Anatomy Lecture 3: Cell Structures HW

What does the fluid mosaic model describe about the structure of plasma membranes? -Membranes are made of water molecules in which proteins and phospholipids dissolve. -Phospholipids in the membrane are not covalently bonded to each other. -A membrane has proteins and other components embedded among the phospholipids. -Plasma membranes have a single layer of phospholipids and proteins.

-A membrane has proteins and other components embedded among the phospholipids. -Phospholipids in the membrane are not covalently bonded to each other

Which eukaryotic cell parts is found in the cytoplasm, provides structure and support to the cell, and is composed of interconnected protein fibers? chromatin cell wall cytoskeleton endoplasmic reticulum

cytoskeleton

Nearly all eukaryotic cells contain a class of small, round organelles that contain oxidative enzymes. The enzymes break down organic substances via oxidation reactions. What are these organelles called? a) peroxisomes b) lysosomes c) ribosomes d) mitochondria

peroxisomes

Select the descriptions that apply to the smooth endoplasmic reticulum. a) a stack of membranes involved with cellular secretion b) a network of membranes associated with protein production c) a membranous structure that surrounds the nucleus without attached ribosomes d) an organelle that synthesizes fatty acids, phospholipids, and steroids e) a membrane‑enclosed organelle that stores digestive enzymes

-A membranous structure that surrounds the nucleus without attached ribosomes -An organelle that synthesizes fatty acids, phospholipids, and steroids

Which statements correctly describe the rough endoplasmic reticulum (rough ER)? a) It produces proteins that need to be modified before use. b) It has ribosomes bound to its membrane. c) It is used to transport mRNA to the cell membrane. d) It is connected to the membrane of the nucleus. e) It stores and releases calcium ions.

-It is connected to the membrane of the nucleus. -It has ribosomes bound to its membrane. -It produces proteins that need to be modified before use.

Which statements about lysosomes are true? a) Lysosomes are membrane spheres containing digestive enzymes. b) Lysosomes neutralize toxic peroxide wastes. c) Lysosomes break down intruding bacteria and viruses. d) Lysosomes are responsible for programmed cell death.

-Lysosomes are membrane spheres containing digestive enzymes. -Lysosomes are responsible for programmed cell death. -Lysosomes break down intruding bacteria and viruses.

What types of proteins does the carboxyl‑terminal domain (CTD) of RNA Polymerase II recruit to the pre‑mRNA? -capping enzymes -protein kinases -endonucleases -elongation factors -splicing machinery components

-capping enzymes -endonucleases -splicing machinery components

Select the phrases that accurately complete the sentence. The mitochondrion a) has an interior membrane with deep folds where ATP synthesis occurs. b) contains digestive enzymes that break down cellular waste and debris. c) contains unique DNA that is different from the cell's nuclear DNA. d) is a series of proteins necessary for cell structure and movement. e) is a system of membranous channels on which ribosomes produce proteins.

-has an interior membrane with deep folds where ATP synthesis occurs. -contains unique DNA that is different from the cell's nuclear DNA.

Which event occurs during eukaryotic translation termination? a) A tRNA binds a codon and the ribosome adds amino acids from each tRNA to the polypeptide chain. b) Codons in the mRNA are recognized by rRNAs, and tRNAs add the amino acid to the polypeptide chain. c) A protein recognizes the stop codon, and the ribosome dissociates from the mRNA. d) The small ribosomal subunit binds with a specific tRNA to the mRNA and scans for a start codon. e) A tRNA recognizes the stop codon, and the ribosome dissociates from the mRNA.

A protein recognizes the stop codon, and the ribosome dissociates from the mRNA.

Each type of pre‑mRNA processing has one or more important functions. Match each function with the appropriate type of processing.

Addition of 5' cap -assists mRNA in binding to the small ribosomal subunit -assists in RNA splicing Addition of poly[A] tail -stabilizes trailing end of mRNA RNA splicing -removes non-coding regions from pre-mRNA -constructs multiple products from a single gene -enables movement of mRNA out of the nucleus RNA editing -alters nucleotide sequence in exons

Multicellular organisms have many types of cells that fulfill specialized roles within the organism. Depending on their role, different cell types can vary in the numbers of certain organelles that they contain. Compare the density of mitochondria in cardiac muscle cells to the mitochondrial density in skin cells. a) Skin cells need more mitochondria because they have lower energy demands. b) Both cell types have the same energy needs, so mitochondrial density is the same in both types. c) Cardiac muscle cells contract frequently and use more energy; therefore, heart muscle cells need more mitochondria than skin cells. d) Skin cells vary throughout the body, so they have higher mitochondrial densities than cardiac muscle cells.

Cardiac muscle cells contract frequently and use more energy; therefore, heart muscle cells need more mitochondria than skin cells.

Identify cell components based on their membrane structure and contents. Some components are enclosed by a double membrane and contain DNA. Others have a single membrane and have other functions within the cell. One is not membrane‑bound. Place each cell component into the category that best describes it.

