Chapter 3 - cellular structure, proteins, and metabolic pathways
A single Krebs cycle directly produces ____
only one molecule of GTP
During translation, ______ delivers amino acids to the ribosome for protein synthesis.
transfer RNA
Which of the following best describes chromatin?
Fine threads of DNA and protein
What are the three main classes of RNA molecules?
Messenger RNA Ribosomal RNA Transfer RNA
DNA is a polymer of _____ each of which consists of a phosphate, a 5-carbon sugar, and a single or double-ringed nitrogenous base.
Nucelotides
The prominent, double membrane-bound structure of the cell that stores genetic information is the
Nucleus
The nuclear envelope is perforated with openings called nuclear ______ that regulate the movement of messenger RNA through the envelope.
pores
The energy process which takes place in the mitochondria of the cell is called ______.
cellular respiration
A slightly amphipathic molecule that associates with the fatty acid tails of phospholipids and influences the fluidity of the plasma membrane at different temperatures is called
cholesterol
Name the fine thread-like form taken by the genetic material (the DNA) within the nucleus of a non-dividing cell.
chromatin
When cells are not dividing, DNA is in a fine, threadlike form called ______ but during cell division it tightly condenses to form ____
chromatin, chromosomes
In non-dividing cells, DNA forms a fine network of threads known as ______, but during cell division it becomes tightly condensed into ______.
chromatin; chromosomes
Cellular structures that propel the contents of hollow organs along epithelial surfaces are known as
cilia
A three-base sequence of mRNA that specifies one amino acid is called a(n)
codon
When a binding site is able to bind multiple ligands, occurs between the ligands for the same site.
competition
Which two terms describe mechanisms by which protein shape and function are regulated?
covalent and allosteric modulation
Glycolysis occurs in the ______ of the cell.
cytoplasm
RNA is translated into proteins mainly in the ______, while DNA remains in the ______.
cytoplasm; nucleus
Give the general name for the network of structures within the cytoplasm that supports the cell, determines its shape, and participates in movement.
cytoskeleton
The network of protein filaments and tubules within the cytoplasm together form the
cytoskeleton
In what location within cells does glycolysis occur?
cytosol
The portion of the intracellular fluid that surrounds the organelles and nucleus is called the
cytosol
Membrane structure is described by the ______-______ model, because proteins are free to move around and form different patterns within a sea of phospholipid molecules.
fluid-mosaic
A cell junction formed by specific proteins called connexins, linking the cytosol of one cell to the cytosol of an adjacent cell, is called a(n)
gap junction
The intercellular junction called a ______ allows the flow of ions between cells, which enables transmission of electrical excitation from cell to cell.
gap junctions
A segment of DNA that specifies the amino acid sequence in a specific polypeptide chain is called a ______.
gene
An information-containing segment of DNA that codes for the production of a protein is termed a(n)
gene
Regulatory proteins turn these on and off in accordance with changing needs for the proteins they encode.
genes
When a woman gives birth, prolactin stimulates her mammary glands to produce casein, a protein that her body has never synthesized before. This demonstrates that _____.
genes can be turned on or off
The information coded in the total DNA of an organism is referred to as its ______.
genome
The term ______ refers to the total genetic information coded in a person's chromosomes.
genome
Red blood cells lack mitochondria, and so must produce ATP via...
glycolysis
The breakdown of glucose into pyruvate in the cytoplasm is known as
glycolysis
The term that describes the 10-step pathway by which glucose is catabolized in the cytosol is
glycolysis
Most of the energy resulting from the Krebs cycle is _____.
harnessed indirectly in oxidative phosphorylation, which utilizes the free hydrogen ions generated by the Krebs cycle
Membrane-bound organelles that contain a mixture of acidic enzymes that digest foreign matter, pathogens, and expired organelles are called _____.
lysosomes
The organelles that digest and dispose of worn-out organelles and play a role in various cells that make up the defense systems of the body are the
lysosomes
The main role of ______ during protein synthesis is to carry the genetic code from the nucleus to the cytoplasm.
mRNA
Which of the following are involved in the initiation of translation?
mRNA Methionine Start codon Ribosomal subunits Methionine-containing tRNA
The genetic language of the cell is similar to written language; the ______ are like letters, and the ______ are like words.
