Exocytosis is the process by which cells transport components into the extracellular fluid from within the cell.
What is the endocytosis procedure?A broad term for the process by which cells take in outside material by enveloping it with their membrane is endocytosis. Pinocytosis and phagocytosis are typically used as subcategories of endocytosis.
What makes endocytosis and exocytosis different from one another?Endocytosis is the process by which a material or particle from the outside of the cell is taken in by the cell membrane and brought inside. Vesicles fusing with the plasma membrane and releasing their contents to the exterior of the cell is referred to as exocytosis.
To know more about Exocytosis process visit:-
https://brainly.com/question/29101406
#SPJ4
you are leading a team of researchers at a pharmaceutical company. your goal is to design drugs that help fight cancer. specifically, you want to focus on drugs that bind to and inactivate certain proteins, thereby halting cell cycle progression. one of your team members suggests targeting the retinoblastoma (rb) protein and inhibiting this protein. will this approach be successful? why or why not?
To design drugs that help fight cancer, targeting the retinoblastoma (rb) protein and inhibiting this protein will not be successful.
What will happen when you target the retinoblastoma (rb) protein ?Targeting the retinoblastoma (rb) protein and inhibiting this protein during the research for designing drugs for cancer will not be a successful approach.
Rb is a tumor-suppressor protein and it functions to inhibit the action of a number of cell cycle regulatory proteins. A drug designed to inactivate the Rb protein would create the same situation as in a cell that lacks both copies of the Rb gene.
Lack of Rb activity releases the inhibition of cell cycle regulatory proteins and thereby promoting cell cycle progression rather than halting it.
To know more about cancer, refer
https://brainly.com/question/26059802
#SPJ4
some flagellated species fail to produce flagella when grown under labortory conditions. what might be the disncetive
Bacteria will not move if they do not have to in order to collect nutrients because they are in favourable conditions, therefore even though the can contains these bacteria, they would not produce flagella.
When favourable circumstances are present, organisms have a tendency to preserve energy and refocus it on reproduction rather than on activities that are no longer necessary given the circumstances. The same holds true for bacteria growing in culture because food is easily available and bacteria no longer need to develop flagella in order to move in order to capture it thus they try to conserve their energy and refocus it on reproduction.
To learn more about flagella click here:
https://brainly.com/question/1845048
#SPJ4
Which of the following is a possible outcome of a disruption to an ecosystem?
O All of the above
O Population size increases
O population size decreases.
O A species may leave or enter and ecosystem.
O A species become extinct
During contraction, the internal chambers of the heart become smaller, which forces roughly 50-75 percent of the blood into the __________.
During contraction, internal chambers of the heart become smaller, that forces 50-75 percent of the blood into the ventricles.
What is the function of ventricles?The left ventricle is the thickest of the heart's chambers and pumps oxygenated blood to tissues all over the body whereas, the right ventricle pumps blood to the lungs.
The first and second ventricles are lateral ventricles and these C-shaped structures are located on each side of cerebral cortex. The third ventricle is a narrow and funnel-shaped structure situated between right and left thalamus.
Diastole and systole are phases of the cardiac cycle n which systole occurs when the heart contracts to pump the blood out and diastole occurs when the heart relaxes after contraction.
To know more about heart, refer
https://brainly.com/question/26387166
#SPJ1
a vector a. allows cells to take up foreign dna. b. encodes herbicide resistance. c. carries cloned dna, allowing it to replicate in cells. d. destroys cells that do not contain cloned dna.
In molecular biology, a vector is a DNA molecule that is used as a vehicle to transfer foreign genetic material into another cell.
The four major types of vectors are plasmids, viral vectors, cosmids, and artificial chromosomes.A vector is a living organism that spreads infectious agents from infected animal to infected animal. Arthropod vectors include mosquitoes, ticks, flies, fleas, and lice. The haematophagous arthropod definition, which defines vectors solely as blood-feeding arthropods such as mosquitoes, ticks, sandflies, tsetse flies, and biting midges, is similar. Vector quantities include displacement, acceleration, force, momentum, weight, the speed of light, a gravitational field, current, and so on.
Learn more about vectors here:
https://brainly.com/question/13322477
#SPJ4
during mitosis, a single cell divides to produce two daughter cells. what must happen in the original
DNA replication ought to show up withinside the original mobileular in order that every of the daughter cells has a entire set of chromosomes.
