Exam #4 Flashcards
(29 cards)
Which of the following is the source of energy for the synthesis of small organic molecules that predated the earliest forms of life?
A. anaerobic respiration B. photosynthesis in algae C. decomposition by fungi D. lightning E. geothermal vents
D. lightning
This question is based on Miller-Urey’s experiment on the chemical origins of life. Several nonorganic molecules (excluding oxygen) were enclosed in a flask and allowed to react with firing electrodes to replicate lightning. There was a significant amount of lightning on primitive Earth, which we believe helped give the “spark” of life. Choices [A], [B], and [C] can be eliminated because they refer to processes by living organisms, and the question asks for the source of energy before life. Geothermal vents are a plausible distractor, but ultimately the source of energy is believed to be lightning, which was replicated in Miller-Urey’s experiment.
Why are chromosomes not visible during interphase?
A. They uncoil to allow replication and transcription
B. They condense into separate small packets of genes
C. Unexpressed genes are degraded to allow the cell to specialize
D. They reform the nuclear envelope
E. They migrate to the cytoplasm to be translated into proteins
A. They uncoil to allow replication and transcription
A cell goes through several phases in the cell cycle. These stages include G1, S, G2, and M phases. Each of these phases has a checkpoint to ensure everything is working properly. The deregulation of the cell cycle leads to cancer.
The G1, S and G2 phases are collectively known as interphase. During this period, the cell grows (G1 and G2 phases, G for “grow”) and replicates its DNA in the S phase (S for synthesis). The M phase stands for mitosis, where the cell spends the least amount of its time.
During mitosis, the chromosomes condense to separate both copies of the DNA to each daughter cell. However, the DNA is so tightly coiled that enzymes cannot transcribe the DNA. During interphase, the DNA uncoils to allow enzymes to transcribe and replicate the DNA.
The second law of thermodynamics can explain which of the following statements?
A. Some of the energy transferred in a cell is lost as heat.
B. The ultimate source of all energy comes from the Sun.
C. Saprophytes recycle unusable energy such as heat.
D. Isolated systems tend to decrease in entropy.
E. Energy can be created through photosynthesis.
A. Some of the energy transferred in a cell is lost as heat.
The second law of thermodynamics states that the entropy in a system always increases. Entropy is a measure of disorder in a system. Anytime we transfer between two types of energy or use energy, we do not have 100% efficiency. This is because a lot of the energy will be lost as heat due to the second law of thermodynamics. Note that the energy is not destroyed, it is simply transformed into a different unusable state. The first law of thermodynamics states that energy cannot be created nor destroyed.
In centrifugation, which factor determines if a cellular component ends up in the pellet or supernatant?
A. size and weight B. ATP production C. polarity D. solubility E. electric charge
A. size and weight
A centrifuge separates a homogenized solution into a precipitate, or a pellet, which is a solid mass at the bottom of the tube, and the supernatant, which is a solution of everything else in the original solution. Centrifugation separates cellular components based on their size and weight. This is why the nucleus pellets from a lysate first – it is the largest and heaviest organelle. Next, mitochondria are pelleted, and then microsomes (vesicles of the ER), and finally ribosomes. Small soluble proteins remain in the supernatant after ribosomes are pelleted.
During cell division, which of the following stages are most similar?
A. Mitotic prophase and meiosis metaphase I
B. Mitotic telophase and meiosis telophase I
C. Mitotic anaphase and meiosis anaphase I
D. Mitotic metaphase and meiosis metaphase II
E. Mitotic metaphase and meiosis metaphase I
D. Mitotic metaphase and meiosis metaphase II
During mitotic metaphase, all of the chromosomes (each with two chromatids) line up on the metaphase plate in the cell. During metaphase II in meiosis, half of the chromosomes (each with two chromatids) also line up on the metaphase plate. Metaphase II is more similar to mitotic metaphase because metaphase II only consists of chromosomes with 2 chromatids each, while metaphase I consists of homologous chromosomes (or tetrads, with 4 chromatids).
During which step can nondisjunction occur in mitosis?
