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

Development of Cancer

• Oncogenes are transformed by carcinogens.
• Cancerous cells do not respond to signals from other cells, so they continue to divide (rapid mitosis).
• Cancerous cells are not removed by the immune system.
• The tumor gets bigger.
• Cells change their characteristics and look different under the microscope.
• The tumor is supplied with blood and lymph vessels.
• Tumor cells spread in blood and lymph to other parts of the body (Metastasis).
• Secondary cancers form throughout the body as tumor cells invade other tissues.

Protein Synthesis

Transcription

The double helix of the DNA is unwound by RNA Polymerase, which docks on the DNA at a special sequence of bases. RNA Polymerase moves downstream, unwinding the DNA. As the double helix unwinds, ribonucleotide... Continue reading "Molecular Biology Processes: Cancer, Protein Synthesis, and DNA" »

The Function of Reproduction

Reproduction is a fundamental biological process involving several key stages:

• Gametogenesis: The formation of gametes (sex cells) which takes place in the gonads.
• Fertilization: The joining of two gametes to form a zygote, typically an internal process in humans.
• Embryo Development: Cell division increases the number of cells that make up the zygote, which becomes an embryo. This continues developing and eventually becomes a fetus.
• Childbirth: The birth of the baby, which is fully formed and alive.
• Development: The baby grows and reaches maturity (adulthood).

Sexual Maturity and Development

Sexual maturity involves significant changes, including the development of primary and secondary sex characteristics.

Puberty

Between... Continue reading "Human Reproduction: Stages, Systems, and Development" »

Antigen-antibody reactions

Ag + Ab AgAb

←

·reversible reaction as there are formed noncovalently biochemical bonds

·strength of such interactions is called affinity

·different immunoglobulins within an individual show a wide range of affinity

·valence - number of epitope-binding sites of one immunoglobulin molecule

·avidity - describes the collective affinity of multiple binding sites (affinity + valence)

·e.g. although IgM has a low affinity, its avidity is quite high due to 10 epitope-binding sites

·...

Primary and secondary immune response

·primary immune response

ofirst contact to a foreign antigen that has to be eliminated from the body

ofirst a lag/induction phase (ca. 7-9 days or even up to months) occurs in which no antibody is produced,... Continue reading "Antibody Reactions, Immune Response, and Immunologic Memory" »

The Origin of Life: Two Key Processes

1. Chemical Evolution

This process created the molecules that make up living things (biomolecules) and subsequently formed structures called protocells.

• Biomolecule Formation: Simple organic molecules originated from meteorites.
• Complexification: More complex biomolecules were created from simple molecules in the primordial soup (the first biomolecules on the planet).
• Protocell Formation: Protocells were formed when biomolecules became organized into hollow, spherical membranes containing proteins and nucleic acids.

2. Biological Evolution

This process led protocells to become different types of cells, resulting in all the organisms that have ever inhabited the Earth.

• Primitive Cells: Similar to prokaryotic cells,

Core Concepts in Biology

Biodiversity

Species that inhabit or have ever inhabited the Earth.

Adaptation

The accumulation of changes in a living being to suit the environment in which it lives.

Types of Adaptation

• Structural: Affects organs and allows for specific functions, e.g., birds' beaks.
• Physiological: Affects the organism's function and metabolism.
• Behavioral: Actions that provide advantages, e.g., migration.

Evolutionary Theories

Biodiversity and Evolution

Slow changes in living beings over millions of years.

Fixism (Georges Cuvier)

Organisms were created through divine creation and became extinct due to catastrophes. This theory posited that species could not change, a view contrasted by later evolutionary theories.

Lamarckism (Jean-Baptiste de

The Digestive System

The digestive system is responsible for the ingestion, digestion, absorption, and elimination of food. It transforms food into nutrients through three main processes:

1. Mechanical Digestion: Chewing, grinding, crushing, and mixing of food to break it down into smaller pieces.
2. Chemical Digestion: Digestive juices break down macromolecules in food into smaller molecules that can be absorbed.
3. Absorption: Nutrients are absorbed into the bloodstream and transported to cells throughout the body.

Ingestion

Ingestion begins when food enters the mouth. Key steps include:

• Mastication (Chewing): Teeth tear and break food into smaller pieces.
• Salivation: Saliva mixes with food, forming a bolus and aiding in swallowing.
• Swallowing: The tongue

Contraceptive Methods

Rhythm Method

Observes the menstrual cycle to calculate the day of ovulation. Advantages: A natural method with no side effects. Disadvantages: Imprecise; not a barrier method and does not protect against STIs.

Body Temperature Method

Observes the basal body temperature in women to calculate the day of ovulation.

Male Condom

A plastic sleeve placed on the penis to stop sperm during ejaculation. Advantages: Very cheap, easy to find, and a barrier method. Disadvantages: 98% effectiveness; some people experience side effects.

Female Condom

A plastic sleeve placed inside the vagina to stop sperm during ejaculation. Advantages: Cheap and a barrier method. Disadvantages: 95% effectiveness; more difficult to find; potential side effects.... Continue reading "Contraceptive Methods and Sexually Transmitted Infections" »

Photosynthesis Fundamentals

Photosynthesis: Carbon Compound Production

• Living organisms require complex carbon compounds to carry out life processes and build the structures in their cells.
• Photosynthesis involves the conversion of light energy into chemical energy (carbohydrates, lipids, proteins, and nucleic acids).
• Chloroplasts absorb light energy from the sun and convert this energy into chemical energy (glucose) to be used by the organisms for energy.

Visible Light Spectrum and Wavelengths

• Light from the sun is composed of a range of wavelengths.
• The visible spectrum is the portion of the electromagnetic spectrum that is visible to or can be detected by the human eye.
• Electromagnetic radiation in this range of wavelengths (380 to 750 nm) is called

Genetic Disorders and Their Causes

Genetic disorders: Most genetic disorders are caused by mutations in one or more genes or by abnormal numbers of chromosomes.

Genetic Disorders Caused by Mutations

Some disorders are caused by mutations in autosomal genes. In the table below, there is a list of genetic disorders caused by a mutation in a single gene.