Ch 3 Activity 1. Briefly describe the fluid mosaic model. Answer: The fluid mosaic model states that the molecular arrangement of the plasma membrane resembles an ever-moving sea of fluid lipids containing a mosaic of many different proteins. 2. The polar portion of a cholesterol molecule, which forms hydrogen bonds with the polar heads of neighboring phospholipids and glycolipids, consists of a a) –OH group. d) –COOH group b) –CH3 group. e) None of these choices is correct. c) –CH4 group 3. Describe five different functions of integral membrane proteins. Answer: Some membrane proteins act as ion channels or carriers that transport substances across the membrane. Other membrane proteins act as receptors that allow the cell to respond to various types of ligands. Other membrane proteins are enzymes that catalyze specific chemical reactions. Still other membrane proteins act as linker proteins that anchor cells to neighboring structures including other cells. Lastly, some membrane proteins serve as cell identity molecules. 4. Which of the following types of membrane proteins function by recognizing and binding to hormones and neurotransmitters? a) transporters d) linkers b) receptors e) cell identification markers c) enzymes 5. This type of membrane protein anchors cells to neighboring cells and to protein filaments found outside or inside the cell. a) transporters d) ion channels b) receptors e) linkers c) ligands 6. Plasma membranes are _____, which means that some chemicals move easily through plasma membrane while other chemicals do not. a) selectively permeable d) selectively soluble b) concentration graded e) electrical insulators c) electrically graded 7. Briefly describe the driving force for the movement of water across plasma membranes. Answer: Water moves across membranes by osmosis, which is driven by solute concentration differences across the membrane. Water moves from the area of low solute concentration to the area of high solute concentrations. 8. In this type of transport process, a solute (e.g. glucose) binds to a specific carrier protein on one side of the membrane. This binding induces a conformational change in the carrier protein that results in the solute moving down its concentration gradient to the other side of the membrane. a) osmosis d) facilitated diffusion b) active transport e) endocytosis c) secondary active transport 9. What transport process uses the energy stored in a Na+ or H+ concentration gradient to drive other substances across the membrane against their own concentration gradients? a) primary active transport d) passive diffusion b) secondary active transport e) osmosis c) facilitated diffusion 10. Which of the following transport processes uses vesicles that fuse with the plasma membrane to secrete materials into the extracellular fluid? a) endocytosis d) osmosis b) exocytosis e) Both endocytosis and exocytosis. c) facilitated diffusion 11. Which of the following transport process uses vesicles formed at the plasma membrane to take up extracellular substances and import them into the cell? a) endocytosis d) osmosis b) exocytosis e) Both endocytosis and exocytosi c) facilitated diffusion 12. List the steps involved in receptor-mediated endocytosis. Answer: The steps involved in receptor-mediated endocytosis include 1)ligand binding, 2)vesicle formation, 3)uncoating of the vesicle, 4)fusion of the vesicle with endosome, 5)recycling of receptors to the plasma membrane, and 6)degradation of the ligand in the lysosome. 13. During phagocytosis, binding of a particle to a plasma membrane receptor triggers formation of _____, which are extensions of the plasma membrane of the phagocyte that eventually surround the particle forming a phagosome. a) podocytes d) pseudopods b) exterior vesicles e) lysosomes c) interior vesicles 14. Which of the following is NOT a characteristic of the cytosol? a) primarily consists of water b) cation of electron transport chain carrier proteins c) site of many important chemical reactions d) often contains aggregates of triglycerides that form lipid droplets e) contains the enzymes of glycolysis 15. Specialized structures within a cell that have a characteristic shape and perform specific functions in cellular growth, maintenance and reproduction are called a) organelles. d) cytosol. b) cytoskeletons. e) nuclei. c) cytoplasm. 16. This cellular organelle is comprised of a pair of centrioles and the surrounding pericentriolar material. a) cytoskeleton d) flagella b) cilia e) peroxisomes c) centrosome 17. Spermatozoa is the only type of human cell that contains a _____, which is a whip-like structure that helps propel the sperm towards an oocyte. a) cilium d) centrosome b) flagellum e) microvillus c) mitochondria 18. Briefly state the functions of the rough and smooth endoplasmic reticulum. Answer: The rough endoplasmic reticulum synthesizes glycoproteins, phospholipids and digestive enzymes that are transferred to other cellular organelles, inserted into the plasma membrane, secreted during exocytosis or stored in the lysosomes. The smooth endoplasmic reticulum synthesizes fatty acids and steroids, detoxifies harmful substances, removes phosphate groups from glucose-6-phosphate, and stores and releases calcium ions that trigger contractions in muscle fibers. 