A. Prophase B. Prometaphase C. Metaphase D. Anaphase E. Telophase
D. Anaphase
Nondisjunction is the failure of one or more chromosome pairs to separate properly during mitotic anaphase, anaphase I, or anaphase II. It most often occurs in embryonic development. The result is two daughter cells with extra or missing chromosomes. If this occurs in meiosis, and the aneuploidic gamete is fertilized, a number of syndromes may result. This is commonly known as trisomy; examples of trisomies include Down’s syndrome (trisomy 21) and Turner syndrome (absence of one X chromosome in females, monosomy X).
Which product(s) is/are common in both glycolysis and the electron transport chain?
I. Oxygen
II. ATP
III. NADH
IV. NAD+
ll. ATP
The products of glycolysis are two pyruvate molecules, NADH, and ATP. The products of the electron transport chain are NAD+, FAD, H2O, and ATP. The only product common to both is ATP, or Choice [B]. Memorize the table below for the reactants and products of the five big cellular respiration pathways. Note: pyruvate is converted into acetyl CoA in a step before the Krebs cycle, releasing 1 NADH and 1 CO2.
All of the following events occur during photosynthesis EXCEPT for one. Which one is the EXCEPTION?
A. Glucose is produced in the stroma
B. The pH inside of the thylakoid is decreased
C. Carbon dioxide is more concentrated in the stroma
D. The inner membrane of the chloroplast absorbs light
E. Photolysis of water provides the source of electrons
D. The inner membrane of the chloroplast absorbs light
The thylakoid membrane contains the chlorophyll molecules that absorb light. The inner membrane does not have a large role in photosynthesis. Most of photosynthesis occurs in the stroma and thylakoid. Water undergoes photolysis inside of the thylakoid to provide electrons for the chlorophyll molecules to excite with photons of light. As the electrons fall through the electron transport chain of the thylakoid membrane, H+ ions flow into the thylakoid (OPPOSITE of mitochondria, where H+ ions flow OUT of the matrix). The flow of H+ ions into the thylakoid decreases the pH because it becomes more acidic. The electrons react with NADP+ to form NADPH. ATP is produced by ATP synthase in the thylakoid membrane. The light dependent reactions generally take place inside of the thylakoid or in the thylakoid membrane.
The LIGHT INDEPENDENT reactions generally take place in the STROMA. CO2 concentrates in the stroma to be fixed into glucose by the Calvin-Benson cycle.
Which organelle is the nucleus attached to?
A. mitochondrion B. endoplasmic reticulum C. nucleolus D. centriole E. Golgi complex
B. endoplasmic reticulum
All of the following are methods plants use to reduce water loss EXCEPT for one. Which one is the EXCEPTION?
A. trichomes and hairs on the leaves B. needle-like leaf structure C. thick waxy cuticles D. reflection of green light E. guard cells in stomata
D. reflection of green light
Plants have evolved many different mechanisms to decrease the amount of water they lose to transpiration. Among them include growing little “hairs” on their leaves to retain more moisture and a thin needle-like leaf structure. Christmas trees and other conifers have needle leaves as an adaptation to growing in a dry environment. Desert plants have thick waxy cuticles as a way to minimize the amount of moisture the plant transpires, and guard cells in the stomata close off the holes in the leaves when activated. The reflection of green light is irrelevant to reducing water loss.
Trichomes (tiny hair-like structures) and hairs on leaves can help prevent water loss by trapping moisture
Guard cells are specialized epidermal cells that control opening and closing of the stomata
Which of the following has a similar function to the cristae of mitochondria?
A. Thylakoid membrane in chloroplast B. Cisternae in Golgi complex C. Nuclear envelope D. Intermembrane space in chloroplast E. Endoplasmic reticulum
A. Thylakoid membrane in chloroplast
The crista of mitochondria houses the electron transport chain (ETC) to create a proton force for ATP synthesis. The thylakoid membrane is the equivalent to this in photosynthesis; this is where the electron transport chain occurs to produce ATP and NADPH in photosynthetic organisms in the light-dependent reactions.
