Biology HW and Recitation Problem Sets

R2.2 Phospholipids are often depicted as the cartoon shown in the image. Which portion(s) of the phospholipid in the image is hydrophilic?

1

HW 2.2 The Golgi consists of flattened membrane-enclosed compartments (cisternae) that move and are renamed as they mature. Sort the Golgi compartments from the least mature to the most mature. 1) Medial Compartment 2) Trans Compartment 3) Cis Compartment

1) Cis Compartment 2) Medial Compartment 3) Trans Compartment

HW 2.2 In eukaryotes, all proteins, including nuclear proteins, are synthesized in the _____. Nuclear proteins a _________that targets them to the nucleus where they enter through _______.

1) Cytosol 2) Nuclear Localization Sequence 3) Nuclear Pore

R2.2 Which of these proteins are integral membrane proteins?

there are 3! All the ones within the bilayer

R2.2 Proteins associated with membranes through non-covalent interactions. Which amino acids would you expect to find on the surface of proteins in the protein coat model?

1) K 2) S 3) N 4) Y

HW 2.2 Insulin is a protein secreted by the cells of the pancreas. Put the following in the correct order to show the pathway for the synthesis and secretion of insulin. 1) Rough ER 2) Cell Membrane 3) Transport Vesicles containing mature proteins 4) Cis-Golgi apparatus 5) Trans-Golgi apparatus

1) Rough ER 2) Cis-Golgi apparatus 3) Trans-Golgi apparatus 4) Transport Vesicles containing mature proteins 5) Cell Membrane

R2.2 Transmembrane proteins often have one or more alpha helices within the membrane, as shown in the image. Recall that amino acid side chains extend out from the alpha helix. What amino acids would you expect to find in the helix?

1) V 2) I 3) A 4) F

R2.2 According to the current theory, all natural membranes possess

1) a lipid bilayer 2) proteins embedded in the membrane 3) phospholipids

R2.2 All natural biological membranes consist of

1) proteins 2) lipids 3) carbohydrates bound to lipids or proteins

R2.2 Which portion(s) of the phospholipid image is hydrophobic?

2 & 3

HW 2.2 Ribosomes

Complex of protein and RNA where translation occurs

HW 2.2 A glycosyltransferase protein that resides in the RER would have which of the following signal sequences? Select all that apply. a) Nuclear Localization Sequence b) ER Signal Sequence c) Peroxisomal Targeting Sequence d) Mitochondrial Targeting Sequence

ER Signal Sequence

R2.2 What is the most likely pathway taken by a newly synthesized protein that will be secreted by a cell?

ER → Golgi → vesicles that fuse with plasma membrane

HW 2.2 The _______ is an organelle that processes, packages, and sends proteins to various destinations in the cell

Golgi apparatus

HW 2.2 Vacuole

Large organelle found most often in plant; fungal; and protist cells that stores water and digest substrates.

HW 2.2 Nucleus

Location of DNA replication and transcription in eukaryotes

HW 2.2 Nucleoid

Location of genetic material in prokaryotic cells

R2.2 What effect would temperature have on the fluidity and movement of molecules of membranes?

Lower temperatures would make the membrane less fluid and decrease the rate of molecular movements.

R2.2 Why is the smooth endoplasmic reticulum unable to synthesize proteins?

No ribosomes are attached to its surface

HW 2.2 Mitochondrion

Organelle where ATP is synthesized through the process of cellular respiration

HW 2.2 Chloroplast

Organelle where light energy is harvested by chlorophyll to make ATP and NADH for the conversion of carbon dioxide to glucose

R2.2 Refer to the table showing the relative amounts of membrane types in two different kinds of eukaryotic cells. Liver hepatocytes are the primary site in the body responsible for synthesizing the lipid components that are incorporated into the lipoprotein particles, HDL and LDL, that circulate in the blood. Pancreatic exocrine cells are the primary site of insulin production. Insulin is a protein hormone necessary for glucose metabolism in body cells. Explain how the data shown in the table support the idea that these cells differentiated to carry out different functions

Proteins are located in Rough ER, which is one of the main reasons that they percentage of the Pancreatic Exocrine Cell has 60% use of the RER, while Liver Hepatocyte, a lipid which is found in the smooth ER, has a lower percentage of RER use and higher percentage in smooth ER. Also though, the percentage is a lot higher based on how lipids and proteins are synthesized within a cell. A protein ends of leaving the cell, but before then it goes from the nuclear membranes, to the mitochondrial, the RER, Golgi, and then to the cell membrane. With lipids, they are synthesized, processes, and recycled through SER, Golgi, and the cell membrane. The percentages differentiate because the way that lipids and proteins go through a cell are different from one another. Proteins use more of the organelles within a cell than a lipid does. (HINTS: RER VS. SER)

HW 2.2 The rough endoplasmic reticulum is the portion of the ER that has _______ attached to it.

Ribosomes

R2.2 Scientists have found that polypeptides which are normally synthesized in the endoplasmic reticulum are about 20 amino acids longer when they are synthesized by ribosomes not attached to the endoplasmic reticulum. What is a possible explanation for the greater length of these polypeptides?

The 20 amino acids serve as a signal (peptide) sequence that directs the forming polypeptides in ER, where they are cleaved off during processing.

HW 2.2 Is the nuclear membrane part of the endomembrane system? Why or why not?

The nuclear membrane is part of the endomembrane system as it is continuous with the rough endoplasmic reticulum.

R2.2 Which of these proteins are transmembrane proteins?

