Ch. 1: The Cell

Question 1

Cell Theory

Answer 1

1. All living 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– it is passed from parent to daughter cell

Question 2

Eukaryotes

Answer 2

membrane bound organelles, nucleus and can form multicellular organisms

Question 3

Cell Membrane and Membranes of Organelles

Answer 3

contain phospholipids which organize to form hydrophilic interior and exterior surfaces w a hydrophobic core

Question 4

Cytosol

Answer 4

Suspends organelles and allows diffusion of molecules throughout the cell

Question 5

Nucleus

Answer 5

Contains linear DNA wound around organizing proteins called histones then is wound/organized into linear strands called chromosomes
- In nucleus allows for compartmentalization of DNA transcription separate from RNA translation

Question 6

Nuclear Membrane/Envelope

Answer 6

Double membrane w nuclear pores for two-way exchange of materials between the nucleus and cytosol; maintains a nuclear environment separate and distinct from cytoplasm

Question 7

Nuclear Pores

Answer 7

In the nuclear membrane, allow selective two-way exchange of material between the cytoplasm and the nucleus

Question 8

Genes

Answer 8

Arrangement of DNA, coding regions

Question 9

Nucleolus

Answer 9

Subsection of the nucleus where ribosomal (rRNA) is synthesized, can be identified as a darker spot in the nucleus, takes up 25% of nucleus volume

Question 10

Mitochondria

Answer 10

Contain an outer and inner membrane
-Outer membrane: forms barrier w cytosol
- Inner membrane: folded into cristae, contains enzymes for the electron transport chain
-Intermembrane space: between the membranes
-Matrix: inside the inner mitochondrial membrane
Can divide independently from nucleus via binary fission (paradigmatic example of cytoplasmic or extranuclear inheritance,

Question 11

cytoplasmic or extranuclear inheritance

Answer 11

The transmission of genetic material independent of the nucleus

Question 12

Mitochondria triggering apoptosis

Answer 12

can trigger apoptosis by releasing mitochondrial enzymes into the cytoplasm (Bax Bcl thing)
- Kidney senses when oxygen is low
- Kidney releases EpO which leads to production of RBCs
- EpO releases Bcl which inhibits Bax
- Bax: forms the pore in mitochondria that releases cytochrome C
which activate caspases (ETC enzymes) which lead to apoptosis

Question 13

Lysosomes

Answer 13

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

Question 14

Endosomes

Answer 14

Transport, package, and sort cell material travelling to and from the membrane: capable of transporting material to the trans-golgi, to the cell membrane, or to the lysosomal pathway for degradation

Question 15

Endoplasmic Reticulum

Answer 15

Series of interconnected membranes and is continuous w nuclear envelope. Double membrane of ER is folded into numerous invaginations, creating complex structures w a central lumen

• Rough ER: studded w ribosomes which permit translation of proteins destined for secretion (endomembrane sys)
• Smooth ER: used for lipid synthesis and detoxification

Question 16

Endomembrane System

Answer 16

Endomembrane System: starts at the ER which releases vesicles that go to golgi, where vesicle is sent to its proper place like lysosomes, plasma membrane, blood etc

• Targeting signal: ~20 amino acids long @ start of polypeptide (N terminal), Used to get protein into SRP to go to the ER, binds to receptor which lets it into lumen of ER
• Signal Recognition Protein (SRP), binds to targeting signal, pauses translation, Binds to surface of ER
• When the ribosome/mRNA/targeting protein/SRP complex binds to the surface of ER: SRP comes off, translation continues, polypeptide snakes into lumen of ER via a pore, A polysaccharide is covalently attached to polypeptide coming in (it’s a glycoprotein), Polypeptide starts folding up– HSP90 chaperone there that is helping w/ folding inside, An enzyme chops off targeting signal, Golgi modifies polysaccharide and sends out vesicle w protein to lysosome, cell membrane or back to ER based on a secondary signal on protein

Question 17

Golgi Apparatus

Answer 17

Consists of stacked membrane-bound sacs in which cellular products can be modified, packaged, and directed to specific cellular locations

Question 18

Peroxisomes

Answer 18

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.