The splitting of water in the plant provides two electrons to be excited by photons of light in Photosystem II, which will then travel through the ETC to produce some ATP. The pair of electrons can be excited again in Photosystem I, where they can go through the ETC again to produce ATP (cyclic photophosphorylation), or react with NADP+ and H+ from splitting water earlier to form NADPH. NADPH and ATP will be used in the light-independent reactions to reduce CO2 into glucose.
While functionally similar, the key difference between the two is that in CHLOROPLAST, H+ MOVE from inside the thylakoid lumen OUTWARD to the stroma to synthesize ATP, while in mitochondria H+ move from outside the cristae (the intermembrane space) inward to the mitochondrial matrix.
Which of the following classes do sponges belong to?
A. Rotifera B. Cnidaria C. Annelida D. Porifera E. Platyhelminthes
D. Porifera
Porifera are the sponges. You can remember this because sponges are porous and “porifera” sounds similar. They are also classified with the parazoa, meaning even though they are multi-cellular, the cells are not organized and no organs develop.
Rotifera are rotifers, again both names sound very similar. Rotifers are especially cool because they are microscopic animals. They have a pseudocoelom.
Cnidaria include hydrozoans, jellyfish, sea anemones, and corals.
Annelida are segmented worms, such as leeches, earthworms, and polychaete worms.
Platyhelminthes are the flatworms and are known to be acoelomate. Some of the flatworms include planarians (planarians, planar meaning flat) and tapeworms (tape is flat). Tapeworms do not have a complete digestive tract because they just absorb pre-digested food from the stomach of their hosts.
Rotifers are very similar in characteristics to the phylum Nematoda, with the exception of excretory system (Rotifers have protonephridia and flame cells). They are typically found in freshwater environments.
Examples of Cnidaria include hydra, jellyfish, sea anemones, and coral. They are diploblasts with radial symmetry.
Examples of Annelida include earthworms and leeches. They are triploblasts with bilateral symmetry, and have segmented bodies.
Porifera are asymmetrical and have no true tissue organization or specialized body systems. They use intracellular digestion, via AMOEBACYTES
Examples of Platyhelminthes include flatworms and tapeworms. They are triplopblasts with bilateral symmetry, and are ACOELOMATE.
A sample of verotoxin, which destroys blood vessels, is exposed to an earthworm and flatworm. It is found that the earthworm died while the flatworm remains unaffected. Which of the following explains why the flatworm survived?
A. Flatworms lack a circulatory system
B. The earthworm has an open circulatory system
C. The earthworm could not excrete the toxin fast enough
D. Verotoxin cannot penetrate the flatworm
E. Flatworms have a closed circulatory system
A. Flatworms lack a circulatory system
This is an application question regarding the circulatory system of different organisms. Flatworms have no circulatory system. All cells can diffuse with the environment. Oxygen can be absorbed and carbon dioxide can be excreted without the need of a medium, like blood. Thus, they lack blood vessels, and are immune to verotoxin. On the other hand, earthworms are annelids, which have closed circulatory systems and do have blood vessels, which explains why they die when exposed to verotoxin.
Open circulatory systems pump blood into sinuses and bathe all tissues with nutrients and oxygen. Open circulatory systems occur in arthopods (insects) and some mollusks.
***Earthworms have METANEPHRIDIA for excretion.
What is the difference between a liposome and micelles?
Liposome= HOLLOW spheres made of phospholipids
Micelles= SOLID sphere made of phospholipids
Liposomes are spherical vesicles with lipid bilayers believed to be PROTOBIONTS
Sebaceous glands can be found in all of the following areas EXCEPT for one. Which one is the EXCEPTION?
A. Eyelids B. Palms C. Scalp D. Underarms E. Earlobes
B. Palms
Sebaceous glands are tiny glands in the skin that secrete an oil called sebum. They are located in the dermis of the skin and found nearly everywhere in human skin EXCEPT for the palms of the hands and soles of the feet. The body releases this oil to waterproof and protect the skin, but it also is a lipid and reduces friction. It doesn’t make sense to make your hands and feet slippery, so we can infer this must be the correct answer.
