Notes, summaries, assignments, exams, and exercises for Biology for University

1. Differentiating Basic Amino Acids (2 Examples Each)

Basic amino acids possess R-chains that contribute negatively charged carboxyl groups or positively charged amino groups. Basic amino acids are characterized by having positively charged amino groups in their R-chains.

• Acidic Amino Acids: Glutamic acid, aspartic acid.
• Basic Amino Acids: Lysine, histidine.

2. Distinguishing Molecules: Glycerides vs. Phosphoglycerides

Phosphoglycerides are lipid molecules where one primary hydroxyl group of glycerol (at carbon 1 or 3) is esterified with phosphoric acid. The other two hydroxyls are esterified with fatty acids, typically an unsaturated fatty acid at carbon 2.

Glycerides (simple or neutral fats) are formed by glycerol esterified with one, two, or...

Glucagon Signaling Pathway During Fasting

During fasting, the predominant hormone is glucagon; there is an increase in the Glucagon/Insulin (G/I) ratio, which promotes the binding of glucagon to its receptor, causing a conformational change in the associated G protein. The G protein consists of three subunits: alpha (α), beta (β), and gamma (γ). The alpha subunit is initially bound to GDP. The conformational change in the G protein after ligand binding causes the alpha-GDP subunit to decrease its affinity for GDP and increase its affinity for GTP. This displacement of GDP by GTP generates a new conformational change, causing the alpha subunit to lose affinity for the beta and gamma subunits. The alpha-GTP subunit then dissociates to diffuse...

Basal Ganglia and Motor Control

The basal ganglia are involved in learning and responding to learned associations. Lesions in this area cause diseases such as Parkinson's. The efferent pathways of the putamen are twofold:

• Direct pathway: Projects to the middle and inner segments of the globus pallidus and substantia nigra.
• Indirect pathway: Projects through the lateral or outer segment of the globus pallidus, which has the effect of inhibiting movement.

The Thalamus and Diencephalon

Anatomically, the hypothalamus is part of the diencephalon. This structure, which takes up only 1% of the brain, triggers an array of effector centers such as viscera, exocrine and endocrine glands, and muscles via two routes:

• Neural route: Constituted by the autonomic

Key Concepts in Bacteriology

Pioneers in Microbiology

• Hans Christian Gram:

  Developed the differential Gram staining method for bacteria.

• Robert Koch:

  Considered the father of bacteriological technique.

• Carl Linnaeus:

  Considered the father of biological classification.

• Paul Ehrlich:

  Proposed the theory of humoral immunity.

• Joseph Lister:

  Established the concept of antisepsis.

• Louis Pasteur:

  Considered the father of bacteriology.

Bacterial Growth Phases

• Phase 1: Lag Phase

  Bacteria recognize and adapt to their environment (initial period).

• Phase 2: Logarithmic (Exponential) Phase

  Characterized by rapid, exponential bacterial growth.

• Phase 3: Stationary (Plateau) Phase

  Growth rate equals death rate; some bacteria may form spores.

• Phase 4: Death Phase

  Bacterial death

Various Types of Twins

A) Fraternal Twins (Dizygotic) (70%)

Fraternal twins result from two different eggs, each fertilized by a different sperm. They may or may not be of the same sex, and their blood groups can be equal or different.

Superfecundation

This occurs when, during a single cycle, one ovary simultaneously releases two oocytes. Each oocyte can be fertilized by sperm from different acts of intercourse.

Superfetation

This is very exceptional, where the two oocytes come from two consecutive cycles. Implantation occurs at two widely separated points with separate placentas.

B) Identical Twins (Monozygotic) (30%)

Identical twins arise from the division of a single egg.

1. Separation in the Blastomere Phase

This results in dichlorionic diamniotic...

Medically Important Bacteria: Pathogens, Diagnosis and Treatment

Gram-Positive Cocci

Streptococcus pyogenes: Gram-positive, catalase-negative cocci. Causes pharyngitis, impetigo, scarlet fever, erysipelas and streptococcal toxic shock. Diagnosis: bacitracin sensitivity and the antistreptolysin O (ASO) or anti-DNase B tests. Treatment: penicillin.

Streptococcus pneumoniae: Gram-positive, lancet-shaped diplococci with a polysaccharide capsule. Causes pneumonia, sinusitis and meningitis. Diagnosis: blood agar (alpha-hemolysis), optochin sensitivity and bile solubility. Treatment: penicillin.

Staphylococcus aureus: Gram-positive, catalase-positive, facultatively anaerobic cocci. Causes food poisoning (enterotoxin), osteomyelitis, sepsis and necrotizing...

Understanding Your Skin's Sensory Receptors

Meissner's Corpuscles: Fine Touch and Texture

Consisting of a coiled axon termination inside an ovoid capsule, Meissner's corpuscles are found in sensitive, hairless areas like the lips, fingertips, nipples, and palms. They are associated with the ability to:

• Read Braille
• Recognize the specific body part being touched
• Identify the texture of objects

Merkel's Discs: Sustained Pressure

Merkel's discs, or Merkel cells, act as sensory receptors that detect stable and prolonged pressure. They are predominantly concentrated on the palms of the hands and the soles of the feet.

Pacinian Corpuscles: Pressure and Vibration

Located deep within the hypodermis, especially in the fingers and toes, Pacinian corpuscles are...

Methods for Determining Vertical Dimension of Occlusion (VDO)

Willis Bite Rule (Gauge Method)

1. Place the rule in the inferior third of the face and measure the distance from the base of the nose to the base of the chin.
2. Compare this measurement with the distance that extends from the outer corner of the eye to the corner of the lips.

Phonetic Method Using a Compass

1. Mark two arbitrary points on the patient (e.g., tip of the nose and chin) while the occlusion rims are in place.
2. Use a compass and a millimeter ruler to measure the distance between these two arbitrary points.
3. Instruct the patient to speak for five minutes, repeating words containing sibilant sounds (e.g., 'S', 'CH', or words like "mo chichiriviche") to relax the jaw muscles.
4. Re-measure the

Meiosis: Cell Division for Genetic Diversity

Meiosis is a specialized process of cell division that reduces the amount of DNA to maintain a constant number of chromosomes across generations. In advanced organisms, specialized tissues called gonads are responsible for reproduction, producing reproductive cells or gametes.

Therefore, gametes must contain half the number of chromosomes as their parent cells. Without this reduction, the amount of DNA would double with each successive generation. Meiosis ensures that the four resulting haploid cells are genetically distinct from one another and from the parent cell.

Meiotic First Division (Meiosis I)

Prophase I: Homologous Chromosome Pairing

Chromosomes pair together to form homologous pairs. This is...

Amino Acids

Proteins are composed of amino acids joined by peptide bonds. Macromolecules consisting of 20 different amino acids are typically made up of 100 to 300 amino acids.

Amino acids are enantiomers, and all share the same general structure. Proteins exclusively utilize the L-series of amino acids.

Amino acids are linked covalently through a peptide bond. Two amino acids react via their carboxyl and amino groups to form this bond through a condensation reaction.

An amino acid may exist as a Zwitterion, possessing a protonated basic amino group and a deprotonated carboxylic acid group, resulting in a net zero charge.

Properties of the Peptide Bond

The peptide bond exhibits partial double bond character between the C and O atoms, and between...