DNA replication is the method through which the DNA molecule of a mobileular is duplicated to shape equal copies of itself.
DNA replication is a ought to for each mobileular this is approximately to undergo cellular division and that is to make sure that every daughter mobileular gets accurate quantity of chromosomes (DNA).
DNA replication takes place withinside the S-section of the mobileular cycle and it permits the daughter cells that outcomes from mitosis to have the identical kind and wide variety of genetic material.
Therefore, DNA replication ought to show up withinside the original mobileular in order that every of the daughter cells has a entire set of chromosomes.
To learn more about DNA replications, click here:
https://brainly.com/question/16464230
#SPJ4
place the following occurrences in order to describe the regulation of rehydration beginning with someone who is dehydrate
The frequency and prevalence of heat illness are reduced when dehydration is identified early. a dehydrated, aware, and conscientious athlete.
How does it take for your body to rehydrate?However, after consuming a considerable amount of water, your body typically needs two hours to thoroughly rehydrate. The greatest option for rehydrating is drinking water. Gatorade and other sports drinks might be advantageous to athletes who must replace their electrolytes.
What is a better hydrator than water?Milk is among the finest drinks for hydration, according to research, even higher than water or drink mixes. Researchers attribute milk's efficiency to its protein, carbs, and natural electrolytes.
To know more about Rehydrate visit:
https://brainly.com/question/7974194
#SPJ4
Which of the following is not an example of how bacteria aid in the nitrogen cycle
changing nitrogen compounds into atmospheric nitrogen
nitrogen fixation
breaking down the tissue of dead organisms
infecting tissueanging nitrogen compounds into atmospheric nitrogen
Infecting tissue is not an example of how bacteria aid in the nitrogen cycle, so the correct option is D.
What is the nitrogen cycle?The nitrogen cycle is a process in which nitrogen is converted into different forms when it circulates through the biosphere, this can be through biological or physical processes. The nitrogen cycle includes fixation, ammonification, nitrification, and denitrification.
This nitrogen to be able to do this will have to enter through bacteria that converts it into biological forms that can be used, this process is called nitrogen fixation. This nitrogen will then be converted to ammonia and absorbed by plants to generate organic molecules.
Therefore, we can confirm that the correct option is D. infecting tissue.
To learn more about nitrogen cycle visit: https://brainly.com/question/1615727
#SPJ1
48 POINTS!!!
Which statement best describes a physical change?
A) Changes can occur to certain chemical properties of the substance, but the overall shape of the substance will remain the same.
B) Changes can occur to certain physical properties of the substance, but the overall shape of the substance will remain the same.
C)Changes can occur to physical properties of a substance, but the chemical composition of the substance remains the same.
D)Changes can occur to chemical properties of a substance, but the chemical composition of the substance remains the same.
Answer:
Answer choice C. is correct.
Explanation:
Physical change is a change in which there is no change in the chemical arrangement and thus there is no redistribution of atoms. No new substances are formed.
abdominal pain is best described as visceral pain that: a. travels from a specific organ to the spinal cord. b. is in concert with the peristalsis of the gastrointestinal tract. c. is diffused, vague, poorly localized, and dull. d. lateralizes from only one side of the nervous system.
Abdominal pain is best described as visceral pain that was diffused, vague, poorly localized as well as dull.
So, the correct option is C.
Epigastrium (upper mid abdomen), or lower abdominal pain is typically felt close to the midline. Having poor localization, being dull rather than sharp, and being challenging to describe the pain The other choices all fall short of really capturing this kind of sorrow. When the pelvis, abdomen, chest, or intestines' pain receptors are activated, visceral pain results. When the tissues and organs inside of us are hurt or damaged, we feel it.
Indefinite, non-localized, poorly understood, and poorly defined visceral pain is also difficult to pinpoint. A deep squeeze, pressure, or aching sensation are frequent sensation. abdomen, chest, intestines, or pelvis may experience nebulous visceral pain. Uncertainty surrounds this condition, which is brought on by harm to internal organs and tissues.
Learn to know more about Visceral pain on
https://brainly.com/question/28498475
#SPJ4
. from the examination of the structures of lactose and starch, which saccharide(s) would be produced from the hydrolysis of each?
