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MCAT Prep > Bio Chap 2 > Flashcards

Bio Chap 2 Flashcards

1
Q

What is Robert Hooke’s cell theory?

A
  1. All living organisms have 1+ cell 2. Cells are most basic unit of life. 3. All new cells are products of pre-existing, living cells
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2
Q

Describe mitosis

A

Prophase - nuclear membrane dissolves, chromatin condenses into chromosomes, spindle apparatus forms, spindle fibers attach chromosomes kinetochore - centrosome and fibers make up aster.

Metaphase -chromosomes align along metaphase plate

Anaphase - centrosomes pull sister chromatids to opposite sites

Telophase + cytokinesis - nuclear membrane reforms and cells separate.

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3
Q

Describe meiosis

A

Prophase 1 - nuclear membrane dissolves, chromosomes form chromatin condensing and spindle apparatus forms, homologous chromosomes pair via synapsis. Homologous chromosomes pair by synaptonemal complex - since each pair has 4 chromatids - tetrads. Chromatids can undergo crossing over if once - single crossover event, twice double crossover event. The spot where crossing over occurs is chiasma

Metaphase I - homologous chromosomes align along metaphase plate

Anaphase I - sent to opposite sides of cells

Telophase I and cytokinesis - cell splits into 2 cells

Meiosis II has same steps as mitosis.

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4
Q

What are the 3 key differences between mitosis and meiosis?

A
  1. Cells undergoing meiosis have 2n but produce n daughter cells. Mitosis 2n → 2n
  2. Meiosis only occurs in germ cells and mitosis in somatic
  3. Homologous chromosomes pair up and crossing over occurs. In mitosis - just sister chromatids.
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5
Q

What is cell cycle?

A

G1, S, G2, M Interphase is G1-G2

  • G1 - cell produces organelles to prep for division - check to make sure that has correct complement of DNA
  • S - cell undergoes DNA replication
  • G2- cell checks to see if ready for division - ensuring DNA synthesis occurred properly and there is enough cytoplasm and organelles to divide.
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6
Q

What happens when checkpoints cail?

A

When checkpoints fail, cancer can occur - often as a result of genetic causes - mutagens - agents that cause DNA mutations. Oncogenes - genes that can promote cell division when overexpressed - result of mutations in proto-oncogenes which have normal functions. Require mutation in only one allele to lead to dysfunctional cell growth. Tumor suppressor genes - can give rise to cancer when mutation inactivates them - mutations at both alleles.

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7
Q

What shapes are prokaryotic cells?

A

cocci, bacilli or spirilli

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8
Q

What are anaerobes?

A

bacteria that don’t need oxygen - aerobes do.

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9
Q

What are obligate anaerobes?

A

organisms that require absence of oxygen

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10
Q

What are aerotolerant anaerobes?

A

can only engage in anaerobic metabolism but oxygen is not toxic.

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11
Q

What are obligate aerobes?

A

Require oxygen

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12
Q

What are facultative anaerobes?

A

Prefer to not have oxygen

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13
Q

What are facultative aerobes?

A

Prefer to have oxygen but can live without.

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14
Q

Describe bacterial cell wall

A

Bacteria have cell wall - some have layer surrounding it called capsule - sticky layer of polysaccharide goo that may surround entire colony - allowing them to survive in animals. Peptidoglycan - most important component of cell wall - cross-linked chains of sugars and amino acids - unique to prokaryotes - target of many antibiotics.

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15
Q

How are peptidoglycan levels differentiated?

A

Gram staining - crystal violet dye to heat-fixed bacteria, adding iodide to trap dye to peptidoglycan layer, washing culture with ethanol or acetone to remove lipopolysaccharide membrane in Gram-negative bacteria and applying counterstain to visualize Gram-negative bacteria - Gram-positive appear dark purple and negative appear pink.

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16
Q

What is gram positive vs. negative? (See images)

A

Gram-positive - thick layer of peptidoglycan outside membrane. Gram-negative - have only thin layer in cell wall. Also have outer membrane with lipopolysaccharide. Gram-negative have resistance to antibiotics.

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17
Q

What other role do prokaryotic cell membranes play?

