Biological Flashcards

During sympathetic stimulation, which of the following would NOT happen?

Answer: dilation of intestinal blood vessels

Sympathetic stimulation initiates the 'fight or flight' response, which prioritizes blood flow to vital organs like muscles, heart, and brain. This involves vasoconstriction of blood vessels to the digestive tract, not dilation, to redirect blood elsewhere. Dilation of bronchioles, secretion of glucagon, and dilation of pupils are all characteristic responses of the sympathetic nervous system.

A disaccharide's breakdown releases energy, which is stored as ATP. This is an illustration of a (n)

Answer: Exothermic reaction

An exothermic reaction is a chemical process that releases energy into its surroundings, often in the form of heat. The breakdown of a disaccharide (catabolism) involves breaking chemical bonds, which releases stored energy that can then be captured to synthesize ATP. This energy release is the defining characteristic of an exothermic process.

Which of the following would raise the blood's pH?

Answer: the digestion of a big meal

The digestion of a big meal, particularly one rich in protein, stimulates the stomach to produce large amounts of hydrochloric acid. This process, known as the 'alkaline tide,' involves the secretion of bicarbonate ions into the blood, which temporarily raises the blood's pH. The other options would generally lead to a decrease in blood pH (acidosis).

Cyanide is a toxin that binds to the active site of the cytochrome c enzyme and stops it from working. Cyanide is a (n)

Answer: Inhibitor

An inhibitor is a molecule that binds to an enzyme and reduces its activity. Since cyanide binds to the active site of the cytochrome c enzyme and prevents it from functioning, it acts as an inhibitor. This specific type of inhibition, where the inhibitor competes with the substrate for the active site, is known as competitive inhibition.

Which of the following produces the least ATP?

Answer: TCA cycle

The TCA cycle (Krebs cycle) primarily functions to generate electron carriers (NADH and FADH2) for oxidative phosphorylation, along with one molecule of GTP (an ATP equivalent) per cycle. While glycolysis directly produces a net of 2 ATP, and oxidative phosphorylation yields the vast majority of ATP, the TCA cycle itself produces the least *direct* ATP compared to the other options.

A virulent phage infects by:

Answer: the lytic cycle

A virulent phage is a bacteriophage that exclusively replicates through the lytic cycle. In this cycle, the phage infects a host bacterium, replicates its genetic material, synthesizes new phage particles, and then lyses (bursts) the host cell to release the progeny phages. This process leads to the destruction of the host cell, unlike the lysogenic cycle.

Disaccharides are decomposed into monosaccharides via which of the following?

Answer: brush border enzymes

Disaccharides like sucrose, lactose, and maltose are broken down into their constituent monosaccharides by specific enzymes located on the brush border of the small intestine. These brush border enzymes (e.g., sucrase, lactase, maltase) are crucial for the final stage of carbohydrate digestion before absorption. While salivary amylase and pancreatic enzymes begin carbohydrate digestion, they do not break down disaccharides.

Hemoglobin has the strongest bonds with which of the following?

Answer: carbon monoxide

Hemoglobin has an affinity for carbon monoxide (CO) that is approximately 200-250 times greater than its affinity for oxygen. When CO is present, it preferentially binds to hemoglobin, forming carboxyhemoglobin and effectively preventing oxygen transport to tissues. This strong, stable binding is why carbon monoxide is highly toxic.

What causes a cell to have extra or fewer chromosomes?

Answer: nondisjunction

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division (meiosis or mitosis). This error results in daughter cells having an abnormal number of chromosomes, either an extra chromosome (trisomy) or a missing chromosome (monosomy). Conditions like Down syndrome are caused by nondisjunction.

Hearing involves which of the following?

Answer: hair cells

Hair cells, located in the organ of Corti within the cochlea of the inner ear, are the specialized mechanoreceptors responsible for hearing. These cells convert mechanical vibrations from sound waves into electrical signals that are then transmitted to the brain via the auditory nerve. Their stereocilia bend in response to fluid movement, initiating nerve impulses.