From the examination of the structures of lactose and starch, Glucose and galactose saccharide(s) would be produced from the hydrolysis of each.
Lactose is a milk disaccharide. It is hydrolyzable to produce one unit of glucose and one unit of galactose. Lactose is the enzyme responsible for catalyzing this hydrolysis. Lactose malabsorption causes digestive symptoms in lactose intolerance. Lactose malabsorption occurs when your small intestine is unable to digest or break down all of the lactose you consume. Lactose is composed of two carbohydrates: -D galactose and -D glucose.. As a result, when hydrolyzed, it yields -D galactose and -D glucose.
Learn more about Lactose here:
https://brainly.com/question/14868133
#SPJ4
Q1 ) Briefly explain how exchange of gases take place in humans.
Q2) Using a venn diagram, compare and contrast between Aerobic Respiration and Anaerobic Respiration
Q3) Paheli participated in a 400m race competition held at her school and won the race. When she came home she had mixed feelings of joy and pain as she had cramps in her leg muscles. After a massage, She was relieved of the pain. Answer the following questions related to the situation.
a) What can be the possible reason for the pain in her legs?
b) Why did she feel comfortable after a massage
Q4) Why does an athelete breathe faster and deeper than usual after finishing the race?
3. (a) The buildup of lactic acid in her muscles may be the source of the pain in her legs.
(b) The massage relieved her because it increases blood circulation, which increases oxygen supply to the muscle cells and aids in the complete breakdown of lactic acid into CO and water.
4. The athlete's body requires extra oxygen as he runs in the race. So that the body may receive more oxygen, its breathing rate quickens.
What is breathing?
The act of breathing, also known as ventilation, involves moving air into and out of the lungs in order to facilitate gas exchange with the body's internal environment, primarily to expel carbon dioxide and draw in oxygen. These gases are moved to and from the cells by the circulatory system of the body, where "cellular respiration" occurs. Lactic acid is produced when muscle cells respire anaerobically during strenuous exercise, jogging, etc.
Hence, the buildup of lactic acid in her muscles may be the source of the pain in her legs, massage relieved her because it increases blood circulation, and an athlete's body requires extra oxygen as he runs in the race so he's breathing faster.
To know more about Breathing, check out:
https://brainly.com/question/25722501
#SPJ9
if an individual who is homozygous for type b blood marries a heterozygous type a individual, what is the chance that their first child will have type ab blood?
50%. Red blood cells with blood group a antigens have anti-B plasma antibodies. Plasma from people with blood group B contains anti-A antibodies and B antigens. Blood group O has both anti-A and anti-B antibodies in the plasma but no antigens.
What about blood groups?Your blood type is determined by the genes you inherited from your parents.Each of the eight different blood types can either be RhD positive or RhD negative.The eight most frequent blood types are A+, A-, B+, B-, O+, O-, AB+, AB-. In addition to the A and B antigens, the Rh factor is a protein that can either be present (+) or absent (-).The least common blood types are B negative (B -ve), which make up just 1.5% of the population. AB negative, or AB -ve, which makes up 0.6% of the population. AB +ve, which is present in 3.4 percent of the population. Red blood cells that are type O negative are thought to be the safest to give to anyone in a life-threatening situation or when there is a shortage of blood that is exactly the right match. Because type O negative blood cells lack antibodies to A, B, or Rh antigens, this is the case. Rh-null is one of the rarest blood types in the world. Due to the absence of any Rh antigens, this blood type can't be Rh negative. Less than 50 individuals have this blood type. Sometimes, it is referred to as "golden blood."Learn more about blood groups here:
https://brainly.com/question/15289194
#SPJ4
Margulis’ theory of the origin of mitochondria proposes that mitochondria ______.
Margulis’ theory of the origin of mitochondria proposes that mitochondria originated when a larger anerobic cell engulfed a smaller aerobic cell.
Margulis wrote in her 1967 essay that the protomitochondrion, an aerobic prokaryotic microbe, was absorbed into the cytoplasm of a heterotrophic anaerobe as the first stage in the genesis of eukaryotes from prokaryotes in order to survive in the new oxygen-containing atmosphere. This can further be proposes that when a bigger anaerobic cell swallowed a smaller aerobic cell, mitochondria were created.