A

Cell membrane also plays role in prokaryotic aerobic respiration - relies on ETC and ATP synthase via cell membrane.

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18
Q

What is the difference between prokaryotic and eukaryotic ribosomes?

A

Prokaryotic ribosomes have 30S and 50S subunit that combine to make 70S ribosome - eukaryotes have 40S and 60S to make 80S ribosome. S is Svedberg unit - sedimentation rate of ribosomes.

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19
Q

What are flagella important for?

A

chemotaxis - movement of bacterium based on chemical signals. There are chemoreceptors on surface of cell that bind attractants or repellents and these molecules dictate which way flagella rotates and which direction bacteria moves.

20
Q

What are pili?

A

long projections on surface that help bacteria attach to surfaces. There is a sex pilus that helps male attach to female and form conjugation bridges.

21
Q

How is DNA stored in prokaryotes?

A

DNA stored on single circular chromosome in nucleoid region of cell. Some bacterial also have small circular DNA pieces called plasmids- often code for advantageous traits in bacteria.

22
Q

Describe the process of binary fission

A

Formation of two identical cells.

  1. Replication - chromosome and plasmid are duplicated.
  2. Segregation - each chromosome is pulled to ne side and new cell wall begins to form in middle
  3. Seperation - two cells have fully formed cell wall and pull away
23
Q

Describe prokaryotic cell growth stages (see image)

A

Lag phase - when bacteria are adapting to new environment.

Log phase - certain number of resources which causes number of bacteria to level off in period known as stationary phase.

Death phase - no more resources left in environment.

Bacterial growth is positive feedback loop

24
Q

What aid with antibiotic resistance and what 4 mutations during binary fission help?

A

Capsule and plasmid DNA help. Possibility of mutations during binary fission also.

4 types of these mutations:

  1. Formation of new enzymes in bacteria that deactivate antibiotic before it is effective
  2. Mechanism allowing bacteria to eject antibiotics from bacteria - rendering them useless
  3. Changes cell wall and prevents antibiotics from entering
  4. Alters function of bacteria that an antibiotic targets
25
Q

What is the Jacob-Monod model?

A

Operon - regulator gene, promoter site, operator site and structural gene.

Structural gene - codes for specific protein

Operator site is binding site for repressor

Promoter - binding site for RNA polymerase

Regulator gene - codes for repressor protein.

26
Q

What does it mean if an operon is inducible? Repressible?

A

If an operon is inducible - repressor is bound to operator site. Removal activates system. If it is repressible the system is activated and the genes are transcribed - system is turned off when repressor occupying the operator site binds with corepressor

27
Q

What are the 3 main methods of horizontal gene transfer? (see image)

A

Transduction - bacterial DNA transferred through viruses - viruses incorporate their DNA to create bacteriophage - can then infect other bacteria and incorporate DNA from original bacterial cell into DNA of new bacteria

Transformation - Bacteria absorb genetic material from environment

Conjugation - similar to sexual reproduction. A sex plasmid is transferred through bacterial bridge - pilus extends from one bacterial F+ to other F- and creates conjugation bridge. The F+ are male and F- are female. The F+ factor itself is transferred to new bacterium creating new F+ cell.

28
Q

What are transposons?

A

jumping genes in prokaryotic and eukaryotic DNA capable of moving around within genome.

29
Q

What are lysosomes?

A

Garbage disposal of cell, contains hydrolytic enzymes to break down waste products and toxins. break down chained structure of old carbs, proteins, nucleic acids etc.

30
Q

What are peroxisomes?

A

Metabolize lipids and toxins using peroxides like H2O2. full of peroxides that produce free radicals that aid in polymer degradation

31
Q

What is chromatin?

A

DNA wrapped around histones. One unit of histone wrapped in DNA is nucleosome. - Euchromatin is open and transcriptionally active, characterized by extensive acetylation of histones. Heterochromatin is closed and transcriptionally silent - extensive methylation

32
Q

How do mitochondria replicate?

A

Mitochondria replicate via binary fission. DNA found in is considered to be extragenomic.

33
Q

What does RER do?

