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

Cell Membrane Transport and Internal Systems

Roles of Membrane Proteins

Membrane proteins perform vital functions necessary for cell survival, communication, and structural integrity.

Adhesion Proteins

• Embedded in the membrane, primarily located on either the outer or inner cell surface.
• They anchor the cell in position within the extracellular matrix or anchor structures inside the cell.

Communication Proteins (Gap Junctions)

• Span the entire membrane.
• Connect to gap junctions in a neighboring cell.
• Form large channels between cells, connecting their cytoplasm.
• Facilitate chemical and electrical signaling between adjacent cells.

Receptor Proteins

• Embedded in the membrane, with the receptor site exposed on one side.
• Signal molecules (i.e., hormones) bind

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" »

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" »

__________ 1. In sexual reproduction of fungi, spores are produce By mitosis.

__________ 2.Yeast is a rapidly growing, asexually reproducing Stage of some types of fungi.

__________ 3.Fungi form mutualistic symbiotic associations with Other organism.

__________ 4.Fungi play important ecological roles by decomposing Organic matter and by

breaking down and absorbing minerals From rocks and soil.

__________ 6.All fungi are helpful.

__________ 7.Plants are multicellular eukaryotes whose cells have cell membrane made of

cellulose.

__________ 8.Reproduction in seed plants is characterized by a Greatly reduced gametophyte

and a dominant sporophyte.

__________ 9. The flowers of many gymnosperms are adapted for Pollination by wind or by

animals.

__________ 10.Although... Continue reading "JHH-7 doubling time" »