cell bio test 1 + Cell List 1

cell and molecular biology

a rapidly growing filed of research with applications to medicine, agriculture, biomedical engineering, and biotechnology

all cells share

common fundamental properties that have been conserved throughout evolution, but present day cells have evolved a variety of different lifestyles

two types of cells

Prokaryotic and Eukaryotic

Prokaryote

lack a nuclear envelope

Eukatyote

have a nucleus that separates genetic material from cytoplasm

eukaryotes and prokaryotes share

the same basic molecular mechanisms

cells first emerged

3.8 billion years ago

what most likely provided the basic material from which the first cells arrived

spontaneous formation

Stanley Muller

demonstrated conditions similar to those of primitive earth can give rise to several organic molecules that are critical to cellular life including amino acids

organic molecules can

spontaneously polymerize

critical characteristic of the macromolecule

is the ability to replicate itself which is where life evolved

nucleic acids can

self-replicate; have templates

Altman and Cech

first discovered that RNA is capable of catalyzing chemical reactions, including the polymerization of nucleotides.

RNA self replication

Complementary pairing between nucleotides (adenine [A] with uracil [U] and guanine [G] with cytosine [C]) allows one strand of RNA to serve as a template for the synthesis of a new strand with the complementary sequence.

DNA -\> to -\> to

RNA to protein

RNA does what

is a template for its own replication and catalyzes reactions

what is the initial genetic system in evolution

RNA, in a period of time known as RNA world

DNA

used by all present day cells as the genetic material and have the same mechanism for replication and gene expression

genes

segments of DNA that encode proteins or RNA molecules and the fundamental units od inheritance

DNA to RNA

transcription

RNA to proteins

translation

the first cell arose when

self replicating RNA was enclosed in phospholipid membrane

phospholipid molecule

two long hydrophobic tails buried in the lipid bilayer attached to a hydrophilic head group exposed to water on both sides of the membrane

cells evolved mechanisms for

generating and synthesizing molecules

what is highly conserved in present day cells

the principle pathways of energy metabolism

all cells use what for their source of metabolic energy

adenosine 5'-triphosphate (ATP)

mechanisms of ATP generation evolved in what three stages

glycolysis, photosynthesis, and oxidative metabolism

all present day cells carry out

glycolysis

Photosynthesis

allowed some cells to harness energy from sunlight; they no longer needed preformed organic molecules.

first photosynthetic bacteria

used H2S to convert CO2 to organic molecules—a pathway still used by some bacteria

how did photosynthesis evolve

Use of H2O in photosynthesis evolved later; it changed Earth's atmosphere by making free O2 available.

evolution of oxidative metabolism

free O2 in atmosphere after photosynthesis evolved

most effective metabolic energy generation

complete oxidative breakdown of glucose yields 36 to 38 ATP molecules.

generation of metabolic energy explained

Glycolysis is the anaerobic breakdown of glucose to pyruvate. Photosynthesis utilizes energy from sunlight to drive the synthesis of glucose from CO2 and H2O, with the release of O2 as a by-product. The O2 released by photosynthesis is used in oxidative metabolism, in which glucose is broken down to CO2 and H2O, releasing much more energy than can be obtained from glycolysis.

Present-day prokaryotes

Archaea and Bacteria

archea

many live in extreme environments

bacteria

large group that live in a wide range of environments

prokaryotic cell characteristics

no nucleus, roughly 1 um diameter, cytoplasmic organelles are absent, 1 x 10^6 to 5 x 10^6 base pair DNA content, single circular DNA molecule chromosomes

eukaryotic characteristics

present nucleus, 10-100 um diameter, present cytoplasmic organelles, 1.5 x 10^7 to 5 x 10^9 base pair DNA content, chromosomes have multiple linear DNA molecules

DNA range of prokaryotes

0.6 mil to 5 mil base pairs, enough to encode about 5000 different proteins

cyanobacteria

a group of photosynthetic, unicellular prokaryotes, are the largest and most complex prokaryotes

example of a typical prokaryotic cell

e. coli

e. coli DNA

a circular molecule in the nucleoid (which is not surrounded by a membrane).

electron micrograph of e. coli

The cell is surrounded by a cell wall, beneath which is the plasma membrane. DNA is located in the nucleoid. The cell shown here has replicated its genome and is about to divide, thus the presence of two nucleoids. Artificial color has been added.

e. coli cytoplasm

The cytoplasm contains approximately 30,000 ribosomes

ribosomes

site of protein synthesis

nucleus

largest organelle

Mitochondria

site of oxidative metabolism

lysosomes and peroxisomes

specialized metabolic compartments for the digestion of macromolecules and for various oxidative reactions

ER

network of intracellular membranes, extending from the nuclear membrane throughout the cytoplasm.
It functions in processing and transport of proteins and lipid synthesis.

