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

Active Transport Across Cell Membranes

Active transport enables certain types of proteins within the cell membrane to move substances. This process consumes energy, typically provided by ATP molecules, allowing transport against a concentration gradient.

The Sodium-Potassium Pump

The sodium-potassium pump is a transmembrane protein that actively transports sodium ions (Na+) out of the cell and potassium ions (K+) into the cell. This counter-gradient transport exhibits ATPase activity, meaning it breaks down ATP to power the movement. For every three Na+ ions pumped out, two K+ ions are pumped in, consuming one ATP molecule. This action generates potential differences across the membrane, contributing to the membrane potential. This potential is... Continue reading "Cellular Membrane Transport and Nerve Signal Transmission" »

English Vowels

Short Vowels

• /ɪ/ (as in: sit): Front, unrounded, between close and half-close.
• /ɛ/ (as in: dead): Front, unrounded, between half-close and half-open.
• /æ/ (as in: cat): Front, unrounded, between half-open and open.
• /ʌ/ (as in: does): Between front and central, unrounded, half-open.
• /ɒ/ (as in: dog): Back, rounded, between half-open and open.
• /ʊ/ (as in: good): Between back and central, rounded, near-close.

Long Vowels

• /i:/ (as in: sweet): Unrounded, almost fully closed.
• /ɜ:/ (as in: bird): Central, unrounded, between half-close and half-open.
• /ɑ:/ (as in: fast): Almost fully back, unrounded, fully open.
• /ɔ:/ (as in: hawk): Back, rounded, between half-close and half-open.
• /u:/ (as in: shoe): Almost fully back, rounded, almost fully

Gene

A gene is an organized, linear sequence of nucleotides in a DNA molecule that contains the information necessary for the synthesis of a macromolecule with a specific cellular function.

Genome

The genome is the entire set of genes of an individual or species, contained in a haploid set of chromosomes.

Genotype

The genotype is the sum total of the genetic information contained in an organism's chromosomes.

Karyotype

A karyotype is a schematic, photograph, or drawing of the metaphase chromosomes of a cell, arranged according to their morphology and size. The karyotype is characteristic of each species, as is the number of chromosomes, and it represents all individuals of that species.

Natural Selection

Natural selection is the process by which species... Continue reading "Fundamental Genetics Terminology Explained" »

Neural Pathway Components

• Integrating center: It contains neurons and analyzes information associations brought by sensory neurons to produce a response.
• Association neuron: Connects sensory and motor neurons.
• Motor or efferent neuron: The nerve impulse leads to an effector.
• Effector: This is the target of the nerve impulse (skeletal muscle, smooth muscle, cardiac muscle, or glands).

Membrane Potential Fundamentals

The membrane consists of a positively charged extracellular environment and a negatively charged intracellular environment. The electric potential of the membrane is recorded using microelectrodes.

Resting Potential

The differential distribution of charges on the sides of the membrane determines that the neuron is electrically polarized.... Continue reading "Physiology of Nerve Impulses and Action Potentials" »

The Organization of the Human Body

Cellular and Tissue Hierarchy

A Cell is the basic structural and functional unit of living things.

• All human cells originate from a single initial cell called the Zygote.
• Although we originate from one cell, we develop several types of specialized cells.
• A group of specialized cells results in a Tissue.

From Tissue to Organism

A Tissue is a set of cells of the same type performing a specific function.

• The combination of various tissues forms an Organ.
• A combination of organs results in an Organ System or Apparatus.

We use the term System when there is only one predominant tissue type (e.g., Nervous System).

The union of all systems and apparatuses results in a Multicellular Organism.

Specific Roles of Human Tissues

Tissues... Continue reading "Human Body Structure and Function: Cells, Tissues, and Organ Systems" »

The Biosphere

The biosphere is the set of all living things on Earth.

Understanding Ecosystems

An ecosystem consists of interconnected components:

• Biotic Components: Living things that inhabit a particular place and interrelate.
• Abiotic Components: All the physical environmental conditions or non-living elements within the dwelling of living beings.

Relations Between Components: Living organisms in a specific location are adapted to certain conditions of their physical environment and, in turn, modify it.

Ecological Relationships

There are relationships between individuals of the same species and between different species, such as predation, parasitism, symbiosis, and commensalism.

Photosynthesis

Photosynthesis is the process of converting light energy... Continue reading "Understanding Earth's Living Systems" »

Fundamentals of Biological Reproduction

Reproduction: The biological method necessary to ensure the survival of species.

Types of Reproduction

• Asexual Reproduction: Requires only one parent; creates exact genetic copies of itself; does not require gametes.

• Sexual Reproduction: Requires two parents who provide the gametes; descendants inherit characteristics from both parents.

Gametes and Gonads

Gamete: Specialized cells formed by meiosis from diploid cells in the gonads.

Reproductive Structures (Gonads)

• Unisexual: Characterized by two distinct types of individuals and gonads (Male and Female). Males and females exhibit traits that differentiate them (sexual dimorphism).

• Hermaphrodite: Individuals possess both male and female gonads.

Key Reproductive

Kinds of Amino Acids

Amino acids can be classified into several categories:

• Nonpolar:
  • Aliphatic
  • Aromatic
• Polar Uncharged
• Charged:
  • Acidic (Anionic)
  • Basic (Cationic)

Proteins: Building Blocks of Life

Proteins are biopolymers formed by molecular chains of 20 different amino acids, each with its own characteristics.

Protein Structures

Primary Structure

The primary structure is characterized by the specific composition of amino acids and their sequential order within the polypeptide chain.

Secondary Structure

The secondary structure refers to the folding of the primary structure due to the formation of hydrogen bonds between the -C=O group of one peptide bond and the -NH group of another. This results in the side chains (R groups) adopting specific spatial arrangements... Continue reading "Amino Acids and Protein Structures: A Comprehensive Look" »

Ecosystems: Definition and Characteristics

An ecosystem is a system formed by the interaction between a community and a biocenosis, or physical environmental factors. An ecosystem model for the subject is closed but open to energy, being capable of regulating itself and remaining in dynamic equilibrium over time.

Population Dynamics

A population is comprised of a set of individuals of the same species living in a particular location. There are some factors that prevent a population from reaching its full biotic potential. These can be external or internal to the population:

• External Factors: These may be biotic (predators, parasites, or diseases caused by other agencies competing for a given resource) and abiotic (climate change, food shortages,