nucleotide bases; triplet codes
DNA is a long threadlike molecule composed of subunits called ______.
nucleotides
The organelle that contains the genetic material of a eukaryotic cell is the
nucleus
the ______ is a cell organelle with a pair of surrounding membranes joined together at intervals to form pores. RNA molecules pass through those pores.
nucleus
The interior of the cells of the human body have a number of membrane-bound compartments called ______, which perform various cell functions.
organelles
The small, membrane-bound structures found inside of eukaryotic cells that perform various specialized cell functions are called
organelles
The transfer of a phosphate to ADP in the electron-transport system is termed _____ phosphorylation.
oxidative
The transfer of a phosphate to ADP in the electron-transport system is termed _______ phosphorylation.
oxidative
What molecule acts as the final electron acceptor in the process of oxidative phosphorylation?
oxygen
A protein that is not integral to the plasma membrane and is often attached to the intracellular face is categorized as a(n) ______ protein.
peripheral
The majority of the plasma membrane can be described as a bilayer of ______ with associated proteins and cholesterol.
phospholipids
A reaction in which a portion of a complex molecule is transferred to ADP to form ATP is referred to as a substrate-level ________ reaction.
phosphorylation
Selective permeability is a property of ______, and it is defined as ______.
plasma membranes; the regulated movement of specific substances between the intracellular and extracellular fluid compartments
Changes to the structure of a new protein (i.e., removal of some amino acids, folding of the protein, adding carbohydrates, etc.) are known as ______.
posttranslational modification
Oxidative phosphorylation _____.
produces ATP by harnessing the energy released when hydrogen ions combine with molecular oxygen to form water directly produces more ATP than glycolysis or the Krebs cycle
A genetic mutation in the gene that codes for ATP synthase, causing a decrease in function, might cause a decrease in the ______.
production of ATP
At the beginning of transcription, RNA polymerase binds to a specific sequence of DNA nucleotides known as a _____.
promoter sequence
The ______ endoplasmic reticulum has a branched, tubular structure, and lacks ribosomes.
smooth
The characteristic of some protein-binding sites that allows them to bind only one particular ligand is known as chemical
specificity
The shape of a binding site on a protein determines the type of ligand that can bind. In other words, the binding site exhibits _____.
specificity
The term ______ refers to triplets of DNA nucleotides that do not encode amino acids.
stop signals
Triplets of DNA nucleotides that do not specify amino acids are known as
stop signals
The substrate-binding site of an enzyme is known as the _____ site.
active
Which of the following are TRUE regarding the structure and function of cholesterol in cell membranes?
- The association of the nonpolar rings of cholesterol limits the ordered packing of phospholipid fatty acid tails, which maintains membrane fluidity. - Cholesterol is slightly amphipathic, so associates with both the polar head and nonpolar tails of phospholipids.
List the steps of translation in correct order as they occur. Start with the earliest at the top.
1. Ribosome binds to mRNA 2. tRNA anticodon binds to complementary mRNA codon 3. New amino acid is linked to the growing peptide chain 4. tRNA is released from ribosome and is available to pick up another amino acid
List these intermediate molecules in the order they occur in the glycolytic pathway by which glucose is metabolized to form ATP.
1. glucose 6-phosphate 2. fructose 6 phosphate 3. fructose 1,6-biphosphate 4. 3-phosphoglyceraldehyde
The net gain of glycolysis is _____ ATP molecules for every molecule of glucose.
2
The number of genes in the human genome is approximately ______ different genes.
20,000
During glycolysis, ____ ATP molecules are utilized to produce a total of _____ molecules of ATP. Thus, glycolysis yields a net of _____ ATP molecules.
2; 4; 2
Which of these demonstrate accurate base pairing of Adenine(A), Cytosine(C), Guanine(G) and Thymine(T)?
A-T
Mitochondria extract energy from organic compounds and transfer it to which of the following for use by the cell?
ATP
Oxidative phosphorylation occurs when ______ is produced during the electron-transport system.
