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MCAT > B 1 - The Cell > Flashcards

B 1 - The Cell Flashcards

1
Q

Describe the four tenets of Cell Theory

A

1 - All livings things are composed of cells
2 - the cell is the basic functional unit of life
3 - cells arise only from preexisting cells
4 - cells carry genetic info in the form of DNA. This genetic material is passed on from parent to daughter cell.

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2
Q

Are viruses considered living organisms?

A

No, because they are acellular, cant reproduce without assistance of a host cell, and may use RNA as their genetic material

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3
Q

Describe what makes eukaryotes unique from prokaryotes

A

Eukaryotes have membrane-bound organelles, a nucleus, and may form multi-cellular organisms

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4
Q

Describe the makeup of cell membrane and membranes of organelles

A

Contain phospholipids, which organize to form hydrophilic interior and exterior surfaces with a hydrophobic core

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5
Q

Define the cytosol

A

Cytosol suspends the organelles and allows diffusion of molecules through-out the cell

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6
Q

Describe the NUCLEUS

A

Nucleus contains DNA organized into chromosomes.

It is surrounded by the nuclear membrane/envelope, a double membrane that contains nuclear pores for two-way exchange of materials between the nucleus and cytosol.

DNA is organized into coding regions called genes.

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7
Q

Define the NUCLEOLUS

A

Nucleolus is a subsection of the nucleus in which ribosomal RNA (rRNA) is synthesized

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8
Q

Define the MITOCHONDRIA

A

Mitochondria contain an outer and inner membrane. The outer membrane forms a barrier with the cytosol; the inner membrane is folded into cristae and contains enzymes for the electronic transport chain.

Between the membranes is the intermembrane space; inside the inner mitochondrial membrane is the mitochondrial matrix.

Mitochondria can divide independently of the nucleus via binary fission and can trigger apoptosis by releasing mitochondrial enzymes into the cytoplasm.

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9
Q

Define the LYSOSOME

A

Lysosomes contain hydrolytic enzymes that can break down substances ingested by endocytosis and cellular waste products. When these enzymes are released, autolysis of the cell can occur.

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10
Q

Define the ENDOPLASMIC RETICULUM (ER)

A

The endoplasmic reticulum is a series of interconnected membranes and is continuous with the nuclear envelope.

The rough ER (RER) is studded with ribosomes, which permit translation of proteins destined for secretion.

The smooth ER (SER) is used for lipid synthesis and detoxification.

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11
Q

Define the GOLGI APPARATUS

A

Golgi apparatus consists of stacked membrane-bound sacs in which cellular products can be modified, packages, and directed to specific cellular locations.

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12
Q

Define the PEROXISOME

A

Peroxisomes contain hydrogen peroxide and can break down very long chain fatty acids via Beta-oxidation. They also participate in phospholipid synthesis and the pentose phosphate pathway.

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13
Q

Define the CYTOSKELETON

A

Cytoskeleton provides stability and rigidity to the overall structure of the cell, while also providing transport pathways for molecules within the cell.

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14
Q

Define MICROFILAMENTS

A

Microfilaments are composed of actin. They provide structural protection for the cell and can cause muscle contraction through interactions with myosin. They also help form the cleavage furrow during cytokinesis in mitosis.

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15
Q

Define MICROTUBULES

A

Microtubules are composed of tubulin. They create pathways for motor proteins like kinesin and dynein to carry vesicles.

They also contribute to the structure of cilia and flagella, where they are organized into nine pairs of microtubules in a ring with two microtubules at the center (9+2 structure).

Centrioles are found in centrosomes and are involved in microtubule organization in the mitotic spindle.

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16
Q

Define INTERMEDIATE FILAMENTS

A

Intermediate filaments are involved in cell-cell adhesion and maintenance of the integrity of the cytoskeleton; they help anchor organelles. Common examples include keratin and desmin.

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17
Q

Define EPITHELIAL TISSUES

A

Epithelial tissues cover the body and line its cavities, protecting against pathogen invasion and desiccation.

Some epithelial cells absorb or secrete substances or participate in sensation.

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18
Q

Define PARENCHYMA

A

In most organs, epithelial cells form the parenchyma, or the functional parts of the organ.

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19
Q

How are epithelial cells oriented?

A

Epithelial cells may be polarized, with one side facing a lumen or the outside world, and the other side facing blood vessels and structural cells.

