Cell and Molecular Biology (BB314)

Kinesin and dynein motor proteins each use the energy of _____1_____ to power their movements along _______2_______

1. ATP 2. Microtubules

Osmosis describes the movement of water across a biological membrane and down its concentration gradient. In chemiosmotic coupling, useful energy is harnessed by the cell from the spontaneous movement of ________1_________across the inner mitochondrial membrane into the matrix ___________2__________ a concentration gradient.

1. Protons 2. down or along

Given the generic signaling pathway in the figure, match the number corresponding to the item on the line next to the descriptor below.

1. signal 2. receptor 3. signaling molecules 4.response proteins

Which of the following statements about a soluble protein in the lumen of the ER is false?

It may end up embedded in the plasma membrane.

Properties of amino acids vary because of the ______.

R-group

Which of the following statements about G-protein-coupled receptors (GPCRs) is false?

The different classes of GPCR ligands (proteins, amino acid derivatives, or fatty acids) bind to receptors with different numbers of transmembrane domains.

Which of the following is NOT a characteristic of mitochondria?

They are small and static in morphology.

Which of the following is NOT a role for the oligosaccharides on glycosylated proteins?

They can provide a source of energy for the cell.

Which of the following statements about proteins destined for the ER is true?

They must contain a second specific signal, in addition to the signal for co-translational ER insertion.

Proteins that begin translation in the cytosol and lack a sorting signal will end up in _____.

the cytosol.

All of the components in the list below exist in either the mitochondria, the chloroplast or they can be found in either. Match up the components to the organelle in which they exist.

1. Porins - Both mitochondria and chloroplasts 2. Electron transport chain - Both mitochondria and chloroplasts 3. ATP synthase - Both mitochondria and chloroplasts 4.Transporter for pyruvate import -Mitochondria only 5.Transporter for ATP export - Mitochondria only 6. Thylakoid membrane - Chloroplasts only 7. triose phosphate exporter - Chloroplasts only 8. Importer for newly synthesized proteins - Both mitochondria and chloroplasts

Match each property with the level(s) of protein structure. Choose the best answer in each case. 1. Examples of this are alpha-helices and beta-pleated sheets. 2. Results from repetitive hydrogen bonds between atoms in the peptide backbone. 3. Can be altered when a protein is reversibly denatured. 4. Results from covalent bonds formed between an amino group and a carboxyl group. 5. Results from covalent bonds between two S-containing R-groups. 6. Results from covalent or non-covalent interactions between R-groups within one polypeptide chain. 7. Is also known as the protein sequence. 8. Results from covalent or non-covalent interactions between different polypeptide chains. 9. Results from non-covalent interactions between the R-groups.

1. Secondary structure 2. Secondary structure 3.Secondary, tertiary, and quaternary structure 4. Primary structure 5. Both tertiary and quaternary structure 6. Tertiary structure 7. Primary structure 8. Quaternary structure 9. Both tertiary and quaternary structure

Select from the drop-down menu the correct cytoskeletal filament that applies to each of the phrases or statements listed below. 1. Monomer that binds ATP 2. Includes keratin and neurofilaments 3. Used in the eukaryotic flagellum microtubules 4.Their stability involves a GTP cap 5. Directly involved in muscle contraction 6. Supports and strengthens the nuclear envelope 7. A component of the mitotic spindle microtubules 8. Important for formation of the contractile ring during cytokinesis

1. actin filaments 2. intermediate filaments 3. microtubules 4. microtubules 5. actin filaments 6. intermediate filaments 7. microtubules 8. actin filaments

G-protein-coupled receptors (GPCRs) all have a similar structure with _____1_______ transmembrane domains. When a GPCR binds an extracellular signal, an intracellular G protein, composed of _____2______ subunits, becomes activated. ____3_____ of the G-protein subunits are tethered to the plasma membrane by short lipid tails. When unstimulated, the α subunit is bound to ___4___ ,which is exchanged for_____5____ stimulation. The intrinsic ____6___activity of the α subunit is important for inactivating the G protein.