ATP
The three-letter abbreviation for the molecule that is the main cellular energy source created from the metabolic breakdown of carbohydrates, proteins, and fats, is
ATP
The enzyme in the inner mitochondrial membrane that catalyzes the addition of a phosphate to adenosine diphosphate (ADP) is
ATP Synthase
If a sequence of nucleotide bases in DNA is TACTAAGTA, what would be the sequences of bases in the primary mRNA transcript?
AUGAUUCAU
Which best describes an integral membrane protein?
An amphipathic protein that associates with polar and nonpolar regions of the phospholipid bilayer, and cannot be easily extracted.
Indicate which of the following statements are true regarding an intron.
An intron is a portion of mRNA that must be removed before translation. An intron is a portion of mRNA that does not code for protein.
Translation can be divided into three stages. These are, in order,________ , _______ , and _________ .
Blank 1: initiation Blank 2: elongation Blank 3: termination
After a protein is synthesized, it undergoes structural modification. Which of the following statements about this process are true?
Carbohydrates may be added to the protein. It may involve removal of some amino acid segments. The protein may be folded and stabilized by disulfide bridges. This process is known as posttranslational modification.
Which of the following best describes the nuclear envelope?
Composed of two membranes containing pores at regular intervals through which RNA passes
Where is the information stored that codes for all of the proteins that can be synthesized in the body?
DNA
Transcription is the process of copying genetic instructions from ___ to _____
DNA to RNA
Which event occurs on the inner membrane of the mitochondria?
Electron transport
Translation occurs in three steps. What are they?
Elongation Initiation Termination
Which is NOT a principal metabolic pathway involved in the breakdown of nutrient molecules to ATP?
Gluconeogenesis
A series of closely apposed, flattened membranous sacs within the cell that modifies proteins arriving from the rough endoplasmic reticulum and packages them into secretory vesicles is known as the
Golgi apparatus
After proteins that are destined for secretion from the cell are synthesized in the rough endoplasmic reticulum, they bud off inside of vesicles that migrate to the _____.
Golgi apparatus
One function of the _____ is to add carbohydrate groups to proteins produced by the endoplasmic reticulum.
Golgi apparatus
When synthesized proteins are to be exported out of the cells (e.g., digestive enzymes), they can be packaged into secretory vesicles that fuse with the plasma membrane and are released through exocytosis. The secretory vesicles originate in what organelle?
Golgi complex
Which of these is NOT one of the mechanisms by which protein shape and function are selectively altered?
Hydrophobic modulation
______ link intracellular proteins to proteins in the extracellular matrix and thus facilitate the organization of cells into tissues.
Integrins
During translation, mRNA does which of the following?
It carries the genetic code from the nucleus to the cytoplasm. It is selectively transported through a nuclear pore and attaches to a ribosome where translation occurs.
How does newly synthesized mRNA pass from within the membrane-bound nucleus into the cytosol?
It passes through nuclear pores.
Which three terms refer to the exact same process?
Krebs cycle TCA cycle Citric acid cycle
In addition to producing carbon dioxide, intermediate in the Krebs cycle generate hydrogen atoms, most of which are transferred to the coenzymes _______ and _______
NAD+ , FAD
In addition to producing carbon dioxide, intermediates in the Krebs cycle generate hydrogen atoms, most of which are transferred to ______.
NAD+ and FAD
Which two statements are true regarding the naming of enzymes?
Naming is based on the job or function of the enzyme. Names end with an "ase."
____ is a process in which ATP is created with energy derived from combining molecular oxygen with free hydrogen ions generated by the Krebs cycle (as NADH and FADH2).
Oxidative phosphorylation
Which are the three major steps of aerobic respiration?
Oxidative phosphorylation Krebs cycle Glycolysis
Select the components that make up ribosomes.
Proteins ribosomal RNA (rRNA)
What product of glycolysis provides the acetyl groups that go into the production of the acetyl coenzyme A that enters the Kreb cycle in aerobic metabolism?
Pyruvate
Indicate true statements comparing human DNA and RNA.
RNA consists of a single nucleotide chain whereas DNA is a double helix. RNA contains a sugar called ribose whereas DNA contains a sugar called deoxyribose. DNA is found within the nucleus, while RNA moves between the nucleus and cytoplasm.
The enzyme that joins ribonucleotides together during the normal transcription of DNA is _____.
