Notes, abstracts, papers, exams and problems of Biology

FUNGI KINGDOM

Cellular Organization:

Unicellular or multicellular, the cells are eukaryotic, they have no tissues.

Size and Shape:

Unicellular fungi, like yeast, are round or oval and microscopic in size.

Nutrition:

Heterotrophic, many are saprophytes, feeding on organic material from animals or plants.

Lifestyle:

They can be free-living symbionts or parasites.

Reproduction:

Unicellular asexual, multicellular asexual, or sexual.

PROTOCTIST KINGDOM PROTOZOA

Cellular Organization:

Unicellular, they have no tissues.

Size and Shape:

Oval, round, oblong, half-moon. All are microscopic.

Nutrition:

Heterotrophic, feeding on bacteria and algae.

Habitat and Lifestyle:

Most are free-living.

Reproduction:

They reproduce asexually by binary fission.

Movement:

They move by using... Continue reading "Characteristics of Fungi, Protozoa, Algae, and Monera Kingdoms" »

Embarrassment:

When something is sudden and unexpected, onlookers are amused. It is a social mistake and makes the person the center of attention. Feeling empathetic for someone else's embarrassment is a display of care. People are often forgiven for their mistakes because they blush, which makes them feel smaller. Embarrassment peaks during teenage years (pregenual ant. cingulate cortex).

Shame:

Shame occurs when a person has failed to live up to expectations or has done something morally wrong. Onlookers are angry, and it often involves poor performance or hurting someone's feelings by failing to meet their expectations.

Guilt:

Guilt is the result of failing to perform one's duty, such as lying, cheating, or stealing (Medial prefrontal, visual... Continue reading "Understanding Emotions and Hormones in Relationships" »

Key Terms in Biology

Water and Macromolecules

• Hydrogen bonds: H2O molecules form these with each other or other polar molecules.
• Carbohydrates: Composed of C, H, and O. Include simple sugars and polysaccharides. Carbohydrate breakdown provides energy.
• Polysaccharides: Carbohydrates made up of 10+ monosaccharides, serving as storage forms of sugars.
• Glycosidic bonds: Bonds formed by a dehydration reaction between two monosaccharides.
• Glycogen/starch: Storage forms of carbohydrates for energy, composed of glucose in alpha configuration (two glucose molecules linked by bonds between C1 and C4).
• Cellulose: Structural component in plants, composed of glucose in beta configuration.
• Chitin: Polysaccharide found in exoskeletons.
• Lipids: Involved in energy storage,

Key Differences Between Bacteria, Archaea, and Eukarya

Cellular Structure

Bacteria: Lack a nuclear membrane, rarely have membrane-bounded organelles, cell walls are constructed of peptidoglycan, possess a single RNA polymerase, and contain histone-like proteins.

Archaea: Lack a nuclear membrane, rarely have membrane-bounded organelles, cell walls are constructed of various materials, possess RNA polymerase II, and contain histones.

Eukarya: Contain a nuclear membrane, possess membrane-bound organelles, some have cell walls, possess RNA polymerase 1, 2, and 3, and contain histones.

Koch's Postulates and Bacterial Shapes

Koch: Discovered Bacillus anthracis (anthrax) and Mycobacterium tuberculosis. His postulates are:

1. Microbes are present in all cases

What Nutrients Do Microbes Need for Growth?

Macronutrients to build macromolecules: carbon, nitrogen, phosphorus, sulfur, oxygen. Various micronutrients are also required by microbes, including several metal ions (cations) like K+, Na+, Mg2+, Ca2+, Fe2+ or Fe3+, Mn2+. Prototrophs synthesize nutrients from inorganic material, while auxotrophs require additional nutrients. Aerobic microbes need oxygen, while anaerobic ones do not. pH and osmotic pressure also affect microbial growth. Different types of media and methods like streak plate, spread plate, and pour plate are used for microbial culture. Antibiotics interfere with various microbial processes like peptidoglycan synthesis, membrane integrity, DNA synthesis, and ribosome function.

