Category: Biology Questions

The series of actions occurring within a fraction of seconds in response to a situation is what refers to control and coordination. How you react to a hot cup of tea when you dip your fingers in it; how you change your path while walking after hearing a car horn, and many more. All these require a response or change to a situation is known as control and coordination.

 

A human body is indeed a complex machine performing several processes and functions to sustain and maintain life. The same way control and coordination take place in human beings through the nervous and endocrine systems. The response and coordination involve the sense organs, hormones, and nervous system.

 

The nervous system consists of nerve cells and nerve fibers that transmit nerve impulses between several parts of the body. The nervous system in animals synchronizes the function by sending signals from and to different parts of the body.

 

The nervous system generally brings it about after detecting any physical response on any body part because of several changes, including pressure, light, temperature, etc.

 

A neuron is the nervous system’s structural and functional unit that receives and transmits electrical nerve impulses. A neuron consists of the cell body, axon, and dendrites, where the dendrites receive the impulses from other neurons then the cyton processes the impulse.

 

Axon then transmits the impulse either to muscles or other neurons. However, the axon is categorized into myelinated or non-myelinated, out of which the myelinated has a faster impulse transmission.

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Muscle contraction generally takes place when thick myosin and thin actin filaments slide past each other. Muscle contraction usually takes place when sarcomeres shorten because the thin and thick filaments skid east each other which are known as the muscle contraction sliding filament model.

ATP endows with the energy for filament sliding and cross-bridge formation. The regulatory proteins like tropomyosin and troponin while controlling the cross-bridge formation.

Let us understand the whole concept of the muscle contraction process by getting acquainted with the steps of the whole process.

The muscular contraction process takes place over several steps including

• Depolarisation and calcium ion release
• Actin and myosin cross-bridge formation
• The sliding mechanism of myosin and actin filaments
• Sarcomere shortening

 

Step 1

Depolarisation and calcium ion release

An action potential from a neuron activates the acetylcholine released into the motor end plate. The released acetylcholine begins the depolarization within the sarcolemma that is spread using the fiber through T tubules.

The depolarization leads to the sarcoplasmic reticulum releasing the calcium ion stores and these calcium ions then play a pivotal role in initiating the muscular contractions.

 

Step 2

Actin and myosin cross-bridge formation

At this stage, the binding sites for myosin heads on actin are covered by the blocking complex namely tropomyosin and troponin. The calcium ions then bind to the troponin and reconfigure the complex while exposing the binding sites for myosin heads. These myosin heads then generate a cross-bridge with the actin filaments.

 

Step 3

Sliding Mechanism of Myosin and Actin

The ATP binds to the myosin head while breaking the cross-bridge between the myosin and actin. The ATP hydrolysis then causes the myosin heads to modify the position and swivel while moving them towards the following actin-binding site.

The myosin heads then bind to the new sites and further return to the original conformation. Thus, this orientation drags the actin beside the myosin in a sliding mechanism. Consequently, myosin heads move towards the actin filaments analogously to the manner in when an oar propels the rowboat.

 

Step 4

Sarcomere Shortening

The myosin heads’ repeated reorientation drags the actin filaments besides the myosin length. Since actin filaments are anchored to the Z lines, the actin dragging pulls the Z lines closer together while shortening the sarcomere.

Since the individual sarcomere becomes shorter in length makes the muscle fibers as a whole contract.

 

Summarizing the Muscle contractions

Motor neuron’s action potential activates the Calcium ions release from the sarcoplasmic reticulum. The ions then bind on actin while causing the tropomyosin to move whilst exposing the binding sites for myosin heads.

The myosin heads and actin filaments form a cross-bridge which is broken by ATP and the hydrolysis of ATP leads to the myosin heads to modify the orientation and swivel. The swiveled myosin heads then bind to the actin filaments prior to returning to the original conformation.

The myosin head repositioning moves the actin filaments towards the sarcomere’s center and the actin sliding along with the myosin shortens the sarcomere while causing the muscle contraction.

