Information

Purpose of intensive protein synthesis in G1 phase of mitosis

Purpose of intensive protein synthesis in G1 phase of mitosis


We are searching data for your request:

Forums and discussions:
Manuals and reference books:
Data from registers:
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

What is the purpose of intensive protein synthesis in G1 phase of mitosis, and what purposes do these synthesized proteins serve? Why are lipids and carbohydrates not synthesized intensively as well?


The G1 phase of eukaryotic cell cycle is part of interphase, which is when the cell is replicating its DNA ready for division. To understand the need for intense protein synthesis, we first need to understand how DNA is organised during mitosis.

Before DNA is condensed into chromosomes ready for nuclear division it is in the form of chromatin, a long fiber-like structure inside the nucleus. In order to condense into chromosomes, this chromatin must undergo a process of coiling and folding in order to create the chromosome 'X' structure we are familiar with. A major part of this DNA 'miniaturization' is the folding of the double helix around proteins called Histones - this creates new structures called nucleosomes.

In order to fully condense the roughly 3 meters of DNA in the average human cell down to a singular chromosome, millions upon millions of these Histone proteins are required.

And that answers your question; intense protein synthesis during the G1 phase is required in order to produce the extremely large amount of Histone proteins that are needed for packaging DNA into chromosomes ready for cellular division.

As for carbohydrates, these are constantly being processed by the body in order for the production of ATP for use as energy. The use of said energy for mitosis is a just another constantly required use of ATP within the body. Therefore there isn't any noticeable increase in carbohydrate processing/production, as it is happening regardless of the cell's stage in its cycle.

-See the image below (from shmoop.com) that explains the process of getting DNA into a chromosome.


Purpose of intensive protein synthesis in G1 phase of mitosis - Biology

Cells must grow and duplicate their internal structures during interphase before they can divide during mitosis.

Learning Objectives

Describe the events that occur during Interphase

Key Takeaways

Key Points

  • There are three stages of interphase: G1 (first gap), S (synthesis of new DNA ), and G2 (second gap).
  • Cells spend most of their lives in interphase, specifically in the S phase where genetic material must be copied.
  • The cell grows and carries out biochemical functions, such as protein synthesis, in the G1 phase.
  • During the S phase, DNA is duplicated into two sister chromatids, and centrosomes, which give rise to the mitotic spindle, are also replicated.
  • In the G2 phase, energy is replenished, new proteins are synthesized, the cytoskeleton is dismantled, and additional growth occurs.

Key Terms

  • interphase: the stage in the life cycle of a cell where the cell grows and DNA is replicated
  • sister chromatid: either of the two identical strands of a chromosome (DNA material) that separate during mitosis
  • mitotic spindle: the apparatus that orchestrates the movement of chromosomes during mitosis

Interphase

During interphase, the cell undergoes normal growth processes while also preparing for cell division. In order for a cell to move from interphase into the mitotic phase, many internal and external conditions must be met. The three stages of interphase are called G1, S, and G2 .

The Stages of Interphase and the Cell Cycle: The cell cycle consists of interphase and the mitotic phase. During interphase, the cell grows and the nuclear DNA is duplicated. Interphase is followed by the mitotic phase. During the mitotic phase, the duplicated chromosomes are segregated and distributed into daughter nuclei. The cytoplasm is usually divided as well, resulting in two daughter cells.

G1 Phase (First Gap)

The first stage of interphase is called the G1 phase (first gap) because, from a microscopic aspect, little change is visible. However, during the G1 stage, the cell is quite active at the biochemical level. The cell grows and accumulates the building blocks of chromosomal DNA and the associated proteins as well as sufficient energy reserves to complete the task of replicating each chromosome in the nucleus.

S Phase (Synthesis of DNA)

The synthesis phase of interphase takes the longest because of the complexity of the genetic material being duplicated. Throughout interphase, nuclear DNA remains in a semi-condensed chromatin configuration. In the S phase, DNA replication results in the formation of identical pairs of DNA molecules, sister chromatids, that are firmly attached to the centromeric region. The centrosome is duplicated during the S phase. The two centrosomes will give rise to the mitotic spindle, the apparatus that orchestrates the movement of chromosomes during mitosis. At the center of each animal cell, the centrosomes of animal cells are associated with a pair of rod-like objects, the centrioles, which are at right angles to each other. Centrioles help organize cell division. Centrioles are not present in the centrosomes of other eukaryotic species, such as plants and most fungi.

