Chapter 3
What are the 3 possible destinies of cells?
(1) Remain alive and functioning without dividing (2) Grow and divide (3) Die Apoptosis Programmed cell death Disease or damage
Antiporter
(also called exchanger or counter-transporter) is a cotransporter and integral membrane protein involved in secondary active transport of two or more different molecules or ions across a phospholipid membrane such as the plasma membrane in opposite directions, one into the cell and one out of the cell
During which phase of mitosis do the sister chromatids move apart? A) Prophase B) Metaphase C) Anaphase D) Telophase
Anaphase
What are 3 functions of membrane enzymes?
Breakdown chemical messenger to stop their signaling effects Final stages of starch and protein digestion in small intestine Produce second messengers (cAMP)
When do cells divide (5 conditions)? When do cells stop dividing (2 conditions)?
Cells divide when: Have enough cytoplasm for 2 daughter cells Open space due to neighboring cell death DNA replicated Adequate supply of nutrients Growth factor stimulation Cells stop dividing when: Contact inhibition Loss of growth factors or nutrients
What are the two gradients we discussed? What happens when you have both?
Concentration gradient: difference in the concentration of a chemical between one side of the plasma membrane and the other Electrical gradient: difference in concentration of ions between one side of the plasma membrane and the other
List and explain the steps of translation including messenger RNA, transfer RNA, and ribosomal RNA. What are the start and stop codons and why are they important?
Converts alphabet of nucleotides into a sequence of amino acids to create a specific protein Initiation Ribosome formation in cytosol or on rough ER Small subunit attaches to mRNA leader sequence Large subunit joins and pulls mRNA along as it "reads" it start codon (AUG) where protein synthesis begins Small subunit binds activated tRNA with corresponding anticodon Large subunit enzyme forms peptide bond Elongation Growth of polypeptide chain Next codon read, next tRNA attached, amino acids joined, first tRNA released, process repeats and repeats Termination Stop codon reached and process halted polypeptide released and ribosome dissociates into 2 subunits Transfer RNA (tRNA) - Focus Figure 3.4 Activation by ATP binds specific amino acid Provides necessary energy to join amino acid to growing protein molecule Anticodon binds to complementary codon of mRNA Protein Synthesis During Translation - Focus Figure 3.4
Explain transcription. How are base triplets and codons used to interpret the DNA code? What is pre-mRNA? What happens to it before it leaves the nucleus? How does it leave the nucleus?
Copying instructions from DNA to RNA Messenger RNA (mRNA) is formed next to an activated gene RNA polymerase binds to DNA Opens DNA helix and transcribes bases from 1 strand of DNA into pre-mRNA Rewinds DNA helix Pre-mRNA is unfinished "Nonsense" (introns) removed by enzymes "Sense" (exons) reconnected and exit nucleus mRNA migrates to cytoplasm
What is the name of the process by which the cytoplasm divides in two? A) Cytokinesis B) Segregation C) Cytoplasmic streaming D) Microtubule shortening
Cytokinesis
What are the differences between DNA and RNA? What are the 3 main components of each? What bases are used in each and how do they pair (what type of bonds are involved?)? What is the law of complementary base pairing?
DNA: deoxyribose, RNA: ribose Main components: Phosphate, ribose/sugar, and nitrogenous base Bases DNA: AT, CG RNA: AU, CG
What is the structure of DNA? What is the function of DNA? What is a gene?
DNA: directs the synthesis of all cell proteins base paris: AT, CG Gene: one of the biological units of heredity located in DNA
How does carrier mediated transport differ from a membrane enzyme? What are the two types of carrier mediated transport and how do they differ?
Differs from membrane enzymes because solutes are unchanged Types of carrier mediated trasnport Uniporter: carries only one solute at a time Symporter: carries 2 or more solutes simultaneously in same direction (cotransport)
The cell cycle is divided into two main parts: interphase and cell division. Interphase is the period in which the cell is performing normal functions and not actively engaged in cell division. Most of your body's cells spend a lot of their time in interphase. Before a cell can divide, what must occur during interphase? Select the best answer. A) The sister chromatids separate into chromosomes. B) The DNA relaxes into chromosomes. C) The cell only performs its normal cell functions. D) Each chromatin fiber is duplicated in the nucleus.