The mitochondria, which are membrane-bound cell organelles, generate the majority of the chemical energy needed to power a cell's metabolic processes (mitochondrion, singular). Adenosine triphosphate, a tiny molecule, serves as a storage container for the chemical energy generated by the mitochondria (ATP).
To know more about mitochondria, refer to the following link:
https://brainly.com/question/11296488
#SPJ4
suppose two aabbcc individuals are mated. assuming that the genes are not linked, what fraction of the offspring are expected to be homozygous recessive for the three traits?
1 is a fraction of the offspring that are expected to be homozygous recessive for the three traits because gamete formed are only abc i.e. abc × abc .
You are seeking for a pair of alleles that are both lower case when we say homozygous recessive. In other words, the recessive feature will manifest itself phenotypically. The genotype that you would want in the Punnet would thus be: aabbcc only .
Heterozygous genotype refers to an organism with one dominant allele and one recessive allele. This genotype's designation in our case is Bb. Finally, homozygous recessive refers to an organism's genotype that consists of two recessive alleles i.e. bb
To learn more about homozygous recessive click here,
https://brainly.com/question/8964169
#SPJ4
the neurotransmitters norepinephrine and epinephrine function as hormones, and are secreted by which structure?
Your adrenal gland, which is also reached by the neurotransmitter noradrenaline, releases the chemicals noradrenaline and adrenaline (epinephrine) (norepinephrine). Your blood carries these hormones to every region of your body. They once again enter your eyes, heart, airways, skin's blood vessels, and adrenal gland.
Epinephrine and norepinephrine are secreted by chromaffin cells, which are adrenal medulla cells.
Two neurotransmitters known as epinephrine and norepinephrine, which are called hormones, are members of the catecholamine chemical class. They act as hormones, affecting various physiological systems and energizing the central nervous system. Nerve cells in the brainstem region and a region close to the spinal cord produce norepinephrine. The sympathetic nervous system, which is a component of your body's immediate "fight-or-flight" response to danger, produces norepinephrine.
To know more about neurotransmitters
https://brainly.com/question/28987403
#SPJ4
How do increased levels of estrogen and progesterone affect the levels of FSH in the blood?
Increased levels of estrogen and progesterone affect the levels of FSH in the blood is FSH allow smaller follicle to die off
Estrogen also stimulates the endometrium to thicken and the increase in the estrogen and progesterone level causes milk duct in the breast to widen and as result the breast may swell and become tender and progesterone is also responsible for stimulating the midcycle rise in FSH and elevated FSH level at this time are thought to free the oocytes from follicular attachments and as follicle grows blood level of estrogen rise significantly by cycle day seven this increase in estrogen begins to inhibit the secretion of FSH and the fall in FSH allows smaller follicles to die off
Know more about progesterone
https://brainly.com/question/17367784
#SPJ1
Which of these
BEST describes why
DNA never leaves
the nucleus?
A. DNA is a very large molecule plus it is a really
important molecule for life that needs
protection.
B. Most DNA serves absolutely no purpose so it
should always stay at home in the nucleus.
C. DNA just cannot compete with other
molecules such as RNA.
Answer:
A. DNA is a very large molecule plus it is a reallyimportant molecule for life that needsprotection.
Explanation:
DNA cannot leave the nucleus because that would risk it getting damaged. DNA carries the genetic code and all of the information needed for cells and organisms to function properly. If it were damaged or mutated, that would be disastrous for the organism, and could cause serious illnesses or even death.
DNA is a very large molecule plus it is a really important molecule for life that needs protection. Thus, option A is correct.
Why DNA cannot leave the nucleus?DNA will not leave the nucleus as it is because that would risk it as getting it damaged. DNA has carries the genetic code and all of the information needed for the cells and the organisms to function properly. If it has been damaged or mutated, that would bethe disastrous for the organism, and could cause the serious illnesses or even death.
mRNA could leave the nucleus, but the DNA cannot leave the nucleus because RNA has been considered as the single-stranded, and DNA has been double-stranded, so RNA has been smaller than the DNA.
DNA would be not a single-stranded structure. While RNA has been present in the single stranded form in the cell. Due to this, the double-stranded structure of the DNA seems longer than that of RNA to cross the nuclear membrane in the cell. As a result of this, RNA can easily leave the nucleus but DNA couldn't.
Therefore, DNA is a very large molecule plus it is a really important molecule for life that needs protection. Thus, option A is correct.
