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My MCAT Biology > Generalized Eukaryotic Cell > Flashcards

Generalized Eukaryotic Cell Flashcards

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1
Q

Which eukaryotic organelles have a double membrane? Which has no membrane?

A

Only the nucleus and the mitochondria have a double membrane. The ribosome has no membrane

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2
Q

What the two different types of chromatin? How do they differ in staining and transcription levels?

A
  1. Heterochromatin: dense staining, little/no transcription

2. Euchromatin: light staining, high transcription

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3
Q

What are the two types of pores and molecules are specific to them?

A
  1. Nucleoporins: ions

2. Karyoporins: nuclear proteins (polymerases), mRNA

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4
Q

How does the nature of the interior between the nucleus and the endoplasmic reticulum compare?

A

They are continuous. Therefore, if a dye was injected in the nucleus, it would also travel to the endoplasmic reticulum

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5
Q

If double stranded DNA was localized to the cytoplasm, would it undergo transcription?

A

Transcription occurs ONLY in the nucleus. The polymerases required for replication and transcription are localized to the nucleus

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6
Q

What are four reasons why the mitochondria is representative of the Endosymbiotic Theory?

A
  1. Independent replication
  2. Does not share the same genome
  3. Double membrane - both a phospholipids
  4. Mitochondrial genome is circular and encodes the same sediment ribosome as prokaryotes (70s)
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7
Q

If a protein that is known to originate from the mitochondria becomes mutated in a father, what proportion of the progeny will express this same mutation?

A

None of the progeny will express the mutated protein because the mitochondrial genome is MATERNALLY inherited.

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8
Q

What is the environmental differences between the inter-mitochondrial membrane space and the mitochondrial matrix in terms of ATP/ADP concentration and acidity/basicity?

A

Inter-mitochondrial membrane space - acidic, high [ADP], low [ATP]

Mitochondrial matrix - basic, high [ATP], low [ADP]

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9
Q

What five metabolic functions are performed in the mitochondrial matrix?

A
  1. Pyruvate Decarboxylation
  2. Krebs Cycle
  3. Beta-oxidation
  4. Gluconeogenesis
  5. Urea cycle
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10
Q

What is the sedimentary difference between the prokaryote and eukaryote ribosome?

A

Eukaryote - 80S - 60S + 40S
Prokaryote - 70S - 50S + 30S

Application: If there are two cells of unknown shape, they can be differentiated based on the sediment size of the ribosome

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11
Q

Name different cell types rich in rough endoplasmic reticulum (need more)

A
  1. Plasma cells (secrete antibodies)

2. Endocrine cells (secrete peptide hormones)

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12
Q

If a protein is being translated on the rough endoplasmic reticulum, what five different places may the protein end up?

A
  1. Golgi Apparatus
  2. Endoplasmic reticulum
  3. Plasma Membrane
  4. Secretory pathway
  5. Lysosome
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13
Q

Name different cell types rich in smooth endoplasmic reticulum (need more)

A
  1. Hepatocytes (drug detoxification)
  2. Spermatocytes (steroid synthesis)
  3. Muscle cells (sarcoplasmic reticulum)
    4.
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14
Q

What two post-translational modifications are performed in the rough endoplasmic reticulum

A
  1. Di-sulfide bond formation

2. N-linked glycosylation (helps w/ protein formation)

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15
Q

What are four main functions of the smooth endoplasmic reticulum?

A
  1. Synthesis of lipids - membrane, prostaglandins
  2. Synthesis of steroids
  3. Detoxification of drugs
  4. Muscle cell contraction
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16
Q

What three main metabolic functions occur in the smooth endoplasmic reticulum?

A
  1. Drugs
  2. Steroid
  3. Carbohydrate (gluconeogenesis)
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17
Q

What four chemical modifications occur in the Golgi Apparatus?

A
  1. Glycosylation - synthesis of glycoproteins
  2. Phosphorylation - mannose 6 phosphate
  3. Sulfation
  4. Proteolysis
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18
Q

What mechanism allows the acid hydrolyses in the lysosome to stay active?

A

H+ ATPase: cytoplasmic ATP binds to the ATPase and pumps hydrogen ions against its gradient from the cytoplasm into the lysosome

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19
Q

What are two occurrences that can cause a lysosomal storage disease? What are two examples and their cause?

A
  1. Block mannose-6-phosphate pathway in golgi apparatus
    * Inclusion cell disease
  2. Mutated lysosomal enzyme
    * Tay-saccs disease: faulty beta-hexosaminidase prevents the breakdown of glycolipids causing an accumulation in ganglion cells in cerebral cortex
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20
Q

What is the composition of a centriole? Are they found in eukaryotes, prokaryotes? What is a centrosome? When do centrioles replicate and separate? In what mitotic phase do centriole pairs move apart?