***The underarms are also one of the few regions of the body that contain APOCRINE glands, a type of SUDORIFEROUS (sweat) gland with viscous secretions that open to hair follicles.
What is the function of Haversian canals in long bones?
A. Provide flexibility to bones
B. Supply nutrients and nerve function in compact bone
C. Form dense lamellae to support the bone
D. Provide space for red bone marrow growth in cancellous bone
E. Surround and protect the shaft of the bone
B. Supply nutrients and nerve function in compact bone
A long bone is made of dense compact bone (cortical bone) on the outside and cancellous bone on the inside (less dense bone). The dense compact bone still needs nutrients and nerve function, and Haversian canals provide this function by having little tubes running parallel to the axis of the long bone. The Haversian canals house blood vessels, nerves, and lymphatic vessels.
Cancellous bone, also known as spongy bone, is less dense and houses red bone marrow and yellow bone marrow. Red bone marrow produces erythrocytes (red blood cells), platelets, and white blood cells. The periosteum surrounds the outer surface of all bones and provides nutrients.
Haversian canals contain blood vessels, nerves, and lymph vessels and are connected horizontally by Volkmann’s canals
During the respiratory cycle, the intrapleural pressure of the lungs is most negative during the:
A. end of exhalation B. end of inhalation C. beginning of exhalation D. beginning of inhalation E. peak relaxation of the diaphragm
B. end of inhalation
During inhalation our diaphragm contracts and therefore the volume in our lungs increases. This increase in volume leads to a decrease in pressure, which causes air to flow into our lungs. At the very end of inhalation is the point where we cannot breathe in anymore because our intrapleural pressure reaches its maximum negative value. During exhalation we relax our diaphragm, the volume of the lungs decreases, and air is pushed out of our lungs.
In a nephron, which of the following changes would increase the osmolarity of the filtrate in the collecting duct?
A. increase of water in the blood B. increase of water in the body cells C. increase in cortisol D. increase in ADH E. decrease in ADH
D. increase in ADH
ADH, or vasopressin, is produced by the hypothalamus and released by the posterior pituitary. It allows the collecting duct of the nephron to become more permeable to water, and as a result more water is reabsorbed from the filtrate. If more water is reabsorbed, then the remaining filtrate will become more concentrated, or have a higher osmolarity.
When there is excess water in the body, the posterior pituitary secretes less ADH (there is less need to reabsorb water). Secreting less ADH would lead to a more dilute urine since the body is already well hydrated. Cortisol is a glucocorticoid released in response to stress. Cortisol provides several functions, including increasing blood glucose, suppressing the immune system, and aids in metabolism.
The somatic nervous system is most related to the release of which neurotransmitter?
A. Acetylcholine B. Ca2+ C. Serotonin D. Glutamine E. Epinephrine
A. Acetylcholine
The somatic nervous system is the voluntary part of our nervous system that controls our skeletal muscles. The neurotransmitter that controls the contraction of our skeletal muscles is acetylcholine. Calcium is also very important in contracting muscle, but it is not a neurotransmitter. Here is a diagram depicting the organization of the nervous system in humans.
Epinephrine, a neurotransmitter derived from amino acids, has many important body functions. It acts on receptors to regulate blood flow during AUTONOMIC NERVOUS SYSTEM action.
Serotonin is a neurotransmitter that is highly active in the GI tract and in the CENTRAL NERVOUS SYSTEM.
Why does oogenesis in humans produce only one viable oocyte and 3 polar bodies instead of four viable oocytes?
A. The three polar bodies form the placenta.
B. To distribute the genetic information in the primary oocyte.
C. One oocyte contains all of the cytoplasm and resources to nourish the embryo.
D. The polar bodies provide nutrients to the viable oocyte.
E. The polar bodies act as a backup for the viable oocyte.
C. One oocyte contains all of the cytoplasm and resources to nourish the embryo.
In oogenesis, one oogenia divides by mitosis to produce a primary oocyte, which will begin meiosis. The cytoplasm from meiosis I will be concentrated in one of the daughter cells. The other daughter cell is called a polar body and will disintegrate. The secondary oocyte will begin meiosis II if it is fertilized by a sperm and will produce an egg. The second daughter cell in meiosis II becomes a polar body and also disintegrates. Developing a child is a very costly expense of resources, so the body will concentrate the nutrients and cytoplasm of four possible oocytes into one oocyte to nourish the embryo, giving it the highest chances of survival.
