base in an original DNA molecule to be in an unstable form just as replication occurs there.
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mutagens are substances that cause mutations
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ultraviolet radiation in sunlight can cause an extra chemical bond to form between thymines that are adjacent on a DNA strand – this bond causes a kink that can cause incorrect base insertions during replication
1) repair enzymes may fix the damage if its not too severe – but in cases of a sunburn, the cell dies because of too much damage, and skin peeling results
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Inborn errors of metabolism are disorders resulting from inheriting a mutation that alters an enzyme.
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the Metabolism enzyme blocks a biochemical pathway and has two general effects:
1) the substance the enzyme acts upon builds up
2) the substance resulting from the enzyme’s normal action becomes scarce
b. these can drastically affect health
1) e.g. PKU
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Degenerate is a genetic code that amino acids can be specified by more than one codon
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ATP provides the energy to form the bond between amino acid and tRNA
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DNA is in the nucleus and protein synthesis occurs in the cytoplasm
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RNA is used to get the genetic information from the nucleus to the cytoplasm
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The sequence of nucleotides in a DNA molecule dictates the sequence of amino acids in a particular protein molecule.
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tissues are layers or groups of similar cells with a common function
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intercellular Junctions – connect cell membranes to each other
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tight junction – membranes of adjacent cells converge and fuse with the area of fusion surrounding the cells like a belt
1) e.g. lining the inside of digestive tract, linings of tiny blood vessels in brain
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desmosomes – rivets or “spot welds” adjacent skin cells, forming a reinforced structural unit
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gap junctions – these are tubular channels that allow ions, nutrients, and other small molecules to move between the cells
1) e.g. heart muscle and muscles of the digestive tract connected by these
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EPITHELIAL TISSUES
- Widespread throughout body.
- Lines body cavities, covers organs.
- Always have a free surface. The underside is anchored to connective tissue by a thin, nonliving layer called the basement membrane.
- Generally lack blood vessels – nutrients diffuse from connective tissue.
- Reproduce rapidly, so injuries heal quickly.
- Tightly packed, with little intercellular material – form effective barriers.
- Classified according to shape of cells and number of layers of cells:
a. simple – one layer
b. stratified – more than one layer
c. squamous – thin, flattened cells.
d. cuboidal – cells are cubelike
e. columnar – cells are elongated – taller than wide - The free surface of epithelial cell are modified to reflect their specialized functions
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EPITHELIAL TISSUES - Widespread throughout body.
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EPITHELIAL TISSUES - Lines body cavities, covers organs.
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EPITHELIAL TISSUES- Always have a free surface.
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basement membrane - The underside of epithelial tissues is anchored to connective tissue by a thin, nonliving layer
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EPITHELIAL TISSUES - Generally lack blood vessels – nutrients diffuse from connective tissue.
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EPITHELIAL TISSUES - Reproduce rapidly, so injuries heal quickly.
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EPITHELIAL TISSUES - Tightly packed, with little intercellular material – form effective barriers.
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EPITHELIAL TISSUES - Classified according to shape of cells and number of layers of cells
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epithelial tissues - simple – one layer
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epithelial tissues - stratified – more than one layer
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epithelial tissues - squamous – thin, flattened cells.
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epithelial tissues - cuboidal – cells are cubelike
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epithelial tissues - columnar – cells are elongated – taller than wide
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EPITHELIAL TISSUES - The free surface of epithelial cell are modified to reflect their specialized functions
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Simple Squamous Epithelium
- Single layer of thin, flattened cells – fit tightly together like floor tiles; nuclei broad and thin.
- Common at sites of diffusion and filtration – air sacs ( alveoli ) of the lungs, walls of capillaries, covers membranes that line body cavities.
- Easily damaged because they are so thin.
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Simple Cuboidal Epithelium
- Single layer of cube-shaped cells with centrally located spherical nucleus.
- Covers the ovaries, lines kidney tubules and ducts of certain glands ( pancreas, salivary glands, and liver ) – functions in secretion and absorption.
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Simple Columnar Epithelium
- Single layer of elongated cells with nuclei usually near the basement membrane.