A

A centriole is composed of microtubule triplets arranged in a cylinder. They are ONLY found in eukaryotes. A centrosome is a pair of centrioles consisting of mother and daughter. They replicate during Interphase and begin separate during G1. Centriole PAIRS move apart in Prophase.

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21
Q

What is the order of cytoskeleton filaments in regards to their size?

A

Microtubules - largest
Intermediate Filaments - medium
Microfilaments - smallest

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22
Q

What is the composition of microtubules, microfilaments, and intermediate filaments?

A
  1. Microtubules - alpha and beta tubulin dimers
  2. Microfilaments - g-actin to form f-actin
  3. Tissue-specific
23
Q

What are four cell types that differ based on intermediate filaments and what are the names of the four different filaments?

A
  1. Neurons - neurofilaments
  2. Epithelial cells - keratin
  3. Muscle cells - desmin
  4. Connective tissue/mesenchymal cells - vimentin
24
Q

What are three main functions of microfilaments?

A
  1. Muscle contraction - actin/myosin
  2. Pseudopod formation
  3. Cytokinesis
25
Q

What are two types of diffusion that confer lipid mobility?

A
  1. Lateral Diffusion

2. Transverse Diffusion (slow)

26
Q

What are the two main contributors to membrane fluidity?

A
  1. Unsaturation of the fatty acids

2. Cholesterol - increases rigidity

27
Q

What are the two main types of transport across the plasma membrane? What are their subdivisions? What types of molecules are transported through each? What are the kinetics of transport?

A

The two types of transport systems are passive and active transport. Passive transport moves ions and molecules DOWN their concentration gradient, whereas active transport moves ions and molecules AGAINST their concentration gradient by hydrolyzing ATP.

Passive transport is broken down to simple and facilitated diffusion. Molecules that undergo simple diffusion are nonpolar small molecules such as oxygen, carbon dioxide, lipids, and some drugs whereas molecules that undergo facilitated diffusion are either large nonpolar molecules, polar molecules, or ions. Simple diffusion displays zero order kinetics (linear relationship between concentration and time) while facilitated diffusion displays first order kinetics.

Active transport is broken down into primary and secondary active transport. Molecules that undergo primary active transport are ions such as sodium and potassium. Molecules that undergo secondary transport are ions and larger polar molecules such as glucose (sodium/glucose sypmort)

28
Q

What is osmosis? What kind of membrane is required to demonstrate osmosis? Describe the two modes of osmosis.

A

Osmosis is the passive flow of water across a semi-permeable from a compartment of low solute concentration to high. A medium that is hypertonic has a higher concentration of solute relative to the other compartment. A medium that is hypotonic has a lower concentration of solute.

29
Q

What are the three cell adhesion/junctions and their functions?

A
  1. Tight junctions: forms watertight seal, separates apical from basolateral membrane
  2. Desmosome: general junction, anchored by intermediate filaments
  3. Gap junctions: cytoplasm continuity. Examples: bone and cardiac cells
30
Q

What are the three phases of Interphase and what are their specific functions?

A
  1. G1 phase: transcription, translation, centriole separation*
  2. Synthetic Phase: replication of chromatin
  3. G2 phase: chromatin condenses
31
Q

What are the four main phases of meiosis and mitosis?

A

Prophase, Metaphase Anaphase, Telophase

32
Q

If a cell is observed to have condensed chromatin, aster formation, and without a nucleolus, what cell cycle phase is the cell undergoing?

A

The cell is undergoing mitosis or meiosis during Prophase. In addition to these characteristics, the nuclear membrane has also been broken down.

33
Q

What can be implicated about translation during prophase?

A

During prophase, the nuclear membrane breaks down and the nucleolus disappears. The nucleolus is the site of rRNA synthesis and ribosome assembly. Without the nucleolus, translation machinery cannot be synthesized, and thus CANNOT occur during this phase or any phase hereafter until the nucleolus reappears during telophase.

34
Q

If the condensed replicated DNA is observed to be aligned in the middle of the cell and there is no trace of the nuclear membrane, what cell cycle phase is the cell undergoing?

A

Metaphase

35
Q

What is the mechanism that allows replicated chromatids to separate to opposite poles during Mitosis? What phase is this?

A

During anaphase, CENTROMEREs divide. Centromeres connect replicated chromatids.