RNA polymerase
The enzyme that synthesizes molecules of RNA complementary to the DNA sequence during transcription is _____.
RNA polymerase
______ is a molecule that consists of a single nucleotide chain containing adenine, uracil, cytosine, guanine, and a sugar called ribose, whereas ______ is a double-helix molecule containing adenine, thymine, cytosine, guanine, and a sugar called deoxyribose.
RNA; DNA
Which best describes histones?
Specialized proteins around which DNA molecules coil for efficient packaging in the nucleus.
One strand of a molecule of DNA has the sequence: ACGTGA. The sequence of the complementary strand of DNA would be
TGCACT
The percent saturation of a binding site on a protein depends mainly on which two factors?
The affinity of the binding site for the ligand The concentration of unbound ligand in a solutio
What is the active site of an enzyme?
The binding site for its substrate
Which three are characteristics of codons?
They are complementary to anticodons. They code for amino acids. They are three-base sequences of mRNA.
Which is NOT true about prokaryotic cells?
They have a membrane-bound nucleus.
______ occurs in the nucleus, where DNA is located, whereas ______ occurs mostly in the cytoplasm.
Transcription; translation
Which best describes the membrane junctions known as tight junctions?
Transmembrane proteins form a band around the apical surface of epithelial cells, that limit the movement of substances between cells.
Pyruvic acid, upon entering the mitochondrion, is changed into ______.
acetyl coenzyme A
The class of cytoskeletal filaments known as microfilaments consist mostly of
actin filaments
Carbohydrates, fats, and proteins are oxidized within cells, which releases heat and transfers energy into the primary energy currency used by cells, which is the nucleotide ______.
adenosine triphosphate (ATP)
The strength of ligand-protein binding is a property of the binding site known as
affinity
The strength of ligand-protein binding is a property of the binding site known as _____.
affinity
The proteome of a cell is defined as _____.
all of the specific proteins expressed within the cell at a particular time
During translation, the role of transfer RNA (tRNA) is to bind a free ______ in the cytosol and deliver it to the ribosome where mRNA specifies the sequence of a growing polypeptide.
amino acid
Each aminoacyl-tRNA synthetase recognizes and attaches a specific _______ to a tRNA molecule based on the anticodon of the tRNA.
amino acid
the role of tRNA during translation is to deliver ______ to the ribosome for protein synthesis.
amino acids
A specific tRNA molecule is covalently linked to a specific amino acid by an enzyme known as _______.
aminoacyl-tRNA synthetase
Reactions in which large organic molecules are synthesized out of smaller precursor molecules are referred to as ______ reactions.
anabolic
The term describing the type of metabolism in which there is synthesis of large molecules such as glycogen and proteins from smaller subunits is called
anabolism
At one end of each tRNA, there is a sequence of three nucleotides known as the _____.
anticodon
The ______ is a 3-base sequence found in tRNA
anticodon
In enzymatic reactions, enzymes ______.
catalyze the conversion of reactants into products, but are not altered themselves
The promoter is a specific sequence of DNA nucleotides that _____
binds RNA polymerase at the onset of gene transcription
An enzyme is a ____.
biological catalyst
The essential function of RNA is to ______ and use those instructions to synthesize ______.
carry a copy of information coded in DNA out of the nucleus; proteins
The genetic code specified and stored in molecules of ______ determines what ______ are synthesized in the body.
deoxyribonucleic acid (DNA); proteins
A small disk-shaped junction that mechanically links two cells together via dense plaques and cadherins is called a(n)
desmosome
______ are disk-shaped connections between cells that involve anchoring proteins known as cadherins, and which provide a strong mechanical attachment of adjacent cells in a tissue.
desmosomes
Without oxygen acting as the final _______ acceptor, oxidative phosphorylation would stop.
electron
An extensive system of cytoplasmic membranes classified as rough or smooth depending on the presence or absence of ribosomes is the ______.
endoplasmic reticulum
Name the membrane-bound organelle that is an extensive network of membranes enclosing a space that is the site of both protein and lipid synthesis.
endoplasmic reticulum
A protein that functions as a biological catalyst is a(n) _____
enzyme
The rate of enzyme-mediated reactions can be increased by increasing ______.