Each chromatin fiber is duplicated in the nucleus.
What is endocytosis? How is receptor-mediated endocytosis different than phagocytosis and pinocytosis?
Endocytosis: transport into cell Phagocytosis: engulfing large particles - Figure 3.12a Pinocytosis: "Cell drinking," taking in droplets of ECF, membrane caves in, then pinches off into the cytoplasm as pinocytotic vesicle - Figure 3.12b Receptor mediated endocytosis - Figure 3.12c Taking in specific molecules bound to receptors through selective endocytosis Receptor specificity Cathrin-coated vesicle in cytoplasm: uptake of LDL from bloodstream
What is unique about the evolution and development of the mitochondrion?
Evolved from bacteria that invaded primitive cell but was not destroyed. Double membrane formed from bacterial membrane and phagosome
What is exocytosis? Explain transcytosis and why it would be useful.
Exocytosis: transport out of the cell Transcytosis: combination of endocytosis and exocytosis used to move substances from one side of a cell, across it, and out the other side
What is the plasma membrane? What are the 3 main components of the plasma membrane? Explain what a phospholipid bilayer is and why it is important to cell function.
Flexible, yet sturdy barrier that surrounds and contains the cytoplasm of the cell Three main components: (1) Membrane Lipids: (1a)Phospholipid bilayer: two parallel sheets of phospholipid molecules lying tail to tail, with their polar heads bathed in water on either side of the membrane. Defines cell boundaries, controls interactions with other cells, controls passage of materials in and out of cell (1b)Cholesterol: wedges platelike hydrocarbon rings between phospholipid tails, which stiffens the membrane (1c)Glycolipids: Glycocalyx (coating on cell surface) (2) Membrane Proteins: 2% of molecules, 50% of its weight (3) Carbohydrates
What are 4 functions of the Na+-K+ pump? What type of pump is it? How does it work?
Four functions: regulation of cell volume heat production maintenance of a membrane potential in all cells secondary active transport Sodium-potassium pump Figure 3.2
What is the glycocalyx? What is it made of? Why is it important?
Glycocalyx: carbohydrate/sugar coating on cell surface that may be used for recognition of the cell or protective coat from host factors
Drinking alcohol makes the blood hypertonic. Which option best describes the consequences of this hypertonic blood? A) Hypertonic blood will lose water to the interstitial fluid, which makes the interstitial fluid hypertonic. This, in turn, causes water to move into the cell. B) Hypertonic blood forces water into the interstitial fluid, which makes the interstitial fluid hypotonic. This, in turn, makes the interstitial fluid lose water to the cells. C) Hypertonic blood draws water out of the interstitial fluid, which makes the interstitial fluid hypotonic. This, in turn, makes the interstitial fluid lose water to the cells. D) Hypertonic blood draws water out of the interstitial fluid, which makes the interstitial fluid hypertonic. This, in turn, draws water out of the cells.
Hypertonic blood draws water out of the interstitial fluid, which makes the interstitial fluid hypertonic. This, in turn, draws water out of the cells.
What is the basic difference between simple diffusion and facilitated diffusion across a cell membrane? A) In simple diffusion, molecules move down the concentration gradient but in facilitated diffusion molecules move up the concentration gradient. B) In facilitated diffusion, molecules only move with the aid of a protein in the membrane. C) Simple diffusion requires molecules to move through special doorways in the cell membrane. D) Simple diffusion is passive but facilitated diffusion is an active process that uses energy.
In facilitated diffusion, molecules only move with the aid of a protein in the membrane.
During which phase of the cell cycle does DNA duplication, or replication, take place? A) Anaphase B) Interphase C) Metaphase D) Prophase
Interphase
Describe each phase of mitosis and the distinguishing characteristics of each phase. Note what is happening to the centrosome and chromatin in each phase.
