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

1.2. Carbohydrates and Lipids: Concept, Classification, and Functions

Carbohydrates

Carbohydrates are biomolecules formed fundamentally by C, H, and O in the proportion C_nH_2nO_n. Hence, H and O are in the same proportion as in water (H₂O), also called hydrates of carbon. Carbohydrate molecules are chains formed by carbon atoms attached to radical groups and hydroxyl (OH) groups. There may be an alcoholic or a carbonyl group; this group may be an aldehyde (gluc aldose) or a ketone (gluc ketonic). For this reason, they are defined as polyhydroxyaldehydes or polyhydroxyketones.

Classification:

Carbohydrates are classified in two forms:

1. According to the functional group they possess:
   • Ketoses: if they have ketone groups.
   • Aldoses: if they have aldehyde groups.

Mitosis and Cytokinesis

Mitosis

Mitosis (discovered by botanist Eduard Strasburger) is a process of nuclear division exclusive to eukaryotes, ensuring the segregation and equal distribution of sister chromatids between the daughter cells during cell division.

Mitosis is an equational division that ensures the conservation of the genetic and chromosomal makeup of the species. Thus, mitosis of a parent cell yields two daughter cells with the same number of chromosomes and genetic information as the parent cell.

Mitosis can be structured into five phases: prophase, prometaphase, metaphase, anaphase, and telophase.

Prophase

During prophase, the following key changes occur:

• Chromatin Condensation: Chromatin condenses into visible chromosomes, each composed

Plant Parts & Functions

• Roots: Anchorage & Absorption

  Roots provide anchorage for the plant and are responsible for the absorption of water and nutrients from the soil.

• Stems: Support & Transport

  Stems hold the leaves, flowers, and fruits, providing structural support. They also transport fluids (water, nutrients, and sugars) throughout the plant.

• Leaves: Gas Exchange & Vital Processes

  Leaves are the primary sites for gas exchange, which is essential for processes like photosynthesis, transpiration, and respiration.

• Flowers: Reproduction

  Flowers are modified leaves specialized for reproduction. They contain the reproductive organs of the plant.

• Fruits: Seed Protection & Dispersal

  Fruits protect the seeds and facilitate their dissemination

2. Genetic Engineering: Genetic engineering is defined as the set of technologies to manipulate the genetic material of a living being, i.e., modifying genes. This manipulation consists basically of: introducing new genes into a genome, removing existing genes from a genome, and modifying the information in a particular gene. The new genetic combinations are introduced into organisms capable of transmission to subsequent generations. It is also called recombinant DNA technology because most techniques rely on DNA fragments that recombine.

2.1. Genetic Engineering Tools To obtain new combinations of heritable material, you must use:

• 1. Restriction Enzymes: They are a type of protein that can recognize a specific DNA fragment and cut it. Using

Levels of Organization: These correspond to degrees of complexity in organized matter. The levels are: subatomic, atomic, molecular, cellular, tissue, system, organelle, and body.

Cell Structure: Eukaryotic cells possess several key elements:

• Plasma Membrane: A thin layer surrounding the cell, composed of proteins and lipids.
• Cytoplasm: An aqueous solution containing organelles.
• Nucleus: A spherical structure containing genetic material, formed by the nuclear membrane, nucleoplasm, chromatin, and the nucleolus.

The major organelles of eukaryotic cells include: mitochondria, endoplasmic reticulum, ribosomes, Golgi complex, vacuoles, lysosomes, and the centrosome.

Tissues: A tissue is a collection of similar cells with a very similar structure that... Continue reading "Biological Organization and Nutrition Fundamentals" »

Elements Involved

In order to perform the transcription of DNA into cells, the following elements are required:

• Original DNA to serve as a template to be copied.
• RNA polymerase: synthesizes RNA from a DNA template.
• Ribonucleotide triphosphates to perform the copy.
• Poly-A polymerase, small nuclear ribonucleoprotein, RNA ligase.

Transcription Mechanism

As in replication, there are differences between prokaryotes and eukaryotes. The main differences are the existence of multiple RNA polymerases in eukaryotes and, above all, the need to produce a "mature" form of some RNAs due to the existence of introns. The process is divided into three stages:

• Initiation: The RNA polymerase binds to a region of DNA prior to the DNA that is to be transcribed. It then

The Journey of Childbirth and Lactation

Understanding Childbirth

Stages of Labor and Delivery

Childbirth begins with labor, typically lasting around 12 hours, characterized by frequent uterine contractions that move the fetus towards the dilating cervix. If the amniotic sac ruptures, amniotic fluid exits through the vagina. The baby then passes through the cervix and vagina during birth, after which the umbilical cord is cut. The process concludes with the expulsion of the placenta and other membranes.

Hormonal Regulation of Childbirth

• Progesterone: This hormone remains in the uterus, maintaining pregnancy conditions, particularly by relaxing uterine walls and keeping the cervix closed.
• Estrogens: During pregnancy, estrogens stimulate the growth

Understanding Immune System Components

Lymphoid Organs: Sites of Immune Activity

Lymphoid organs are specialized sites where immune system cells concentrate and function. They are classified into two main types:

• Primary Lymphoid Organs: These are the sites where lymphocytes mature. Stem cell precursors originate in the bone marrow. T lymphocytes mature in the thymus, while B lymphocytes mature in the bone marrow (or the Bursa of Fabricius in birds).
• Secondary Lymphoid Organs: These are the locations where mature lymphocytes accumulate, encounter antigens, and initiate adaptive immune responses. Examples include the spleen (which filters blood), lymph nodes (which filter lymph), and various lymphoepithelial structures (like tonsils and Peyer's patches)

The Skeletal System: Bones and Structure

Axial Skeleton

Vertebral Column

The vertebral column, or spine, holds the skull, attaches to the ribs, protects the spinal cord, and allows for the insertion of a large number of muscles. It consists of:

• Cervical vertebrae
• Thoracic vertebrae
• Lumbar vertebrae
• Sacrum
• Coccyx

Thoracic Cage

The thoracic cage includes the ribs and sternum.

• Ribs:
  • True ribs (first 7 pairs) join directly to the sternum.
  • False ribs (next 3 pairs) join the sternum indirectly via cartilage.
  • Floating ribs (last 2 pairs) do not join the sternum.
• Sternum: Composed of 3 parts:
  • Manubrium
  • Body
  • Xiphoid process

Appendicular Skeleton

The appendicular skeleton comprises the bones of the limbs and their girdles.

• Upper Extremities:
  • Girdle: Clavicles and scapulae
  • Arm:

The Organs of Speech

The Lungs

The lungs hold air when we breathe in. We enlarge the chest cavity (in part by lowering the diaphragm). This, in turn, expands the lungs, and air rushes in to fill the vacuum. Breathing out involves the opposite procedure. The chest is contracted, and air is squeezed out of the lungs, passing through the two bronchi (or bronchial tubes), then through the windpipe (more technically the trachea), and finally emerging in the throat.

The Larynx

Before the air reaches the throat, it has to pass through one of the most important speech organs: the larynx. It is at this point that the first possibilities occur for modifying the airstream and generating sound.

The larynx can conveniently be thought of as an irregularly shaped... Continue reading "The Organs of Speech and Sound Production" »