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CBH 201 > General Organization Of The Cell > Flashcards

General Organization Of The Cell Flashcards

1
Q

What are the 4 nucleotide bases and and how are they paired?

A

Adenine pairs with thymine and cytosine pairs with guanine.

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2
Q

How is the DNA strands bonded to form a double helix?

A

Each DNA molecule is composed of two strands of four different nucleotides covalently linked in linear polymers.The two strands pair, forming a double helix held together by interactions (hydrogen bonds) between complementary pairs of nucleotide bases with one on each strand.

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3
Q

Which enzymes transcribe the information stored in genes into linear sequences of nucleotides of RNA molecules?

A

RNA polymerases

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4
Q

Which is the most abundant type of RNA in cells?

A

Ribosomal RNA

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5
Q

What are the functions of ribosomes?

A

• Catalyze the synthesis of proteins,
• Use the nucleotide sequences of mRNA molecules to specify the sequence of amino
acids.
• Ribosomes free in the cytoplasm synthesize proteins that are released for routing
to various intracellular destinations.

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6
Q

What are polysomes?

A

Multiple ribosomes on the mRNA strand

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7
Q

All living organisms separate their cytoplasm from the external environment by means of phospholipid membranes containing:

A

pumps, carriers, and channels

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8
Q

What are peroxisomes and what is their role in the cell?

A

They cause breakdown of free radicals and are involved in oxidative reactions. Peroxisomes are membrane-bound organelles containing enzymes that participate in oxidative reactions. They are involved in various metabolic processes, including the breakdown of fatty acids and the detoxification of harmful substances.

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9
Q

Endosomes

A

Intracellular sorting organelles
They transport materials from the golgi to the lysozyme/vacuole.

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10
Q

What is the plasma membrane?

A

The plasma membrane is the interface of the cell with its environment

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11
Q

What kind of interior does plasma membrane have?

A

• It has a hydrophobic interior of its lipid bilayer → Impermeable to ions and most water-soluble molecules→these cross the membrane only through
transmembrane channels, carriers, and pumps.

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12
Q

What are PM adhesion proteins?

A

PM adhesion proteins allow cells to bind specifically to each other or to the extracellular matrix (ECM). These selective interactions allow cells to form multicellular associations, such as epithelia (sheets of cells that separate the interior of the body from the outside world). Similar interactions allow white blood cells to bind bacteria so that they can be ingested and killed.

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13
Q

How does transmembrane carrier proteins transport nutrients?

A

Transmembrane carrier proteins use these ion concentration gradients to transport of nutrients into the cell. Selective ion channels regulate the electrical potential across the membrane. A large variety of receptors bind specific extracellular ligands and send signals across the membrane to the cytoplasm.

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14
Q

What is the double membrane?

A

Double membrane
Separates the nucleus from the cytoplasm

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15
Q

Inbound traffic of nucleus includes:

A

all nuclear proteins and ribosomal proteins destined for the nucleolus.

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16
Q

Outbound traffic of nucleus includes:

A

mRNAs and ribosomal subunits.

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17
Q

What are centromeres?

A

Centromeres are the regions in the middle of the chromosomes that are important for
chromosome segregation into different cells during mitosis.

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18
Q

What is ER?

A

The ER is a continuous system of flattened membrane sacs and tubules.

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19
Q

How does the ER membrane become a branching network?

A

Motor proteins move along microtubules to pull the ER membranes into a branching network spread throughout the cytoplasm.

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20
Q

How is the cytoplasmic Ca2+ concentration regulated?

A

ER pumps and channels regulate the cytoplasmic Ca 2+ concentration.

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21
Q

What is the Golgi apparatus and where is it located?

A

Consists of a stack of flattened, membrane-bound sacks with many associated vesicles.
• Located in the middle of the cell near the nucleus and the centrosome.
• Processes the sugar side chains on transmembrane and secreted proteins.

