Biology Chapter 2.3 - The Cell Cycle

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Questions and Answers

What is the 'cell cycle'?

A regulated process in which cells divide to produce two genetically identical daughter cells for growth, repair, and asexual reproduction.

Why does mitosis not provide any genetic variation?

Because all the cells produced by mitosis are genetically identical.

What are the three stages of the cell cycle?

Interphase, mitosis, cytokinesis.

What occurs during the interphase part of the cell cycle?

The cell grows, DNA replicates, and the cell is prepared for cell division. Signup and view all the answers

What occurs during the mitosis part of the cell cycle?

The division of the nucleus. Signup and view all the answers

What occurs during the cytokinesis part of the cell cycle?

It is the division of the cytoplasm, which produces two daughter cells. Signup and view all the answers

What are the four stages of mitosis?

Prophase, metaphase, anaphase, telophase. Signup and view all the answers

What cycle does the cell go through when it divides?

The cell cycle. Signup and view all the answers

How long could it potentially take for a cell to divide? Explain why.

Depending on the type of cell and the organism, it can take between 24 hours to a few years for the cycle to occur. Signup and view all the answers

What are the three phases which interphase consists of?

G1 (gap 1), S (synthesis), and G2 (gap 2). Signup and view all the answers

What occurs during the G1 phase of the cell cycle?

<ol> <li>The cell grows and develops, 2) normal processes occur, 3) cell makes proteins needed for cell division, 4) ATP is produced for the energy-intensive process of cell division.</li> </ol> Signup and view all the answers

What occurs during the S phase of the cell cycle?

<ol> <li>The genetic material is copied, 2) chromosomes replicate and become double stranded chromatids.</li> </ol> Signup and view all the answers

What occurs during the G2 phase of the cell cycle?

<ol> <li>More cytoplasm is produced as the cell grows further ready for division, 2) the organelles duplicate, and 3) the DNA is checked for errors.</li> </ol> Signup and view all the answers

What controls the timing of each stage at which the cell cycle occurs?

Different cyclins. Signup and view all the answers

What do cyclins bind to?

Enzymes called cyclin-dependent kinases, which then become active. Signup and view all the answers

What is the process which occurs after cyclins bind to cyclin-dependent kinases?

<ol> <li>The cyclin-dependent kinases become active, 2) they cause phosphate groups to attach to proteins, 3) these proteins then become active and carry out tasks specific to one of the phases of the cell cycle.</li> </ol> Signup and view all the answers

What are the four main types of cyclins in human cells?

Cyclin A, cyclin B, cyclin D, and cyclin E. Signup and view all the answers

What must the four main types of cyclin in human cells reach, in order to progress to the next stage of the human cycle?

A threshold concentration. Signup and view all the answers

How does cytokinesis occur in animal cells?

A contractile ring of fibers tightens around the center of the cell; they continue to contract until the two cells have been separated. Signup and view all the answers

How does cytokinesis occur in plant cells?

A cell plate is formed across the center of the cell; a middle lamella forms first and the cellulose is deposited here by both of the cells on either side to form the cell walls. Signup and view all the answers

What are the number of places at which control in the cell cycle happens?

Checkpoints. Signup and view all the answers

What do the complexes from when the cyclins build up and bind to cyclin-dependent kinases bring about?

The next stage in the cell cycle. Signup and view all the answers

What must all of the DNA in a cell carry out before the cell divides?

All of the DNA in a cell must duplicate. Signup and view all the answers

Why must all of the DNA in a cell duplicate before the cell divides?

This is so one copy of the DNA can go into each of the daughter cells. Signup and view all the answers

Why must the DNA become more organized and easier to move around the cell for cell division?

Because initially, the DNA is normally in a quite disorganized state called chromatin. Signup and view all the answers

What is chromatin organized into?

Structures called chromosomes. Signup and view all the answers

What is the process in which chromosomes are formed?

<ol> <li>The DNA molecule winds around proteins called histones to form nucleosomes, 2) they then supercoil.</li> </ol> Signup and view all the answers

Study Notes

The Cell Cycle

The cell cycle is a regulated process allowing cells to divide and produce two genetically identical daughter cells for growth, repair, and asexual reproduction.
Mitosis does not provide genetic variation because it generates genetically identical cells.
The cell cycle consists of three main stages: interphase, mitosis, and cytokinesis.

Interphase

Interphase involves cell growth, DNA replication, and preparation for cell division. Chromosomes condense to form chromatin.
Interphase is further divided into three phases:
- G1 Phase: The cell grows, develops, performs normal processes, synthesizes proteins for division, and produces ATP.
- S Phase: Genetic material is copied; chromosomes replicate into double-stranded chromatids.
- G2 Phase: The cell produces more cytoplasm, duplicates organelles, and checks DNA for errors.

Mitosis

Mitosis is the phase where the nucleus divides, resulting in daughter cells each with identical genetic material.
There are four stages in mitosis: prophase, metaphase, anaphase, and telophase.

Cytokinesis

Cytokinesis involves dividing the cytoplasm to produce two separate daughter cells.
In animal cells, a contractile ring tightens to separate the cells.
In plant cells, a cell plate forms across the center, with cellulose deposited to create new cell walls.

Control of the Cell Cycle

Timing of the cell cycle stages is regulated by proteins called cyclins.
Cyclins bind to cyclin-dependent kinases (CDKs), activating them to facilitate progress through the cell cycle.
Four major types of cyclins in human cells are cyclin A, B, D, and E, which must reach a threshold concentration to transition between stages.

Checkpoints and DNA Replication

Checkpoints throughout the cell cycle act as control mechanisms, ensuring proper progression.
Before division, all DNA must duplicate to ensure each daughter cell receives a complete copy.
The DNA must organize from a disorganized state, known as chromatin, into structures called chromosomes for effective movement during cell division.

Chromatin and Chromosomes

Chromatin consists of DNA wound around proteins called histones, forming nucleosomes, which then supercoil to create chromosomes.

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Explore the essential concepts of the cell cycle through this flashcard quiz. Test your understanding of cell division, mitosis, and the stages involved in cellular processes. Perfect for reinforcing your knowledge in biology.