G2 Phase (Second Gap)

In the G2 phase, the cell replenishes its energy stores and synthesizes proteins necessary for chromosome manipulation. Some cell organelles are duplicated, and the cytoskeleton is dismantled to provide resources for the mitotic phase. There may be additional cell growth during G2. The final preparations for the mitotic phase must be completed before the cell is able to enter the first stage of mitosis.


The Genome

Chromosome Dynamics During the Cell Cycle

The G1, S, and G2 phases are often referred to as interphase, and the M phase is the mitotic phase. During interphase, chromosomes are replicated, and during mitosis they become highly condensed and then are separated and distributed to the two daughter nuclei. The highly condensed chromosomes in a dividing cell are known as mitotic chromosomes. During the portion of the cell cycle when the cell is not dividing, the chromosomes are extended and much of their chromatin exists as long, thin tangled threads in the nucleus ( Fig. 5.2 ).

Fig. 5.2 . The stages of mitosis in an animal cell, starting with interphase in which chromosomes are extended and uncoiled into chromatin. Prophase then causes chromosomes to coil and condense, while centrioles divide and move apart. In prometaphase, chromosomes are double structures, and centrioles are on opposite poles of the cell while spindle fibers form. Centromeres then align along the metaphase plate during metaphase. The aligned centromeres then split, and individual chromatids migrate to opposite poles of the cell in anaphase. Lastly, daughter chromosomes arrive at the poles in telophase, and the cells separate through cytokinesis.

As the cell enters M phase, the nuclear membrane is disassembled, and sister chromatids condense into compact structures that remain bound together. The centromeres of the condensed sister chromatids bind microtubules, which form the mitotic spindle. The spindle organizes the sister chromatid pair at the center of the cell, which is known as the kinetochore. Subsequently, each sister chromatid moves to the opposite pole on the spindle. The set of chromosomes at each pole become encapsulated by a nuclear membrane, and the cell divides into two daughter cells. Therefore, the chromosome structure is a dynamic structure that can be condensed and extended throughout the cell cycle.

Condensed human mitotic chromosomes have been studied under the microscope for many years. The display of the chromosome set of an individual, lined up from the largest to the smallest, is called a karyotype ( Fig. 5.3 ). Therefore, a karyotype is referred to as the microscope images of metaphase chromosomes when the sister chromatids are maximally condensed but have not yet separated.

Fig. 5.3 . Karyotypes of human chromosomes. This is a representation of a male karyotype visualized with Giemsa dye.


Polypeptides and Proteins

When speaking of protein synthesis it is important to make a distinction between polypeptide chains and proteins. All proteins are polypeptides but not all polypeptides are proteins however, both proteins and polypeptides are composed of amino acid monomers.

The difference between a protein and a polypeptide is the form. Smaller chains of amino acids – usually less than forty – remain as single-chain strands and are called polypeptides. Larger chains must package themselves more tightly they fold into fixed structures – secondary, tertiary, and quaternary. When a polypeptide chain folds, it is called a protein.

Polypeptide chains are formed during the translation process of protein synthesis. These polypeptides may or may not fold into proteins at a later stage. However, the term ‘protein synthesis’ is used even in the scientific community and is not incorrect.

Understanding protein synthesis is easy when we imagine our DNA as a recipe book. This book lists the instructions that show a cell how to make every tiny part of every system, organ, and tissue within our bodies. All of these individual parts are polypeptides. From the keratin in your hair and fingernails to the hormones that run through your bloodstream, polypeptides and proteins are the foundation stones of every structure. Our DNA does not code for lipids or carbohydrates – it only codes for polypeptides.