- Cells may be ciliated or nonciliated.
a. cilia, which are 7-10 um in length, extend from the free surface of cells and move constantly
1) e.g. move egg cells through the oviducts to the uterus 3. Nonciliated epithelium lines the uterus and portions of the digestive tract.
a. this tissue is thick, enabling it to protect underlying tissues
b. cells of digestive tract secrete digestive fluids and absorb nutrients from digested food - Cells that are specialized for absorption often have many tiny, cylindrical processes extending from their surfaces.
a. these processes are called microvilli and are from 0.5 to 1.0 um long – they increase the surface area of the cell membrane - Goblet cells are typically scattered among the cells of this tissue. They secrete a protective fluid called mucus onto the free surface of the tissue.
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Simple Columnar Epithelium - Single layer of elongated cells with nuclei usually near the basement membrane.
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Simple Columnar Epithelium - Cells may be ciliated or nonciliated.
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Simple Columnar Epithelium - cilia, which are 7-10 um in length, extend from the free surface of cells and move constantly
1) e.g. move egg cells through the oviducts to the uterus
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Simple Columnar Epithelium - Nonciliated epithelium lines the uterus and portions of the digestive tract.
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Nonciliated epithelium - this tissue is thick, enabling it to protect underlying tissues
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Nonciliated epithelium - cells of digestive tract secrete digestive fluids and absorb nutrients from digested food
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Simple Columnar Epithelium Cells that are specialized for absorption often have many tiny, cylindrical processes extending from their surfaces.
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microvilli - many tiny, cylindrical processes
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microvilli are from 0.5 to 1.0 um long – they increase the surface area of the cell membrane
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Goblet cells are typically scattered among the cells of Simple Columnar Epithelium tissue.
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Goblet Cells secrete a protective fluid called mucus onto the free surface of the tissue.
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Pseudostratified Columnar Epithelium - The cells appear stratified due to the nuclei being at different levels and the cells vary in shape – but it is only one layer.
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Pseudostratified Columnar Epithelium - Often fringed with cilia. Goblet cells secrete mucus, which the cilia sweep away.
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Pseudostratified Columnar Epithelium - lines passages of respiratory system – mucus traps dust and microorganisms that enter with air, cilia moves mucus and trapped particles upward and out of the airways
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Stratified Squamous Epithelium - Several layers of cells – the outermost layers have flattened cells while the deeper layers, where cell division occurs
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Stratified Squamous Epithelium - consist of cuboidal or columnar cells
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The epidermis consists of Stratified Squamous Epithelium tissue
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as the older Stratified Squamous Epithelium cells are pushed outward, they accumulate a protein called keratin, then harden and die
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Stratified Squamous Epithelium produces a dry, tough, protective material that prevents water from escaping and blocks chemicals and microorganisms entering.
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Stratified Squamous Epithelium lines oral cavity, throat, esophagus, vagina and anal canal. The tissue is not keratinized in these regions and the cells remain alive.
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Stratified Cuboidal Epithelium - Consists of two or three layers of cuboidal cells that form the lining of a lumen.
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Stratified Cuboidal Epithelium - Lines the ducts of mammary glands, sweat glands, salivary glands, and pancreas; also lining of developing ovarian follicles and seminiferous tubules.
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Stratified Columnar Epithelium - Several layers of cells with the surface cells being elongated and the basal layers consisting of cube-shaped cells.
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Stratified Columnar Epithelium - Found in the vas deferens, part of the male urethra, and in parts of pharynx
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Transitional Epithelium - Specialized to change in response to increased tension.
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Transitional Epithelium - Inner linings of urinary bladder, ureters, and part of urethra.
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Transitional Epithelium - forms an expandable lining as these structures fill with urine – forms barriers so that the contents can’t diffuse back into internal environment
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Glandular Epithelium - Cells specialized to produce or secrete substances
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Glandular Epithelium - these cells usually found in cuboidal or columnar epithelium
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Glandular Epithelium - one or more of these cells make up a gland
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Endocrine glands - secrete their products into tissue fluid or blood.
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Exocrine glands - secrete their products into ducts that open onto some internal or external surface.
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Exocrine glands are unicellular glands and multicellular glands
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unicellular gland – consists of a single epithelial cell – e.g. goblet cell
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