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The Cell Flashcards

Cell Theory Eukaryotic Cells Prokaryotic Cells Viruses and Subviral Particles

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1
Q

Describe eukaryotic cells

A

cells that contain a true nucleus enclosed in a membrane, including membrane bound organelles

DNA is tightly wrapped around histone proteins in chromosomes in the nucleus.

Larger and more complex than bacterial cells

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2
Q

Describe Membrane Bound organelles and their role in function.

A

Structures within the cells that allow for the compartmentalization of functions

“Organs of the cell”

Major difference between Eukaryotic and Prokaryotic Cells

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3
Q

Describe the function of the cytosol.

A

The soluble portion of the cytoplasm, allows for the diffusion of molecules throughout the cell

Includes small particles, such as ribosomes, but not the organelles covered with membranes.

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4
Q

What is Deoxyribonucleic acid (DNA)?

A

A nucleic acid molecule, usually a double stranded helix, in which each polynucleotide strand consists of nucleotide monomers with a deoxyribose sugar and the nitrogenous bases A T C G; capable of being replicated and determining the inherited structure of cell’s proteins.

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5
Q

Describe Mitosis.

A

A process of nuclear division in eukaryotic cells conventionally divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase. Mitosis conserves chromosome number by equally allocating replicated chromosomes to each of the daughter nuclei.

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6
Q

Describe the role of the nucleus in cellullar function.

A

Control center of the cell contains all the genetic material, DNA and RNA necessary, for replication of the cell

Responsible for growth and reproduction

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7
Q

Nuclear Membrane/Envelope

A

Double membrane that maintains a nuclear environment separates and distinct from the cytoplasm; present in eukaryotes

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8
Q

Describe the role of nuclear pores in cellular transport.

A

Pores in the nuclear membrane that allow for selective two way exchange of material between the cytoplasm and the nucleus

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9
Q

What are Genes?

A

Coding regions/segments of DNA that code for specific traits

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10
Q

Chromosomes

A

Single piece of coiled DNA and associated proteins found in linear forms in the nucleus of eukaryotic cells and circular forms in the cytoplasm of prokaryotic cells

Contains genes that encode for traits. Each species has a characteristic number of chromosomes.

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10
Q

Explain the function of Histone Proteins.

A

Globular protein that assists in DNA packaging in eukaryotes. Histones form octamers around which DNA is wound to form a nucleosome.
Rich in amino acids lysine and arginine

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11
Q

Explain the function of nucleolus.

A

Subsection of the nucleus where ribosomal RNA - rRNA is synthesized

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12
Q

What is rRNA and its role in cell function?

A

The most abundant type of RNA, which together with proteins, forms the structure of ribosomes.

Ribosomes coordinate the sequential coupling of tRNA molecules to mRNA codons. Helps make proteins

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13
Q

What are Peroxisomes?

A

Contain hydrogen peroxide

Primary functions of breaking down long chains of fatty acids via Beta Oxidation

Participate in the synthesis of phospholipids and contain enzymes involved in the pentose phosphate pathway

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14
Q

Describe the function of the cytoskeleton.

A

Provides structure to the cell and helps maintain its shape

Provides a conduit of transport of materials around the cell

Composed of:

Microfilaments
Microtubules
Intermediate Filaments

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15
Q

Describe Microfilaments.

A

Polymerized rods composed of actin

Organized into bundles/networks

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16
Q

What is the Mitochondria?

A

The power plants of the cell, site of cellular respiration; uses oxygen to break down organic molecules and synthesize ATP

Composed of outer membrane and inner membrane

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17
Q

Describe the function of the outer mitochondrial membrane.

A

Serves as the barrier between cytosol and the inner environment

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18
Q

What is the Intermembrane Space?

A

Space between the inner and outer membrane

A “large amount of H+ is concentrated here” for the “electron transport chain”

H+ are pushed out during ETC

Creates a proton motive force

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19
Q

Mitochondrial Matrix

A

The interior of a mitochondrion (the region bounded by the inner membrane).

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20
Q

Mitochondrial Cytoplasmic/Extranuclear Inheritance

A

Transmission of genetic material independent of the nucleus

Mitochondrial DNA is passed on outside of the nucleus

Mitochondria evolved from anaerobic prokaryotes engulfing anaerobic prokaryotes

Circular, double stranded DNA

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21
Q

Describe Apoptosis.