1. seven 2. three 3. two 4. GDP 5. GTP 6. GTPase

Newly synthesized proteins destined for the lysosome bind a specific receptor in the ________and are released from their receptor in the_________

1. trans Golgi Network 2. Endosome

The black lines in the three images below each represent one of the types of skeletal filament. What are they? The nucleus is shown as a grey circular structure near the center of these animal cells.

A) Microtubules B) Intermediate C) Actin

The thylakoid membrane and lumen contain which of the following? Choose all that apply.

ATP synthase ETCs Chlorophyll and other light harvesting pigments

Which of the following statements about the cytoskeleton is true? Choose all that apply.

Actin is the smallest filament. The cytoskeleton controls the location of organelles in eukaryotic cells. The cytoskeleton of a cell can change in response to the environment. The cytoskeleton is made up of three types of protein filaments. Intermediate filaments are so named because their size is 'intermediate', compared to the other two.

In the figure shown, which letter is associated with the line that is pointing to the interpolar microtubules?

E

Which of the following choices reflects the appropriate order of locations through which a protein destined for the plasma membrane travels?

ER, Golgi, plasma membrane

The movement of materials from the plasma membrane, through endosomes, and then to lysosomes describes which type of pathway?

Endocytic Pathway

In the Fluorescence-Activated Cell Sorting (FACS) readout below, the peak labeled C will represent _____-phase cells in an unmutated population of cells that is cycling through the cell cycle normally. Choose all that apply

G2-phase

The N-terminal tail of histone H3 can be extensively modified, and depending on the number, location, and combination of these modifications, these changes may promote the formation of heterochromatin. What is the result of heterochromatin formation?

Gene silencing

Challenge question! Which of the statements about glycosylation in the list below is true? Choose all that apply.

Glycolsylated proteins are not found in the cytosol. The glycosylation state of a protein can determine its fate along the secretory pathway.

The classic "beads-on-a-string" structure is the most decondensed chromatin structure possible and can only be produced experimentally. Which chromatin components are not retained when this structure is generated?

H1 histone

This figure clearly depicts the nucleolus, a nuclear structure that looks like a large, dark region when stained. The other dark, speckled regions in this image are the locations of particularly compact chromosomal segments called _____.

Heterochromatin or heterochromatin

The side chains of the amino acids of a membrane protein that interact with the internal portion of the membrane will typically be _____________ (Hydrophobic or Hydrophilic). Another word for this type of side chain is ___________ (polar or nonpolar)

Hydrophobic nonpolar

Which of the following is NOT a chemical modification commonly used on core histones to promote chromatin remodelling?

Hydroxylation

Choose all that apply. The nucleolus _____

Is the site of ribosome biogenesis is a darkly stained region on an electron micrograph. is an area of intense rRNA transcription activity.

A primary transcript in the nucleus of a eukaryotic cell is -____________ the functional mRNA, while a primary transcript in a prokaryotic cell is __________ the functional mRNA.

Larger than Smaller than

Which of the following is true of lysosomes?

Lysosomal enzymes are optimally active in the acidic conditions maintained within lysosomes.

Of the cellular compartments listed below, which one is the most acidic?

Lysosome

In the polymerization in vitro of actin filaments and microtubules from their subunits, what does the "lag phase" correspond to?

Nucleation

Which of the following is NOT a primary function for the chloroplast?

Produce ATP that is directly used by the rest of the cell.

The matrix of a mitochondrion contains which of the following? Choose all that apply.

Protein synthesis components Ribosomes TCA cycle enzymes Mitochondrial DNA

Which of the following statements regarding secretory vesicles is FALSE? Choose all that apply.

Proteins destined for the lysosome are packages into the same vesicles as other secretory vesicles. The lumen of secretory vesicles is generally less acidic than the lumen of the TGN from which they originate. Regulated secretion is considered to be the 'default pathway' through the endomembrane system.