A

ribosomes make proteins then passed through to begin post-translational mods then sent to Golgi

34
Q

What does SER do?

A

synthesizes lipids - can have other specialized functions ie. detoxification of drugs or catabolism of glycogen in liver.

35
Q

What are the 3 regions of the Golgi?

A

3 regions - cis (faces nucleus) trans (faces membrane) and medial in between. Proteins move cis to trans - undergoing further mods. Packaged in vesicles in trans.

36
Q

What are the 3 components of the cytoskeleton?

A

Microfilaments - 2 strands of actin - movement of cell, endo/exocytosis, cell cleavage and muscle contraction

Microtubules - tubulin polymers of alpha and beta tubulin - wider than microfilaments - maintain cell structure, compose cilia and flagella, facilitate intracellular transport and make up mitotic spindles

Intermediate filaments - each monomer has head, tail and long center can be single, two aligned or many - structural support, cellular adhesion, example: keratin

37
Q

Where do cytoskeletal elements originate in normal cell?

A

In normal cell function, cytoskeletal elements originate from one region close to nucleus - microtubule organizing center - where alpha and beta-tubulin subunits polymerize to form long microtubule structures. Also contains centrioles - serve as additional sites for cilia formation and polymerization of mitotic spindle in cell division.

38
Q

What structure are cilia and flagella?

A

Are 9+2 structure - outer ring of 9 pairs of microtubules and inner ring of 2.

39
Q

Describe epithelial cells

A

tend to be cube shaped, squamous cells are flat and thin. Epithelial cells found in linings of body cavities and vessels and squamous on areas of body that encounter wear.

40
Q

Describe intracellular junctions

A

ight (sealed connection, do not allow for passage of fluid = commonly found in storage organs ie. stomach and kidney), gap (form connexons (passage) for ions and nutrients, found in cardiac muscle) and desmosomes (anchoring of cytoskeletons - found in tissues that require tensile strength ie. skin and muscles)

41
Q

What are the 3 types of stem cells?

A

Multipotent - differentiate into a particular group ie. hematopoietic - blood cells

Pluripotent - differentiate into embryonic germ layer but not extra-embryonic cells ie. placenta - ie can give rise to any cells that develop from mesoderm.

Totipotent - differentiate into any cell from any germ layer or into any extra-embryonic cell.

42
Q

Describe virus structure

A

None living, need host to replicate, have genetic material and capsid (protein coat), smaller than eukaryotes and prokaryotes, 20-400 nm. Viral genetic material can be DNA or RNA. Single-strand viral genomes can be broken down into positive-sense or negative-sense viruses. Negative-sense RNA - RNA is complementary to mRNA to be translated and positive-sense RNA is already in correct form of mRNA to be translated.

43
Q

Describe viral functioning

A

Virus attaches to host cell by penetrating membrane/wall and injecting its DNA/RNA. Genetic material is replicated by host cell, viral components assemble and repeat.
When host cell is a bacteria, the combination of virus and host is a bacteriophage - virus attaches outside and injects in material. When host is animal cell, entire virus is brought in.

44
Q

Describe the two life cycles for bacteriophages (see image)

A
  1. Lytic cycle - replicating genome at full speed to make viruses until bacteria bursts.
  2. Lysogenic cycle - viral genetic material becoming part of bacteria’s genome and laying silent. Lytic cycle induced when certain environmental triggers are observed - bacteria with viral genetic material is prophage/provirus.
45
Q

What is a retrovirus?

A

has single-stranded RNA and a slightly diff method of replication - enzyme reverse transcriptase creates new DNA from RNA genome. DNA is then incorporated into host DNA - DNA replicated as cell replicates and is hard to remove - ie. HIV

46
Q

What are prions and viroids?

A

Subviral particles are prions and viroids. Prion - protein that is folded incorrectly and causes correctly folded proteins to become misfolded - considered infectious - ie. mad cow disease, Creutzfeldt-Jakob disease and fatal familial insomnia. Viroids are short pieces of single-stranded RNA that can silence gene expression by binding RNA sequences not allowing them to be translated - most are found in plants but Hep D in humans.

MCAT Prep (6 decks)

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