A

Programmed cell death - controlled and intentional (important distinction from autolysis)

initiated by the release of enzymes from the electron transport chain from the mitochondria

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22
Q

Lysosomes

A
  • Membrane-bound structures containing hydrolytic enzymes that are capable of breaking down different substrates, including substances ingested by endocytosis and cellular waste products
  • works in conjunction with endosomes
  • sequesters its enzymes to prevent damage to cell
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23
Q

Autolysis

A

Release of enzymes in the lysosomes that results in cell death - these enzymes can be released into the extracellular environment

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24
Q

Describe the Endoplasmic Reticulum.

A

Series of interconnected membranes that are actually contiguous with the nuclear envelope

Folded numerous times to create complex structures in the lumen

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25
Q

Rough Endoplasmic Reticulum - RER

A

Membranes studded with ribosomes, which permit the translation of proteins destined for secretion directly into the lumen

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26
Q

Smooth Endoplasmic Reticulum - SER

A

Membranes that lack ribosomes and primarily for the synthesis of phospholipids and detoxication of drugs and poisons in the cell

Transports proteins from the RER to the Golgi Apparatus

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27
Q

Golgi Apparatus

A

Series of stacked membrane bound sacs that modify cellular products via the addition of groups like carbohydrates, phosphates, and sulfates. Can also modify with signal sequences, which direct delivery of the product

Direct delivery of the products to specific cellular location via vesicles (EX: outside the cell, to lysosome, to plasma membrane)

Essentially the shipping center of the cell

Can send products outside the cell via secretory vesicles, exocytosis

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28
Q

Exocytosis

A

A process in which a cell releases substances to the extracellular environment by fusing a vesicular membrane with the plasma membrane, separating the membrane at the point of fusion and allowing the substance to be released.

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29
Q

What does “Form Follows Function” in relation to cells?

A

Not all cells have the same relative distribution of organelles
- Ex: cells that require a lot of energy for location (sperm cells) have high concentration of mitochondria; cells involved in secretion (pancreatic islet cells) have high concentrations of RER and Golgi apparatuses

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30
Q

What are the 4 tenets of Cell Theory?

A

-All living things are composed of cells
- The cell is the basic functional unit of life
- Cells arise only from preexisting cells

4th Recently Developed Tenet of Cell Theory

  • Cells carry genetic information in the form of deoxyribonucleic acid . This genetic material is passed on from parent to daughter cell
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31
Q

What is the role of Actin in cell function?

A

Protein that polymerizes to form microfilaments

Use ATP to generate a force for movement by interacting with Myosin - for muscle contraction

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32
Q

Cytokinesis

A

Division of materials amongst the daughter cells

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33
Q

Describe Cleavage Furrow.

A

Microfilament structure that organizes as a ring at the site of divisions between each daughter cells

Actin filaments then contract and the ring becomes smaller pinching off the connection between daughter cells

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34
Q

Microtubules

A

Hollow polymers of “tubulin” proteins that provide primary pathways along the cell which motor proteins carry vesicles like kinesin and dynein

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35
Q

Kinesin

A

binds ATP, is an ATPase, uses tubulin as stepping stone, moves towards positive end

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36
Q

Dynein

A

binds ATP (ATPase), uses tubulin as a stepping stone, moves toward negative end directed

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37
Q

Cilia

A

Structure composed of “microtubules” that project from the cell

Involved in the movement of materials along the cell surface

Ex : Respiratory system - movement of mucus

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38
Q

Flagella

A

Structure composed of “microtubules” that are involved in the movement of the cell itself

Ex : sperm cells

Often form the 9+2 structure in Eukaryotic cells

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39
Q

9+2 Structure

A

The structure is found in both eukaryotic cilia and flagella
9 pairs microtubules form an outer ring structure with 2 microtubules running down the center.

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40
Q

Centrioles

A

Found in the centrosome, organizing center for microtubules

Structured as 9 triplets of microtubules with a hollow center

Migrate to opposite poles of the dividing cell and attach to the chromosomes via Kinetochores

Pull the sister chromatids apart

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41
Q

Kinetochores

A

Anchor on the Sister Chromatid that attaches to the fiber that pulls the sister chromatids apart.

