Answer:
Thanks to the fossil record, direct evidence of the evolution and change of species can be given over the years. The fossil record tells us the natural history of the species in the different geological ages and allows us to see the changes in the distributions of the species, extinction and diversification from comparison and measurement.
Plant cells differ from animal cells because only plant cells have _________
a. Cell wall and chloroplasts
b. Cell wall and centriole
c. Cell membrane and mitochondria
d. Lysosomes and central vacuole
Answer:
a. Cell wall and chloroplasts
Explanation:
The cell wall in plants facilitates the retention of the cell shape during over-hydration. The chloroplasts are organelles in plants that carry-out photosynthesis and produce glucose.
Products of glycolysis include:
a. a total of 2 ATP
b. a net gain of 4 ATP
c. 2 pyruvate molecules
d. all of the above
The products of glycolysis include a net gain of 2 ATP and 2 pyruvate molecules, so the correct answer is 'all of the above'.
Explanation:The correct answer to the question, 'Products of glycolysis include' is d. all of the above. This is because glycolysis, a pivotal process in cellular respiration, indeed yields these outcomes. First, there is a net gain of 2 ATP, meaning that while four ATP molecules are produced during glycolysis, two are consumed, resulting in an overall gain of 2 ATP. Secondly, 2 pyruvate molecules are produced during the final phase of glycolysis. Therefore, answering all of the above is accurate considering these facts.
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The products of glycolysis include a total of 2 ATP, a net gain of 4 ATP, and 2 pyruvate molecules.
Explanation:
The products of glycolysis include:
a total of 2 ATPa net gain of 4 ATP2 pyruvate moleculesTherefore, the correct answer is d. all of the above. Glycolysis is the first step in cellular respiration and occurs in the cytoplasm of cells. It is an anaerobic process that breaks down glucose into two molecules of pyruvate, resulting in a net gain of 2 ATP (although 4 ATP are produced in total, 2 ATP are used during glycolysis).
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Choose one property of water that makes it unique. Describe the property and explain the chemical or physical reason that causes water to have that property.
Answer:
Water has a pH value of 7. It is colorless and has a fixed boiling point at 100 Degree Celsius.
Explanation:
Answer: Water has many properties in it which makes it unique. This is because the reason water is known as universal solvent.
Explanation:
The water is considered as universal solvent because it has the ability to dissolve many solutes in it.
This ability of water is due to the presence of hydrogen bonding which dissolves different types of solutes in water.
The presence of hydrogen bonding in water provides it some more properties like surface tension, adhesion, cohesion.
Chorionic villus sampling is a prenatal test usually performed in the second trimester.
a. True
b. False
Answer:
b. False
Explanation:
Chorionic villus sampling test is used to determine the genetic disorder or chromosomal disorder in a fetus. Chorionic villus test is done by the PCR or by FISH. This test can take place usually performed in 10 to 12 weeks gestation i.e. first trimester, before amniocentesis. Chorionic villus can be removed by a needle. Pregnancy loss in CVS (Chorionic villus sampling) is 2-3 percent. So it is highly accurate.
Chorionic villus sampling is a prenatal test performed in the first trimester, specifically at 10-12 weeks of pregnancy, not in the second trimester. It is used to diagnose genetic abnormalities and determine the sex of the fetus, offering an earlier alternative to amniocentesis.
Explanation:The statement that chorionic villus sampling (CVS) is a prenatal test usually performed in the second trimester is false. CVS is an alternative method of prenatal diagnosis to amniocentesis and is typically performed earlier in pregnancy, between 10-12 weeks, during the first trimester. This procedure involves extracting a small amount of placental tissue, either through the abdominal wall or through the vagina, which provides cells for testing. The extracted cells can be used to diagnose over 100 genetic abnormalities, including chromosomal abnormalities like Down syndrome, enzymatic defects, and determining the sex of the fetus.
Unlike amniocentesis, which is done after 14-22 weeks and involves extracting amniotic fluid to obtain fetal cells for analysis, CVS allows for earlier detection and the possibility of a simpler process if an abortion is considered. Moms-to-be are also advised to avoid substances that can be fetotoxic as these can cross the placenta and affect the developing fetus, potentially leading to disorders like Fetal Alcohol Spectrum Disorders (FASD).
Tuberculosis is caused by the pathogen Mycobacterium tuberculosis, which currently latently infects nearly a third of the world's population. It is thought that host fatty acids can serve as a sole carbon source during infection. How does M. tuberculosis most likely metabolize fatty acids as an energy source?