19. Briefly describe how proteins move through the Golgi complex. Answer: Proteins are packaged into transport vesicles by the rough endoplasmic reticulum membrane. These vesicles enter on the (cis) face of the Golgi complex, and the proteins move through the cisternae, from (cis) face through to exit (trans) face. Proteins will leave from the (trans) face of the Golgi complex in vesicles that will deliver the protein to plasma membrane, secretory vesicles, or to other organelles in the cell. 20. Which of the following membrane-enclosed organelles contains several oxidases that are involved in oxidation of fatty acids and amino acids during normal metabolism and in detoxification of chemicals like alcohol in the liver? a) peroxisomes d) ribosomes b) mitochondria e) lysosomes c) proteasome 21. The major function of mitochondria is to a) move the cell. d) oxidize organelles. b) generate ATP. e) synthesize glycolipids. c) produce proteins. 22. What is the major function of histones? a) needed for helix formation of the DNA b) add negative charge to the DNA c) help organize coiling and folding of the DNA d) degrade faulty proteins in the nucleus e) catalyze methylation of the DNA 23. Briefly explain the difference between transcription and translation. Answer: Transcription is making mRNA from DNA and it occurs in the nucleus, while translation is making a protein from the information in mRNA and happens in the cytosol of the cell. 24. This portion of a DNA segment does not code for a protein. a) RNA d) polyribosome b) introns e) ribosome c) exons 25. Briefly describe alternative splicing. Answer: Alternative splicing of mRNA is a process in which the pre-mRNA transcribed from a gene is spliced in different ways to produce several different mRNAs. The different mRNAs are used to make different proteins. 26. Define homologous chromosomes. Answer: Homologous chromosomes contain similar genes arranged in the same (or almost the same) order. 27. Most intravenous solutions are _____ with respect to blood cells? a) tonicity b) isotonic c) hypertonic d) osmotic e) hypotonic 28. In the diagram, which organelle is responsible for autophagy and autolysis? a) C b) B c) F d) J e) D 29. In the diagram, which organelle is used to modify, sort and transport proteins? a) D b) I c) A d) J e) G 30. In the diagram, which organelle aids movement of the cell? a) A b) G c) H d) D e) I 31. In the diagram, this structure directs cellular activities. a) D b) F c) G d) A e) H 32. In the diagram, which one represents carrier-mediated facilitated diffusion? a) A b) B c) C d) Both A and C e) Both B and C 33. In the diagram, which one represents a hypertonic solution a) A b) B c) C d) Both B and C e) All of these choices are correct. 34. Describe briefly what is occurring at each step in the figure. Answer: This figure represents protein synthesis. Step one, the initiator tRNA attaches to a start codon. In step two, the large and small ribosomal subunits join to form a functional ribosome and initiator tRNA fits into P site. In step three, the anticodon of an incoming tRNA pairs with the next mRNA codon at A site. Step four, the amino acid on the tRNA at P site forms a peptide bond with the amino acid at A site. Step five, the tRNA at the P site leaves the ribosome and the ribosome shifts down by one codon. The tRNA previously at the A site is now at the P site. Step six is when protein synthesis stops when the ribosome reaches one of three potential stop codons on the mRNA strand. 35. Compare and contrast primary and secondary active transport. Answer: Both are energy requiring transport processes that are capable of moving substances against their concentration gradients. Energy obtained from hydrolysis of ATP drives primary active transport, while energy stored in an ionic concentration gradient drives secondary active transport. 36. Compare mitosis to meiosis. Answer: Mitosis is somatic cell division that produces two identical cells with the same number (diploid) and kinds of chromosomes as the original cell. Meiosis is reproductive cell division that produces cells in which the number of chromosomes in the nucleus is reduced in half (haploid) 38. In the diagram, which panel shows events occurring during anaphase? a) A d) D b) B e) E c) C 39. In the diagram, which panel shows the kinetochore of the centromeres aligning along the center of the mitotic spindle of the cell? a) A d) D b) B e) E c) C 40. In the diagram, which panel shows cells that are in interphase? a) A only d) A and F b) C only e) A, C, and F c) F only 41.