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42
Q

Intermediate filaments

A

Diverse group filamentous proteins
- keratin, desmin, vimentin, and lamins

Many involved in cell-cell adhesion or maintenance of cytoskeleton integrity

Withstand tension to make cell structure more rigid

Anchor other organelles

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43
Q

Describe the process of tissue formation.

A

Formation of tissues allows for the division of labor

Different cells in a tissue carry out different functions

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44
Q

Epithelial Tissue

A

Covers the body and lines its cavities providing a means for protection against pathogen invasion and desiccation

In certain organs, involved in absorption, secretion, and sensation

Tightly joined together and to an underlying layer of connective tissue

Often polarized, one side of the cell faces the lumen, the other sided faces interacts with blood vessels and structural cells

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45
Q

Basement Membrane

A

Underlying layer of connective tissue that composes the floor of epithelial tissue

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46
Q

Parenchyma

A

Functional parts of the organ that are largely composed of highly diverse epithelial cells that perform a wide array of functions

Ex tissues of the bronchioles, alveoli, ducts, and sacs, that perform respiration, nephrons, hepatocytes, acid producing cells in the stomach

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47
Q

Simple Epithelia

A

Single layer of cells. Characteristics: absorbs, secretes, filtrates, very thin

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48
Q

Stratified Epithelia

A

Two or more layers of cells; shape can change in different layers.

Regenerates from below: basal cells divide and cells migrate to the surface.

More durable than simple epithelia and protection is the major role

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49
Q

Pseudostratified Epithelia

A

Appears like multiple layers due to a difference in cell height, but are really one layer

Ex: Lines respiratory tract

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50
Q

Three main shapes of epithelial cells

A

Cubiodal - Cube shaped cells
Columnar - long and thin
Squamous - flat and scalelike

51
Q

Connective Tissue

A

Supports the body and provides a framework for the epithelial cells to carry out their functions

Contribute to the stroma of organs

Most cells in connective tissue produce and secrete materials such as collagen and elastin to form extracellular matrix

Ex : bones, cartilage, tendons, adipose tissue, and blood

52
Q

Stroma

A

the supportive tissue of an organ, tumor, gonad

Consisting of connective tissues and blood vessels.

53
Q

Prokaryotic Cells

A

Cells that do not contain membrane-bound organelles or a nucleus

Simplest of all cells, includes all bacteria

54
Q

Nucleoid Regions

A

Single circular molecule of DNA in the middle of prokaryotic cell

55
Q

Prokaryotic Domains

A

Classification and Structure of Prokaryotic Cells

2 Domains:
Archea
Bacteria

56
Q

Archaea

A

Single-celled organisms that are visually similar to bacteria, but contain genes and metabolic pathways more similar to eukaryotes

Considered extremophiles but are now noted to be found in a variety of habitats

Notable for ability to use alternative sources of energy (photosynthetic, chemosynthetic - generating energy from inorganic compounds)

57
Q

Extremophiles

A

Archea that are found in isolated harsh environments: extremely high temperatures, high salinity, or no light

58
Q

Describe the characteristics of bacteria.

A

Cells that contain a cell membrane and cytoplasm

Flagella and Fimbrea

Bacteria and eukaryotes share analogous structures

59
Q

Cell Membrane

A

A thin, flexible barrier around a cell; regulates what enters and leaves the cell

60
Q

Fimbriae

A

Surface appendages that allow a bacterium to stick to a surface.

61
Q

Mutualistic Symbiotes

A

Both humans and bacteria benefit from their relationship

Examples include bacteria that produce vitamin K or biotin (vitamin B7) in our intestines

62
Q

Pathogens / Parasites

A

Provide no advantage or benefit to the host, but rather cause disease
Can live intracellularly or extracellularly

63
Q

Cocci

A

Spherical bacteria
- Ex: Streptococcus pyogenes

64
Q

Bacilli

A

Rod shaped bacteria
- Ex: Escherichia coli

65
Q

Spirilli

A

spiral shaped bacteria
- Treponema pallidum (Causes syphilis)