A) By converting the fatty acids directly to glucose, which is then oxidized via glycolysis and the citric acid cycle
B) By a process called beta-oxidation, in which two carbon groups are removed to form acetyl-coA that enters the citric acid cycle and is oxidized to form ATP and reducing power.
C) By substrate level phosphorylation that removes phosphate groups from the fatty acids and transfers them to ADP to form ATP.
D) By reducing them and taking the electrons and protons and entering them into the electron transport chain to set up a proton motive force to generate ATP via ATP synthase.
Answer:
Option B is correct.
Explanation:
By a process called beta-oxidation, in which two carbon groups are removed to form acetyl-coA that enters the citric acid cycle and is oxidized to form ATP and reducing power.
Make connections Imagine you want to study one of the human crystallins, proteins present in the lens of the eye (see Figure 1.8). To obtain a sufficient amount of the protein of interest, you decide to clone the gene that codes for it. Assume you know the sequence of this gene. How would you go about this?
Answer:
In order to clone the sequence of the gene for one of the human crystallins found in the eye, there is a need for the application of polymerase chain reaction. In the process, the particular sequence of gene is denatured and then replicated various times to generate various clones of the gene sequence.
By producing various copies of the gene sequence for the human crystallin, that is, desirable, a scientist can examine various distinct characteristics of the protein as there is always more to examine with.
Before Baby A was born, she was not sending much blood to her lungs. Instead, the blood passed through the septal defect into the left atrium, which sent it to the left ventricle and to her body. But why didn't the baby die if no blood was going through her lungs?
(A) She was so small that the small amount of blood that did go through her lungs was enough
(B) She was getting her oxygen from placenta, not from breathing
(C) Before the last trimester, babies use anaerobic respiration, so she did not need oxygen
(D) She sent her blood out into her mother's body and through her mothers lungs instead
The right answer is B.
The purpose of breathing is to do homeostasis, which means, to take CO2 out and get oxygen to our blood.
Babies live into the wound surrounded by liquid, so they don't need to breathe with their lungs.
All the things they needed to survive are taken from the mother thought the placenta.
Answer:
The correct answer is option (B) "She was getting her oxygen from placenta, not from breathing".
Explanation:
In order to get the oxygen we need to live is necessary that the blood gets through our lungs. If an unborn baby has a problem that does not allow her to get blood to her lungs, she is still able to survive because she could get her oxygen from placenta, not from breathing. Placenta has a respiratory function that allows the baby for fetal oxygen supply and fetal carbon dioxide removal.
How can a stem cell contain the same genetic information, yet specialize as bone cells nerve cells, muscle cells and connective tissue cells?
Answer: All cells in the body contain the same DNA, but different RNA, according to which proteins need to be synthesized.
Explanation:
DNA is the molecule that contains the genetic information necessary to generate proteins. This is due to the sequence of nucleotides, which are monomers of DNA. Each nucleotide contains a different base: Adenine (A), Timine (T), Guanine (G), Cytosine (C). But when the cell needs to synthesize proteins, DNA is not used directly but transcribed into RNA. This RNA is directed to the ribosomes, organelles where protein synthesis takes place, and according to the sequence of RNA (which is complementary to DNA), a different amino acids is coded. During translation, aminoacids are joined together to form proteins.
All cells in the body contain the same DNA, but different RNA, according to which proteins need to be synthesized. For example, a stem cell can give rise to any specialized cell in the body such as a nerve or muscle cell. All three have the same DNA but a nerve cell specializes in the transmission of impulses and neurotransmitters so it will replicate only the DNA genes that are necessary for this and this is how only part of the genetic material is replicated into RNA. The same goes for the muscle cell, which needs genes necessary for force and motion.
Which of the following sequences in double-stranded DNA is most likely to be recognized as a cutting site for a restriction enzyme?
a. AAGG
TTCC
b. GGCC
CCGG
c. ACCA
TGGT
d. AAAA
TTTT
Answer:
b. GGCC
CCGG
Explanation:
Restriction enzyme cleaves DNA at the restriction site. Restriction site has 4-8 nucleotide base pairs which are recognized by the restriction enzyme. This site usually has a palindromic sequence which means that the sequence is read as same on both the strands in 5' to 3' direction. Palindromic sequence is used because it increases the chances that both the strands are cut. Enzyme is also able to recognize the sequence no matter from which side it approaches the DNA. The enzyme also works as homodimers sometimes so having the same sequence makes the dimers easier to recognize it. Here, the sequence is GGCC in 5' to 3' direction on both the strands making it a palindromic sequence. Hence it is most likely to be recognized as a cutting site for a restriction enzyme.