Interphase: time between mitosis G1: organelles grow and replicate with the cell conducting specialized functions, centrioles start replication S: DNA replication produces copies of all the chromosomes that appear as two sister chromatids G2: Second period of growth and normal metabolism follows the DNA synthesis Prophase: Chromatin concentrates by folding and forming secondary coiling into chromosomes, consisting of elongated chromatids united by a centromere Nucleoli and nuclear membrane disappear into the cytoplasm Centrioles are located in the centrosome and start movement to the opposite ends of the cell, spindle fibers form between the centrioles, and complete the spindle apparatus. Metaphase: Centromeres of each chromosome line up on the metaphase plate between the two poles Anaphase: The centromeres split in half and each sister chromatid separates from its partner to become an individual chromosome. You will see two close but distinct rows of chromosomes. The spindle fibers attached to the centromeres appear to be pulling (or pushing) the chromosomes to the poles. Telophase: The two identical sets of chromosomes have reached the opposite poles. As the nuclear membrane starts to reform, the chromatin starts to unravel from their secondary folds and coils to disperse within the nucleus. The chromosomes will disappear while the nucleoli and cell membrane reappear. The spindle fibers and astral rays are reabsorbed and disappear. Cytokinesis, the division of cytoplasm, occurs at the same time as the processes of telophase. The cell membrane begins to pinch inward between the two masses of chromosomes. This cleavage furrow resembles a constricting ring and eventually cuts the cell completely in two.
Describe the structure and function of: lysosomes, peroxisomes, and proteasomes. What are the similarities and differences between them?
Lysosomes: spherical membranous organelles containing activated hydrolytic (digestive) enzymes Peroxisomes: (small lysosomes) spherical membranous sacs containing a variety of powerful enzymes, the most important which are oxidases and catalases Proteasomes: giant "waste disposal" complexes composed of protein-digesting enzymes
During which phase of mitosis do sister chromatids line up at the center of the cell? A) Metaphase B) Prophase C) Telophase D) Anaphase
Metaphase
What is the difference between microtubules, microfilaments, and intermediate filaments? Where would you find each?
Microfilaments: thinnest element of cytoskeleton; semiflexible strands of the protein actin (muscle cells) Intermediate filaments: tough, insoluble protein fibers that resemble woven ropes; made of twisted units of tetramer fibrils (nerve cells, keratin filaments in epithelial cells) Microtubules: hollow tubes made of spherical protein subunits called tubulin (centrosome)
Where would you find microvilli? Cilia? What is the difference between the two structures?
Microvilli: tiny, fingerlike extensions of the plasma membrane that project from an exposed cell surface increase the plasma membrane surface area Found on absorptive cells such as intestinal and kidney tubule cells Cillia: whiplike, motile cellular extensions that occur, typically in large number, on the exposed surfaces of certain cells Moves substance sin one direction across cell surfaces Respiratory tract
Select the best answer describing the importance of the active second messenger. A) Molecules like cAMP or ions like Ca2+ will perpetuate the 1st messengers signal intracellularly. B) The 2nd messenger is used to deactivate the G protein for the next reaction sequence. C) Molecules like cAMP or ions will inactivate cell proteins. D) 2nd messengers are used specifically to activate proteins.
Molecules like cAMP or ions like Ca2+ will perpetuate the 1st messengers signal intracellularly.
Which of the following is most likely to move through the cell membrane by facilitated diffusion? A) O2 B) Na+ C) small lipids D) CO2
Na+
What is an organelle? What does anucleate mean? What does multinucleate mean? Give an example of an each.
Organelle: small subcellular structures that perform specific functions for the cell as a whole (ribosomes, mitochondria, and others). Anucleate: cell without a nucleus (e.g., red blood cells). Multinucleate: cell with more than one nucleus (e.g., skeletal muscle cells).
Explain osmosis and isotonic. What happens to cells in a hypotonic solution? What happens to cells in a hypertonic solution?
Osmosis: diffusion of a solvent through a selectively permeable membrane Isotonic: normal saline Hypotonic: low concentration, high water concentration; cells absorb water, swell and lyse Hypertonic: high concentration, low water concentration; cells lose water, shrivel (crenate)
What is the difference between passive and active membrane transport? Give an example of each.