Cell components with double membranes and DNA -nucleus -mitochondrion -chloroplasts Cell components with single membranes and no DNA -endoplasmic reticulum -lysosome -vesicle Cell component with no membrane -ribosome

All cells share certain structural features, but some structures are unique to eukaryotes. Identify whether these cell components are common to all cells or unique to eukaryotic cells by classifying each cell component to the correct category.

Common to all cells -cytosol -DNA -ribosome Unique to eukaryotes -Golgi apparatus -nucleus -mitochondrion

Why is a cap added to mRNA, but not to tRNA or rRNA? a) Transfer RNA and rRNA exhibit complex structures with double stranded regions. The three-dimensional shapes of these molecules keep the 5' end of the RNA away from the enzymes that process the cap. b) Messenger RNA is transcribed and processed in the nucleus, where it can interact with the cap binding proteins that transfer the cap to the 5' end. Transfer RNA and rRNA are transcribed and processed in the cytoplasm and do not encounter capping enzymes. c) Only mRNA contains introns. The capping process requires RNA to interact with the proteins that remove introns. Therefore, the capping and splicing processes occur at the same time. d) Each of the three types of RNA are transcribed by different RNA polymerases. Only RNA polymerase II, involved in mRNA synthesis, contains a domain capable of interacting with enzymes that form the cap.

Each of the three types of RNA are transcribed by different RNA polymerases. Only RNA polymerase II, involved in mRNA synthesis, contains a domain capable of interacting with enzymes that form the cap.

Phospholipids are molecules that have two regions, the head and the tail, with distinct chemical properties. Classify the descriptions as characteristics of the heads or tails of phospholipids.

Heads -hydrophilic -polar Tails -does not mix with water -hydrocarbon-rich

How do the nucleus and ribosomes work together to generate a protein? a) In the nucleus, DNA is transcribed to mRNA, which the ribosomes use as instructions to synthesize a specific protein. b) Ribosomes migrate into the nucleus, attach to a gene in the DNA, and use the gene as a transcript to synthesize a specific protein. c) Ribosomes produce mRNA that migrates into the nucleus and uses a gene in the DNA as instructions to synthesize a specific protein. d) The segment of DNA that contains a gene leaves the nucleus and is used by the ribosomes as instructions to synthesize a protein.

In the nucleus, DNA is transcribed to mRNA, which the ribosomes use as instructions to synthesize a specific protein.

Protein synthesis is an essential part of cellular metabolism, and it requires the involvement of a number of molecules, structures, and organelles. List the molecules, structures, and organelles in the order that enables protein synthesis. Start with the instructions that encode a protein, and end with the structure through which a protein leaves the cell.

Initial Instructions DNA RNA ribosomes rough endoplasmic reticulum golgi apparatus plasma membrane Protein Leaves the Cell

Match each description to a phase of transcription in humans.

Initiation: -transcription factors and RNA polymerase bind the gene promoter Elongation: -RNA polymerase reads the template strand and synthesizes RNA Termination: -the RNA strand is cleaved and released from the transcription complex

Match each of the characteristics to the part of the lipid bilayer that has that property

Interior of lipid bilater -hydrophobic -fatty acid chains -repels polar molecules Surface of lipid bilayer -hydrophilic -contains phosphate

Which of the statements describes the structure of a centriole? a) a cylinder made up of nine sets of triplet microtubules b) a cluster of centrosomes arranged to form a cylinder c) a cylinder made up of the various fibers of the cytoskeleton d) a cylinder made up of nine sets of triplet intermediate filaments

a cylinder made up of nine sets of triplet microtubules

What transformation occurs during each of these processes?

Translation: RNA -> protein Transcription: DNA -> RNA Replication: DNA -> DNA

Which phrase best describes chromatin? a) a constricted area of the condensed form of DNA b) DNA in its duplicated, tightly condensed form c) single‑stranded DNA that cannot undergo replication d) a fiber composed of DNA and protein molecules

a fiber composed of DNA and protein molecules

Which description best describes the function of chromosomes? a) hold the strands of the DNA double helix together b) provide genetic variation that is acted upon by natural selection c) allow genes from both parents to combine during fertilization d) enable more efficient packing and transport of genetic material in mitosis

enable more efficient packing and transport of genetic material in mitosis

Select the phrases that describe the plasma membrane. a) provides a rigid structure that allows the cell to hold its shape b) regulates transport of molecules into and out of the cell c) creates a barrier between DNA and other intracellular structures d) creates a barrier between the inside and outside of the cell

regulates transport of molecules into and out of the cell creates a barrier between the inside and outside of the cell

Which cellular structure synthesizes proteins? lysosome rough endoplasmic reticulum ribosome nucleus

ribosome

Some ribosomes are used to make proteins, such as insulin, that will be modified and sent out of the cell. Where in the cell are these ribosomes most likely found? a) Golgi apparatus b) cell wall c) rough endoplasmic reticulum d) smooth endoplasmic reticulum

rough endoplasmic reticulum

What is the nuclear envelope? -one lipid bilayer that separates the intracellular space from the extracellular space -two lipid bilayers with an inner membrane that folds into cristae -two lipid bilayers that separate the contents of the nucleus from the cytoplasm -a spherical, dark‑staining body within the nucleus that generates ribosomal RNA

two lipid bilayers that separate the contents of the nucleus from the cytoplasm