66
Q

Obligate Aerobes

A

Bacteria that require oxygen for metabolism

67
Q

Anaerobes

A

Bacteria that use fermentation/ another metabolism that does not require oxygen

68
Q

Obligate Anaerobes

A

Bacteria that can not survive in the presence of oxygen

Produce oxygen-containing free radicals leading to cell death

69
Q

Faculative Anaerobes

A

Bacteria that can toggle metabolic processes using oxygen for aerobic metabolism if present and switching to anaerobic metabolism if not present

70
Q

Aerotolerant Anaerobes

A

Bacteria that cannot use oxygen for metabolism but are not harmed by its presence

71
Q

Prokaryotic Cell Stucture

A

Contain Cell wall followed by cell membrane: together known as the envelope

Primitive Cytoskeleton (not as complex as euk.)

No nucleus, or membrane-bround organelles (lacking mitochondria)

Contain ribosomes (with no membrane) made up of 30 and 50s subunits (euk have 40S and 60S)

Single-cell organisms: each cell able to perform all functions for life but may live in colonies and signal these cells to share info about environment

72
Q

Cell wall Prokaryotes (two types)

A

Forms the outer barrier of the cell, protecting it from the environment

Provides structure and controls the movement of solutes in and out of the bacterium, maintaining concentration gradients

73
Q

Gram Positive Bacteria

A

Cell wall is composed of a thin layer of peptidoglycans also containing lipoteichoic acids

74
Q

Gram Negative Bacteria

A

Cell wall is a very thin layer of peptidoglycan, adjacent to the plasma membrane separated by a periplasmic space

Also has an outer membrane containing phospholipids, lipopolysaccharides and porins

Lipopolysaccharides trigger the immune response in the body (much more so than to lipoteichoic acid)

75
Q

Gram staining

A

A method of differentiating bacteria into Gram-positive and Gram-negative.

Gram positive bacteria stain purple because the thick peptidoglycan layer retains the crystal violet stain during the alcohol step

Gram negative bacteria become colorless during the alcohol step and then stain red-pink with safranin, the counterstain

76
Q

Bacteria Cell Membrane

A

Composed of phospholipids similar to that of eukaryotes

Used for the electron transport chain and generation of ATP

77
Q

Peptidoglycan

A

Found in both gram positive and negative cells

Larger concentration in gram positive cells

Polymer substance made from peptides (chain amino acids) and sugars

May aid a pathogen by providing protection from hosts immune system

78
Q

Lipoteichoic Acid

A

Also found in gram-positive cell walls

Provides an unknown function

Human immune system is activated by this substance

79
Q

Lipopolysaccharides

A

Found in the outer membranes of gram-negative bacteria

Containing lipid and polysaccharide parts

Can be known as endotoxins

80
Q

Flagella Bacteria

A

Composed of Basal body, Hook, and Filament

Whiplike structure used for propulsion; bacteria may have one, two, or many

81
Q

Flagellin

A

Polymerized protein that forms the long, hollow, helical structures in the filaments of prokaryotic flagellum.

82
Q

Chemotaxis

A

Ability of a cell to detect chemical stimuli and move towards or away from them

83
Q

Basal Body

A

Complex structure that anchors the flagellum to the cytoplasmic membrane

The motor of the flagellum (rotates at rates up to 300 Hz)

84
Q

Hook

A

Connects the filament and the basal body so that as the basal body rotates it exerts torque on the filament

Causing spinning and thus movement of the bacteria

85
Q

Plasmids

A

Circular DNA structures that are acquired from external sources

Carry DNA that is not necessary for surival of the prokaryote

Not considered part of the genome, but are often advantageous

Ex : Antibiotic Resistance

86
Q

Binary Fission

A

Simple form of asexual reproduction seen in prokaryotes

  1. Circular chromosome attaches to inside of inner membrane and replicates (starting at replication origin) while the cell grows in size
  2. Chromosome separates to opposite sides of the cell
  3. Plasma membrane and cell wall begins to grow inward and invaginate (pinch off)
  4. Two daughter cells are produced

(E. coli can replicate every 20 min)

87
Q

Genetic Recombination

A

Many bacteria contain plasmids that carry genes that benefit the bacterium (EX antibiotic resistance)

May also carry virulence factors

Helps increase bacterial diversity and thus permits the evolution of a bacterial species over time

Through the methods of :