 

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Mitosis refers to an asexual reproduction process observed in unicellular organisms. Cell division is basically the reproduction’s diving process at the cellular level. Several eukaryotic cells split in a way where the number of chromosomes remains the same except in the germ cell case where the chromosome number is halved.

The mitosis process shows the equational division as depicted in the below-mentioned diagram indicating the five phases of mitosis

Here

• Stage 1 shows Interphase
• Stage 2 shows Prophase
• Stage 3 shows Metaphase
• Stage 4 shows Anaphase
• Stage 5 shows Telophase

Mitosis basically refers to the cell cycle’s phase where the cell’s nucleus is split into two nuclei containing an equal amount of genetic material in the daughter nuclei.

Mitosis is an essential process for cell growth and the replacement of worn-out cells. Let us get acquainted with each stage individually.

 

Mitosis stages

Before the occurrence of prophase, a cell spends most of its life in the interphase. Here the preparations are generally made before the mitosis begins.

As the process involves nucleus division, prophase is the technically first stage but indeed the interphase is also essential.

 

Interphase

Before entering the actual mitosis process, a cell generally spends its growth period under interphase. Here it undergoes the following phases:

G1 Phase: It’s a period before DNA synthesis

S Phase: It’s a phase during which the synthesis of DNA takes place

G2 Phase: It’s a phase that occurs between the DNA synthesis and prophase beginning.

 

Prophase

Prophase immediately follows the G2 and S phases of the whole cycle. It is generally marked by genetic material condensation to form a compact mitotic chromosome comprised of two chromatids attached at the centromere.

The Prophase completion is generally characterized by the initiation of the mitotic spindle’s assembly, the proteinaceous and microtubules components of cytoplasm which help in the process and the nuclear envelope begins disintegrating.

 

Prometaphase

Here the nuclear envelope disintegrates. In this phase, the microtubules are permitted to extend from centromere to chromosome. The microtubules are usually attached to the kinetochores that permit the cell to move the chromosome around.

 

Metaphase

During Metaphase, the microtubules begin pulling the chromosomes with equivalent force. The chromosomes end up in the middle of the cell and this region is called the metaphase plate. And therefore, each cell gets a complete functioning genome.

 

Anaphase

The sister chromatid’s splitting marks the onset of anaphase. These sister chromatids become the daughter nuclei’s chromosomes. The chromosomes are then pulled towards the pole by the fibers attached to each chromosome’s kinetochores. Each chromosome’s centromere leads at the edge while the arms trail behind.

 

Telophase

The chromosomes that cluster at the two poles begin coalescing into an undifferentiated mass because the nuclear envelope begins forming around it. The ER complex, the Golgi bodies, and nucleolus that had disappeared post prophase begin to reappear.

Telophase is generally followed by cytokinesis that denotes the cytoplasm’s division to form two daughter cells. Therefore, it marks the cell division completion.

 

Bottom Line!

Mitosis undergoes the five phases to perform two essential functions. This includes

• The mitosis process helps in organism development. In single-celled organisms, mitosis is a process of asexual reproduction.
• Mitosis also helps in damaged tissues replacement. The cells present near the damaged cells initiate mitosis when they do not sense the neighboring cells and the dividing cells reach each other and cover the damaged cells.

 

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Understanding the difference between Mitosis and Meiosis is imperative. Let us start with the definitions of each.

Meiosis

Meiosis refers to a cell division type, which results in the four daughter cells formation, each one with half the chromosomes like the parent cell.

Mitosis is a cell duplication process during which a cell gives rise to two genetically indistinguishable daughter cells. The term mitosis is generally used to describe the distribution and duplication of chromosomes.

 

Mitosis

Mitosis refers to the cell division type, resulting in the formation of two daughter cells with a similar number of chromosomes as the parent cell.

 

Meiosis is a specialized cell division type that diminishes the number of chromosomes by half, creating the four haploid cells where each one is genetically distinct from the parent cells that give rise to them.

