DP Biology I: Origin of Cells

What is a cell?

a structural and functional unit of all living organisms (the building blocks of life)

Who first coined the term "cell"?

Robert Hook

What are cells made up of?

Two thirds water, one thirds other molecules (proteins, lipids, carbohydrates)

atoms

smallest unit of matter, both living and non living

molecules

building blocks of matter composed of two or more atoms

organelles

parts of a cell that carry out a particular function or role, are made of molecules

cell

the smallest unit of life and the building block of all living organisms

tissues

formed when cells combine to carry out a task (ex. muscles that move your eyes)

what is an example of a tissue

muscles used to move your eyes

organs

two or more tissues combined to work together (ex. heart, lungs)

systems

organs working together (ex. respiratory system)

organisms

living beings composed of many systems (ex. humans)

level of organization in living organisms

atoms, molecules, organelles, cells, tissues, organs, systems, organisms

what are the key points of cell theory?

the cell is the smallest unit of life, all living things are composed of cells, and cells can only arise from pre-existing cells

Panspermia Theory

life came to earth on asteroids

self-sustaining

living organisms can maintain all conditions needed to continue their existence, especially reproduction

why aren't viruses considered living organisms?

they lack metabolism and rely on host cells; they must infect the host cell and use its machinery to replicate

spontaneous generation theory

the idea that living organisms can be produced from non-living things

abiogenesis theory

the first cells must have arisen from non living matter through natural processes

Why is the abiogenesis theory difficult to test?

the pre-biotic conditions of earth can't be exactly replicated, and the first photocells did not fossilize, so there is no clear evidence

Optaron and Aldane theory (the soup hypothesis)

chemical evolution preceded life formation

Miller-Urey Experiment

Stanley Miller and Harold Urey conducted an experiment in 1953 in which they demonstrated the synthesis of organic compounds from non living materials.

true or false: all living things are composed of cells or cellular products

true

true or false: atoms are the smallest unit of life

false (cells are the smallest living unit)

how many years ago did the sun form

4.6 billion

how many years ago did earth form

4.5 billion

primordial soup

how different elements began to mix together and create life in the beginning of earth's time

true or false: units smaller than a cell can carry out all of the life functions autonomously

false

why is it so difficult to test hypotheses on the origin of the first cells

the conditions on earth during the first formation of cells were so different that it is nearly impossible to replicate them, and there is no evidence to compare them to

how many years did spontaneous theory exist for until it was disproved?

around 2000 years

who conducted the experiment that disproved the theory that maggots spontaneously generate

Francesco Redi

What is another name for the Oparin and Aldane Theory

The Soup Theory

What does ISSOL stand for

the INternational Society for the Study of Life

What does the ISSOL do?

They try to determine how life came to be and why we exist in a scientific matter

What were some of the differences in earth back then vs. now that cause experiments focusing on the beginning of life to be difficult?

high temperature, uv radiation, reducing atmosphere, high CH4 and CO2, no major water source

How many amino acids were discovered in the mixture used in the Miller-Urey Experiment?

four

What were the four amino acids found in the Miller-Urey Experiment?

glycine, alanine, aspartic acid, and aminobutyric acid

True or False: DNA is presumed to be the first genetic material

false; RNA

What kind of genetic material do viruses have?

RNA

What does LUCA stand for?

last universal common ancestor

What does FUCA stand for?

first universal common ancestor

What evidence is there for LUCA?

universality of the genetic code, conserved gene sequences

Universality of the genetic code

almost all living organisms share the same genetic code

conserved gene sequences

certain genes are broadly conserved across prokaryotic cell types, and these genes provide indication of the characteristics of the LUCA

biosignature

chemicals produced by cellular processes that provide evidence of past life

what does a "molecule clock" do?

estimates the time since the divergence based on the number of mutations, assuming the mutation rate is stable/constant

what is the estimated time of the evolution of bacteria from LUCA?

2-4 billion years ago

stromatolites

layered sedimentary deposits formed by cells

what does a cell need to be self sustaining?

organic compounds that act as self replicating genetic material and act as catalytic agrents

true or false: RNA is presumed to be the first genetic material

true

what are the four basic structures of a cell?

a cell membrane, cytoskeleton, genetic material, and ribosomes

what are examples of prokaryotes?

bacteria, archaea

what are examples of eukaryotes?

protists, fungi, plant and animal cells

symbiosis

A close relationship between two species that benefits at least one of the species.

endosymbiosis

A theorized process in which early eukaryotic cells were formed from simpler prokaryotes.

what two parts of the cell are thought to have evolved through endosymbiosis

mitrchondria, chloroplast

multicellularity

The state of being composed of many cells that adhere to each other and do not all express the same genes with the result that some cells have specialized functions.

what are some advantages of multicellularity?

exceeded size limits, longer lifespans, differentiation of cell types

what is one disadvantage of multicellularity?

potential occurrence of cancer (mutations, growths)

differentiation

process in which cells become specialized in structure and function