Passive transport: movement down concentration gradient that does not require ATP. Simple diffusion, Facilitated diffusion, Osmosis Active transport: movement against the concentration gradient and requires ATP. Active transport, Vesicular transport
What is a polyribosome? What is the advantage of a polyribosome over a ribosome?
Polyribosome: multiple ribosome, mRNA complex efficiently produces multiple copies of the same protein
What is primary active transport? What is different about secondary active transport? Give an example of each.
Primary active transport: energy derived from ATP changes the shape of a transporter protein which pumps a substance across a plasma membrane against its concentration gradient Na+-K+ pump Secondary active transport: hydrogen or sodium concentration gradient used to drive other substances against their own concentration gradients ATP used to generate H+ or Na+ gradient
During which phase of mitosis do the nuclear envelope and nucleoli disappear? A) Metaphase B) Prophase C) Anaphase D) Telophase
Prophase
Why are signaling peptides important? What types of posttranslational modification occur? Where?
Proteins destined for secretion or packaging are assembled on rough ER and sent to Golgi complex Signal recognition particle (SRP) Drags new protein from ribosome through pore into cisterna of ER Posttranslational modification of protein in ER Remove some amino acids, fold the protein adding disulfide bridges or adding carbohydrates Rough ER pinches off transport vesicles Fuse with and empty into nearestGolgi complex
How does the second messenger system work? What are the steps of the second messenger cascade?
Second messenger systems are messages that come to the cell and start a response leading to physiological changes in the cell Steps: Chemical messenger/ligand (epinephrine) binds to a surface receptor Receptor activates G protein G protein binds to adenylate cyclase (membrane enzyme) which converts ATP to cAMP(2nd messenger) cAMP activates a kinase in the cytosol Kinases activate or inactivate other enzymes triggering physiological changes in cell
What is the structure of RNA? What is the function of RNA?
Single stranded, AU, CG Carries out DNA's instructions for polypeptide synthesis
What are the factors affecting the diffusion rate through a membrane? How do cells control permeability?
Steepness of concentration gradient= ↑ difference, ↑ rate Temperature= ↑ temp., ↑ motion of particles Molecular weight= Larger molecules move slower Membrane surface area= ↑ area, ↑ rate Membrane permeability= ↑ permeability, ↑ rate
How is DNA replicated? What does semiconservative replication mean? How do humans reduce errors during DNA replication? What are two possible reasons for mutations?
Steps of replication process DNA helicase opens short segment of helix Replication Fork is point of separation of 2 strands DNA polymerase assembles new strand of DNA next to one of the old strands DNA polymerase enzymes at work simultaneously Semiconservative replication: each new DNA molecule contains one new helix and one conserved from parent DNA
During which phase of mitosis do nuclear envelopes and the nucleoli reappear? A) Metaphase B) Anaphase C) Prophase D) Telophase
Telophase
What are the 5 tenants of modern cell theory?
The cell is the smallest unit/simplest structure of life All organisms are made of one or more cells Calls only arise from other cells Organism's structure and functions are due to the activities of its cells Cells of all species have many fundamental similarities
If a person is severely dehydrated, their extracellular fluids will become hypertonic to the intracellular fluid. What do you predict will happen to the person's cells? A) The cells will lose water and shrink. B) The cells will rupture. C) Extracellular fluids do not impact cell size, because cells contain intracellular fluid. D) The cells will swell.
The cells will lose water and shrink.
How do phospholipids form the "bilayer" of the plasma membrane? A) Phospholipids orient themselves in two layers so that the tails of one layer of phospholipids are attracted to the heads of another layer. B) The hydrophilic heads face the extracellular fluid and cytosol while the hydrophobic tails face each other. C) The hydrophilic heads face each other while the hydrophobic tails face the extracellular fluid and the cytosol. D) Phospholipids randomly arrange themselves in two layers with no particular orientation.
The hydrophilic heads face the extracellular fluid and cytosol while the hydrophobic tails face each other.
Which of the following is characteristic of cilia? A) They are substantially longer than flagella, and are less common than flagella in humans. B) They are used for cellular adhesion. C) They are whiplike, motile cellular extensions that occur in large numbers on the exposed surfaces of certain cells. D) They move substances in many directions across a cell's surfaces.