The enzyme RNA polymerase opens the DNA recipe book that sits inside the cell nucleus. It uses certain pieces of code as bookmarks to find the right page. This recipe book is written in a foreign language – mRNA copies what is written without understanding it. The recipes are translated into a language that other molecules can decipher at a later stage. The translators are ribosomes and tRNA. They read the recipe and can collect the right ingredients and, in the correct order, make the finished polypeptide product.


Cytokinesis is the second part of the mitotic phase during which cell division is completed by the physical separation of the cytoplasmic components into two daughter cells. Although the stages of mitosis are similar for most eukaryotes, the process of cytokinesis is quite different for eukaryotes that have cell walls, such as plant cells.

In cells such as animal cells that lack cell walls, cytokinesis begins following the onset of anaphase. A contractile ring composed of actin filaments forms just inside the plasma membrane at the former metaphase plate. The actin filaments pull the equator of the cell inward, forming a fissure. This fissure, or “crack,” is called the cleavage furrow. The furrow deepens as the actin ring contracts, and eventually the membrane and cell are cleaved in two (Figure 6.5).

In plant cells, a cleavage furrow is not possible because of the rigid cell walls surrounding the plasma membrane. A new cell wall must form between the daughter cells. During interphase, the Golgi apparatus accumulates enzymes, structural proteins, and glucose molecules prior to breaking up into vesicles and dispersing throughout the dividing cell. During telophase, these Golgi vesicles move on microtubules to collect at the metaphase plate. There, the vesicles fuse from the center toward the cell walls this structure is called a cell plate. As more vesicles fuse, the cell plate enlarges until it merges with the cell wall at the periphery of the cell. Enzymes use the glucose that has accumulated between the membrane layers to build a new cell wall of cellulose. The Golgi membranes become the plasma membrane on either side of the new cell wall (Figure 6.5).

Figure 6.5 In part (a), a cleavage furrow forms at the former metaphase plate in the animal cell. The plasma membrane is drawn in by a ring of actin fibers contracting just inside the membrane. The cleavage furrow deepens until the cells are pinched in two. In part (b), Golgi vesicles coalesce at the former metaphase plate in a plant cell. The vesicles fuse and form the cell plate. The cell plate grows from the center toward the cell walls. New cell walls are made from the vesicle contents.


Purpose of intensive protein synthesis in G1 phase of mitosis - Biology

** Study Guide 2** This is the Guide given to all of the Biology Classes.
All questions from all tests and quizzes fair game. You need to read, study, and talk to each other.
Get in study groups! If there is issue with a question, LOOK IT UP!