Question 19

Cytoskeleton (not under organelles):

Answer 19

Provides stability and rigidity to the overall structure of the cell while also providing transport pathways for molecules within the cell:

Question 20

Microfilaments

Answer 20

part of cytoskeleton: Composed of actin, provide structural protection for the cell and can cause muscle contraction through interactions with myosin, also help form the cleavage furrow during cytokinesis in mitosis

Question 21

Microtubules

Answer 21

Composed of tubulin (non covalently bonded), create pathways for motor proteins like kinesin and dynein to carry vesicles, contribute to cilia and flagella structures where they are organized into 9 pairs of microtubules in a ring w 2 microtubules at the center (9+2 structure)
- Centrioles: found in centrosomes and are involved in microtubule organization and the mitotic spindle

Question 22

Cilia vs Flagella

Answer 22

Both made of microtubules , cilia move materials along, flagella moves cell itself

Question 23

Intermediate filaments

Answer 23

Involved in cell-cell adhesion or maintenance of the integrity of the cytoskeleton; help anchor organelles, common examples include keratin and desmin

Question 24

Epithelial Tissues

Answer 24

Cover the body and line its cavities, protecting against pathogen invasion and desiccation. Tightly joined to each other and and to an underlying layer of connective tissue known as the basement membrane. Some epithelial cells absorb or secrete substances, or participate in sensation:

Question 25

Parenchyma

Answer 25

Functional parts of the organ, formed of epithelial cells

Question 26

Epithelial cells

Answer 26

often polarized: one side facing a lumen or outside world and the other side facing blood vessels and structural cells

Question 27

Epithelia classification by layers

Answer 27

Simple epithelia: one layer Stratified epithelia: many layers Pseudostratified epithelia: appear to have multiple layers bc of differences in cell heights, but actually have only one layer

Question 28

Epithelia classification by shapes of cells

Answer 28

Cuboidal cells: cube shaped Columnar cells: long and narrow Squamous cells: flat and scalelike

Question 29

Connective Tissues (not part of epithelia):

Answer 29

Support the body and provide a framework for epithelial cells: bone, cartilage, tendons, ligaments, adipose tissue, blood

Question 30

Stroma

Answer 30

Support structure, formed of connective tissues that secrete materials to form an extracellular matrix

Question 31

Prokaryotes

Answer 31

Do not contain membrane-bound organelles; organize their genetic material in a single circular molecule of DNA concentrated in the nucleoid region

Question 32

3 overarching domains of life

Answer 32

1. Archaea: often extremophiles, live in harsh environments (high temp, high salinity, no light), often use alternative sources of energy like chemosynthesis, similarities to both eukaryotes (start translation w methionine, similar RNA polymerases, histones) and bacteria (single circular chromosome, divide by binary fission or budding) 2. Bacteria: many similar structures to eukaryotes, and have complex relationships w humans including mutualistic symbiosis and pathogenesis 3. Eukarya: only non-prokaryotic domain

Question 33

Bacteria relationship to humans

Answer 33

Mutualistic symbiotes: both humans and bacteria benefit vs Pathogens or parasites

Question 34

Bacteria classification by shape

Answer 34

- Cocci: spherical - Bacilli: rod shaped - Spirilli: spiral shaped

Question 35

Bacteria classification by metabolic processes

Answer 35

- Obligate aerobes: require oxygen for metabolism - Obligate anaerobes: cannot 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 metabolic processes based on the environment - Aerotolerant anaerobes: cannot use oxygen for metabolism, but can survive in an oxygen containing environment

Question 36

Envelope

Answer 36

Formed by cell wall and cell membrane of bacteria, together control the movement of solutes into and out of the cell

Question 37

Bacteria classification by Gram staining

Answer 37

Color their cell walls turn during Gram staining w crystal violet stain followed by a counterstain w safranin. - Gram positive: turn purple, thick cell wall composed of peptidoglycan (polymeric substance made from amino acids and sugars) and lipoteichoic acid (may activate human immune sys) - Gram negative bacteria: pink-red, thin cell wall composed of peptidoglycan and an outer membrane containing phospholipids and lipopolysaccharides

Question 38

Bacterial movement:

Answer 38

Bacteria may have 1, 2 or many flagella that generate propulsion to move the bacterium toward food or away from immune cells. Bacterial flagella contain a filament composed of flagellin, a basal body that anchors and rotates the flagellum and a hook that connects the two

Question 39

Chemotaxis

Answer 39

moving in response to chemical stimuli

Question 40

Motion by flagella

Answer 40

Composed of a filament, a basal body, and a hook: - filament: hollow helical structure composed of flagellin - basal body: complex structure that anchors the flagellum to the cytoplasmic membrane and is also the motor of the flagellum - hook: connects the filament and basal body so that as the basal body rotates, it exerts torque on the filament, which can spin and propel the bacterium forward

Question 41

Prokaryotes carry out the electron transport chain using

Answer 41

The cell membrane

Question 42

Prokaryotic ribosomes are ______ than eukaryotic ribosomes

Answer 42

Smaller than (30S and 50S vs 40S and 60S)

Question 43

Binary fission

Answer 43

Method by which prokaryotes multiply, circular chromosome attaches to cell wall and replicates while cell grows in size until cell wall begins to grow inward along the midline of the cell and divides it into two identical daughter cells. Proceeds rapidly, fewer steps than mitosis

