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

Actin Cytoskeleton Dynamics and Regulation

The actin cytoskeleton provides thin, flexible mechanical support to cells. Actin monomers are added and removed at distinct ends of the filaments, influencing their dynamics and cellular functions.

• Actin-ATP Addition: ATP-bound actin is primarily added to the barbed (plus) end of the filament.
• Molecular Timer: Older filaments contain ADP-bound actin, making them unstable and prone to disassembly. This acts as a molecular timer for filament turnover.
• Cellular Movement: Actin dynamics are crucial for various cellular processes, including movement and phagocytosis.

Key Regulators of Actin Filaments

Several proteins precisely control actin filament assembly and disassembly:

• Nucleation Factors: Dictate the rate

Darwin and the Theory of Natural Selection

The principal merit of Darwin's theory, in addition to the many evidence that he provided to it, is the discovery of the mechanism that governs the entire evolutionary process of species: the natural selection.

1. Firstly, when environmental resources become scarce, an inevitable competition occurs and, consequently, the struggle for survival begins in which most individuals die.
2. Secondly, it is also obvious that individuals of the same species have different features or characteristics that appear randomly and make individuals different from each other.
3. Third, these characteristics make some individuals more advantaged than others. Those whose characteristics are favorable to the demands of the environment

Kidney and Urinary Tract Conditions

Renal Failure Explained

Renal failure signifies insufficient filtration of blood at the Malpighian glomeruli. This leads to reduced urine production and inadequate elimination of excretory substances.

Symptoms include nausea, vomiting, seizures, and fainting. If untreated, it can lead to death.

Common causes include:

• Renal injuries
• Deficient blood pressure in the kidneys
• Urine retention due to an obstruction in the urinary tract

Nephritis: Kidney Inflammation

Nephritis is kidney inflammation resulting from infectious or non-infectious causes. Symptoms typically include pain, goosebumps, and fever.

Cystitis: Bladder Inflammation

Cystitis refers to inflammation of the bladder, generally caused by an infection. It results... Continue reading "Human Body Systems: Renal, Reproductive, and Cellular Functions" »

Cellular Energy Production

Cells use energy for all their reactions and processes. These vital processes include:

• Movement
• Making new substances from small molecules
• Growth and repair
• Active transport
• Nerve impulses
• Heat production

Aerobic Respiration: Energy with Oxygen

Aerobic respiration is the release of energy using oxygen. Oxygen is carried by the blood in red blood cells within hemoglobin and diffuses into cells. Glucose also travels to the cells in the blood.

In the cytoplasm of cells, there are specific organelles called mitochondria. Oxygen diffuses into the mitochondria and is used to react with glucose to produce carbon dioxide and water. The chemical energy is transferred to a substance called ATP, which stores a small amount of energy.

The... Continue reading "Cellular Respiration and Human Breathing Explained" »

All Cells Form from Existing Cells

• Centipedes: 1 pair of legs per each section
• Millipedes: 2 pairs per each section

• All organisms are composed of one or more cells
• The cell is the basic unit of life in all living things
• Cells are produced by the division of pre-existing

Excretion

Elimination of waste substances from blood is performed by the urinary system and other organs.

Urinary System

• Kidneys: bean-shaped organs behind the abdomen, filtering blood to form urine.
• Ureter: thin tubes transporting urine to the bladder.
• Urinary bladder: elastic bag storing urine.
• Urethra: duct transporting urine outside.

Other organs involved in excretion are lungs, liver, and sweat glands.

The Circulatory System

Function: Transporting O2, nutrients, and collecting CO2 and waste substances.

Blood

• Blood Plasma: 55% of blood, transporting nutrients, waste substances, and CO2.
• Blood Cells: red blood cells, white blood cells, and platelets.

Blood Vessels

Arteries, veins, and blood capillaries carry blood around the body.

Heart

Hollow muscular... Continue reading "Excretion and Circulatory System Overview" »

Protein Structure:

It is a three-dimensional structure. Polypeptides are folded to produce a globular shape. The structure is stabilized by intermolecular bonds between amino acids.

Primary Structure:

Is the sequence of amino acids in the polypeptide chain. It is codified by a gene. The sequence of nucleotides in a gene codify the sequence of amino acids in a polypeptide chain.

Secondary Structure:

3-dimensional conformation. It's the formation of beta-pleated and alpha helices, established by hydrogen bonds. It's the bond formed between the carboxyl group and the amino group.

Tertiary Structure:

The polypeptide chain is folded and established by interactions between R groups. The conformation is established by intramolecular bonds and interactions... Continue reading "Protein Structure and Functions" »

Polymerization –plus and minus ends of actin, Kd, critical concentration, phases of growth of polymers (lag, growth, and steady-state), nucleating factors, why growth occurs preferentially at plus end.

a.High Kd and Cc= ADP + Factin lower affinity actin so dissociate

b.Lower kd and Cc= Gactin/Factin + ATP higher affinity actin so dissociate

c.Profilin and thymosin: Profilin binds to (-) end = plus end grow fast

d.Thymosin buffer + actin monomer = prevent polymerization or ATP hydrolysis.

e.Actin monomer (is above Kd) & regulates actin filament assembly.

Arp2/3 comples to make a seed (nucleate) acting growth. Can create tree-like web

Myosin II structure: motor protein makes force in skeletal contraction muscles.

a.Heavy chain with NT head (ATPase... Continue reading "Cell Biology: Actin, Myosin, and Microtubules" »

Basic Nutrients

The human body is two-thirds water. Water is an essential nutrient that is involved in every function of the body. Water helps transport nutrients and waste products in and out of cells. Water is necessary for all digestive, absorption, circulatory, and excretory functions. Water is needed for the utilization of the water-soluble vitamins. It is needed for the maintenance of proper body temperature. It is recommended that you drink at least eight 8 glasses of water each day.

Dietary Recommendations

Carbohydrates

• It is recommended that about 60 percent of your total daily calories come from carbohydrates.
• If much of your diet consists of healthy complex carbohydrates, you should easily fulfill the recommended daily minimum of 25 grams

A Minimal pair is a pair of words that vary by only A single sound, usually meaning sounds that may confuse English learners, like The /f/ and /v/ infanandvan, Or the /e/ and /ɪ/ indeskanddisk

Minimal Pairs /ɪ/ and /i:/sit Seat

Minimal Pairs /e/ and /ɪ/desk disk

Minimal Pairs /e/ and /eɪ/wet wait

Minimal Pairs /æ/ and /ʌ/bat but

Minimal Pairs /əʊ/ and /ɔ:/sosaw

Minimal Pairs /ɒ/ and /əʊ/not note

Minimal Pairs /æ/ and /e/bad bed

Minimal Pairs /ɑ:/ and /ɜ:/fast first

Consonant Sounds

Minimal Pairs /b/ and /v/berryvery

Minimal Pairs /b/ and /p/buypie

Minimal Pairs /n/ and /ŋ/thinthing

Minimal Pairs /l/ and /r/alive arrive

Minimal Pairs /ʧ/ and /t/catchcat

Minimal Pairs /s/ and /ʃ/seashe

Minimal Pairs /f/ and /v/fanvan

Minimal Pairs /f/ and /h/