Cellular Respiration
1. What is the equation for aerobic cellular respiration?
2. List the individual processes of cellular respiration and identify where each takes place.
3. How is energy released from ATP? How many phosphates does ATP have? ADP?
4. What is the difference between aerobic and anaerobic respiration?
5. Which is used for a longer period of time, aerobic or anaerobic respiration? Why?
DNA Structure and DNA Replication
1. Describe the structure of DNA and its nitrogen bases.
2. List the three parts of a nucleotide.
3. Why can only a purine and pyrimidine be paired together?
4. How are two strands of DNA held together?
5. What are chromosomes made of?
6. Compare DNA and RNA.
7. Why is DNA extraction important?
8. Describe the main steps of DNA replication.
9. When and where does DNA replication take place?
10. Who was the woman who took the first picture of DNA?
11. Who proposed the DNA double helix in 1953?
Cell Cycle and Mitosis
1. Draw and label the major parts of the cell cycle.
2. What is the difference between G1, S phase and G2 in Interphase?
3. What type of cell goes through mitosis? Where does mitosis occur?
4. When and why do cells divide? Why is cell division through out an organism’s life beneficial?
5. Explain the importance of spindle fibers in cell division.
6. What is cancer? Why and how is it harmful?
7. How many chromosomes are in a haploid cell and a diploid cell?
8. What is the difference between a chromatid, chromosome and chromatin?
9. What is a telomere and why are they important?
Protein Synthesis
1. List the major steps of protein synthesis.
2. How are transcription and translation different?
3. What is the importance of RNA processing?
4. What codes for an amino acid? What is the monomer of a protein? How many nitrogen bases are in a codon? How many codons does a ribosome read at a time?
5. How are genes expressed?
6. What is the difference between a point mutation and frameshift mutation?
Vocabulary for Scientific inquiry
hypothesis ,prediction, probability, scientific model, variables, independent variable, dependent variable, sample size, trial,
data analysis, error in data collection, prediction, hypothesis, scientific evidence
Vocabulary for content
Mitochondria, ATP, ADP, phosphate, pyruvate, lactic acid, glycolysis, fermentation, Krebs cycle, electron transport chain, aerobic, anaerobic, carbon dioxide, glucose
nucleus, chromosome, nucleolus, centriole, DNA, double helix, hydrogen bond, deoxyribose sugar, phosphate, nucleotide, adenine, guanine, cytosine, thymine, DNA polymerase, helicase, replication fork/bubble, complimentary and anti parallel strand
gene, chromosome, chromatin, chromatid
mitosis, interphase (G1, Sphase, G2), prophase, metaphase, anaphase, telophase, cytokinesis, centriole, spindle fibers, centromere
gene, promoter, terminator
RNA polymerase, uracil, adenine, guanine, thymine, cytosine, RNA, mRNA, rRNA, tRNA, codon, start codon, stop codon, intron, exon, ribosome, amino acid, peptide bond, polypeptide
Performance objectives, can you …
Explain the system of ATP production (required: cellular respiration).
Describe the system of DNA replication.
Describe how mitosis and the cell cycle maintain genetic continuity.
Describe the purpose and process of protein synthesis.
Outline the relationships among nucleic acids, genes, chromosomes (and karyotype in viruses, prokaryotes, and) eukaryotes.
Explain how mutations lead to genetic variation, cancer, and genetic disorders.
Honors students are expected to go beyond the level 3 POs described above and demonstrate level 4s in order to achieve an A grade.


Duration of the Cell Cycle

The time required to complete certain events varies greatly from one cell type to another, even in the same organism. A typical human cell might takes 24 hours to divide. Conversely, mammalian cells that line the intestine can complete the cycle in every 9-10 hours.

The G1 phase will continue for approximately 11 hours, S phase will continue for 8 hours, G2 phase for nearly 4 hours. The complete process of mitotic cell division (M phase) is nearly 1-1.5 hours. Prophase is the longest among six phases of mitosis i.e., 30-60 minutes. While metaphase is 2-10 minutes, anaphase 2-3 minutes and telophase is 3-12 minutes long. Some cells may divide faster than human cells whereas some cells may take more time to complete an entire cell cycle. For example “budding yeast” will complete the entire cell cycle (4 stages of the cell cycle) in about 90 minutes.


Interphase

The interphase portion of the cell cycle is relatively long compared to mitosis. Interphase consists of three stages: first gap (G1), synthesis (S) and second gap (G2). The cell replicates DNA only in the S phase. Before the cell can transition from G1 to S, it must clear the G1 checkpoint. The cell will only enter the S phase if the DNA is undamaged and the cell has grown sufficiently in the G1 stage. The protein p16 normally represses the beginning of the S phase. When a cell passes through the checkpoint, it overcomes p16 repression by building other proteins that allow the S phase to begin.


Difference Between G1 Phase and G2 Phase

Division or reproduction is a basic need and function of a cell. The division of cell is of two types, mitosis, and meiosis. This division further has sub-steps or stages, one of these steps is interphase in which G1 phase and G2 phase are also included. G1 phase is also known as Gap 1 phase. It is the first sub-phase in the interphase of the cell cycle that is seen in eukaryotic cell division. In this phase, messenger RNA (mRNA) and proteins are synthesized in the cell for the preparation of mitosis. G1 phase is the longest phase of the cell cycle, whereas G2 phase or Gap 2 phase is the second sub-phase or stage of interphase in the cell cycle that further proceeds to mitosis. G2 phase follows the proper completion of S phase of the cell cycle during which the DNA of a cell is replicated. G2 phase is shorter as compared to G1 phase, and it further leads to prophase of mitosis.