Differences between Mitosis and Meiosis

Comparison Parameters	Mitosis	Meiosis
Cell it produces	It creates somatic or body cells	It creates germ or sex cells
Where it occurs	It occurs in all organisms except viruses	It occurs in plants, animals, and fungi
Reproduction Mode	Asexual Reproduction	Sexual Reproduction
Discovered by	It was discovered by Walther Flemming	It was discovered by Oscar Hertwig
Function	Its function is to general growth and repair and cell reproduction	Its function is genetic different through sexual reproduction
Number of chromosomes	It produces diploid cells that are 46 chromosomes	It produces haploid cells including 23 chromosomes
Stages	It consists of one stage	It consists of two stages
Interphase	Here each chromosome replicates	Here, chromosomes are not visible but the DBA has been replicated
Prophase Length	Its Prophase length is short	Its Prophase I length is longer
Cell Divisions Number	One cell division including 4 stages in total	Two cell divisions including 8 stages in total
Crossing over/ Recombination	No crossing over/ recombination in prophase	Crossing over/ Recombination of chromosomes during the prophase I
Anaphase	During the anaphase, the sister chromatids move to the cell’s opposite ends.	During anaphase I, the sister chromatids move collectively to the same cell pole whereas, during anaphase II, the sister chromatids are separated to the cell’s opposite ends.
Metaphase	During metaphase, individual chromosomes line up on the equator of the cell	During Metaphase I, the chromosome pairs line up on the equator of the cell.
Cytokinesis	It occurs in the Telophase	It occurs in the Telophase I and Telophase II
Ploidy	It creates the diploid daughter cells	It creates the haploid daughter cells
Number of cells created	Two daughter cells are created as a result	Four daughter cells are created as an outcome
Genetics	Here, daughter cells are genetically identical	Here, daughter cells are genetically dissimilar

 

 Bottom Line!

Mitosis is basically a continuous cell division process that occurs in all living cells. In contrast, meiosis is a nuclear cell division, resulting in the daughter cells with half the number of chromosomes as the original cells. Both have several differences that we have compiled above. Hope it gave you a clear idea about both the processes!

 

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Enzymes are proteins that are amino acids that are folded chains with a particular shape. The shape is generally determined by the sequence of amino acids held together by the bonds.

These are the biological catalysts that speed up the reactions but are not changed in the reaction. Enzymes generally speed up the reactions by bringing the reactants together and diminishing the activation energy needed to initiate the reaction.

Main Characteristics of Enzymes

• It speeds up the chemical reactions
• Enzymes have a specific shape
• Enzymes are required in minute amounts
• Enzymes are particular in their actions.
• Enzymes are affected by temperature.
• Enzymes are affected by pH.
• Inhibitors inhibit enzymes
• Some enzymes require coenzymes
• Some enzymes catalyze reversible reactions

Enzymes are proteins. And the characteristics and properties they exhibit reflect the protein’s properties. Enzymes are organic catalysts that speed up biological reactions, specifically in the metabolism and digestion of food substances.

Here are the characteristics and properties of enzymes

• Enzymes work rapidly

The action and speed of the enzyme are generally expressed as its turnover number, and the turnover number represents the substrate molecule’s number which one mole of enzyme turns into the products per minute.

Catalase is a well-known fastest enzyme that is found in hydrogen peroxide. In hydrogen peroxide, catalase catalyzes its decomposition into oxygen and water. Catalase has the fastest turnover number of 6 million.

• Enzymes can word in either direction.

The metabolic reactions are reversible. The direction of these reversible reactions to proceed dramatically depends on the relative amount of products formed and reacting substrates.

An enzyme that catalyzes the product formation from substrate causes the products to be split into component substrates whenever the product is in excess to maintain an equilibrium.

• Enzymes are sensitive to pH modifications.

Enzymes generally operate at particular pH ranges. And modifications in the pH can adversely affect their efficiency and action.