Transformation
Conjugation
Transduction

88
Q

Virulence Factors

A

Traits that increase how pathogenic a bacterium is

Can cause toxin production, attachment to specific cells, and evasion of a hosts immune system

89
Q

Episomes

A

Plasmids that are capable of integrating into the genome of the bacterium

90
Q

Transformation

A

Results from the integration of the foreign genetic material into the host genome

Genetic material most often comes from other bacteria that have lysed, spilling contents to the environment

Common in Gram-negative rods

91
Q

Conjugation

A

Bacterial form of mating

Involves to bacterium forming a conjugation bridge that allows the transfer of material

Transfer is unidirectional (from donor male to recipient female)

92
Q

Conjugation Bridge

A

Structure formed between two bacterial cells that allow for the transfer of genetic material

Made from appendages called sex pili

93
Q

Donor Male +

A

Bacterium that donates the genetic material during conjugation

94
Q

Recipient Female -

A

Bacterium that recieves the genetic material during conjugation

95
Q

Conjugative (sex) Pili

A

Appendages that form the conjugation bridge

Can only be formed if sex factors are present in the bacterium, the donor male, typically as a plasmid, but it’s possible to be integrated into the host genome (transformation)

96
Q

Sex Factors

A

Plasmids containing the necessary genes that allows for the formation to sex pili

Most common is the Fertility Factor, F, in E. coli

97
Q

F - Fertility Factor

A

Allows genes to be transferred from one bacterium carrying the factor to another bacterium lacking the factor by “conjugation”.

F+ cells contain the F factor and form a single sex pilus that connects to F- cell

The F factor is then replicated via DNA polymerase

F- cell now gains replicated F factor cell becoming F+

98
Q

Hfr - High Frequency of Recombination

A

Cells that have undergone genetic recombination via conjugation and then through processes, such as transformation, integrated a sex factor plasmid into the host genome

Donor cell will now attempt to transfer entire copy of genome into recipient during conjugation but bridge usually breaks before full DNA sequence is done

99
Q

Transduction

A

Only genetic recombination process that requires a vector to transmit new genetic material

Typically the vector is a virus

Bacteriophage can accidentally trap segment of host DNA during assembly. When bacteriophage infects another bacterium, it can release the trapped DNA which can then integrate into the new host genome giving the new host additional genes

100
Q

Vector

A

Virus that carries the genetic material from one bacterium to another

Obligate intracellular pathogens - require host cell in order to reproduce

101
Q

Bacteriophages

A

Viruses that infect bacteria

Can accidentally trap a segment of host DNA during assembly

This vector can transfer host DNA to other bacterial cells that integrate into the genome

contains tail sheath and tail fibers

102
Q

Transposons

A

Genetic elements capable of inserting and removing themselves from the genome

Seen in both prokaryotes and eukaryotes

If inserted into a coding region of a gene, gene may be disrupted

103
Q

Bacterial Growth

A

Under the implication that bacteria in colonies are all the same and no bacteria divide faster than the others

Graph shows several phases of colony populations - y-axis is logarithmic

Lag Phase - adapting to new environment
Exponential or Log Phase - as bacteria adapt, growth increases
Stationary phase - as number in colony grows, resources become limited slowing reproduction
Death Phase - resources depleted/bacteria exceeded ability of environment to support number

104
Q

Virus

A

Any of a large group of submicroscopic infective agents that typically contain a protein coat surrounding an RNA or DNA core of genetic material but no semipermeable membrane , that are capable of growth and multiplication only in living cells, and that cause various important diseases in humans, animals, or plants.

105
Q

Capsid

A

Protein coat that encases a virus

May be surrounded by envelope which is composed of phospholipids and virus-specific proteins
- Envelope sensitive to heat, detergents, and desiccation, making enveloped viruses easier to kill

106
Q

Host Cell

A

Living cell in which a virus can actively multiply and replicate genetic information or in which a virus can hide until activated by environmental stimuli

107
Q

Virions

A

Viral progeny that is produced within the host cell by hijacking cell’s machinery

Are released from host cell to infect other cells

108
Q

Tail Sheath

A

Region of a virus that acts to inject the genetic material

109
Q

Tail Fibers

A

Allow the bacteriophage to recognize the connect to host cell
Some have enzymatic activity allowing for both penetration and formation of pores

