Notes, summaries, assignments, exams, and problems for Biology

Traits are characteristics present in an organism that can be inherited by its offspring.

Homozygotes and Heterozygotes

• Two identical alleles (AA or aa): Homozygous
• Two different alleles (Aa): Heterozygous

A: Dominant allele

a: Recessive allele

Genotype is an organism's set of genes.

Phenotype is the way in which... Continue reading "Understanding Traits, Genes, and Mutations" »

The Urinary System and Excretion

Elimination of Waste Products

The urinary system plays a crucial role in eliminating waste products, including toxic substances produced during cellular metabolism, that are released into the blood.

Organs Involved in Excretion

• Kidneys (Urinary System)

  Eliminate toxic substances resulting from cell metabolism through urine.

• Lungs

  Eliminate carbon dioxide (resulting from cell metabolism: cell respiration).

• Liver

  Eliminates waste from digestion through bile, which is eventually eliminated with feces.

• Sweat Glands

  Eliminate waste* through sweat, a liquid similar to urine but more diluted.
  *Toxic substances resulting from cell metabolism.

Kidneys

Two bean-shaped organs located along the posterior wall of the abdominal cavity.... Continue reading "The Urinary System and Excretion: A Comprehensive Guide" »

Internal Environment and the Circulatory System

1.) Internal environment: Refers to the fluids that surround the cells in the body. Conditions of the internal environment, like temperature or the composition of the fluid, must be stable for cells to work properly. This stable internal environment, called homeostasis, is maintained by the organ systems of the body.

• The internal environment consists of:
• Interstitial fluid (tissue fluid): It surrounds and bathes the cells.
• Blood and lymph: They collect and distribute substances the cells need, and eliminate waste from the cells through the circulatory system.

The lymphatic system:

• Transport absorbed fat from the small intestine to the blood.
• Defend the body as part of the immune system.

Lymphatic System

2.

Homeostasis and Body Interaction

The interaction process fulfills two objectives:

• Adapt the body to changing conditions.
• Connect and coordinate the different parts of our body.

Homeostatic process is a series of different processes in which the body's stability is maintained. These processes allow the organs to maintain a balanced condition so they can function properly.

Components of the Nervous System Pathway

• The sensory organ: Receives information from the environment.
• The nervous system: Transforms the stimuli into nerve impulses.
• The effector organs: Receive the response from the nervous system.

Types of Effector Systems

1. Locomotor system: Formed of muscles and bones.
2. Endocrine system: Produces regulating hormones.

Neurons: Specialized Nerve Cells

Neurons... Continue reading "Human Body Homeostasis and Nervous System Function" »

DNA replication involves several steps:

1. Initiation: Initiator proteins bind to the origin of replication.
2. Unwinding: DNA helicase unwinds the DNA strands.
3. Single-strand binding: Proteins bind to exposed single-stranded DNA to keep them apart.
4. Topoisomerase: Moves ahead of replication fork and removes torque by making a double-stranded break in one DNA double helix and passing another segment of helix through it.
5. Primase: Lays down an RNA primer (10-12 nt long) that provides a 3’OH group to start synthesizing DNA.
6. Elongation: DNA polymerase III synthesizes DNA on both strands in the 5’-3’ direction. The leading strand is replicated continuously, while the lagging strand is replicated discontinuously.
7. Removal of RNA primers: DNA polymerase I removes

Meselson-Stahl Experiment and DNA Replication

The Meselson-Stahl experiment tested the hypotheses of DNA replication. They cultured bacteria in a ¹⁵N medium. ¹⁵N is a heavy isotope of nitrogen, so the synthesized DNA is of heavy density. They then shifted the bacteria to a ¹⁴N medium, and DNA was isolated at different times corresponding to replication cycles 0, 1, and 2.

Results of the Experiment

After one replication cycle, the DNA was all of intermediate density. This rules out the conservative replication model, which predicts that both heavy density DNA and light density DNA will be present, but none of intermediate density will be present. This result is consistent with the semi-conservative replication model, which predicts that all DNA... Continue reading "Meselson-Stahl Experiment: Unraveling DNA Replication" »

The end of the 20th century brought constant changes and noticeable evolution, especially in science and technology. Every day, technologies that previously seemed remote and unattainable are announced. Thereby, nanotechnology was born—a technology dedicated to the design and manipulation of matter at the atomic or molecular level, for industrial or medical purposes. As a result, nanorobots arose, which are machines, or robots, of nanometric dimensions—an ultra-small measure compared to that of an atom—making their debut in 1949. From then on, literature and cinema have included these tiny robots, making people fantasize about the future of living with them. Furthermore, they are considered the fountain of youth, as they will help us... Continue reading "How Nanorobots Will Revolutionize Healthcare and Extend Lifespans" »

Embryonic Development and Labor Stages

• Acrosome: The tip of the sperm’s head that releases enzymes that digest egg caps.
• Cleavage: A series of cell divisions without cell growth during the first four days after fertilization.
• Morphogenesis: The process of physical change where an organism becomes several different types of cells.
• Chorion: The outermost membrane.
• Neural groove: Becomes the brain and spinal cord.
• Pharyngeal arches: Become part of the face, neck, and mouth.
• Dilation stage: The first stage of labor is the longest and involves three phases: the Early Labor Phase is the time from the onset of labor until the cervix is dilated to 3 cm.

Hormones and Their Source Organs

Match the hormone with the organ that makes it and/or its effect on the... Continue reading "Human Embryology and Endocrine System Fundamentals" »

Translation

Translation refers to the process of polymerization of amino acids to form a polypeptide. The order and sequence of amino acids are defined by the sequence of bases in the mRNA. The amino acids are joined by a bond known as a peptide bond. Formation of a peptide bond requires energy. Therefore, in the first phase itself amino acids are activated in the presence of ATP and linked to their cognate tRNA–a process commonly called as charging of tRNA or aminoacylation of tRNA to be more specific. If two such charged tRNAs are brought close enough, the formation of peptide bond between them would be favored energetically. The presence of a catalyst would enhance the rate of peptide bond formation.

DNA Fingerprinting

As stated in the preceding... Continue reading "Biotechnological Applications in Medicine and Agriculture" »

Levels of Organization

From Atoms to Organisms

Atom, molecule, organelle, cell, tissue, organ, organ system

Inorganic Biomolecules

• Water
• Mineral salts

Organic Molecules

• Carbohydrates
  • Monosaccharides: one molecule; examples: glucose, fructose
  • Disaccharides: two monosaccharides; examples: sucrose, maltose
  • Polysaccharides: many monosaccharides; examples: glycogen, cellulose
• Proteins: macromolecules composed of small molecules called amino acids; examples: collagen, hemoglobin, antibodies
• Lipids: examples: fats, phospholipids, cholesterol. Fats break down into fatty acids and glycerol.
• Nucleic acids: macromolecules composed of nucleotides, two types: DNA and RNA; examples: genes

Cells

Simplest living unit. Living things can be unicellular organisms or multicellular... Continue reading "Levels of Organization in Biology: From Atoms to Organisms" »