• Enzymes are not altered or destroyed by the reactions they catalyze

Enzymes can easily be reused as they are not destroyed but the reactions they catalyze. But on the contrary, they cannot be used indefinitely as they are unstable and can be inactivated by acids, alkaline substances, and heat.

• Enzymes are inactivated by excessive heat.

As enzymes are proteins, they are averse to excessive heat because they get denatured whenever they are exposed to high temperatures.

• Enzymes are specific in their actions.

Enzymes are more particular in the reactions they catalyze as compared to inorganic catalysts. However, the catalytic specific degree varies from one enzyme to another.

Most of the intracellular enzymes function on the specific substrate, while several digestive enzymes function on a comparatively extensive substrate range that is associated.

For example, catalase would only split the hydrogen peroxide, but the enzymes like pancreatic lipase are less specific and digest different fats.

Bottom Line!

Enzymes are proteins that speed up reactions and have specific characteristics and properties. Enzymes are highly particular for a specific substrate and adhere to the characteristics mentioned above.

 

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An amino acid is an organic molecules group that comprises an acidic carboxyl group (-COOH), a basic amino group (-NH2) and an organic R group unique to each amino acid.

What are amino acids?

Amino acid is referred to as a building block of proteins that play a critical role in the body. These are necessary for several vital processes like hormones and neurotransmitter synthesis, and protein building.

The term “amino acid” is a short form of alpha-amino carboxylic acid. Here each molecule comprises a central carbon atom (C) known as the α-carbon to which both the carboxyl group and an amino group are attached.

However, the remaining α-carbon atom bonds are usually satisfied by the R group and a Hydrogen atom (H). The formula of a general amino acid is represented as:

Each amino acid differs from the other in a specific chemical structure of the R group.

Essential amino acids

Amino acids are basically organic compounds that are composed of carbon, nitrogen, oxygen, and hydrogen along with a variable side chain group. The human body generally require around 20 diverse amino acids to function and grow appropriately.

Although all 20 amino acids are essential, nine of them are considered imperative. This includes

• Isoleucine
• Histidine
• Lysine
• Leucine
• Phenylalanine
• Methionine
• Valine
• Threonine
• Tryptophan

The essential amino acid roles in the body

• Threonine

It is an essential part of structural proteins like elastin and collagen that provide a structure to the skin and linked tissues and facilitate blood clots formation while preventing bleeding. It also helps in boosting immune function and fat metabolism.

• Phenylalanine

It is referred to as a precursor for brain chemicals, including epinephrine, norepinephrine, and dopamine. These chemicals are the known brain messengers that help in structure formation and protein functioning, enzymes, and other amino acids synthesis.

• Valine

Valine facilitates tissue regeneration, muscle growth and is needed for energy production.

• Leucine

Leucine facilitates muscle repair, protein synthesis, wound healing, muscle growth, blood sugar levels regulation, and growth hormones synthesis.

• Tryptophan

It helps in maintaining an appropriate nitrogen balance. It is also well known for facilitating serotonin synthesis, which regulates appetite, sleep, and mood.

• Methionine

It helps in metabolism, growth, the body’s detoxification, and the absorption of essential minerals like selenium and zinc.

• Histidine

It is involved in histamine synthesis, a neurotransmitter that helps in immune functioning, sleep, digestion, and IQ regulation. It also helps to maintain the myelin sheath, which is a protective barrier surrounding the nerve cells.

• Lysine

It helps in protein synthesis, hormones, enzymes, energy production, calcium absorption, and immune functioning.

• Isoleucine

It helps in boosting immune functioning, hemoglobin synthesis, energy regulation, and muscle metabolism.

However, the best sources of essential amino acids include animal products like eggs, meat, and poultry.

Potential health benefits of supplementing the body with essential amino acids

While the essential amino acids are found in ample food items, taking them in concentrated dosages, and supplemental form links its effects to several health benefits. This includes

• Improves sleep and mood
• Boosts exercise performance
• Prevents muscle loss
• Promotes weight loss