Question 44

Plasmids

Answer 44

In addition to single circular chromosome in prokaryotes, extrachromosomal material can be carried in plasmids, may contain antibiotic resistance genes or virulence factors

Question 45

Episomes

Answer 45

Plasmids that can integrate into the genome

Question 46

Bacterial genetic recombination:

Answer 46

Increases bacterial diversity: transformation, conjugation, transduction, transposons

Question 47

Transformation

Answer 47

Acquisition of genetic material from the environment, which can be integrated into the bacterial genome

Question 48

Conjugation

Answer 48

Transfer of genetic material from one bacterium (+) to another (-) across a conjugation bridge made from appendages called sex pili found on the donor male (+): a plasmid can be transferred from F^+ cell to F^- cells or a portion of the genome can be transferred from an Hfr cell to a recipient.

Question 49

Sex factors

Answer 49

To form the pilus bacteria must contain plasmids know as sex factors that contain the necessary genes. Best studied sex factor is the F (fertility factor) in e. Coli bacteria w this plasmid are termed F+ cells without are called F- cells. During conjugation F+ cell replicates its F factor and donates the copy to the recipient converting it to a F+ cell this allows for rapid aquisition of antibiotic resistance or virulence factors throughout a colony

Question 50

Transduction

Answer 50

Transfer of genetic material from one bacterium to another using a bacteriophage as a vector

Question 51

Transposons

Answer 51

Genetic elements that can insert into or remove themselves from a genome

Question 52

Pattern of bacterial growth

Answer 52

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 become insufficient, bacteria begin to die

Question 53

Capsid

Answer 53

Viruses contain genetic material, a protein coat (capsid) and sometimes a lipid containing envelope-- viruses without envelope are more resistant to sterilization and are likely to persist on surfaces for an extended period of time

Question 54

Presence of a viral envelope

Answer 54

if an envelope is present, it will surround capsid and is composed of phospholipids and virus-specific protein. It is very sensitive to heat, detergents and desiccations so enveloped viruses are easier to kill

Question 55

Host cell

Answer 55

Viruses are obligate intracellular parasites, meaning that they cannot survive and replicate outside of a host cell as they dont have the “machinery”: ribosomes for protein synthesis

Question 56

Virions

Answer 56

Individual virus particles, viral progeny

Question 57

Bacteriophages

Answer 57

Viruses that target bacteria. Contain a tail sheath which injects the genetic material into a bacterium and tail fibers which allow the bacteriophage to attach to the host cell. Remaining structures stay outside of bacterial cell

Question 58

Viral Genomes

Answer 58

May be made of various nucleic acids. May be composed of DNA or RNA and may be single or double stranded. Circular or linear. Few genes or several hundred

Question 59

Positive sense virus

Answer 59

Single stranded RNA viruses have RNA which can be translated by the host cell-- like mRNA

Question 60

Negative Sense virus

Answer 60

Single stranded RNA virus which have RNA where a complementary strand must be synthesized using RNA replicase. Complementary strand can be translated. Must carry RNA replicase in the virion

Question 61

Retroviruses

Answer 61

Contain a single-stranded RNA genome to which a complementary DNA strand is made using reverse transcriptase. The DNA strand can then be integrated into the genome

Question 62

Ways viruses infect cells

Answer 62

Attach to specific receptors and then either fuse with the plasma membrane, get brought in by endocytosis, or inject their genome into the cell

Question 63

Virus Reproduction

Answer 63

Replicate and translate genetic material using host cell’s ribosomes, tRNA, amino acids and enzymes

Question 64

Viral progeny release methods

Answer 64

Cell death: spilling of viral progeny, lysis as a result of filling w progeny (disadvantage bc virus can no longer use cell for reproduction), or extrusion: keeps cell alive to allow for continued use of the host cell by the virus--productive cycle

Question 65

Life cycles of bacteriophages

Answer 65

1. Lytic cycle: bacteriophage produces massive numbers of new virions until the cell lyses. Bacteria in the lytic phase are termed virulent 2. Lysogenic cycle: the virus integrates into the host genome as a provirus or a prophage which can then reproduce along with the cell. The provirus then leaves the genome in response to stimulus at some later time and enters the lytic cycle.

Question 66

Prions

Answer 66

Infectious proteins that trigger misfolding of other proteins usually converting alpha helical structure into beta pleated sheet decreasing the solubility and degradability of the misfolded protein

Question 67

Viroids

Answer 67

Plant pathogens that are small circles of complementary RNA that can turn off genes, resulting in metabolic and structural derangements of the cell and--potentially--cell death