They are whiplike, motile cellular extensions that occur in large numbers on the exposed surfaces of certain cells.
What are the 4 types of membrane channel proteins? What is the difference between a membrane channel protein and a membrane carrier protein?
Transmembrane proteins with pores Gated channels Open channels Transmembrane proteins that bind to solutes and transfer them across membrane Pumps that consume ATP
What is the transport maximum?
Transport rate when all carriers are occupied/saturated Compare and contrast simple and facilitated diffusion.
List and describe 6 functions of membrane proteins.
Transport: channels/carriers for membrane transport Receptors for signal transduction: binding site that fits specific chemical messengers Enzyme Activity: metabolic pathways Cell-cell recognition: identification tags for other cells Attachment to the cytoskeleton and extracellular matrix (ECM): maintain cell shape Cell-to-cell joining: intercellular junctions
Compare and contrast uniporters, antiporters, and symporters.
Uniporter: carries only one solute at a time Symporter: carries 2 or more solutes simultaneously in same direction (cotransport) Antiporter: carries 2 or more solutes in opposite directions (countertransport
Polyribosome
a cluster of ribosomes linked together by a molecule of messenger RNA and forming the site of protein synthesis
Nitrogenous base
a nitrogen-containing organic compound that has the chemical properties of a base, especially a pyrimidine or purine
DNA
a nucleic acid found in all living cells; it carries the organism's hereditary information
Base triplet
a sequence of three bases that codes for a specific amino acid
Thymine
a single-ring base (a pyrimidine) found in DNA
Uracil
a smaller, single-ring base (a pyrimidine) found in RNA
Isotonic
a solution with a concentration of nonpenetrating solutes equal to that found in the reference cell
What is a membrane potential? A) the ability of the cells to perform their specialized functions B) a voltage or electrical charge across the plasma membrane C) cooperation between cells D) the possibility of cell activity
a voltage or electrical charge across the plasma membrane
Membrane pumps
active transport system that uses ATP to power transport proteins
Symporter
an integral membrane protein that is involved in the transport of many differing types of molecules across the cell membrane
Uniporters
an integral membrane protein that transports a single type of substrate species (charged or uncharged) across a cell membrane
In which stage of the cell cycle does a cell contain twice its normal number of chromosomes? A) prophase B) metaphase C) anaphase D) S phase of interphase
anaphase
Which of the following membranous proteins help a cell maintain its shape and structural integrity? A) attachment proteins B) transport proteins C) glycoproteins D) enzymes
attachment proteins
Hypotonic
below normal tone or tension
Nucleotide
building block of nucleic acids; consists of a sugar, a nitrogen-containing base, and a phosphate group
Select the most appropriate description of the figure just above. A) cAMP activates enzymes that in turn, produce a further cascade of cellular responses. B) Three activated kinase enzymes are responsible for metabolic and structural changes in the cell. C) Activated kinase enzymes act upon cAMP to produce a further cascade of cellular responses. D) The cascade of events is finished when the kinase enzymes are activated.
cAMP activates enzymes that in turn, produce a further cascade of cellular responses.
Cytoskeleton
cell skeleton; elaborate series of structural proteins running through the cytosol, supporting cellular structures, and providing the machinery to generate various cell movements.
Which of the following is not required for osmosis to occur? A) selectively permeable membrane B) water C) cellular energy D) concentration gradient
cellular energy
When a double helix of DNA is replicated, two complete helices are formed. Together, these helices are called sister __________. A) chromosomes B) chromatids C) telomeres D) centromeres
chromatids
Nucleus
control center of a cell that contains genetic material.