How Do

Gap Junctions

Gap junctions are specialized intercellular connections that allow direct communication and exchange of ions, small molecules, and signaling molecules between adjacent cells. These junctions play a crucial role in coordinating cellular activities in various tissues and are found in both animal and plant cells.

Key Points About Gap Junctions

1. Structure

• Gap junctions are formed by connexins in animals and pannexins in plants.
• Connexins and pannexins oligomerize to create connexons or pannexons, respectively.
• Each connexon/pannexon is a hexamer, and two hemichannels (half of a connexon or pannexon) from adjacent cells align to form a gap junction channel.

2. Function

• Gap junctions facilitate direct cell-to-cell communication, allowing

Metabolism

Chemical reactions within the cells convert nutrients into energy or convert simple substances into more complex ones.

Respiratory System

The respiratory system consists of the esophagus, stomach, liver, gallbladder, pancreas, large intestine, small intestine, appendix, and rectum. Cellular respiration is the process carried out in the mitochondria in which oxygen is used to extract energy from nutrients. External respiration, or breathing, is the process carried out in the respiratory system in which oxygen is inhaled from the environment and carbon dioxide is exhaled. The trachea is a tube located in the abdomen with small openings called spiracles. Vertebrate lungs have different structures depending on the species:

• Amphibians: Relatively

The urea cycle, also known as the ornithine cycle, is a critical metabolic pathway that primarily occurs in the liver, and to a lesser extent, in the kidneys. Its main function is to convert excess nitrogen from protein and amino acid breakdown into urea, a less toxic compound than ammonia, for safe excretion in urine.

Steps in the Urea Cycle

The urea cycle involves several enzymatic reactions within the mitochondria and cytoplasm of liver cells. Key molecules include ammonia, carbon dioxide, ornithine, citrulline, argininosuccinate, and arginine.

1. Formation of Carbamoyl Phosphate

• Ammonia (NH₃) and carbon dioxide (CO₂) combine in the mitochondria.
• This reaction, catalyzed by carbamoyl phosphate synthetase I (CPS I), produces carbamoyl phosphate.

The Nephron

The nephron is the functional unit of the kidneys, responsible for filtering blood and producing urine. Each kidney contains over one million nephrons.

Parts of the Nephron

• Bowman's Capsule: Surrounds a tiny network of capillaries.
• Tubule: Shaped like a handle, the tubule of several nephrons empties into a larger tube called a collecting duct.
• Collecting Ducts: Move urine into the renal pelvis.

Kidney Function

1. Filtration: Molecules exit the bloodstream and enter the Bowman's capsule, forming filtrate.
2. Reabsorption: As filtrate travels through the tubule, some molecules are reabsorbed by the capillaries. Glucose, 99% of water, a small amount of urea, and salts return to the blood.
3. Excretion: The remaining filtrate forms urine, which is excreted

Degradation of Purine Nucleotides + 50. Synthesis of Uric Acid and Its Secretion. Hyperuricaemia (Gout) - p.298

Digestion of dietary NA (dietary nucleotides):

• Small intestine: Pancreatic enzymes hydrolyze the NAs to nucleotides
• Inside mucosal cells: Degradation of purine nucleotides to nucleosides, free bases, and uric acid as end product

Degradation of de novo nucleotides:

• In liver
• Free bases are sent out from the liver and sent to peripheral tissues for salvage

Degradation of Dietary Nucleic Acids in the Small Intestine:

a) Ribonucleases and deoxyribonucleases (secreted by pancreas) hydrolyze dietary RNA and DNA to oligonucleotides

b) Pancreatic Phosphodiesterases produce a mixture of mononucleotides

c) Intestinal mucosal cells: Nucleotidases remove... Continue reading "Purine Nucleotide Degradation and Uric Acid Synthesis" »