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22
Q

What is the function of lysosomes?

A

Store degradative enzymes.
• Lysosomal proteins move from the ER to the Golgi apparatus, where enzymes add
the modified sugar, phosphorylated mannose (Mannose-6-Phosphate) and are
targeted to the lysosome.

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23
Q

How does mitochondria respond to toxic stimuli?

A

Mitochondria also respond to toxic stimuli from the environment including drugs used in cancer chemotherapy by activating controlled cell death called apoptosis.

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24
Q

What are the three protein filaments in the cytoskeleton?

A

• Actin filaments – also called thin filaments
• Intermediate filaments
• Microtubules

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25
Q

Functions of actin filaments and microtubules?

A

-
Tracks for the ATP-powered motor proteins that produce most cellular movements, including:
o locomotion
o muscle contraction
o transport of organelles through the cytoplasm
o mitosis
o the beating of cilia and flagella.
o The proteins are also used for highly specialized motile processes, such
as muscle contraction and sperm motility.

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26
Q

How dos kinesin move vesicles and RNA protein particles?

A

Kinesin moves its associated cargo (vesicles and RNA-protein particles) along the
microtubule network radiating away from the centrosome.

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27
Q

How does Dynein move its cargo?

A

Dynein moves its cargo toward the centrosome.

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28
Q

What are nuclear lamins?

A

Nuclear lamins are intermediate filaments inside the nucleus that support the nucleus. They form the nuclear lamina.

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29
Q

What does stimulation of receptors lead to?

A

Stimulation of receptors:
-Activates diverse signal-transducing mechanisms
-Amplify the message and generate a wide range of cellular responses.

These include:
-Changes in the electrical potential of the plasma membrane
-Gene expression
-Enzyme activity

30
Q

What is the role of feedback loops?

A

Feedback loops assure that the conditions are suitable for each transition such as the onset of DNA synthesis and the decision to begin mitosis. Feedback loops also regulate enzymes that synthesize and degrade proteins, nucleic acids, sugars, and lipids to ensure the proper levels of each cellular constituent.

31
Q

What is the role of regulatory proteins?

A

Regulatory proteins turn specific genes on and off and modulate the rates of translation of mRNAs into protein; synthesis balanced by the rates of degradation determines the abundance of specific RNAs and proteins.

32
Q

How do cellular membranes grow?

A

Cellular membranes composed of lipids and proteins grow by expansion of preexisting lipid bilayers rather than forming de novo(anew).

33
Q

What are some examples of cellular constituents that move by motor proteins?

A

Motor proteins use energy from ATP hydrolysis to move organelles and other cargo along microtubules or actin filaments.

34
Q

What are the key steps involved in DNA replication during the cell cycle?

A

The key steps in DNA replication include checking for damaged or unduplicated DNA, chromosome duplication, and checking for chromosome attachment to the mitotic spindle.

35
Q

What are some examples of macromolecular components that assemble spontaneously in cells?

A

Chromosomes assembled from DNA and proteins, actin filaments in a filopodium assembled from protein subunits, and the plasma membrane formed from lipids and proteins.

36
Q

What happens during mitosis in the cell cycle?

A

During mitosis, chromosome duplication occurs, followed by checking for DNA nicks and chromosome attachment to the mitotic spindle.

37
Q

What is the function of transport proteins in moving molecules across cell membranes?

A

Transport proteins facilitate the movement of molecules across cell membranes by providing channels or using ATP-powered pumps.

38
Q

What is the role of ATP in active transport?

A

ATP provides the energy needed for transport proteins to move molecules against their concentration gradient.

39
Q

How does ligand binding activate a receptor?

A

When a ligand binds to a receptor, it turns the receptor on, initiating signal transduction.

40
Q

How do vesicles contribute to protein targeting and secretion?

A

Vesicles move proteins from the Golgi apparatus to lysosomes, the plasma membrane, or target membranes. They also transport soluble enzymes and return membrane proteins to the ER.