Ribosome
cytoplasmic organelles at which proteins are synthesized
Mitochondria
cytoplasmic organelles responsible for ATP generation for cellular activities
Pinocytosis
engulfing of extracellular fluid by cells
Phagocytosis
engulfing of solids by (phagocytic) cells
Hypertonic
excessive, above normal, tone or tension
A vesicle fuses with the plasma membrane and releases its contents to the extracellular fluid. This statement describes _____. A) endocytosis B) facilitated diffusion C) exocytosis D) simple diffusion E) active transport
exocytosis
Some transport processes use transport proteins in the plasma membrane, but do not require ATP. This type of transport is known as _____. A) active transport B) simple diffusion C) facilitated diffusion D) endocytosis E) exocytosis
facilitated diffusion
The majority of water molecules moving across plasma membranes by osmosis do so via a process that is most similar to ____. A) active transport B) cotransport c) facilitated diffusion D) simple diffusion E) a process that requires energy from the cell
facilitated diffusion
Which of the following is not a major function of proteins in the cell membrane? A) forming the entire glycocalyx B) anchoring cells to other structures C) acting as receptors D) forming channels
forming the entire glycocalyx
Which of the following would be found in the glycocalyx of a cell? A) attachment proteins B) phospholipids C) glycoproteins D) enzymes
glycoproteins
Which of the following solutions contains the most solute? A) hypotonic B) isotonic C) equilibrium D) hypertonic
hypertonic
Transmembrane protein
integral proteins that span the entire membrane and protrude on both sides
Second messenger system
intracellular system that begins by an effector protein enzyme; second messengers (cAMP or ionic calcium) activate other enzymes or ion channels
In general, to maintain homeostasis the relationship between our intracellular and extracellular fluids should be which of the following? A) intracellular and extracellular should both be hypertonic B) isotonic to each other C) intracellular should be hypotonic to extracellular D) intracellular should be hypertonic to extracellular
isotonic to each other
When does cytokinesis begin? A) late anaphase B) late prophase C) late interphase D) late telophase
late anaphase
Messenger RNA (mRNA)
long nucleotide strands that reflect the exact nucleotide sequences of the genetically active DNA and carry the DNA's message
Pre-mRNA
mRNA that is initially made and is still littered with introns
Endocytosis
means by which fairly large extracellular molecules or particles enter cells
Exocytosis
mechanism by which substances are moved from the cell interior to the extracellular space as a secretory vesicle fuses with the plasma membrane
Plasma membrane
membrane composed of phospholipids, cholesterol, and proteins; encloses cell contents
Active transport
membrane transport processes for which ATP is directly or indirectly required
Peroxisome
membranous sacs in cytoplasm continuing powerful oxidase enzymes that use molecular oxygen to detoxify harmful or toxic substances, such as free radicals
Golgi complex
membranous system close to the cell nucleus that packages protein secretions for export, packages enzymes into lysosomes for cellular cuse, and modifies proteins destined to become part of cellular membranes
Smooth ER
meshwork of fine disklike tubular membrane vesicles, part of a continuous membrane organelle within the cytoplasm of eukaryotic cells, that is involved in the synthesis and storage of lipids, including cholesterol and phospholipids, which are used in the production of new cellular membrane. Unlike rough ER, there are no ribosomes in its structure.
A primary active transport process is one in which __________. A) molecules pass directly through the phospholipid bilayer of the plasma membrane B )molecules move across the plasma membrane without an input of energy C) the plasma membrane folds inward to form a vesicle containing extracellular material D) molecules move through transport proteins that have been activated by ATP E) an intracellular vesicle fuses with the plasma membrane and releases its contents to the extracellular fluid
molecules move through transport proteins that have been activated by ATP
Which of the following best explains diffusion? A) movement of molecules from an area of high concentration to an area of low concentration B) movement of molecules from where there are fewer of them to where there are more C) movement of molecules farther away from equilibrium D) exchange of nonpolar molecules for polar molecules
movement of molecules from an area of high concentration to an area of low concentration
Cytosine
nitrogen-containing base that is part of a nucleotide structure
RNA
nucleic acid that contains ribose and the bases A, G, C, and U. Carries out DNA's instructions for protein synthesis
Gene
one of the biological units of heredity located in DNA; transmits hereditary information
Adenine
one of the two major purines found in both RNA and DNA; also found in various free nucleotides of importance to the body, such as ATP
