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

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" »

Abiogenesis

Process through which life appeared from non-living matter, such as simple organic molecules.

Cyanobacteria

Photosynthetic organisms responsible for the existence of oxygen in the atmosphere.

Homologous Organs

Organs that share an evolutionary origin and structure, but may have different functions. They evidence divergent evolution. Examples: whale and bat extremities.

Analogous Organs

Organs with the same function but different evolutionary origins. They evidence convergent evolution. Examples: insect and bird wings.

Vestigial Organs

Organs that are disappearing because they are no longer useful. Examples: kiwi and cassowary wings.

Evolutionary Lineage

Fossils show progressive transformations, providing evidence of evolution and allowing... Continue reading "Key Concepts in Evolutionary Biology" »

Lymph Nodes and Nephrons

Lymph Nodes

Lymph nodes are made of lymphatic tissue located in specific areas of some lymphatic vessels. They make lymphocytes and release lymph plasma.

Nephrons

Nephrons are the structural and functional units of the kidneys. They are tubes with one closed end and are surrounded by blood capillaries. Nephrons are responsible for filtering blood and forming urine, regulating water and mineral content.

• Bowman's Capsule: Initial zone
• Convoluted Tube: Long twisted tube with two main parts, proximal and distal
• Loop of Henle: Section located between the proximal convoluted tube and the distal zone

Urinary System

Ureters

Ureters are thin tubes that start from each kidney and end in the bladder, an elastic bag in which urine accumulates.... Continue reading "Human Body Systems and Health" »

Su,Aalo Iyo Jawabo biology 

• 1. a) i) Define transport

• Movement of substances from one part of the body to another

  ii) Explain the necessity of transport in plants and animals

• make nutrients move from one point to another

• movement of respiratory gases i.e. oxygen and carbon IV oxide

• elimination of metabolic wastes

• movement of hormones

• movement of water

• movement of salts

• movement of enzymes

  b) i) Describe the structure and function of root hair

• root hairs are found near the root tip

• they are cells with elongated finger-like projections which are in contact with soil particles

• they are permeable to water and mineral salts hence are used to absorb Water and mineral salts

• There large number offers a large surface area for absorption of water and mineral salts.