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20
Q

What are the LAYERS of Epithelial Cells?

A

Simple epithelia have one layer

Stratified epithelia have many layers

Psuedostratified epithelia appear to be multi-layered due to differences in cell heights, but actually have only one layer

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21
Q

What are the SHAPES of Epithelial Cells?

A

Cuboidal Cells are cube-shaped

Columnar Cells are long and narrow

Squamous Cells are flat and scalelike

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22
Q

Define CONNECTIVE TISSUES

A

Connective tissues support the body and provide a framework for epithelial cells

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23
Q

Define STROMA of connective tissues and what it creates

A

In most organs, connective tissues form the stroma or support structure by secreting materials to form an extracellular matrix

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24
Q

Give examples of CONNECTIVE TISSUES

A

Bone, cartilage, tendons, ligaments, adipose tissues and blood

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25
Q

Define PROKARYOTE

A

Prokaryotes do not contain membrane-bound organells; they contain their genetic material in a single circular molecule of DNA located in the NUCLEOID REGION

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26
Q

What are the 3 overarching domains of life?

A

Prokaryotes (Archaea and Bacteria)

Eukaryotes

27
Q

Define ARCHAEA

A

Archaea are often extremophiles, living in harsh environments (high temp, salinity, no light) and often use chemical sources of energy (chemosynthesis) rather than light (photosynthesis).

They have similarities to both eukaryotes (start translation with methionine, similar RNA polymerases, histones) and bacteria (single circular chromosome, divide by binary fission or budding)

28
Q

Define BACTERIA

A

Bacteria have many similar structures to eukaryotes, and have complex relationshisp with humans, including MUTUALISTIC SYMBIOSIS and PATHOGENESIS

29
Q

Define EUKARYA

A

Eukarya are the only non-prokaryotic domain

30
Q

What are the classifications of BACTERIA by shape?

A

Cocci - spherical bacteria
Bacilli - rod-shaped bacteria
Spirilli - Spiral-shaped bacteria

31
Q

What are the classifications of BACTERIA by metabolic process?

A

OBLIGATE AEROBES - require oxygen for metabolism
OBLIGATE ANAEROBES - cant survive in oxygen-containing environments and can only carry out anaerobic metabolism
FACULTATIVE ANAEROBES - can survive in environments with or without oxygen and will toggle between metabolic processes based on the environment
AEROTOLERANT ANAEROBES - cannot use oxygen for metabolism, but can survive in an oxygen-containing environment

32
Q

Define the cell’s ENVELOPE

A

The ENVELOPE is made up of the cell wall and cell membrane of bacteria. Together, control movement of solutes into and out of the cell

33
Q

Describe GRAM STAINING process and results based on bacterial cell walls

A

Bacteria can be classified by the color their cell walls turn during Gram Staining with a crystal violet stain, followed by a counterstain with safranin.

Gram-Positive bacteria turn purple
Gram-Negative bacteria turn pink-red

34
Q

Describe the chemical structure of the cell wall of a GRAM-POSITIVE BACTERIA

A

Gram-positive bacteria have a thick cell wall composed of peptidoglycan and lipoteichoic acid

35
Q

Describe the chemical structure of the cell wall of a GRAM-NEGATIVE BACTERIA

A

Gram-negative bacteria have a thin cell wall composed of peptidoglycan and an outer membrane containing phospholipids and lipopolysaccharides

36
Q

Describe motility for bacteria

A

Bacteria may have one, two or many flagella that generate propulsion to move the bacterium toward food or away from immune cells.

Moving in response to chemical stimuli is called CHEMOTAXIS

Bacterial flagella contain a filament composed of flagellin, a basal body that anchors and rotates the flagellum, and a hook that connects the two

37
Q

How do prokaryotes carry out the Electron Transport Chain?

A

Prokaryotes use the CELL MEMBRANE to carry out ETC

38
Q

How are ribosome sizes different between pro- and eu- karyotes?

A

Prokaryotic ribosomes are smaller than eukaryotic ribosomes

Pro- 30S & 50S
Eu- 40S and 60S

39
Q

Define BINARY FISSION

A

Prokaryotes multiply thru BINARY FISSION, in which the chromosome replicates while the cell grows in size, until the cell wall begins to grow inward along the midline of the cell and divides into two identical daughter cells

40
Q

Define PLASMIDS

A

Plasmids are extrachromosomal material , which may contain antibiotic resistance genes (VIRULENCE FACTORS).