If a disease is continually present in a population in small amounts, it is considered an endemic disease.
a. True
b. False
Answer:
TRUE
Explanation:
Endemic diseases are the diseases or infections that are persistently present in the population of a particular geographical area.
An endemic infection or disease does not increase at an exponential rate and also does not get eliminated entirely. Therefore, such an infection is constantly maintained without any external outputs and thus reaches the endemic steady state.
Each of these practices has greatly reduced the spread of infectious diseases in the developed world except
A) vaccination.
B) antibiotics.
C) reduced population growth.
D) water purification.
Answer:
C) Reduced population growth
Explanation:
Vaccination avoids that an infectious agent causes a disease in a person, so it stops the spread of these diseases. Also, antibiotics kill bacteria responsible for infections in an ill person, therefore, they also end the spread. Water purification eliminates pathogens from the water such as bacteria or fungus, so it helps to prevent infections in a population. Finally, reducing the growth of the population doesn't directly affect the spread of infectious diseases.
Describe the key steps in the semiconservative replication of DNA.
Answer:
Semi-conservative replication is meant for the description of DNA replication and it i s called so because parent DNA helix produces two copies of original DNA, one of which consist of original DNA.
The three main steps in DNA replication includes Initiation, Elongation and Termination.
In the initiation phase, replication begins at origin of replication where helicase enzyme breaks the hydrogen bonds between base pairs and tends to unwind the double helix where the topoisomerase stabilizes the newly formed single strand DNA. DNA polymerase allows elongation to occur in leading direction and catalyses the addition of new nucleotide to new single strands. short sequences of RNA called primers paired to template strands with the help of primase. replication of both strands occurs at the same time one in continuous (3'-5') and other in discontinuous (5'-3') direction, which are called leading strands. new nucleotides added in 3' end and moving to replication fork while discontinuous synthesis occur on parent strand (5'-3') called lagging strand and completed in segments called okazaki fragments. Then primase add primers ahead at 5' end of the lagging strand. DNA polymerase ||| adds short sequences of nucleotides to the primer. During termination, exonuclease replaces DNA primer and DNA nucleotide and DNA ligase helps in making bonding between fragments and replaced nucleotide. Another exonuclease helps in proofreading the newly formed DNA and corrects the errors in sequences. At the end of the parent strands, telomeres are present which keeps on catalyzing by telomerase and completes, the formation of copies of parent DNA.
The semiconservative replication of DNA is a process where each new DNA molecule consists of one parental and one new strand. This process includes unwinding the DNA, helicase creating replication forks, binding proteins stabilizing single strands, and enzymatic actions such as Primase synthesizing RNA primers, DNA polymerase elongating new strands, and DNA ligase sealing the strands.
Explanation:Semiconservative Replication of DNAThe key steps in the semiconservative replication of DNA involve several critical actions and proteins to ensure that the DNA is copied accurately. The term semiconservative relates to the fact that each resultant DNA molecule consists of one old (parental) strand and one new (daughter) strand. The replication process can be described as follows:
DNA unwinds at the origin of replication.Helicase opens up the DNA, forming replication forks; these extend bidirectionally.Single-strand binding proteins coat the DNA strands to prevent them from rewinding.A short RNA primer is synthesized by Primase, which is necessary for DNA polymerase to begin synthesis of the new strand.DNA polymerase III attaches nucleotides to the 3'-OH group of the RNA primer, elongating the new strand.As synthesis proceeds, DNA polymerase continually adds new nucleotides to the growing strand in accordance with the base-pairing rules (A pairs with T, C pairs with G).Once the entire DNA molecule has been copied, DNA polymerase I replaces the RNA primers with DNA nucleotides.The DNA ligase enzyme seals the gaps between the newly synthesized DNA fragments, finalizing the strand.The result is two DNA molecules, each with one parental strand and one new strand - this conservation of the parental strand is why the process is known as semiconservative.List and describe the function of each of the four components of blood.
Answer:
The four components of blood are RBC, WBC, Platelets, and blood plasma.
Explanation:
The major 4 components of blood are RBC, WBC, platelets, and plasma. Plasma is the fluid part of the blood and the remaining 3 are the cellular part.