There is 1! the one that goes through the entire membrane! Reaches the top and bottom

R2.2 Which of the following best describes the fluid mosaic model of plasma membranes?

a bilayer composed of phospholipid molecules with embedded proteins

HW 2.2 Which of the following is most likely to have the greatest concentration of smooth endoplasmic reticulum (SER)? a) a cell that secretes enzymes b) a cell that destroys pathogens c) a cell that makes steroid hormones d) a cell that engages in photosynthesis

a cell that makes steroid hormones

HW 2.2 Plant cells and animal cells share many of the same structures, but each type of cell also has unique structures. Which of these structures are found in BOTH plant and animal cells? a) Mitochondrion b) chloroplast c) centriole d) Nucleus e) cell wall composed of cellulose f) Endoplasmic Reticulum g) central vacuole h) Golgi Apparatus

a) Mitochondrion d) Nucleus f) Endoplasmic Reticulum h) Golgi Apparatus

HW 2.2 Which of the following are components of the endomembrane system? a) Rough Endoplasmic Reticulum b) Golgi Apparatus c) Lysosome d) Smooth Endoplasmic Reticulum e) peroisome f) mitochondria g) chloroplast

a) Rough Endoplasmic Reticulum b) Golgi Apparatus c) Lysosome d) Smooth Endoplasmic Reticulum

R2.2 One end of a phospholipid molecule is hydrophilic, and the other end is hydrophobic. Molecules with both a hydrophobic and a hydrophilic portion are ___.

amphipathic

HW 2.2 The Golgi apparatus packages and sorts proteins to their final location. Which of the following is not a location the Golgi will send proteins to? a) To the cell membrane for secretion b) To the mitochondria c) To the cell membrane for fusion. d) To the lysosome e) Retained with the golgi (if resident proteins)

b) To the mitochondria

HW 2.2 The side of the Golgi apparatus facing the ER is the ___ face and the side facing the cell membrane is the ___ face. a) medial; cis b) cis; trans c) trans; medial d) trans; cis e) medial; trans

b) cis; trans

HW 2.2 Which of the following statements about nuclear pores is NOT true? Select all that apply a) Nuclear pore complexes control the movement of molecules across the nuclear envelope b) Small molecules such as ATP and ions can pass through freely c) Movement of large molecules such as protein complexes is completely blocked by the nuclear pore complex. d) The nuclear envelope contains thousands of nuclear pores. e) A nuclear pore is a part of a large complex of proteins known as a nuclear pore complex that spans the nuclear envelope f) A nuclear pore is a big hole created in the phospholipid bilayers due to strong hydrophobic interactions in the double membranes.

c) Movement of large molecules such as protein complexes is completely blocked by nuclear pore complex. f) A nuclear pore is a big hole created in the phospholipid bilayers due to strong hydrophobic interactions in the double membranes.

R2.2 Peroxisome

collects toxic peroxides and breaks them down

R2.2 Lysosome

contains digestive enzymes to break down macromolecules and cell components

HW 2.2 What happens to the proteins that are synthesized on free ribosomes and fully folded in the cytoplasm? Do they go through the Golgi apparatus? a) These proteins move through the Golgi apparatus and enter in the nucleus b) These proteins go through the Golgi apparatus and remain in the cytosol c) The proteins do not go through the Golgi apparatus and move into the nucleus for processing d) The proteins do not go through the Golgi apparatus and remain free in the cytosol e) These proteins move through the Golgi apparatus and move into the plasma membrane.

d) The proteins do not go through the Golgi apparatus and remain free in the cytosol

HW 2.2 In addition to a plasma membrane, eukaryotic cell organelles such as mitochondria also have membranes. In which way would these membranes differ? a) The proportion of phosphate within the phospholipids will vary. b) Only certain membranes contain phospholipids c) Only certain membranes are selectively permeable d) The proportions of proteins, lipids, and carbohydrates will vary

d. The proportions of proteins, lipids, and carbohydrates will vary

HW 2.2 In eukaryotic cells, sugar residues are covalently attached to proteins through the process of glycosylation. This posttranslational modification occurs: (select all that apply) a) in the nucleus. b) on free ribosomes. c) in mitochondria. d) in lysosomes. e) in the RER. f) in the Golgi apparatus.

e) in the RER. f) in the Golgi apparatus.

HW 2.2 A vesicle carries a protein to the cell membrane, where it is inserted into the phospholipid bilayer. The vesicle budded off from which sub-cellular structure before making the trip through the cytoplasm to the cell membrane? a) cis-Golgi b) Rough ER c) medial-Golgi d) Smooth ER e) trans-Golgi

e) trans-Golgi

R2.2 What type of molecule makes up part 3 of the phospholipid?

fatty acid

R2.2 The difference in lipid and protein composition between the membranes of the endomembrane system is largely determined by the ____.

function of the Golgi apparatus in sorting and directing membrane components

R2.2 In the protein coat model, which portion of the lipid bilayer are proteins associated with?

hydrophilic portion of the bilayer

R2.2 Smooth Endoplasmic Reticulum

location of lipid and steroid synthesis

R2.2 Membrane phospholipid molecules are free to do all the following EXCEPT

move from one leaflet (layer) to other

R2.2 Golgi Apparatus

processes and packages proteins for delivery

R2.2 Mitochondrion

produces ATP in cellular respiration

R2.2 Chloroplast

produces ATP in photosynthesis

R2.2 Proteins coded for by nuclear DNA but found within mitochondria move from the cytoplasm into mitochondria using ____.

signal sequences (peptides)

R2.2 Rough Endoplasmic Reticulum

site of protein folding and glycosylation

R2.2 Vacuole

stores water and other materials

R2.2 Which of the proteins in this image are peripheral membrane proteins?

the ones on top of the hydrophilic heads. Top middle one and bottom right one!