Golgi apparatus

proteins are further processed and sorted for transport to their final destinations. Is also a site of lipid synthesis; and (in plant cells) synthesis of some polysaccharides that compose the cell wall.

cytoskelaton

Provides structural framework, Determines cell shape and organization, Involved in movement of whole cells, organelles, and chromosomes during cell division.

vacuoles

in plant cells; perform a variety of functions, including digestion of macromolecules and storage of waste products and nutrients.

organelles that provide compartments that localize different metabolic activities

mitochondria, chloroplasts, lysosomes and peroxisomes, and vacoules

chloroplasts

site of photosynthesis

cell wall in plant cells

Provides structural framework, Determines cell shape and organization, Involved in movement of whole cells, organelles, and chromosomes during cell division.

cytoskelaton

network of protein filaments extending throughout the cytoplasm

evolution of cells

Present-day cells evolved from a common ancestor that gave rise to the two prokaryotic domains of life, the Archaea and Bacteria. The evolution of eukaryotic cells (Eukarya) from the Archaea involved the formation of mitochondria by endosymbiosis. Plants and green algae subsequently evolved by the endosymbiotic formation of chloroplasts.

eukaryote organelles are thought to have arisen by

endosymbiosis or a prokaryotic cell living inside the ancestors of eukaryotes

mitochondria and chloroplasts evidence of endosymbiosis

Like bacteria, they reproduce by dividing in two.Both contain their own DNA, which encodes some of their components. The DNA is replicated when the organelle divides; the genes are
transcribed within the organelle and translated on organelle ribosomes.

ribosomes in mitochondria and chloroplasts

The ribosomes and ribosomal RNAs are more closely related to those of bacteria than to those encoded by the eukaryote nuclear genome.

mitochondria are thought to have evolved from

aerobic bacteria

chloroplasts are thought to have evolved from

photosynthetic bacteria like cyanobacteria

eukaryotes are thought to be what due to endosymbiosis

a fusion of archaea bacteria and bacterial genomes

Mitochondria Endosymbiosis

Mitochondria arose from aerobic bacteria living with the archaeal ancestor to eukaryotes. Most bacterial genes were subsequently transferred to the nuclear genome.

Similarities between prokaryotes and eukaryotes mitochondria and chloroplasts

organelles similar in size to bacteria, reproduce by dividing in two, own DNA, replication, transcription occurs in the organelles where translation is on organelle ribosomes, genomes are more closely related to bacteria genomes

many eukaryotes are

unicellular organisms

the simpliest eukaryotes

yeast; S. cerevisiae

S. Cerevisiae

are yeast and are about 6 um in diameter and contain 12 million base pairs of DNA

paramecium

ciliated protozoan that can be 350 um long and is specialized for movement and for feeding on bacteria and yeast

chlamydomonas

green algae have chloroplasts and can carry out photosynthesis

example of unicellular eukaryotes that are more complex than yeast

paramecium and chlamydomonas

multicellular organisms

evolved 1 to 2 billon years ago

volvox represents what

represents evolutionary transition from single cells to multicellular organisms

volvox

is a multicellular algae that consists of appox. 16 germ cells and 2000 somatic cells embedded in a gelatinous matrix

Dictyostelium discoideum

amoeba that was an example of the transition to multicellularity that alternates between unicellular and multicellular forms depending on food availability

Dictyostelium discoideum food availability

If food is unavailable, the unicellular amoebas aggregate to form a multicellular fruiting body, specialized for the dispersal of spores

what did increasing specialization and division of labor among the cells of multicellular organisms led to

the complexity and diversity of present day plants and animals

animals 5 main tissue types

epithelial cells, connective tissue, blood, nervous tissue, and muscle cells

epithelial cells

form sheets that cover the surface of the body and line internal organs

connective tissues

include bone, cartilage, and adipose tissue. Loose connective tissue is formed by fibroblast

blood

contains several cell types like red blood cells and white blood cells

red blood cells

erythrocytes function in oxygen transport

white blood cells

(granulocytes, monocytes, macrophages, and lymphocytes) function in inflammatory reactions and the immune response

nervous tissue

supporting cells and nerve cells, or neurons, and various types of sensory cells

muscle cells

are responsible for the production of force and movement

epithelial cells representative animal cells

of the mouth form a thick, multilayered sheet

connective tissue representative animal cells

fibroblasts characterized by their elongated spindle shape

human blood representative animal cells

erythrocytes and lymphocytes

cell genomes in animal models for evolution

have higher protein coding genes than humans

what does the fundamental properties of all cells being conserved during evolution do

the basic principles learned from experiments on one type of cell are generally applicable to other cells

E. Coli as an experimental model

e. coli is grown on the surface of an agar-containing medium which is particularly useful because of its simplicity and ease of culture in the laboratory

E.coli is what

the most thoroughly studied species of bacteria

e. coli studies did what

studies of this bacterium derived our understanding of DNA replication, the genetic code, gene expression, and protein synthesis

advantage of e. coli

the small genome is an advantage in genetic analysis because there are 4.6 million base pairs and 4300 genes

e. coli divides

every 20 cells (10^8 develop overnight) a clonal population can be isolated as a colony grown on agar medium

selecting genetic variants on E. coli strains

is easy and rapid and the simple nutritional requirements of e. coli facilitated fundamental experiments in molecular biology and biochemistry

genome of S. cerevisiae

12 million base pairs of DNA and has 6500 protein-coding genes which make them the simplest eukaryotes as a model for fundamental studies of eukaryote biology

unity of molecular cell biology

is the general principles of cell structure and function revealed by studies of yeasts applied to all eukaryotic cells

simplest model for studying eukaryotic cells

yeast or S. cerevisiae