Plasma is the yellow color liquid. In the plasma, all cellular components float. Plasma constitutes approximately 55% of the total volume of the blood.
The various functions of plasma are - It carries different nutrients from the alimentary canal to the liver and other parts of the body. Simultaneously it carries the CO2 from the different tissues and reaches them to lungs for expiration. It distributes the hormones and vitamins from endocrine glands to different target organs. Plasma also plays a role in the water balance in the body. It supplies water to tissues and receives excess water from them. Thus regulate the water balance in the body.
RBC is the enucleated cellular organelle of blood. The absence of nucleus enables it to carry more oxygen. It is red due to the presence of Hb and carries O2 and CO2 in the form of oxyhemoglobin and carbaminohemoglobin. It also helps in releasing energy through the metabolic process.
WBC is concerned with the immunity of the body. It acts as a defense mechanism of the body. The components of leukocytes such as granulocytes and agranulocytes are phagocytic. They engulf bacteria and viruses. Eosinophils fight against the allergic reaction in the body.
The blood platelets have blood clotting factors. There are 12 blood clotting factors which help in the clotting of blood.
The final product of the Calvin cycle is:
a. RuBisCo
b. ATP
c. CO2
d. G3P
Answer:
The correct answer will be option-D
Explanation:
Calvin cycle or C₃ cycle is a set of a cyclic reaction which takes place in the light-independent reactions of photosynthesis. Calvin cycle proceeds in three phases: carboxylation, reduction and regeneration.
The cycle produces two molecules of Glyceraldehyde-3-phosphate (G3P) molecule during the reductional step of the cycle. Out of these two molecules, one G3P undergo for the regeneration of RuBP and one G3P undergo for the formation of a glucose molecule.
Thus, option-D is the correct answer.
Some of our neurons (cells of our nervous system) have ATP-gated calcium (Ca+2) channels in both their plasma membrane and nuclear envelope. (tricky
a. True
b. False
Answer:
The given statement is true.
Explanation:
Some of the neurons possess ATP-gated calcium channels in both their nuclear envelope and plasma membrane. The majority of the ion channels are ligand-gated and stays in their position, which shows that they do not move from one membrane to another.
However, the ATP gated calcium channels have been located in both the nuclear envelopes of some of the neurons and plasma membrane, which signifies that the channel may socialize between the two compartments.
Both plant and animal cells have a chloroplast.
a. True
b. False
Answer:
False
Explanation:
Only plants have chloroplast.
This statement is FALSE. Only plant cells contain a chloroplast.
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In evolution, why is it important that individuals vary from each other?
A. Variation allows some individuals to do better than others, so those variations are selected for.
B. If variations or mutations are extreme enough, new species can result.
C. Variations are important because individuals have to change through time.
D. Variations are important because they're inherited.
E. Variation gives every individual an equal chance of surviving so they can be selected for.
Answer:
D. Variations are important because they're inherited.
Explanation:
A. False
Not all variations are just beneficial, there are variations that can be harmful, leading natural selection to eliminate these individuals.
B. False
Without some environmental pressure, that is, any change that drives the selection of an individual, mutation alone cannot generate a new individual. If this mutation is not selected as "beneficial" and is not passed on to future generations, this mutation will disappear in that individual.
C. False
Not necessarily. Genetic variations occur at random, so those species that survive are selected and able to adapt.
E. False
It does not give an equal chance of surviving.
Prokaryotes used to be classified into one group, but now they are classified in the Domains Bacteria and Archaea.
a. True
b. False
Answer:
True.
Explanation:
Three domains of life are prokarya, eukarya and archae. Prokaryotes are the organism that lacks the well developed nucleus and membrane bound cell organelle.
Earlier the prokaryotes are classified in the one group. But the prokaryotes are now further classified into the domains archaea and bacteria. As prkaryotic organism shows the similar characteristics with the archae and prokarya. To make the study more simpler, prokaryotes are splits into the domains of bacteria and archaea.
Thus, the answer is true.
Explain how a testcross can provide evidence for or against linkage.
Answer:
Testcrosses clarify linkage because each phenotypic class of progeny corresponds to each gamete type produced by the dihybrid parent.
