Notes, abstracts, papers, exams and problems of Biology

Essential Nutrients for Adolescents

Fruit and Vegetables

These are essential every day. Fruit juice, for example, rich in vitamin C, contributes to preventing reduced defenses at a time of change like adolescence.

Dairy

Daily consumption of dairy products promotes growth and provides the calcium you need to properly feed your skeleton.

Fish and Seafood

Oily fish (Tuna, sardines, salmon, and mackerel) is especially recommended because it provides high concentrations of vitamins A and D, much needed during periods of growth. Squid, cuttlefish, and mussels are also high in RD.

Proteins

Are vital for building strong muscles and also for proper brain function. If you do not eat enough protein, your intellectual ability will be diminished. Do not forget... Continue reading "Essential Nutrients for Adolescents: A Comprehensive Guide" »

Infectious Disease

is caused by agents that have invaded the body

Pathogen

any agent that causes disease

Koch Postulates

rules for determining the cause of a disease

Mucous Membrane

epithelial tissue that protects the inferior surface of the body that might be exposed to pathogens

Inflammatory Response

events that suppress infection and speed recovery

Histamine

substance that increases the permeability of surrounding capillaries

Phagocytes

type of white blood cell that pass through capillary walls, ingest and destroy foreign matter

Neutrophil

type of phagocyte that squeeze through capillary walls

Macrophage

type of phagocyte that engulfs pathogens and cellular debris

Natural Killer Cells

large white blood cells that attack pathogen-infected cells

Complement System

proteins... Continue reading "Understanding Infectious Diseases and the Immune System" »

Understanding Inheritance and Continuous Variation

This type of inheritance refers to continuous characteristics regulated by genes that are inherited independently.

Sometimes, continuous variation does not only depend on one quantitative inheritance but also on the influence environmental factors have on the genotype. The height and weight of a population are classic examples of continuous characteristics that are affected by environmental factors.

Mendel's Laws of Inheritance

Mendel's First Law: Law of Uniformity

When two pure-bred individuals are crossed, all offspring of the first filial generation (F1) have the same genotype and phenotype.

Mendel's Second Law: Law of Segregation

When two individuals from the first filial generation are crossed,... Continue reading "Understanding Inheritance, Cell Theory, and the Origin of Life" »

Ovaries:

• Composed of ovarian follicles (sac-like structures)

Gametes

produced by gonads

Uterus:

• Located between the urinary bladder and rectum
• 3 layers: 1. Endometrium 2. Myometrium 3. Perimetrium
• Functions of the uterus:
  • Receives / retains a fertilized egg
  • Nourishes the fertilized egg

Penis:

• Delivers sperm into the female reproductive tract
• Regions:
  • Shaft
  • Glans penis (enlarged tip)
  • Prepuce (foreskin)
• Internally 3 areas of spongy erectile tissue around the urethra

Ovulation:

when the egg is mature the follicle ruptures

Haploid:

1N

Oocyte:

The oocyte is viable for 12 to 24 hours after ovulation

Sperm:

are viable for 12 to 48 hours after ejaculation

• Sperm cells must make their way to the uterine tube for fertilization to be possible

Fertilization:

When sperm nucleus... Continue reading "Female Reproductive System and Endocrine Glands" »

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" »

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" »