It’s Alive.  The Characteristics of Life

An AP Biology Study Sheet on the Characteristics of Life

• All life is cellular
• Life is based on aqueous solutions
• The SPONCH elements are essential to all molecules
• Biochemical pathways are essential for life
• All proteins are composed of the same amino acids
• All DNA contains the same four bases ( ATCG) and all RNA contains the same four bases( AUCG)
• All carbohydrates are formed from a small group of sugars.
• All phospholipids contain a small group of fatty acids in combination with a phosphate group
• The flow of energy is accompanied by the formation of phosphate bonds( making ATP) and the hydrolysis of these bonds( breaking down ATP)
• All cells have membranes that are composed of lipids and proteins
• The genome of all organism undergoes replication, transcription, and translation
• All cells have ribosomes
• All reactions in cells require and enzyme
• Reproducing biological systems undergo change and evolve

The Steps in Evolution

• 4 billion years ago the earth’s surface was hot,the atmosphere surrounding the earth was a reducing atmosphere with no free oxygen
• The molecules involved in the soup( highly concentrated ions in the aqueous soup) using basic reactions like dehydration synthesis and polymerization. ( Monomers forming macromolecules called polymers)
• Proteins, fatty acids, sugars, and purines and pyrimidines were formed.
• RNA emerged as the information molecule and catalyst
• RNA made DNA
• DNA replaced RNA as the information molecule
• Phospholipids formed around DNA and proteins in the molecular soup
• Biochemical pathways and reactions were born
• Primitive prokaryote cells emerged( Bacteria and Archaea )

Principles

• Principle of continuity – all cells contain the same molecules
• Signature principle – The origins of cells are apparent in modern day organisms.  Biochemical pathways from  the beginning of time are present in organisms today.
• No- free lunch – Energy is required for the existence of all cells.  Energy processes developed at the origin of life are present in today’s organisms.

From Prokaryote to Eukaryote – The Dawn of Eukarya

• Loss of the cell wall
• Infolding of the cell membrane to increase the surface area of the cell as well as increase the efficiency of transport across the membrane
• Internal membranes collect ribosomes
• Internal cytoskeleton forms in the interior
• A nuclear membrane is formed by the attachment of the DNA to a part of the cell membrane.
• The acquisition of other prokaryotes into the cytoplasm of the prokaryote cell –
• The ENDOSYMBIONT THEORY- Lynn Margulis -prokaryotes within prokaryotes led to the formation of organelles like the peroxisomes, mitochondria, and chloroplasts.  Ingestion of a heterotrophic aerobic bacterium led to the formation of the mitochondria.  Ingestion of a cyanobacteria led to the formation of the first chloroplasts
• Early digestive vacuoles formed the lysosomes
• Chromosomal material duplicated and increased.  Linear chromosomes were born

Support for these theories

1.        Giardia lamblia – protozoan without mitochondria

2.       Euglena – capable of photosynthesis in light but can exist without light and convert to regular heterotrophic metabolism

3.       Structures of mitochondria and chloroplasts comparable to prokaryotes

4.       Many protests today contains endosymbionts or guests like the radiolarians that contain different organisms that provide them with color.

The New Protists – A diverse are diverse not monophyletic.  There are many different members of this Kingdom

1.Euglenozona- Euglena

2.Kinetoplastids – Unicellular parasites like the Trypansomes that carry the sleeping sickness

3.Alveolata include ciliates, Apicomplexans, and dinoflagellates.

Ciliates – Paramecium, Stentor, Blepharisma

Apicomplexans- Malaria

Dinoflagellates – the “ Red Tide”

4.Stramenopila – water molds, diatoms, brown algae( kelp)

5. Rhodophyta- red algae

6. Chlorophyta – green algae – Ulothrix, volvox, spirogyra

7. Amoebas and slime molds( fungi )

Amoebas also include the raiolarioans and foraminiferans

Slime molds are also referred to a myxomycetes or myxamoeba