Explanation:
A test cross involves the crossing of an individual with another phenotypically recessive individual so as to determine the zygosity of the former by analyses of the proportions of offspring phenotypes.In order to determine linkage, the test cross shows that if the parentals are more than the recombinants, we can say that the two genes such as b and c are genetically linked and therefore, they must be on the same chromosome.Also, the test-crosses help to find out which alleles came from which parent.By setting up testcrosses in which one parent is homozygous for the recessive alleles of both genes,we can analyze the gene combinations received in the gametes from the other, doubly heterozygous parent.Describe the key events of meiosis that explain Mendel's first and second laws.
Answer:
Explained
Explanation:
During Meiosis the Chromosomes line up or assort independently from one another. Therefore, genes located on each chromosomes are also segregate of one another. Therefore, the gene for seed color (G & g) will assort independent of the gene for plant height (T & t) , thus producing 4 different gene combinations of gametes,they are : GT, Gt, gT & gt.
ATP molecules from Glycolysis + Krebs cycle are _______________
a. 12 ATP
b. 28 ATP
c. 32 STP
d. 4 ATP
Answer:
The correct answer will be option-D.
Explanation:
Cellular respiration proceeds in four stages: glycolysis, link reaction, Krebs cycle and electron transport chain. ATP is produced in each step along with other reducing equivalents which gets reduced during the electron transport chain to form ATP.
In the given question, only ATP molecules formed during both glycolysis and Krebs cycle will be 4 ATP as 2 ATP are produced in glycolysis and 2 ATP are produced in the Krebs cycle per two molecules of pyruvic acid.
Thus, option-D is the correct answer.
The citric acid cycle occurs in the:
a. Golgi apparatus
b. Thylakoid lumen
c. Mitochondrial matrix
d. Across the inner membrane of the mitochondria
Answer:
The correct answer will be option-C.
Explanation:
Cellular respiration is a slow process which breakdown the food components via oxidation to convert them into energy molecules. The respiration proceeds in four stages: Glycolysis, pyruvate decarboxylation, citric acid cycle and electron transport chain.
All these processes take place in different compartments of the cell-like glycolysis takes place in the cytoplasm and citric acid cycle or Kreb cycle takes place in the matrix of the mitochondria. The matrix of the mitochondria provides the necessary environment to proceed the step of the respiration.
Thus, option- C is the correct answer.
Which of these is not a feature that links "dinosaurs' to modern day extant birds"?
a. A furcula
b. Feathers
c. S-shaped neck
d. Nasal turbinates
e. The flight stroke
Answer:
The correct answer is option d. "Nasal turbinates".
Explanation:
Most mammals and modern day birds have nasal turbinates that perform two functions: improve the sense of smell by providing a wider area for airborne chemicals absorption and warm and moisten inhaled air while extracting heat and moisture during air exhalation. On the other hand, no evidence have been found that suggest that dinosaurs had nasal turbinates. Although most dinosaurs had nasal passages, they were too narrow and short to accommodate nasal turbinates.
Which gland of the cane toad produces poison?
a. parotoid gland
b. tympanic membrane
c. glottis
d. eustachian tubes
Answer:
The correct option is: a. parotoid gland
Explanation:
Cane toads, also known as Bufo marinus or Rana marina Linnaeus, are the giant old species of the terrestrial true toads. The female cane toads are longer than the male cane toads.
The skin of the cane toad is highly toxic. An adult cane toad has large parotoid gland behind each eye, which secretes a milky-white toxic fluid called bufotoxin.
What feature distinguishes male embryo from female at eight weeks of age?
a. males have a Y chromosome
b. males have well developed primary reproductive organs
c. male testes have descended into the scrotum
d. in males, the ovaries have degenerated
e. all of the above
Answer:
A, B & D
Explanation:
It is not possible to distinguish the sex of a fetus below seven (7)weeks. At this stage only observation of chromosomes through karyotype can determine the sex. The male fetus will have an XY sex chromosome pair while females will have an XX chromosome pair. After the eighth weeks internal and external genitalia begins to differentiate. The testes and ovaries (the primary reproductive organs) begin to develop in males and females respectively. In males the paramesonephric ducts regresses while the mesonephric ducts begin to develop into testes. In females the mesonephric ducts regresses while the paramesonephric ducts begin to develop into ovaries.
Why would you not expect amylase to digest protein?
Sauropod dinosaurs are more closely related to Aves than Ornithischian dinosaurs.
a. True
b. False
Answer:
TRUE
Explanation:
The Sauropods were the enormous herbivore dinosaurs that had a long neck and a tail, but the size of their head was relatively small. The fossil remnants of a previously existed unknown sauropod dinosaur species named 'Tataouinea hannibalis' were obtained from the rocks of the southern side of Tunisia.