Learn more about DNA on:
https://brainly.com/question/264225
#SPJ2
two parts of your brain that are critical to regulating circadian rhythm are the hypothalamus and the group of answer choices pineal body. amygdala. cerebellum. brain stem.
Two parts of your brain that are critical to regulating circadian rhythm are the hypothalamus and the Pineal body.
Your hypothalamus, a structure deep in your brain, acts as your body's clever control coordinating middle. Its principal function is to hold your body in a solid kingdom known as homeostasis. It does its job through immediately influencing your autonomic frightened device or through handling hormones.
The function of the hypothalamus is to maintain your body's internal stability, which is called homeostasis. To try this, the hypothalamus facilitates stimulate or inhibit many of your frame's key tactics, such as:
* Heart rate
* Blood strain.
Hypothalamus performs a critical role in many vital functions, along with:
1) Releasing hormones.
2) Maintaining daily physiological cycles.
3) Controlling urge for food.
4) Managing sexual behavior.
Learn more about Hypothalamus here:-https://brainly.com/question/11352172
#SPJ4
If one DNA strand reads CCGTAATGCAT, what will be the sequence of the complementary strand?
Which of these is produced during photosynthesis?
A. chemical energy
B. water
C. carbon dioxide
Answer:
it's A
Explanation:
the chemical energy is in the glucose it produces along with the oxygen.
in a pcr reaction, which step allows the primer to form hydrogen bonds with the template dna strand? g
The Annealing stage is where the primer is allowed to create hydrogen bonds with template DNA strand. Primers are single stranded DNA or RNA sequences, 20-30 bases long.
What is PCR?
The polymerase chain reaction (PCR) is a lab technique used to quickly amplify millions of copies of DNA segments, to be studied in detail. The Polymerase chain reaction is highly precise and is used for copying, amplifying specific DNA from a mixture containing different DNA molecules.
It has three simple steps:
Denaturation is where the double helix is denatured to single strands
Annealing is where primers are attached to the initial strands for synthesis of new strand.
And Extension is where the DNA strands are extended from primers.
PCR is now widely used for many things such as, cloning, mutation detection, microarrays, forensics, genotyping, etc.
Hence, annealing is the stage where primer forms hydrogen bonds with template DNA.
Learn more about PCR here: https://brainly.com/question/7177771
#SPJ4
Claims. Evidence Reasoning How
is the structure of a unicellular organism
different than the structure of a
multicellular organism? How does this affect
function? Summarize evidence to support
your claim and explain your reasoning.
A multicellular organism is made up of numerous cells that cooperate, whereas a unicellular organism only contains one cell. Each function must be managed by a single cell, whereas in multicellular organisms.
What is in a unicellular organism?Any living creature only with one cell, which performs all crucial body functions like metabolism, waste, and fertilization, is referred to as a "unicellular organism." Unicellular organisms can either be prokaryotes or eukaryotes. Unicellular organisms include bacteria, archaea, unicellular fungi, and unicellular protists.
How is it important to unicellular organisms?Cell division in unicellular organisms is crucial only for reproduction. They divide their cells through a process called mitosis to create their daughter cells. Cell division is crucial for the development of new cells and reproduction in multicellular animals.
To know more about Unicellular organism visit:
https://brainly.com/question/27753005
#SPJ13
concentration gradient
Answer:
Is the difference between the concentration of the molecules between the region of the high concentrations and that of the lower concentration
which of the following are reasons for why many environmentalists do not see nuclear energy as a clean alternative energy source pols 2401
The production of radioactive wastes, such as spent (used) reactor fuel and other radioactive waste, is a significant environmental hazard associated with nuclear power. These substances may continue to be radioactive and hazardous to human health for tens of thousands of years.
The creation of electricity by nuclear reactions is known as nuclear power. Nuclear processes such as nuclear fission, nuclear decay, and nuclear fusion may all provide nuclear energy. Nuclear power plants currently generate the great majority of the world's electricity from nuclear energy through the fission of uranium and plutonium. Hazardous waste comes in the form of radioactive waste when radioactive material is present. Numerous operations, including nuclear research, nuclear energy production, rare-earth mining, and the reprocessing of nuclear weapons, produce radioactive waste.