Which of the following occurs during embryonic cleavage from zygote to morula?
A. Decrease in morula size
B. Decrease in blastomere size.
C. Differentiation of blastomeres to pluripotent cells.
D. Formation of the blastocyst
E. Invagination into zygote to form the neural tube.
B. Decrease in blastomere size.
During cleavage of the zygote, each new blastomere becomes increasingly smaller. However, the size of the entire zygote/morula does not change. Each division gives less cytoplasm to the daughter cell in preparation for cell differentiation.
A pluripotent stem cell is a cell that can differentiate into any of the three germ layers (ectoderm, mesoderm, endoderm), but cannot develop into an entire individual because it cannot produce extra-embryonic germ layers. Gastrulation occurs when a group of cells invaginate into a blastula.
Cleavage from a zygote to a morula involves the change from a single celled structure to a hollow ball of cells that resemble a berry (morula). However, the actual embryonic size does not dramatically change during this process. As a result, more blastomeres (the cells that make up the morula) have to fit in the same volume, which means that they have to decrease in size
Which of the following is the location for the final maturation and storage of sperm?
A. Seminiferous tubules B. Vas deferens C. Epididymis D. Sertoli cells E. Oviduct
C. Epididymis
- Spermatogenesis begins at puberty and starts with spermatogonia cells in the seminiferous tubules.
- Spermatogonia divide by mitosis to produce primary spermatocytes, which undergo meiosis I and II. Unlike females, who only keep one of the 4 possible daughter cells, males keep and develop all 4 daughter cells.
- The sperm finally complete their maturation and are stored in the epididymis.
The oviduct is a female structure that transports oocytes to the uterus.
Sertoli cells provide nourishment to the sperm while they mature.
“The epididymis is where sperm matures and is stored for ejaculation”
Which of the following facilitates the penetration of an animal sperm cell into an egg?
A. Amount of time the egg has developed. B. Enzymes released by the acrosome. C. Contractions in the uterus. D. Amount of sperm available to fertilize the egg. E. Enzymes released by the egg.
B. Enzymes released by the acrosome.
All sperm cells have an acrosome at the tip of their cell. This is a modified lysosome organelle. Upon contact with the egg, the sperm and egg undergo the acrosome reaction, where the contents of the acrosome begin to digest away at the plasma membrane of the egg and allow the sperm to penetrate. To prevent other sperm from also penetrating the egg, the egg undergoes the cortical reaction, which hardens the plasma membrane so no other sperm can penetrate it.
When the sperm makes contact with the zona pellucida of the egg, the acrosome reaction begins. Theacrosome is a Golgi-derived organelle in sperm cells. During the acrosome reaction, the acrosomal membrane fuses with the plasma membrane of the egg, which exposes the egg to the enzymes held inside of the acrosome. These enzymes help to break down the egg’s coating and induce fertilization
Which of the following would increase the expression of a eukaryotic gene?
A. Acetylation B. RNA interference C. Methylation D. Heterochromatin packaging E. Repressor proteins
A. Acetylation
DNA is coiled around histones in eukaryotes and some Archaea. The combination of DNA and histones is called a nucleosome. Recall that DNA has a slight negative charge. If we attach methyl groups to the histone, we will make the histone more positively charged. This will attract the negatively charged DNA more, and will bind the DNA to the histone tighter, decreasing transcription. If we add acetyl groups to the histones, we would make the histone groups more negative, and they would repel the negatively charged DNA to make the DNA more accessible, thus there will be more transcription and more expression of the gene. RNA interference is a method of gene control where siRNAs will degrade mRNA, which will decrease the expression of a gene.
Heterochromatin is tightly packed DNA that consists of genes not transcribed.
On the other hand, euchromatin consists of more “open” DNA that is transcribed and expressed.