From the fossil evidence, it was observed that a sizable opening was present in the ischium, which actually opens into a large air chamber. This observation supported the theory that considers the presence of abdominal air sacs in this type pf dinosaur species that are similar to the respiratory system of Aves (birds).
Thus, the Sauropods and Aves are closely related to one another.
Hence, the above statement is TRUE.
Consider this pathway: epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP. Identify the second messenger.
a. cAMP
b. G protein
c. GTP
d. adenylyl cyclase
Answer:
a. cAMP
Explanation:
Secondary messengers are signaling molecules which are present intracellularly and play a great role in amplification of a signal during signal transduction pathway.
cAMP, DAG and IP3 are common secondary messengers in GPCR signalling. GPCR are largest family of cell surface receptors which are associated with various functions like control of blood vessel dialation, interstitial epithelial cells, glycogen breakdown, inflammation, photoisomerization reaction etc.
The second messenger in the given pathway is cAMP.
Explanation:The second messenger in the given pathway is cAMP. In this pathway, epinephrine binds to a G protein-coupled receptor, which activates a G protein. The G protein then activates adenylyl cyclase, an enzyme that converts ATP into cAMP. Therefore, cAMP acts as the second messenger in this pathway.
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A planet is inhabited by creatures that reproduce with the same hereditary patterns seen in humans. Three phenotypic characters are height (T = tall, t = dwarf), head appendages (A = antennae, a = no antennae), and nose morphology (S = upturned snout, s = downturned snout). Since the creatures are not "intelligent," Earth scientists are able to do some controlled breeding experiments using various heterozygotes in testcrosses. For tall heterozygotes with antennae, the offspring are tall-antennae, 46; dwarf-antennae, 7; dwarf-no antennae, 42; tall-no antennae, 5. For heterozygotes with antennae and an upturned snout, the offspring are antennae-upturned snout, 47; antennae-downturned snout, 2; no antennae-downturned snout, 48; no antennae-upturned snout, 3. Calculate the recombination frequencies for both experiments.
Answer:
For the first experiment, the recombination frequency is shown below. This experiment comprises the cross between the Tall and the Antennae.
Tall-antennae - 46% - Expected
Dwarf-no antennae - 42% - Expected
Dwarf-antennae - 7% - Recombinant
Tall-no antennae - 5% - Recombinant
Total = 100%
For the recombinants, the recombination frequency is:
= 7 + 5 = 12%
Thus, the recombination frequency between the T and A genes is 12%.
For the second experiment, the cross takes place between the heterozygous antennae and the upturned snout. The results are shown below:
Antennae-upturned snout - 47% - Expected
No antennae-downward snout - 48 % - Expected
Antennae-downward snout - 2% - Recombinant
No antennae-upturned snout - 3% - Recombinant
Total = 100%
The recombinant frequency is = 2 + 3 = 5%
Thus, the recombination frequency between the A and S genes is 5%.
Answer:
For experiment 1, the recombinant frequecy is 12%
For experiment 2, the recombinant frequency is 5%
Explanation:
please look at the solution in the attached Word file
The androgen-binding protein functions to
A. Confer responsiveness of certain cells to male sex hormones.
B. Transport androgens in the plasma.
C. Bind and maintain high concentrations of testosterone in the seminiferous tubules.
D. A and B.
E. A, B and C
Answer:
C. Bind and maintain high concentrations of testosterone in the seminiferous tubules.
Explanation:
Seminiferous tubules are present within the testis of male reproductive system. In adults, each testis is oval in shape and is about 4-5 cm in length. Each testis has about 250 compartments called testicular lobules. These compartments contain highly coiled tubules called seminiferous tubules.
Within the seminiferous tubules, the male gamete i.e sperms are produced. Seminiferous tubules are lined inside by two types of cells called male germ cells (spermatogonia) and sertoli cells.
Spermatogonia give rise to spermatozoa which are released into the lumen of the tubule. In between spermatogenic cells, sertoli cells or sustentacular cells or nurse cells are present which provide nourishment to developing spermatozoa.
One of the function of sertoli cells are to release androgen binding protein (ABP) which binds and concentrates testosterone with in the seminiferous tubules.
The hormone testosterone is produced by the interstitial cells of Leydig located around the seminiferous tubules.