If blood pressure drops, which of the following will happen?

Answer: secretion of EPO

A drop in blood pressure, particularly if it leads to reduced oxygen delivery to the kidneys, stimulates the kidneys to secrete erythropoietin (EPO). EPO is a hormone that signals the bone marrow to increase red blood cell production. This increase in red blood cells enhances the blood's oxygen-carrying capacity, helping to restore blood pressure and oxygenation.

When intraocular pressure rises, which of the following happens?

Answer: glaucoma

Glaucoma is a group of eye conditions characterized by damage to the optic nerve, often due to abnormally high pressure inside the eye (intraocular pressure). This elevated pressure can compress and damage the nerve fibers, leading to progressive vision loss and potentially blindness if left untreated. The other options describe different eye conditions not primarily caused by increased intraocular pressure.

Ribosomes are generated in which nonmembranous compartment in a eukaryotic cell?

Answer: nucleolus

The nucleolus is a dense, nonmembranous structure found within the nucleus of eukaryotic cells. Its primary function is the synthesis of ribosomal RNA (rRNA) and the assembly of ribosomal subunits. These subunits are then exported to the cytoplasm, where they combine to form functional ribosomes responsible for protein synthesis.

The insulated wrapping on axons is made up of which cells?

Answer: Schwann cells

Schwann cells are a type of glial cell found in the peripheral nervous system (PNS) that form the myelin sheath around axons. This myelin sheath acts as an electrical insulator, significantly increasing the speed of nerve impulse conduction along the axon. In the central nervous system (CNS), oligodendrocytes perform a similar function.

Which of the following energy production statements is correct?

Answer: The cell requires energy to move NADH into the mitochondria.

NADH produced during glycolysis in the cytoplasm cannot directly enter the mitochondria for oxidative phosphorylation. It must transfer its electrons to shuttle systems (like the malate-aspartate or glycerol-phosphate shuttle) to cross the inner mitochondrial membrane, a process that consumes energy. The other statements contain inaccuracies regarding ATP production.

Blood goes from the mitral valve to the

Answer: left ventricle

The mitral valve (also known as the bicuspid valve) is located between the left atrium and the left ventricle. Oxygenated blood flows from the lungs to the left atrium, passes through the mitral valve, and then enters the left ventricle. From the left ventricle, the blood is then pumped into the aorta to be distributed throughout the body.

The primary source of energy for ATP production is

Answer: proton gradient

In cellular respiration, the electron transport chain pumps protons (H+ ions) across the inner mitochondrial membrane, creating an electrochemical gradient known as the proton gradient. This gradient represents potential energy, which ATP synthase then harnesses as protons flow back into the mitochondrial matrix to drive the synthesis of ATP. This process is called chemiosmosis.

Which of the following conditions is NOT caused by a viral infection?

Answer: Syphilis

Syphilis is a sexually transmitted infection caused by the bacterium *Treponema pallidum*. In contrast, genital warts are caused by Human Papillomavirus (HPV), the common cold by various rhinoviruses or coronaviruses, and AIDS by Human Immunodeficiency Virus (HIV). Therefore, syphilis is the only condition listed that is bacterial, not viral.

The heart's rhythm is determined by:

Answer: SA node

The sinoatrial (SA) node, located in the right atrium, is the natural pacemaker of the heart. It spontaneously generates electrical impulses that initiate each heartbeat, setting the rhythm and rate of contraction for the entire heart. While other components like the AV node and Purkinje fibers are involved in conduction, the SA node is the primary determinant of the heart's rhythm.

If the SA node stops operating, the heart will instantly stop: Is it true or false?

Answer: A) False

If the SA node stops operating, the heart will not instantly stop. Other parts of the cardiac conduction system, such as the AV node or Purkinje fibers, possess intrinsic automaticity and can take over as secondary pacemakers. While these secondary pacemakers generate impulses at a slower rate, they ensure that the heart continues to beat, preventing immediate cardiac arrest.