41
Q

What are some examples of molecular feedback loops in cellular regulation?

A

Examples include the control of the synthesis of aromatic amino acids and the regulation of the cell cycle through checkpoints that halt the cycle until key preceding events are successfully completed.

42
Q

How do receptors and signaling mechanisms allow cells to adapt to environmental conditions?

A

Cells have an elaborate repertoire of receptors for a multitude of stimuli, including nutrients, growth factors, hormones, neurotransmitters, and toxins. Stimulation of receptors activates diverse signal-transducing mechanisms, generating a wide range of cellular responses.

43
Q

What is the purpose of molecular feedback loops in controlling molecular composition, growth, and differentiation?

A

Molecular feedback loops control molecular composition, growth, and differentiation in living cells. They fine-tune cellular composition in response to external stimuli, nutrient availability, and internal signals.

44
Q

How do molecular pumps transport molecules across membranes against concentration gradients?

A

Molecular pumps use energy provided by ATP hydrolysis or electrochemical gradients to drive molecules across membranes against concentration gradients.

45
Q

How does diffusion occur across a concentration gradient?

A

Diffusion occurs when molecules move from an area of higher concentration to an area of lower concentration, down their concentration gradient.

46
Q

How does activation of cellular metabolism by an extracellular ligand occur?

A

Activation of cellular metabolism by an extracellular ligand involves binding of the ligand to trigger a series of linked biochemical reactions, leading to regulation of metabolic enzymes.

47
Q

What is the role of CAMP in signal transduction?

A

CAMP, a second messenger, activates protein kinases, which phosphorylate and activate enzymes.

48
Q

What is the role of the Golgi apparatus in processing proteins?

A

The Golgi apparatus processes the sugar side chains on transmembrane and secreted proteins before they segregate into different vesicles destined for lysosomes or the plasma membrane.

49
Q

What is the role of intermediate filaments in cells?

A

Intermediate filaments provide flexibility and strength to cells subjected to physical stresses. They reinforce epithelial cells and form bundles that link the plasma membrane to the nucleus. For example, lamin intermediate filaments reinforce the nuclear envelope.

50
Q

How do microtubules contribute to cellular dynamics and transport?

A

Microtubules are rigid cylindrical polymers that resist compression and have distinctive polarity. They provide tracks for motor proteins, such as kinesin and dynein, to transport cargo along the microtubule network. Microtubules are involved in various cellular processes, including mitosis, intracellular transport, and the motile apparatus of cilia and flagella.

51
Q

What are the distinctive properties and functions of actin filaments?

A

Actin filaments reinforce the surface of the cell by forming networks anchored to the plasma membrane. They also support finger-like projections called filopodia and microvilli, which increase the surface area of the plasma membrane. Actin filaments participate in cellular movements by protruding pseudopods or lamellipodia and generating force through myosin motor proteins.

52
Q

What is the function of the nuclear lamina?

A

The nuclear lamina, composed of intermediate filaments called lamins, supports the nucleus. It forms a meshwork beneath the inner nuclear membrane and provides structural integrity to the nucleus.

53
Q

How do macromolecular structures assemble in cells?

A

Macromolecular structures assemble from subunits through self-assembly without the aid of templates or enzymes. The molecules themselves contain the information required for assembly, and exclusion of water and intermolecular interactions provide the energy to hold the subunits together. Protein chaperones may assist with assembly by preventing aggregation of incorrectly folded intermediates.

54
Q

Why is the impermeability of the mitochondrial membrane important for ATP synthesis?

A

The impermeable membrane around mitochondria allows for the establishment of a proton gradient, which drives enzymes in the membrane to synthesize ATP.

55
Q

What is the role of selective ion channels in regulating the electrical potential across the membrane?

A

Selective ion channels regulate the flow of specific ions, thereby controlling the electrical potential across the membrane

56
Q

Why are phospholipid membranes important for cells?