If a cell is treated with the drug Vinblastine, which cellular property/process would NOT be affected?

Reformation of the nuclear envelope

In order to allow gene expression, histone modifying enzymes interact with core histones to modulate their affinity for the DNA and/or other histones, so that specific sequences can be exposed to allow for transcription. From the list below, choose all of the statements that are true.

The 'tails' of core histones are an important site for covalent modifications by histone modifying enzymes. Histones can be chemically modified in a variety of ways. One example is methylation. Histone modifying enzymes can slide the core histones along the DNA without removing them.

Which of the following statements about S-phase are FALSE?

The activation of S-Cdk helps prevent the onset of M-phase.

Which of the following statements best describes the relationship between the light-dependent and light-independent reactions of photosynthesis?

The light-dependent reactions produce ATP and NADPH, which are then used by the dark reactions to make sugars.

A peptide-bonded backbone of a polypeptide chain has key characteristics. Select all that apply from the following list.

The structure is flexible due to single bonds on either side of the peptide bonds in the backbone. The backbone has an amino group on one end and a carboxyl group on the other end thus providing directionality. Each amino acid contains R-groups (side chains) project out from the backbone such that they may interact with each other and create higher orders of protein folding..

One way a chemical modifcation of the histones can lead to changes in chromatin structure is by what mechanism?

They act as binding sites for remodeling complexes.

Which of the following is NOT an integral membrane protein? a transmembrane protein that spans the lipid bilayer a monolayer associated protein tucked into the inner leaflet of the lipid bilayer a lipid-linked protein anchored to the outer leaflet of the membrane a protein attached to the membrane by non-covalent interactions with other membrane proteins

a protein attached to the membrane by non-covalent interactions with other membrane proteins

Membrane proteins, like membrane lipids, can move laterally by exchanging positions with other membrane components. Which type of membrane proteins is expected to be the least mobile, based on their function? anchors enzymes receptors channels

anchors

What pieces of evidence formed the basis for the endosymbiont theory? Choose all that apply. Chloroplasts and mitochondria _____

arise by division of pre-existing chloroplasts/mitochondria. have double membranes. have similar gene sequences as several bacteria. have circular genomes.

Which of the following amino acids are positively charged in an aqueous solution? 1. acidic 2. basic 3. nonpolar 4. polar uncharged

basic

Histones are said to belong to a family of basic proteins, because they are rich in _____

basic amino acyl residues carrying an overall positive charge.

Most proteins destined to enter the endoplasmic reticulum _______.

begin to cross the membrane while still being synthesized.

Chromatin remodeling enzyme complexes ______. Choose all that apply.

bind to chromatin by binding to chemical modifications in the histone tails. are essential for regulating gene expression. are non-histone proteins that can bind to the chromatin in interphase nucleus. cause DNA to be repositioned for access or tighter packing.

The RNA component within snRNP complexes _______.

can complementarily bind to specific sequences at intron/exon boundaries.

The low pH inside endosomes _____.

causes internalized receptors to release their cargo.

Indicate which phrase in the pair that is likely to occur more rapidly in response to an extracellular signal.

changes in protein phosphorylation

Which of the following membrane lipids does not contain a long fatty acid tail? 1. cholesterol 2. phosphatidylcholine 3. phosphatidylserine 4. a glycolipid

cholesterol

Vesicles from the ER enter the Golgi at the ______.

cis cisternae.

Eukaryotic cells continually ingest bits of their plasma membrane, along with small amounts of extracellular fluid. The lost pieces of membrane are replaced by the process of

consitutive exocytosis

Choose all that apply. A 30 nm chromatin fibre is made of ______

core histone proteins H1 histone proteins DNA

For both actin and microtubule polymerization, nucleotide hydrolysis is important for...

decreasing the binding strength between subunits on filaments.