enzyme concentration substrate concentration enzyme activity
The human body is made up of _____ cells (eukaryotic or prokaryotic?).
eukaryotic
Not all regions of a primary mRNA transcript actually code for amino acids and are transcribed. Regions that code for amino acids and are transcribed are called _______ , while non-encoding regions removed prior to translation are referred to as ________.
exons, introns
True or false: An enzyme is consumed by the reaction it catalyzes.
false
True or false: Chemical bonds link phospholipids to one another, preventing membrane fluidity.
false
True or false: Messenger RNA (mRNA) is the only type of RNA involved in producing proteins in a cell.
false (there are 3)
Specialized proteins which help package DNA into nucleosomes are called ______.
histones
The rate of enzyme-mediated reactions is (increased or decreased?) by increasing the enzyme concentration.
increased
The percent saturation of binding sites ______ with increasing ligand concentration.
increases
The rate of an enzyme-mediated reaction _____ (increases or decreases?) as substrate concentration increases.
increases
The rate of an enzyme-mediated reaction _______(increases or decreases?) as substrate concentration increases.
increases
If there are two competing ligands for one binding site, ______ the concentration of one ligand will ______ the binding of the other ligand.
increasing; decrease
In eukaryotes, the proteins of the electron transport system that mediate oxidative phosphorylation are embedded in the ______.
inner mitochondrial membrane
Transmembrane proteins that link intracellular proteins to proteins in the extracellular matrix and contribute to the organization of cells into tissues are known as
integrins
In the electron-transport chain, proton pumps move hydrogen ions into the ______.
intermembrane space of the mitochondria
A peripheral membrane protein is one that ______.
is associated only with the polar heads of phospholipids on the inner surface of the plasma membrane and can be easily extracted
The enzyme RNA polymerase _____.
joins ribonucleotides together when DNA is transcribed into mRNA
A cyclic series of reactions that results in the complete breakdown of nutrient molecules into CO2, NADH + H+, FADH2 and ATP, is called the _______ cycle.
krebs
The tricarboxylic acid cycle is also known as the citric acid or ______cycle.
krebs
The fluidity, or motion, of the plasma membrane is primarily provided by the ______.
lack of chemical bonding and flexibility of phospholipids
The heart, brain and other tissues convert _____ back to pyruvate to be used as an energy source.
lactate
In each specialized human cell, the number of genes that are expressed will be ______ the number of genes in the genome.
less than
Compare written language to genetic language by matching these components of each.
letters --> nucleotide bases Words --> triplet codes Sentences --> Genes
A chemical that binds reversibly to a receptor site on a protein, like a neurotransmitter that binds to a membrane receptor, is described in general as a chemical ______.
ligand
______ is a general term describing a molecule that binds to a specific region on a protein by electrical or hydrophobic forces.
ligand
Based on what you know of the naming of enzymes, which of the following would be an example of an enzyme?
lipase
Lactic acid formed during glycolysis is taken up by the _____ and used as a precursor to glucose formation.
liver
Which class of RNA molecules codes for the entire sequence of a protein?
messenger RNA
RNA molecules that are directly involved in producing proteins are ribosomal RNA, _______ RNA (mRNA), and _______ RNA (tRNA).
messenger, transfer
The synthesis and breakdown of organic molecules required for cell structure and function and the release of chemical energy for cell functions are collectively referred to as
metabolism
Cytoskeletal elements called _____ form the central core of the cilia and radiate from a region of the cell known as the centrosome
microtubules
The largest and most rigid of the cytoskeletal elements, which provide the framework that maintains the long cylindrical shape of neuronal processes, are called
microtubules
Name the cellular location for the Krebs cycle.
mitochondria
The organelle that contains the enzymes necessary to produce ATP for use by the cell is the
mitochondria
The rate-limiting reaction of a multienzyme pathway is likely to occur ______.
more slowly than all the others
Environmental factors, such as chemicals or radiation, that cause alterations from the normal nucleotide sequence are called
mutagens
Any change in the nucleotide sequence of a coding region of a DNA molecule, often resulting in a change of structure and function in the protein produced, is known as a(n)
mutation
The plasma membrane is made up mainly of phospholipids and _____.
