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

Steroid Hormones

Steroid hormones are a type of hormone consisting of four rings made of carbon atoms. They are derived from cholesterol and have three primary modes of action:

• Binding to membrane receptors
• Binding to and activating proteins in the cytoplasm
• Acting on receptors linked to chromosomes

Sex Hormones

Gonadal steroid hormones are produced by the gonads, which include the ovaries and testes. These hormones include:

• Androgens (e.g., testosterone, dihydrotestosterone)
• Estrogens
• Progesterone

It is important to note that gonads can produce both types of hormones, with the aromatase enzyme mediating conversions between them.

Organizing Effects of Sex Hormones

Organizing effects refer to the hormonal effects on the brain and genitals that occur during... Continue reading "Steroid and Sex Hormones: Organizing and Activating Effects" »

Saturated Fats

Carbon atoms fully saturated with hydrogen atoms. (meats, animal fats, lard, whole milk, butter, cheese, ice cream, coconut oil, palm oil)

Trans Fatty Acids

Solidified fat forms by adding hydrogen to MUFA and PUFA to increase shelf life

Osteoporosis

Condition of softening, deterioration, or loss of bone mineral density that leads to disability, bone fractures, and even death from medical complications

Protein

Classification for nutrients consisting of complex organic compounds containing nitrogen and forms by combinations of amino acids; the main substances used in the body to build and repair tissues

Amino Acids

Chemical compounds that contain nitrogen, carbon, hydrogen and oxygen; the basic building blocks the body uses to build different... Continue reading "Understanding Nutrition: Fats, Proteins, Vitamins, and Minerals" »

This document outlines the defining features of various biological phyla, including protists, algae, and fungi-like organisms, highlighting their unique characteristics and ecological roles.

Phylum Apicomplexa

Unicellular parasites of vertebrates, known for possessing non-photosynthetic plastids (apicoplasts) essential for fatty acid synthesis.

Phylum Bacillariophyta

Non-motile freshwater and marine diatoms, known for glistening when sunlight hits them.

Phylum Chlorophyta

Commonly known as green algae, possessing the same types of chloroplasts as plants.

Phylum Chrysophyta

Marine and freshwater algae, known for their golden and brown carotenoids. Also called Golden Algae.

Phylum Ciliophora

Ciliated protozoans, known for having both a macronucleus and... Continue reading "Diverse Phyla: Key Characteristics of Protists & Algae" »

Key Structures of the Digestive System

Small Intestine Structures

The villi of the small intestine project into the intestinal cavity, greatly increasing the surface area for food absorption and aiding digestive secretions.

Microvilli: Are microscopic cellular membrane protrusions that increase the surface area of cells and minimize any increase in volume. They are involved in a wide variety of functions, including absorption, secretion, cellular adhesion, and mechanotransduction.

Ileocecal Valve: Is a sphincter muscle valve that separates the small intestine and the large intestine. Its critical function is to limit the reflux of colonic contents into the ileum.

The Large Intestine

The large intestine, also called the colon or the large bowel, is... Continue reading "Digestive System Anatomy, Nutrient Absorption, and Common Disorders" »

1. The Circulatory System

The circulatory system carries substances via the blood, which circulates through the blood vessels and is pumped by the heart.

1.1 Blood

Human blood is a thick, red liquid composed of plasma and blood cells.

Types of Blood Cells:

• Red Blood Cells: Small cells without a nucleus. They are the most numerous in the body and contain iron. This protein helps transport oxygen and carbon dioxide.
• White Blood Cells: Larger and less numerous. They defend our bodies against pathogens and tumor cells.
• Platelets: Are not true cells, but pieces of cytoplasm. They help our bodies to clot.

The Functions of Blood:

• Transport Substances: Transport nutrients and waste substances.
• Regulates Body Temperature: Maintain body temperature by distributing

Nerve Impulse

A stimulus occurs, sensory receptors detect the stimulus, sensory neurons receive the information and transmit it to the central nervous system (CNS). The CNS receives the information and a response is decided. Motor neurons transmit the response to the effectors, which carry out the response. The response is given through motor responses carried out by muscles and secretory responses carried out by glands.

Nervous System

The nervous system receives and transmits information rapidly through electrical impulses. Information is transmitted through sensory neurons and processed in the CNS.

Endocrine System

The endocrine system consists of glands that secrete hormones. These hormones are carried in the blood to the cells of the target... Continue reading "Understanding the Nervous and Endocrine Systems" »

Neuron Structure and Function

The basic unit of structure and function in the nervous system is called the neuron, or nerve cell. Neurons (NYOO-rons) conduct impulses throughout the nervous system. As shown below, a neuron is a long cell that consists of three regions:

• Cell body
• Dendrites (DEN-drites) are branchlike extensions of the neuron that receive impulses and carry them toward the cell body.
• Axon is an extension of the neuron. It carries impulses away from the cell body and toward other neurons, muscles, or glands.

Neurons fall into three categories: sensory neurons, motor neurons, and interneurons.

• Sensory neurons carry impulses from the body to the spinal cord and brain.
• Interneurons are found within the brain and spinal cord. They process

Nucleic Acid Structure and Function

• Nucleoside: A part of a nucleotide made up of one sugar (ribose or deoxyribose) and one nitrogenous base (pyrimidine or purine) joined together by N-glycosidic bonds.
• Nucleotide: Simple molecules that form large molecules called nucleic acids. It is formed by a nitrogenous base, sugar, and three phosphate groups.
• Chromatin: Bundles of DNA and proteins; the normal state of the genetic material during interphase.
• Chromosome: Structures formed by the condensation of chromatin that appear when the cell is about to divide.
• Centromere: A bond that joins two sister chromatids; it's where the microtubules are attached to the chromosome during the division process.
• Telomere: The end of the arms of a chromosome, which prevents