biology quiz 12.19.25

Why do cells need to divide?

Most cells in your body divide regularly to allow for growth, repair, and replacement of cells.

What problems would occur if cells didn't divide?

The instructions in the DNA would be overloaded, and the cell would not be able to exchange materials quickly enough.

How do cells solve these problems?

Cells divide to maintain a large surface area-to-volume ratio.

Why must all living things reproduce?

All living things must reproduce to ensure the survival of the species.

How do unicellular organisms reproduce?

Most unicellular organisms reproduce through asexual reproduction, in which one cell divides into two.

How do multicellular organisms reproduce?

Multicellular organisms can reproduce asexually, but many also reproduce sexually.

What is sexual reproduction?

Sexual reproduction involves the joining of two reproductive cells from two parents.

Why is sexual reproduction beneficial?

It mixes genetic information, which can improve a species' survival.

Where is genetic material found in eukaryotic cells?

In the nucleus.

What is chromatin?

DNA is arranged in long strands called chromatin during most of the cell's life.

What happens to chromatin when a cell divides?

It is wrapped up to prevent tangling and breaking.

How is DNA organized into chromosomes?

DNA is wrapped around proteins called histones and organized into X-shaped chromosomes.

How is DNA organized in prokaryotic cells?

Prokaryotic cells have one circular piece of DNA that does not organize into chromosomes.

How do prokaryotic cells divide?

By making a copy of their DNA and then pinching the cell in half, a process called binary fission.

Where is most of the cell cycle spent?

In interphase, when the cell is growing.

What are the three parts of interphase?

G₁, S, and G₂.

What happens during G₁ phase?

The cell grows and duplicates organelles.

What happens during S phase?

The cell copies its chromosomes.

What happens during G₂ phase?

The cell grows and checks duplicated chromosomes.

Why is it important for chromosomes to be copied?

So each new cell has the same genetic information as the original cell.

What happens during prophase?

Chromatin coils into chromosomes, the nuclear envelope disappears, centrioles move to the poles, and spindle fibers form.

What happens during metaphase?

Chromosomes attach by their centromeres to spindle fibers and line up along the middle of the cell.

What happens during anaphase?

Centromeres split and sister chromatids are pulled to opposite ends of the cell.

What happens during telophase?

Chromatids reach opposite poles, nuclear envelopes form around chromosomes, and spindle fibers disappear.

What is cytokinesis?

It divides the cytoplasm; in animal cells, the cell membrane pinches together, while in plant cells, a cell plate forms.

What is the result of mitosis?

It produces two identical daughter cells that are identical to the parent cell.

Why does the cell cycle need to be controlled?

To allow growth and healing without overpopulating space or exhausting nutrients.

How is the cell cycle regulated from the outside?

External regulatory proteins receive signals on the cell membrane that can speed up or slow down the cell cycle.

How is the cell cycle regulated from the inside?

Proteins called cyclins regulate the timing of the cell cycle from within the cell.

What happens at checkpoints in the cell cycle?

Cyclins join with proteins to form a complex called Cdk; if the cell clears the checkpoint, cyclins degrade.

What happens when the cell cycle is disrupted?

Cells that fail to stop at checkpoints divide too rapidly, forming a mass of abnormal cells called a tumor.

What causes cancer?

When DNA is damaged and does not correctly code for proteins that regulate the cell cycle.

How is cancer treated?

Through surgery, radiation, and chemotherapy.

What is metastasis?

When cancer cells spread to other parts of the body.