110
Q

Viral Genomes

A

Come in a variety of shapes and sizes

Some are made of a few genes while others are several hundred

Can be DNA or RNA, and Double-stranded or Single-stranded in both cases

Single Stranded RNA can be positive or negative sense

111
Q

Positive Sense RNA Virus

A

Single-stranded RNA virus. Genome is directly translated to functional proteins by the ribosomes of the host cell

112
Q

Negative Sense

A

Single-stranded RNA virus
RNA requires synthesis of an RNA strand complementary to the negative-sense RNA strand, which is then used as a template for protein synthesis
Negative-sense RNA viruses must carry RNA replicase in the virion to ensure complementary strand is synthesized

113
Q

Retroviruses

A

Enveloped single stranded RNA viruses with two identical RNA moluecules

Carry enzyme reverse transcriptase which synthesizes DNA from ssRNA

DNA then integrates into host cell genome, to be replicated and transcribed as if it were host cell’s own DNA

Only way to cure infection is kill infected cell Ex: human immunodeficiency virus - HIV; also known to lead to cancer

114
Q

Reverse Transcriptase

A

Synthesizes DNA from single-stranded RNA

DNA is then integrated into host cells genome

115
Q

Infection

A

Viruses can only infect a specific set of cells

In order to infect, viruses has to bind to a specific receptor on a host cell (Ex: HIV binds receptor on white blood cells)

Once bound virus fuses with the membrane to infect the cell, depending on virus different portions will enter the cell:
- Enveloped virus fuse with plasma membrane
- Sometimes host cells is confused and bring virus into cytoplasm via endocytosis
- Bacteriophages only insert genetic material

116
Q

Translation

A

After infection genetic material must be translated for viral reproduction

Viral DNA is translated to mRNA in nucleus prior to entry of the cytoplasm
Positive sense RNA stays in cytoplasm

117
Q

Describe Progeny Assembly of viruses.

A

Through the use of tRNA, Amino Acids and enzymes of the host cell viral RNA is translated into proteins

Many proteins are the structural capsid proteins and allow for the creation of virions in the cytoplasm in the host cell

New copies of viral genome (in its original form) must be made and packaged for these new virions before progeny release

118
Q

Progeny Release

A

Viral progeny can be released by multiple ways:
- viral invasion may initiate cell death, results in spilling of viral progeny
- host call may lyse as result of being filled with large numbers of virions (disadvantageous for virus because it can no longer use cell)
- can leave by fusing with plasma membrane, i.e. extrusion, allowing virus continued use of host cell: called productive cycle

119
Q

Describe the Lytic Cycle of Bacteriophage.

A

Occurs when the bacteriophage makes the maximal use of the cell’s machinery with little regard to host cell survival

Host cells becomes swollen causing the cells to lyse and release virions

120
Q

Virulent

A

Viruses that reproducing by the lytic cycle. Causing acute cell death

121
Q

Provirus / Prophage

A

Occurs when the virus integrates itself into the host cells genome, beginning lysogenic cycle

122
Q

Lysogenic Cycle

A

Occurs when the virus replicates as the bacterium/host cell reproduces due to viral genome being integrated in host genome as provirus/prophage

Viral DNA is added to the host cell’s DNA and is copied along with the host cell’s DNA

Typically changes to the lytic cycle when environmental factors act on the host cell (radiation, light, or chemicals) - could remain integrated indefinitely

Can be advantageous in preventing superinfections (simultaneous infection)
- since prophage is relatively innocuous, may be some evolutionary advantage

lysogenic - long-term

When provirus leaves genome transduction of genes from one bacterium to another may occur

123
Q

Prions

A

Infectious proteins, non-living things, that cause disease by triggering misfolding of other proteins

Usually involves conversion of alpha helices to beta sheets

Due to reduced solubility of protein and ability of cell to degrade misfolded protein, protein aggregates form and function of the cell is reduced

124
Q

Viroids

A

Small pathogens consisting of short circular single-stranded RN that infect plants (some human viroids exist)

Bind to a large number of RNA sequences and silence the plant genome

Ex: hepatitis D, which alone is innocuous but coinfected with hepatitis B is able to exert silencing function

Biology MCAT (9 decks)

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