A

Phospholipid membranes separate the cytoplasm from the external environment and contain pumps, carriers, and channels that regulate the movement of substances into and out of the cell.

57
Q

How do changes in genes affect the fitness of an organism?

A

Many changes in genes have no obvious effect on the fitness of an organism, but some reduce it while others improve fitness. Over time, competition between individuals with different gene variations determines which organisms survive in various environments.

58
Q

How do membranes contribute to the advantages of eukaryotic cells?

A

Membranes provide a barrier that allows each type of organelle to maintain unique ionic and enzymatic environments. This segregation of environments favors specific biochemical reactions required for life.

59
Q

How do transmembrane carrier proteins utilize ion concentration gradients?

A

Transmembrane carrier proteins use the ion concentration gradients established by ATP-driven enzymes to transport nutrients into the cell.

60
Q

What are the main differences between eukaryotic and prokaryotic cells?

A

Eukaryotic cells have a compartmentalized cytoplasm with membrane-bound organelles, including a nucleus. Prokaryotic cells lack membrane-bound organelles and have chromosomes in the cytoplasm.

61
Q

What is the function of the lipid bilayer in the cell?

A

lipid bilayer acts as a permeability barrier between the cytoplasm and the extracellular environment.

62
Q

What are some features shared by all forms of life?

A

All forms of life share features such as storing genetic information in nucleic acids (usually DNA), using a common genetic code, transferring genetic information from DNA to RNA to protein, and employing proteins and RNAs to catalyze chemical reactions and synthesize proteins.

63
Q

What is the role of ribosomes in protein synthesis?

A

Ribosomes catalyze the synthesis of proteins by using the nucleotide sequences of mRNA molecules to specify the sequence of amino acids. Free ribosomes in the cytoplasm synthesize proteins that are released for routing to various intracellular destinations.

64
Q

How is genetic information stored in the nucleus?

A

The nucleus stores genetic information in DNA molecules called chromosomes. Chromosomes consist of DNA strands assembled with proteins to form chromatin, which then folds into structures called chromosomes.

65
Q

What are telomeres and centromeres, and what roles do they play in chromosome structure?

A

Telomeres stabilize the ends of chromosomes, while centromeres direct the distribution of chromosomes to daughter cells during cell division.

66
Q

What is the function of the plasma membrane in a cell?

A

The plasma membrane is the interface of the cell with its environment. It has a hydrophobic interior and controls the passage of ions and water-soluble molecules through transmembrane channels, carriers, and pumps.

67
Q

How do ribosomes use mRNA to synthesize proteins?

A

Ribosomes use the nucleotide sequences of mRNA molecules as templates to specify the sequence of amino acids during the synthesis of polypeptides, which eventually fold into unique three-dimensional protein structures.

68
Q

What role do ATP-driven enzymes play in establishing concentration gradients across the lipid bilayer?

A

ATP-driven enzymes pump Na+ out of and K+ into the cell, creating concentration gradients that are essential for various cellular processes.

69
Q

What are some examples of membrane-bound organelles in eukaryotic cells?

A

Some examples of membrane-bound organelles in eukaryotic cells include the endoplasmic reticulum (ER), Golgi apparatus, lysosomes, peroxisomes, and mitochondria.

70
Q

What is the role of the nuclear envelope in eukaryotic cells?

A

The nuclear envelope separates the synthesis and processing of RNA in the nucleus from the translation of mature mRNAs into proteins in the cytoplasm.

71
Q

How do transcription factors and polymerases contribute to gene expression?

A

Transcription factors regulate gene expression by binding to specific DNA sequences, while polymerases carry out the process of RNA transcription, producing RNA molecules that specify the amino acid sequences of proteins.

72
Q

How is genetic information transferred from DNA to RNA to protein?

A

Genetic information is transferred from DNA to RNA through transcription, and then from RNA to protein through translation.

CBH 201 (2 decks)

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