Which of the following mechanisms is not directly involved in inactivating an activated RTK?

dephosphorylation by serine/threonine phosphatases

If a cell is in M-phase, but has nuclear lamins that cannot be phosphorylated, the cell will be unable to _____.

disassemble its nuclear lamina at prometaphase

A region of a protein that forms a functional component of a protein is called a(n) _____.

domain

Signal sequences that direct proteins to the correct compartment are _____.

encoded in the amino acid sequence.

In a centrosome (i.e. an MTOC), which structures serve as nucleation sites for the formation of microtubules?

gamma-tubulin rings

During G1, cells ____. Choose all that apply.

grow

Which of the following does not occur during M-phase in animal cells?

growth of the cell

Choose all that apply. The NLS (Nuclear Localization Signal/Sequence) _____

has a consensus basic amino acid residue sequence, KKKRK. is recognized by a soluble nuclear import receptor protein in the cytoplasm and taken to the nuclear pore complexes, for entry into the nucleus. is a short stretch of amino acyl residues in the protein destined to the nucleus.

The amino acids glutamine and glutamic acid are shown in the figure below. They differ only in the structure of their side chains (circled). At pH 7, glutamic acid can participate in molecular interactions that are not possible for glutamine. What types of interactions are these?

ionic bonds

Choose all that apply. The nuclear lamina _____

is a meshwork of intermediate filament proteins called the lamins. has a structural role in providing support to the nuclear envelope. breakdown can cause the breakdown of the nuclear envelope during mitosis. breakdown is caused by the phosphorylation of lamin proteins.

A protein kinase can act as an integrating device in signaling if it _____.

is activated by two or more proteins in different signaling pathways.

Choose all that apply: The design of the nuclear envelope is such that _____

it is a double membrane. the chromatin is able to attach to the inner envelope at discrete regions. its outer membrane is continuous with the ER. the nuclear pores dispersed throughout the envelope connect the cytoplasm with the inside of the nucleus (nucleoplasm).. the space between the inner and outer membrane (perinuclear space) is continuous with the ER lumen (fluid inside the ER).

In an experiment with fluorescently labeled lipids, a bleached area of membrane gradually regains fluorescence because of _____.

lateral diffusion of non-bleached lipids into the bleached area

_______ are the motor protein that move directionally along actin filaments.

myosin myosins

Interphase cells contain chromosomes that are less densely packed and ______.

occupy discrete territories in the nucleus.

Challenge question! You are viewing a sample of pond water under the microscope. The sample contains a variety of microorganisms, some moving faster than others. You spot a Paramecium that is being followed by a Didinium almost as large as itself; the Paramecium initially swims away and tries to escape, but Didinium, which moves in faster bursts, finally stops it and attaches firmly onto the side of the Paramecium and proceeds to eat it. Enter the name of the type of endocytosis that it will use for this process. Note, you MUST spell it correctly or your answer will not be accepted.

phagocytosis

Which type of lipids are the most abundant in the plasma membrane? 1. glycolipids 2. sterols 3. phospholipids 4. triacylglycerides

phospholipids

Choose all that apply. Transport in and out of the nucleus of molecules larger than 9 nm _____

requires a nuclear import receptor protein in the cytoplasm to recognize the NLS and bring it to the nuclear pore for entry into the nucleus. must have a nuclear localization sequence (NLS) for entry into the nucleus, that is NOT removed after entry. requires energy. is an active transport process.

A plasma membrane protein that contains an N-terminal signal sequence and an internal stop transfer sequence at its final destination is a _____.

single pass transmembrane protein with its N-terminus in the extracellular space

Membrane lipids are capable of many different types of movement. Which of these does not occur spontaneously in biological membranes? rotation lateral movement flexing of hydrocarbon chains switching between leaflets of the bilayer

switching between leaflets of the bilayer

In stage 1 of photosynthesis, a proton gradient is generated and ATP is synthesized. Where do protons become concentrated in the chloroplast?

thylakoid lumen

Photosynthesis is a process that takes place in chloroplasts and uses light energy to generate high-energy electrons, which are passed along an electron-transport chain. Where are the proteins of the electron-transport chain located in chloroplasts?

thylakoid membrane