Comparison Chart

G1 PhaseG2 Phase
Interphase StepG1 phase is also known as Gap 1 phase, and it is the first sub-step in interphase of the cell cycle.G2 phase is also known as Gap 2 phase, and it is the second sub-step in interphase of the cell cycle.
Time TakenG1 phase is a long process.G2 phase is a shorter process as compared to G1 phase.
Leads ToG1 phase leads to S-phase.G2 phase indicates the successive completion of S phase.
OrganellesIn G1 phase, there is an increase in the size of the cell but the organelle does not increase in number.In G2 phase cell size increases in which nucleus also grow, almost all the cell organelles increase in number.
Main FunctionIn G1 phase, synthesis of useful RNAs and proteins (histone) that are required for the synthesis of DNA and another process in the cell occur here.In G2 phase, RNAs and proteins that are required for spindle formation are synthesized.

What is G1 Phase?

G1 phase is also known as Gap 1 phase. It is the first sub-step in interphase of the cell cycle. It is a long process as compared to G2 phase. In G1 phase, there is an increase in the size of the cell but the organelle does not increase in number. Synthesis of useful RNAs and proteins (histone) that are required for the synthesis of DNA and another process in the cell occur in this state. G1 phase next leaders to the S phase. The average time for the G1 phase is up to 18 hours that may vary from cell to cell. Moreover, G1 phase has many factors upon which it depends. These factors are also called growth factors such as the environment of cell, temperature, supply of nutrients, proteins and amino acids, etc. The optimum temperature for proper growth is 98.6 degrees F (37 degrees C). Regulation of G1 phase is controlled by cell cycle control system that regulates the timing and increases the coordination.

What is G2 Phase?

G2 phase is also known as Gap 2 phase. It is the second sub-step in interphase of the cell cycle. It is a shorter process as compared to G1 phase. In G2 phase, there is rapid cell growth and protein synthesis. This phase is not the necessary part of the cell cycle, but it allows the cell to be fully prepared for mitosis. G2 phase indicates the successive completion of S phase, in which DNA replication takes place. Cell size increases in which nucleus also grow, almost all the cell organelles increases in number. RNAs and proteins that are required for spindle formation are synthesized in this phase. G2 phase ends as prophase (the first step in mitosis), and it is regulated by the cell itself as it all depend upon genetic information of the cell.

G1 Phase vs. G2 Phase

  • G1 phase is also known as Gap 1 phase, and it is the first sub-step in interphase of the cell cycle, whereas G2 phase is also known as Gap 2 phase and it is the second sub-step in interphase of the cell
  • G1 phase is a long process whereas, G2 phase is a shorter process as compared to G1 phase.
  • G1 phase leads to S-phase, whereas G2 phase indicates the successive completion of S phase
  • In G1 phase, there is an increase in the size of the cell but the organelle does not increase in number, on the other hand, in G2 phase cell size increases in which nucleus also grow, almost all the cell organelles increase in number.
  • In G1 phase, synthesis of useful RNAs and proteins (histone) that are required for the synthesis of DNA and another process in the cell occur here whereas, in G2 phase, RNAs and proteins that are required for spindle formation are synthesized.

Comparison Video

Janet White

Janet White is a writer and blogger for Difference Wiki since 2015. She has a master's degree in science and medical journalism from Boston University. Apart from work, she enjoys exercising, reading, and spending time with her friends and family. Connect with her on Twitter @Janet__White


Purpose of intensive protein synthesis in G1 phase of mitosis - Biology

The cell cycle has two major phases: interphase (G0, G1, S, G2) and the mitotic phase (M).

The cell cycle is an ordered series of events involving cell growth and cell division that produces two new daughter cells. Cells undergoing cell division proceed through a series of precisely timed and carefully regulated stages of growth, DNA replication, and division that produces two identical (clone) cells.

During interphase, the cell grows, and DNA replicates. In the mitotic phase, the replicated DNA and cytoplasmic contents separate, and the cell divides.

