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

Cell Transport: Endocytosis vs. Exocytosis

• Similarity and Difference:

• Both are forms of active transport (specifically vesicle transport).
• Endocytosis brings materials into the cell, while exocytosis moves them out.

Cell Response to Solute Concentration

Understanding how a cell reacts to different external solute concentrations:

• Hypertonic: More solute outside the cell than inside. Water travels out of the cell.
• Isotonic: Balanced solute concentration inside and outside the cell. Water travels in and out at the same rate.
• Hypotonic: More solute inside the cell than outside. Water travels into the cell.

The Endosymbiotic Theory

Origin of Eukaryotic Organelles

This theory states that organelles such as chloroplasts and mitochondria were once free-living... Continue reading "Cell Transport and Organelle Evolution Concepts" »

Spermatogenesis

Occurs in the seminiferous tubules, which contain interstitial cells that secrete testosterone. The walls of the tubules contain germ cells. As they multiply, they move towards the end until they mature to become spermatozoa.

Oogenesis

Takes place in the ovaries and is divided into two stages:

1. Fetal Development: The female develops immature ova while still an embryo in the mother's womb. Each ovum is surrounded by cells to form structures called follicles. Follicles with immature ova inside stop developing until the woman reaches puberty.
2. Ovarian Cycle: Occurs in cycles of approximately 28 days. Follicles grow, and the ovum inside matures. The release of the mature ovum from the ovary is called ovulation. Typically, females ovulate

Fat vs. CHO

CHO is both aerobic and anaerobic, BUT it has limited stores. It does, however, have a greater energy yield per unit of O2 (fat is about 10% less).

Sparing CHO

Sparing CHO by upregulating lipid oxidation should be advantageous. This leads to:

• More lipid oxidation
• Decreased sympathetic nervous system activity (recruitment of CHO)
• Increased mitochondrial volume and enzymatic adaptations
• Reduction in signals that activate major CHO metabolic enzymes

In lower exercise intensity, more FFA and TG are present in plasma. The more intense the exercise becomes, the more glycogen/glucose is used. At ~62% of VO2 max, the highest lipid oxidative rate is experienced.

Nutritional Strategies to Improve Lipid Oxidation

• High-fat diets: long term vs. short

Human Nutrition

Human nutrition requires the coordinated function of the digestive, respiratory, circulatory, and excretory systems.

The Human Digestive System

The human digestive system involves the following processes:

• Ingestion: Intake of food.
• Digestion: Mechanical and chemical breakdown of food.
• Absorption: Transfer of nutrients from the digestive tract into the blood or lymph.
• Egestion: Elimination of substances that can't be absorbed.

Organs of the Digestive System

• Mouth: The entrance to the digestive tract.
• Pharynx: A muscular tube that connects the digestive system to the respiratory system.
• Esophagus: A muscular tube around 25 cm long; it is normally closed but opens when food is ingested.
• Stomach: Connected to the esophagus via a sphincter,

Protein Synthesis and Protein Structure

Definition of Proteins

Proteins are large molecules formed by the union of amino acids. There are 20 unique amino acids, of which 8 are considered essential because they cannot be synthesized by living organisms. Proteins differ from each other based on the specific order (sequence) of these amino acids.

Functions of Proteins

• They form part of cellular structures.
• They are involved in cellular metabolism.

The Synthesis Process (Gene Expression)

Protein synthesis occurs in two main phases:

1. Transcription: Information transfer from DNA to mRNA (occurs in the nucleus).
2. Translation: Information transfer from mRNA to Protein (occurs in the cytoplasm, involving ribosomes).

Transcription: DNA to mRNA

Genetic information... Continue reading "Molecular Mechanisms of Gene Expression and DNA Replication" »

Genetics and Heredity

• Allele: Different forms of genes.
• Genotype: Genetic makeup of an organism.
• Phenotype: Physical characteristics.
• Homozygous: Having both dominant or both recessive alleles.
• Heterozygous: Made up of one dominant and one recessive allele.

Plant Anatomy and Physiology

• Xylem: Tubes that transport water.
• Phloem: Tubes that transport sugar.
• Root hairs: Absorption of water to enter the plant.
• Stomata: The opening where water vapor leaves.
• Guard cells: Each pair of curved cells that regulate the stomata.
• Stamen: The male reproductive organ that consists of two parts.
• Pistil: The female reproductive organ that consists of three parts.
• Pollen: The grain containing male gametes.
• Ovary: The enlarged structure at the bottom of the pistil.
• Ovule: The

What is Genetic Engineering?

Genetic engineering is the direct modification of an organism’s genome, which is the list of specific traits (genes) stored in the DNA. Changing the genome enables engineers to give desirable properties to different organisms. Organisms created by genetic engineering are called genetically modified organisms (GMOs).

What is Biotechnology?

Biotechnology is the use of organisms and their genetics in industries to make products.

How is it Possible?

Because all living organisms have DNA, by moving DNA from one organism to another, it is possible to transfer different traits.

The GMO Process

• All genetic changes affect the protein synthesis of the organism.
• By changing which proteins are produced, genetic engineers can affect

The Human Nervous System: Divisions and Functions

The human nervous system is a complex network responsible for controlling all body activities. It is broadly divided into two main parts:

• Central Nervous System (CNS): Protected by bones (skull and spine) and three membranes called meninges.
• Peripheral Nervous System (PNS): Composed of nerves that connect receptors and effectors to the central nervous system.

Central Nervous System (CNS)

The Central Nervous System (CNS) is the body's control center, formed by the brain (located inside the skull) and the spinal cord (located inside the spine).

The Brain: Control Center of the Body

The brain is the most complex organ in the human body, responsible for thought, emotion, memory, and movement. It comprises... Continue reading "Human Nervous System: Central and Peripheral Divisions" »