Medical Biology: chapter 1

Polynucleotides

• Polynucleotides are random in length and sequence.
• They can act as a template for the synthesis of another polynucleotide.
• They are made of nucleotide pairs: G with C and U with A
• Polynucleotides can direct their own synthesis.

Self-replicating Molecules

• RNA molecules can adopt a distinctive shape due to nucleotide pairing.

Evolution of Cells

• RNA molecules can catalyze biochemical reactions.
• DNA is the repository of genetic information, RNA acts as a go-between to direct protein synthesis.

First Cells

• Membranes were critical for forming the first cells.
• Phospholipids create the fundamental building blocks of all cell membranes.
• Membranes define the first cell.

Prokaryotic Cells

• Prokaryotic cells are significantly smaller than eukaryotic cells, meaning they can grow faster and multiply more rapidly.
• They come in many shapes and sizes.
• Bacteria are the most numerous prokaryotes.
• Cyanobacteria can be single-celled or filamentous chains of cells.
• Prokaryotic cells have been found 7 miles deep in the ocean and 40 miles up in the atmosphere.

Prokaryotic Cell Structure

• Appendages: Pili, Flagella, Axial Filaments
• Cell Envelope: Glycocalyx (Capsule), Outer Membrane, Cell Wall, Periplasm, Plasma or Cell Membrane

The Human Body

• Begins as a single cell (zygote).
• Has about 60-100 trillion cells.
• Contains about 200 different types of cells.
• Embryonic stem cells give rise to the entire body.

Comparative Sizes and Levels

• Cells can vary between 1 micrometer and hundreds of micrometers in diameter.
• Reductionism helps understand complex systems by studying their parts: atoms, molecules, chain molecules, molecular structures, cells, organs, organisms, populations, communities, ecosystems.
• Each level encompasses all lower levels.

Energy Flow in an Ecosystem

• Ecosystems require a constant supply of energy from sunlight or chemicals.
• Producers (Autotrophs) use sunlight or chemicals to make food.
  • Photoautotrophs use sunlight: plants, algae, some bacteria.
  • Chemoautotrophs use chemicals: microbes found in various inhospitable environments.
• Consumers (Heterotrophs) get energy by eating food.
  • Herbivores: eat plants.
  • Carnivores: eat animals.
  • Omnivores: eat both plants and animals.
• Decomposers get energy by decomposing dead organisms.
  • Fungi are the only organisms that decompose wood.

Monomers and Biopolymers

• Cells produce three types of large polymers: polysaccharides, proteins, and nucleic acids.
• Covalent and noncovalent interactions stabilize the molecules.

Proteins

• Proteins vary greatly in size, shape, and function.
• They enable different functions: small size hormones transmit signals, ion channels control ion concentration, and enzymes catalyze chemical reactions.
• Proteins commonly range in length from 100 to 1000 amino acids.
• If a protein is about 400 amino acids long, there are 20400 possible different protein sequences.

Nucleic Acids

• Nucleic acids carry coded information for making proteins.

Genome and Chromosomes

• The genome is packaged into chromosomes.
• Each chromosome contains a single linear DNA molecule associated with certain proteins.
• The genome of an organism comprises its entire complement of DNA.

Explore the fundamental concepts of polynucleotides, the evolution of cells, and the characteristics of prokaryotic cells in this informative quiz. Delve into the roles of RNA and DNA in biological processes and understand the significance of cell membranes in the formation of life.