The Stages of Interphase and the Cell Cycle: The cell cycle consists of interphase and the mitotic phase. During interphase, the cell grows and the nuclear DNA is duplicated. Interphase is followed by the mitotic phase. During the mitotic phase, the duplicated chromosomes are segregated and distributed into daughter nuclei. The cytoplasm is usually divided as well, resulting in two daughter cells

G0 Phase

Not all cells undergo mitotic phase. Cells in the G0 phase are not actively preparing to divide. The cell is in a quiescent (inactive) stage that occurs when cells exit the cell cycle. Some cells enter G0 temporarily until an external signal triggers the onset of G 1 . No more DNA replication or cell division happens at this phase. The cells that never or rarely divide include mature cardiac muscle and nerve cells, and they remain in G0 permanently.

G1 Phase (First Gap)

The first stage of interphase is the G 1 phase (first gap), the growing phase. All cells undergo G 1 . Here, the cell is quite active at the biochemical level. The cell grows and accumulates the building blocks of chromosomal DNA and the associated proteins as well as sufficient energy reserves to complete the task of replicating each chromosome in the nucleus. Cells increase in size and produce organelles.

The cell has two choices at this point: to divide or not to divide. Between G 1 and S phase, the cell decides if it wants to grow.

Some cells that do not divide include bone cells and blood cells (they do not undergo mitosis). These cells do not go through S or G 2 . They stop at G 1 or G 0 .

S Phase (Synthesis of DNA)

The synthesis phase of interphase takes the longest because of the complexity of the duplicated genetic material. The S phase is where DNA replication occurs, and centrioles replicate. The two centrosomes give rise to the mitotic spindle, the apparatus that orchestrates the movement of chromosomes during mitosis. At the center of each animal cell, the centrosomes of animal cells associate with a pair of rod-like objects, the centrioles, which are at right angles to each other. Centrioles help organize cell division.

G2 Phase (Second Gap)

In the G2 phase, the cell replenishes its energy stores and synthesizes proteins necessary for chromosome manipulation. This phase is where the cell prepares for division. Here, the cell has double the DNA and again increase in size. Some cell organelles are duplicated, and the cytoskeleton is dismantled to provide resources for the mitotic phase. There may be additional cell growth during G2.

M Phase

Following the interphase, the cell enters the multistep mitotic phase, where cell nucleus divides, and the cell components split into two identical daughter cells.


Practice Questions


MCAT Official Prep (AAMC)

Biology Question Pack, Vol. 1 Passage 4 Question 22

Biology Question Pack, Vol 2. Question 41

Biology Question Pack, Vol 2. Passage 17 Question 111

Practice Exam 1 B/B Section Passage 8 Question 40

Practice Exam 4 B/B Section Question 59


Key Points

• There are three stages of interphase: G1 (first gap), S (synthesis of new DNA ), and G2 (second gap).

• Cells spend most of their lives in interphase, specifically in the S phase where genetic material must be copied.

• Some cells that do not divide or replicate stops at G1 or G0 G0 and G1 are sometimes the same thing.

• The cell grows and carries out biochemical functions, such as protein synthesis, in the G1 phase.

• During the S phase, DNA as well as centrioles are replicated.

• In the G2 phase, energy is replenished, new proteins are synthesized, and additional growth occurs.

• After interphase, mitosis follows.

interphase: the stage in the life cycle of a cell where the cell grows and DNA is replicated

centrosome: an organelle near the nucleus of a cell that contains the centrioles (in animal cells) and from which the spindle fibers develop in cell division.

mitotic spindle: the apparatus that orchestrates the movement of chromosomes during mitosis

quiescent: in a state or period of inactivity or dormancy

centrioles: the main centers that help in the formation of microtubule fiber


G0 Phase

G0 phase can occur right after mitosis and right before G1 phase, or a cell in G1 phase can enter G0 phase. Entry into G0 is known as leaving the cell cycle. Cells that mature to become highly specialized cells are said to differentiate. Cells exit the cell cycle and enter G0 in order to differentiate. Terminally differentiated cells are those that never enter the cell cycle again, meaning they stay in G0 and never divide. However, some cells can be triggered to leave G0 and re-enter G1, which allows them to divide again.


Watch the video: Ηλεκτρική νοσοκομειακή κλίνη για μονάδα εντατικής θεραπείας DIAS (May 2022).