proteins
The term that refers to all of the specific proteins expressed in a particular cell at a particular time is the _____ of the cell.
proteome
The action of _____ creates a higher concentration of hydrogen ions in the mitochondrial intermembrane space than the matrix.
proton pumps
In the equation describing glycolysis, one molecule of glucose is broken down and the products include two ATP, two NADH, two H+, two molecules of H2O, and two molecules of
pyruvate
Ribosomes are made of _____.
rRNA and protein
In a multienzyme metabolic reaction, the step that determines the overall activity of the pathway is called the ______.
rate-limiting reaction
The ______ of a cell are responsible for protein synthesis.
ribosomes
The cellular structures that serve as the protein factories of a cell are the
ribosomes
Proteins destined to be secreted from a cell are manufactured in the ______.
rough ER
You were able to radioactively tag and thereby trace an amino acid that is used to make insulin, a hormone that will be exported out of the cell. The pathway of the tagged amino acid would be ______.
rough ER; Golgi apparatus; Golgi vesicle; extracellular fluid
The endoplasmic reticulum that has a flattened-sac appearance and is covered with ribosomes is the
rough endoplasmic reticulum
With regard to ligand binding to proteins in solution, the fraction of binding sites occupied at any given time is referred to as the percent
saturation
Some of the Golgi vesicles become lysosomes, while others become ______ containing proteins that are released from the cell through exocytosis.
secretory vesicles
Proteins manufactured for incorporation into cell membranes or for secretion from a cell have a 15-30 amino segment at the beginning called a(n)
signal sequence
The substance that an enzyme acts upon is the
substrate
The substance upon which an enzyme acts is called a(n) ____
substrate
During translation, the molecule that binds to a free amino acid in the cytosol and delivers it to the ribosome is
tRNA
The initiation of protein synthesis occurs when a ______ molecule containing the amino acid methionine binds to the small ribosomal subunit.
tRNA
An example of catabolism is _____.
the breakdown of a triglyceride to glycerol and fatty acids
Catabolism is ______.
the breakdown of larger molecules into smaller ones
The polar head groups of plasma membrane phospholipids face ______; the nonpolar tails face ______.
the extracellular and intracellular fluid spaces; the interior of the membrane bilayer
The portion of plasma membranes that acts as the main barrier to the movement of polar molecules across the lipid bilayer of cells is ______.
the nonpolar tails of phospholipids
What portion of a cell's structure confers the property of "selective permeability?"
the plasma membrane
The definition of the term metabolism is ______.
the synthesis and breakdown of organic molecules required for cell structure and function and the release of chemical energy used for cell functions
Substrate-level phosphorylation involves _____.
the transferring of phosphate to ADP from another molecule
A consecutive sequence of ______ DNA nucleotides codes for one ______.
three; amino acid
Cells that lack mitochondria, like red blood cells, must derive all of their energy _____.
through glycolysis
The type of cell junction that holds cells together and seals off the space between adjacent cells making it difficult for substances to pass between cells is a(n)
tight junction
The type of intercellular junctions in which neighboring cells are connected in a band around the entire circumference of the cell, and which typically create barriers to movement of molecules between epithelial cells are known as ______.
tight junctions
The enzyme RNA polymerase participates in _____.
transcription
The process of copying the information encoded in DNA into messenger RNA is called ______.
transcription
During protein synthesis, the step using DNA to make mRNA is called ______, and the step in which mRNA is "read" to make protein is called ______.
transcription; translation
Indicate the events that occur during translation (select all that apply)
transfer RNA (tRNA) delivers an amino acid to the ribosome transfer RNA (tRNA) anticodon binds to complementary mRNA codon ribosome binds messenger RNA (mRNA) a new amino acid is linked to the growing peptide chain
Conversion of nucleotide sequences into amino acid sequences is known as ______.
translation
The process of synthesizing a protein from the nucleotide sequence encoded by an mRNA molecule is known as
translation
An integral membrane protein that associates with phospholipid fatty acid tails and phospholipid polar head groups on both surfaces of the bilayer would be categorized as a(n)
transmembrane protein
One amino acid is coded for by a ______ of DNA nucleotides.
triplet