Guanine
one of the two major purines occurring in all nucleic acids
Rough ER
organelle found in eukaryotic cells with a main function of producing proteins
Lysosome
organelles that originate from the golgi apparatus and contain strong digestive enzymes
Facilitated diffusion
passive transport process used by certain large or charged molecules (glucose, Na+) that are unable to pass through the plasma membrane unaided. Involves movement through channels or movement facilitated by a membrane carrier
Carrier mediated transport
passive transport that occurs as lipid-insoluble solutes move across the membrane in a carrier specific protein
What part of a cell membrane is usually in contact with the interstitial fluid? A) fatty acid tails B) cholesterol C) hydrophobic molecules D) phosphate heads of phospholipids
phosphate heads of phospholipids
Which of the following is the main component of the cell membrane? A) carbohydrates B) phospholipids C) water D) cholesterol
phospholipids
The sodium-potassium pump uses ATP to move sodium and potassium ions across the plasma membrane. This statement describes _____. A) facilitated diffusion B) exocytosis C) simple diffusion D) primary active transport E) secondary active transport
primary active transport
Mitosis
process during which the chromosomes are redistributed to two daughter nuclei; nuclear division (prophase, metaphase, anaphase, and telophase)
Alternative splicing
process that enables a messenger RNA (mRNA) to direct synthesis of different protein variants (isoforms) that may have different cellular functions or properties
Signal peptide
properties of the amino acids that constitute the signal peptide region of a protein are the significant factors determining interaction with the protein transport system, hence the destination to which that protein is delivered
In which stage of the cell cycle does the cell condense chromatin into chromosomes? A) prophase B )interphase C) anaphase D) metaphase
prophase
Peripheral protein
proteins that are attached loosely to integral proteins or have a hydrophobic region that anchors them to membranes.
Which of the following parts of the plasma membrane would most likely respond to a hormone in the bloodstream? A) enzymes B) phospholipids C) receptor proteins D) glycoproteins
receptor proteins
Which of the following is a characteristic of the cell membrane? A) not permeable B) impermeable C) fully permeable D) semipermeable
semipermeable
Transfer RNA (tRNA)
short-chain RNA molecules that transfer amino acids
Which of the following is least likely to increase the rate of diffusion? A) higher concentration of molecules B) small concentration gradient C) small molecule size D) high temperature
small concentration gradient
Organelle
small subcellular structures (ribosomes, mitochondria, and others) that perform specific functions for the cell as whole.
Chromatin
strands of DNA (genes) and associated proteins; forms chromosomes when condensed (tightly coiled)
Passive transport
substances cross the membrane without any energy input from the cell
Cytoplasm
the cellular material surrounding the nucleus and enclosed by the plasma membrane.
Translation
the second major step in the transfer of genetic code information, in which the information carried by mRNA is decoded and used to assemble polypeptides
Receptor mediated endocytosis
the type of endocytosis in which engulfed particles attach to receptors before endocytosis occurs
Codon
three-base sequence on a messenger RNA molecule that provides the genetic information used in protein synthesis; codes for a given amino acid
What is the purpose of the S phase of interphase? A) to produce enough cytoplasm for the cell to divide into two new cells B) to divide the cytoplasm and separate the cell into two new cells C) to synthesize additional chromosomes before mitosis begins D) to form sister chromatids that can be separated during mitosis
to form sister chromatids that can be separated during mitosis
Transcription
transfer of genetic code information from a DNA base sequence to the complementary base sequence of an mRNA molecule; the first major step in polypeptide synthesis
Membrane carriers
transmembrane proteins that are specific for transporting certain polar molecules or classes of molecules, such as sugars and amino acids, that are too large to pass through membrane channels
Membrane channel proteins
transmembrane proteins that transport substances, usually ions or water, through aqueous channels from one side of the membrane to the other
Phospholipid bilayer
two layers of phospholipids arranged in such a way that their hydrophobic tails are projecting inwards while their polar head groups are projecting on the outside surfaces
Semiconservative replication
two parental strands separate and each makes a copy of itself. After one round of replication, the two daughter molecules each comprises one old and one new strand
Simple diffusion
unassisted transport across a plasma membrane of a lipid-soluble or very small particle
Transport maximum
when all carriers are engaged or saturated