Plasmids are contained potentially within prokaryotes, along with their singular/circular chromosome

41
Q

Define EPISOMES

A

Episomes are plasmids that can integrate into the genome

42
Q

What are the 4 types of BACTERIAL GENETIC RECOMBINATION?

A

Transformation
Conjugation
Transduction
Transposons

43
Q

Define TRANSFORMATION

A

Transformation occurs when genetic material from the surroundings is taken up by a cell, which can incorporate this material into its genome

44
Q

Define CONJUGATION

A

Conjugation is the transfer of genetic material from one bacterium to another across a CONJUGATION BRIDGE

e. g. a PLASMID can be transferred from F+ cells to F- cells
e. g. a portion of the genome can be transferred from an Hfr cell to a recipient

45
Q

Define TRANSDUCTION

A

Transduction is the transfer of genetic material from one bacterium to another via a bacteriophage vector

46
Q

Define TRANSPOSONS

A

Transposons are genetic elements that can insert into or remove themselves from the genome

47
Q

Define BACTERIAL GROWTH pattern

A

1 - LAG PHASE - bacteria adapt to new local conditions
2 - EXPONENTIAL (LOG) PHASE - growth then increases exponentially
3 - STATIONARY PHASE - as resources are reduced, growth levels off
4 - DEATH PHASE - as resources are depleted, bacteria die

48
Q

What are the components of a VIRUS?

A

Viruses contain genetic material, a protein coat (called a CAPSID), and sometimes a lipid-containing envelope

49
Q

Define OBLIGATE INTRACELLULAR PARASITE

A

Viruses are obligate intracellular parasites, meaning they cannot survive and replicate outside of a host cell

50
Q

Define VIRION

A

An individual virus particle

51
Q

Describe a BACTERIOPHAGE

A

Bacteriophages are viruses that target bacteria

In addition to other structures, they contain a TAIL SHEATH and TAIL FIBERS

Tail Sheath - Injects the genetic material into a bacterium

Tail Fiber - allows the bacteriophage to attach to the host cell

52
Q

How are VIRAL GENOMES composed?

A

They can exist in many different forms: DNA or RNA, single- or double- stranded

53
Q

Define POSITIVE SENSE Viruses

A

Positive Sense viruses are SINGLE-STRANDED RNA viruses that can be TRANSLATED by the host cell

54
Q

Define NEGATIVE SENSE Viruses

A

Negative Sense viruses are SINGLE-STRANDED RNA viruses, but require a complementary strand to be synthesized by RNA replicase enzyme before translation

55
Q

Define RETRO Viruses

A

Retroviruses contain a single-stranded RNA genome, from which a complementary DNA strand is made using REVERSE TRANSCRIPTASE enzyme

The DNA strand can then be integrated into the genome

56
Q

How do viruses infect/integrate into host cells?

A

Viruses infect cells by attaching to specific receptors, and can then enter the cell by fusing with the plasma membrane, being brought in by endocytosis, or injecting their genome into the cell

57
Q

How do viruses reproduce?

A

Viruses reproduce by replicating and translating genetic material using the host cell’s ribosomes, tRNA, amino acids, and enzymes

58
Q

How are viral progency released into host to infect other cells?

A

Viral progeny are released through cell death, lysis or extrusion

59
Q

What are the 2 life cycles possible for bacteriophages?

A

Lytic Cycle

Lysogenic Cycle

60
Q

Define LYTIC CYCLE

A

Bacteriophage produces massive numbers of new virions until the cell lyses. Bacteria in the lytic phase are termed VIRULENT

61
Q

Define LYSOGENIC CYCLE

A

Virus integrates into the host genome as a pro-virus or pro-phage, which can then reproduce along with the cell

The provirus can remain in the genome indefinitely, or may leave the genome in response to a stimulus and enter the lytic cycle

62
Q

Define PRIONS

A

Prions are infectious proteins that trigger misfolding ofo other proteins, usually converting alpha-helical structure to a beta-pleated sheet

This decreases the solubility of the protein and increases its resistance to degradation

63
Q

Define VIROIDS

A

Viroids are plant pathogens that are small circules of complementary RNA that can turn off genes, resulting in metabolic and structural changes and, potentially, cell death

MCAT (8 decks)

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