36
Q

What cytoskeletal filament is responsible for the cleavage furrow? During what phase does this appear?

A

During telophase, microfilaments g-actin polymerize to f-actin to form the cleavage furrow which functions begin separating the parent cell into two daughter cells.

37
Q

If karyotyping is performed on human cells undergoing MITOSIS and 92 chromosomes (4N) are observed, what two phases could the cell possibly be in?

A

During Anaphase and Telophase, the replicated chromatids are separated but are still located in one cell. The parent cell doesn’t return to 2N until it undergoes cytokinesis.

38
Q

Compare and contrast prophase in mitosis and meiosis. What are the signature events in Prophase I of Meiosis?

A

There are three similarities between prophase in mitosis and meiosis: chromosome condensation + nucleolus disappears + breakdown of nuclear membrane

In Prophase I of Meiosis, homologous chromosomes with their replicated chromatid pair up is a process known as SYNAPSIS to form tetrads (bivalent) to set up for CROSSING OVER. The location where crossing over occurs is known as the chiasmata.

39
Q

What is the difference between Anaphase in mitosis to Anaphase I of Meiosis? What are possible complications of Anaphase I?

A

In Anaphase I of Meiosis, centromeres DO NOT divide to separate the replicated chromatids. Instead, the dyads separate resulting in haploid gametes. Nondisjunction may occur here.

40
Q

What is the difference between nondisjunction in Anaphase I and II? What are examples of each?

A

During Anaphase I, if dyads fail to separate for a given chromosome number, chromosomes from BOTH parents will be present in the gamete. In essence, the gamete will be diploid for that chromosome number. If Nondisjunction occurs during Anaphase II for a given chromosome number, the gamete will also be diploid for that chromosome number but the extra chromosome came from the SAME parent (i.e. it is NOT the homologous pair).

Klinefelters Syndrome can result from nondisjunction in Anaphase I in a male and Anaphase II in a female.

41
Q

Describe the differences between the two types of signal sequences. Where are the signal sequences located? What happens to them after translation? How often do they appear?

A
  1. Signal sequence for secreted, Golgi, ER, lysosome: appears once, located first few amino acids, removes when translation finished
  2. Signal sequence for membrane-bound proteins: appears multiple times, located anywhere in AA sequence, NOT removed when translation finished
42
Q

What is the purpose of a signal sequence? Can a protein not have a signal sequence? If so, what is an example?

A

If a AA sequence has a signal sequence, translation is transported and finished on the Rough ER via signal recognition particle. Without the signal sequence, translation remains in the cytoplasm. Examples of proteins without signal sequences are glycolytic enzymes (remain in cytoplasm).

43
Q

What is the default pathway for proteins synthesized with a signal sequence? What is the name of the signal that prevents it from going to this default pathway? Proteins with this type of signal can end up to which organelles?

A

Without a targeting signal, the default pathway for proteins synthesized with signal sequences is the secretory pathway/plasma membrane. Targeting signals are organelle-specific. There are three organelles that require targeting signals: endoplasmic reticulum (smooth or rough), golgi apparatus, lysosome.

44
Q

If a protein is destined for the nucleus, mitochondria, or peroxisome, what is the name of the signal that is required?

A

Localization signal

45
Q

Antibodies, neurotransmitters, and peptide hormones have which sequence(s)/signal(s)?

A

Signal sequence only

46
Q

Receptors and channels have which sequence(s)/signal(s)?

A

Signal sequences and transmembrane domains

47
Q

Protein modification enzymes, lipid synthesis enzymes, and acid hydrolyses have which sequence(s)/signal(s)?

A

Signal sequences and targeting signals

48
Q

Histones, polymerases, transcription factors have which sequence(s)/signal(s)?

A

Localization signals only

49
Q

Metabolic enzymes (beta-oxidation, krebs cycle, PDC, urea cycle, gluconeogenesis) have which sequence(s)/signal(s)?

A

Localization signals only

50
Q

Catalase has which sequence(s)/signal(s)?

A

Localization signals only

51
Q

Which cytoskeletal filaments support cell shape by bearing tension/compression?

A

Microfilaments and intermediate filaments - bear tension

Microtubules - bear compression

52
Q

What are three ways which can cause growth arrest?

A
  1. Too much genomic mutation - arrest in M phase
  2. Contact inhibition - epithelial cells
  3. Lack of food
53
Q

Suppose a drug prevents spindle formation. What effect will this have on sister chromatids?

A

Centrioles, asters, and spindles are required for pulling apart the sister chromatids. Without either 3, chromatids will not be pulled apart

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