Biology -- The Cell

Tenets of Cell Theory

1. All living organisms are composed of one or more cells.

2. The cell is the basic unit of structure and organization in organisms.

3. Cells arise from pre-existing cells.

4. Cells carry genetic information in the form of DNA. This genetic material is passed on from parent to daughter cell.

Eukaryotes

cells that contain membrane bound organelles

Why are viruses not considered living?

Accellular, cannot reproduce with the assistance of a host cell, may contain RNA as their genetic material

Genes

coding regions of DNA

Nucleolus

Found inside the nucleus and produces ribosomes

Mitochondria

organelle that is the site of ATP (energy) production

Inner membrane of mitochondria

site of electron transport chain

Cristae

what the inner mitochondrial membrane is folded into

mitochondrial matrix

The compartment of the mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the Krebs cycle.

how do mitochondria divide

binary fission

Mitochondria can trigger apoptosis by

releasing mitochondrial enzymes into the cytoplasm

Lysosomes

contain hydrolytic enzymes for digestion

When hydrolytic enzymes are released from the lysosome,

autolysis of the cell occurs

Autolysis

self-destruction of cells; decomposition of all tissues by enzymes of their own formation without microbial assistance

Rough ER

studded with ribosomes, translation of proteins for secretion happens here

Smooth ER

lipid synthesis and detoxification

Golgi apparatus

A system of membranes that modifies and packages proteins for export by the cell

Peroxisomes

contain hydogen peroxide and can break down very long chain amino acids via beta oxidation, participate in phospholipid synthesis and pentose phosphate pathway

Cytoskeleton

provides stability and rigidity to the overall structure of the cell, provides transport pathways for molecules in the cell

Three components of cytoskeleton

microfilaments, intermediate filaments, microtubules

Microfilament structure

solid polymers of actin

Microfilament physical properties

resistant to compression and fracture

Microfilament function

1. Structural rigidity to cell

2. Actin filaments interact with myosin, generating contractile force in muscle

Microfilament role in cell division

Form cleavage furrow: actin filaments contract, pinching off cell

Microtubule structure

hollow polymers of tubulin protein

Microtubule physical properties

rigid; dynamic (undergo continual assembly and disassembly)

MIcrotubule function

1. Create pathways for movement of motor proteins

2. Form cilia and flagella for cell locomotion

Microtubule role in cell division

form centrioles to create mitotic spindle: tubulin attaches to chromosomes, pulling them apart

Intermediate filaments structure

filaments of diverse proteins

Intermediate filaments physical properties

resistant to tension

Intermediate filaments function

1. Integrity of cytoskeleton

2. Cell to cell adhesion

Intermediate filaments role in cell division

N/A

Epithelial tissues

form a protective covering for all of the internal and external surfaces of the body

Role of epithelial tissues

protection against pathogen invasion and desiccation

Parenchyma

essential, distinguishing tissue of any organ or system

Simple epithelia

single layer of cells

Stratified epithelia

multiple layers of cells

Pseudostratified epithelia

appear to have muiltiple layers because of differences in cell height but actually have only one layer

cuboidal epithelium

Type of epithelial tissue with cube-shaped cells.

Columnar epithelium

Cells shaped like bricks standing on end.

Squamous cells

Flat, scale-like epithelial cells.

Connective tissues

support and connect organs and other body tissues

In most organs, connective tissues form the ____ or support structure by secreting materials to form an _________.

stroma, extracellular matrix

Examples of connective tissues

bone, cartilage, tendons, ligaments, adipose tissue, and blood

Prokaryotes

Single-celled organisms without a nucleus.

Bacteria can be classified by

shape and metabolic processes

Cocci

spherical bacteria

Bacilli

Rod shaped bacteria

Spirilla

spiral shaped bacteria

Obligate aerobes

require oxygen for metabolism

Obligate anaerobes

cannot survive in oxygen-containing environments and can carry out only anaerobic metabolism

Facultative anaerobes

can survive in environments with or without oxygen and toggle metabolic processes based on the environment

Aerotolerant anaerobes

cannot use oxygen for metabolism but can survive in an oxygen-containing environment

How do prokaryotes carry out the electron transport chain

using the cell membrane

Gram positive bacteria

Bacteria that have a thick peptidoglycan cell wall that also contains lipoteichoic acid and no outer membrane. They stain very darkly (purple) in Gram stain.

Gram negative bacteria

Bacteria that have a thin peptidoglycan cell wall covered by an outer plasma membrane that contains phospholipids and lipopolysaccharides. They stain very lightly (pink) in Gram stain. These are typically more resistant to antibiotics

Chemotaxis

Cell movement that occurs in response to chemical stimulus

Bacterial flagella contain a filament composed of ______, a _______ that anchors and rotates the flagellum, and a ______ that connects the two.

flagellin, basal body, hook

Prokaryotes multiply through

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 it into two identical daughter cells

Plasmid

A small ring of DNA that carries accessory genes separate from those of the bacterial chromosome

Virulence factors

traits of a microbe that promote pathogenicity

Episomes

plasmids that can integrate into the genome

Transformation

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

Conjugation

the transfer of genetic material from one bacterium to another across a bridge

In conjugation, a plasmid can be transferred from

F+ cells to F- cells, or from an Hfr cell to a recipient

Transduction

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

Transposons

(jumping genes) short strands of DNA capable of moving from one location to another within a cell's genetic material

Four phases of bacterial growth

lag phase, exponential phase, stationary phase, death phase

Parts of a virus

genetic material, protein coat (capsid), sometimes a lipid-containing envelope

What type of parasite is a virus?

obligate intracellular parasite

Virions

individual virus particles

Bacteriophage

virus that targets bacteria

Tail sheath

part of a bacteriophage that injects the genetic material into a bacterium

Tail fiber

allows the bacteriophage to attach to the host cell

Viral genomes

may be composed of DNA or RNA and may be single- or double-stranded

negative sense RNA

a complementary strand must be synthesized using RNA replicase, which can then be translated

positive sense RNA

Single-stranded RNA genomes ready for immediate translation into proteins

Retrovirus

contain a single-stranded RNA genome to which a complementary DNA strand is made using reverse transcriptase

Viral progeny are released through

cell death, lysis, or extrusion

Extrusion

virus leaves cell by fusing with plasma membrane

Two life cycles of bacteriophages

lytic cycle and lysogenic cycle

Lytic cycle

a viral reproductive cycle in which copies of a virus are made within a host cell, which then bursts open, releasing new viruses

lysogenic cycle

The virus integrates into the host genome as a provirus or prophage, which can then reproduce along with the cell. The provirus then leaves the genome in response to a stimulus at some later time and enters the lytic cycle

Bacteria in the lytic phase are termed

virulent

Prions

infectious proteins that trigger misfolding of other proteins, usually converting an alpha-helical structure to a beta-pleated sheet

Viroids

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