Learn more about nuclear energy here:
https://brainly.com/question/12793906
#SPJ4
how can the nonrecombining part of the y chromosome help researchers trace the origins of modern humans
NYR i.e the non recombinating part of y chromosome enables researchers to identify the most recent common ancestor for the chromosome.
The Y chromosome makes up over 2% of all DNA in cells and spans more than 59 million base pairs, the basic unit of DNA.
Because the Y chromosome is only passed down from the father, it is frequently used in genealogy to track the male ancestry.
Every person with a Y chromosome is connected to everyone else through an XY ancestor who (presumably) lived roughly 300,000 years ago.
To know more about genetics , Refer:
https://brainly.com/question/8868332.
#SPJ4
What is determined by genes that direct the amount of eumelanin or pheomelanin produced by
melanocytes associated with hair follicles?
The type and amount of melanin produced by melanocytes is determined by genes. Eumelanin is a dark brown to black pigment that is responsible for brown and black hair colors. Pheomelanin is a reddish-brown pigment that is responsible for red and blonde hair colors.
What are eumelanin and pheomelanin?
A dark pigment called eumelanin is the main component of black and brunette hair. The pigment eumelanin comes in two varieties (brown eumelanin and black eumelanin). Blond hair is reportedly caused by a minor amount of brown eumelanin in the absence of other pigments. The redder parts of the skin, such as the lips, are concentrated with pheomelanin, a lighter pigment that is present in red hair. People with red hair typically have fairly pale skin that burns rapidly when exposed to the sun because they are less able to produce the dark eumelanin pigment.
The amount of a pigment called melanin in hair determines hair color. People with black or brown hair have high levels of eumelanin, one kind of melanin. Red hair is caused by an excess of pheomelanin, another pigment.
Hence, eumelanin and pheomelanin are responsible for hair color.
To learn more about melanin and pheomelanin the link is given below:
https://brainly.com/question/28900116?
#SPJ13
homo erectus skull morphology includes group of answer choices thick bones and pink browridges. thin bones and small browridges. thick bones and small browridges. thick bones and large browridges.
Large browridges, a long, low, and wide base, as well as thick bones, are all characteristics of the Homo erectus cranium.
What exactly is skull morphology?The auditory bulla of otic capsule, which is variously fused, imbedded, or connected to the skulls of vertebrates, houses the inner and middle ear systems. We can learn a lot about an animal's environmental adaptations from its morphology, or the variances for how these attachments have evolved.
Does nutrition alter skull shape?According to the investigation, which was reported in the Proceedings of the National Academy od Sciences, those that ingested dairy and cereals had slight alterations in their skull shape. One of the main chewing muscles, the temporalis, altered position and shrank as humans migrated toward agriculture.
To know more about skull shape visit:
https://brainly.com/question/28289646
#SPJ4
An evaluation on using light technology (Lasik)
The evaluation on using light technology (Lasik) is it being a fast procedure which has less complications.
What is Technology?This is referred to as the application of scientific knowledge into practical use and it helps in the reduction of errors and makes work easier and faster.
Light technology (Lasik) is a type of procedure which involves the use of excimer laser which emits a cool ultraviolet light beam and is used to reshape the cornea of individuals with astigmatism, nearsightedness etc.
This method was evaluated and was found to be a fast and reliable method of treatment for different types of eye defects. It also results in little or no complications arising from it because it is bloodless and there is no risk of contamination by foreign bodies.
Read more about Technology here https://brainly.com/question/7788080
#SPJ1
a pure white chicken and a pure black chicken are crossed. the f1 progeny all are checkered. this is an example of:
The f1 progeny all are checkered It is an example of codominance.
In genetics, codominance refers to a kind of inheritance inside which two variants (alleles) with same gene are activated separately to produce distinct features in a person. Codominance may be seen in spotted cows and plants with petals of two distinct hues.
Codominance can also be seen in less obvious features such as type of blood. Both the A and B blood type alleles can be produced simultaneously at the same time, producing in type AB blood. Codominance, as distinguished to partial domination, occurs when both parents' traits are manifested in the same child organism.
Codominance is a widespread phenomena that is likely to be a major driver of community composition, ecosystem function, and both community and ecosystem stability. While researching polygenetic features and their inheritance, Gregor Mendel identified the phenomena of codominance.
Learn more about codominance here:
https://brainly.com/question/14053639
#SPJ4