organism regulation

why do cells divide?

allow multicellular organisms to grow. reproduce and create identical copies of themselves and repair damaged or dead cells in multicellular organisms.

what is binary fission

an asexual reproduction process in prokaryotes and single-celled eukaryotes, where bacterial cells replicate their DNA, form a wall, and divide into two daughter cells.

mitosis is

The process by which a cell replicates its chromosomes and then segregates them, producing two identical nuclei in preparation for cell division.

what are the phases of mitosis

prophase, metaphase, anaphase, telophase, and cytokinesis

interphase

refer to event between mitosis. (when the cell is not dividing) the cell replicates the nuclear material ready

early prophase of mitosis is when

mitotic spindle starts to form, the chromosomes start to condense, and the nucleolus disappears.

late prophase of mitosis

the mitotic spindle begins to capture and organize the chromosomes.

Metaphase is when

some spindle fibers attach to and organize the chromosome on the equator of the cell (middle). some spindle fibers span the cell.

Anaphase is when

Spindle fiber attached to chromatids shorten, pulling the chromatids apart.

telophase is when

a nuclear membrane forms around each set of chromosomes to separate the nuclear DNA from the cytoplasm.

cytokinesis is the

physical process of cell division, which divides the cytoplasm of a parental cell into two daughter cells.

what occurs in G1 phase

cell growth, protein production and some organelles

what occurs during s-phase

growth and DNA replication in perpetration for nuclear division

G1 phase interphase

growth and preparation for mitosis. it stores energy and all of the other organelles have to be replicated.

G0 of interphase

when a cell does not need to undergo mitosis it may go into G0 phase.

CELL REGULATION:

our cell has a control system to check whether all the important processes have been performed correctly before moving into the next phase.

3 checkpoints: is a critical regulatory point in the cell cycle.

• G1 checkpoint

• G2 checkpoint

• M checkpoint

G1 checkpoint:

pass the checkpoint if:

• cell size is large enough

• sufficient nutrients are available

• signals from other cells have been received.

G2 checkpoint:

pass the checkpoint if:

• cell size i large enough

• replication of chromosomes has been successfully completed

• protein required for mitosis have been synthesized.

Metaphase checkpoint:

pass the checkpoint if:

• all chromosomes are attacked to the mitotic spindle.

APOPTOSIS

Programmed cell death that eliminates faulty or infected cells through a controlled sequence of events like cell shrinking, blebbing, and removal by macrophages.

APOPTOSIS Cell goes through a sequence of events:

1. Cell volume decreases and start shrinking.

APOPTOSIS Cell goes through a sequence of events:

2. Cell develops blebs (bubbles) at the membranes.

APOPTOSIS Cell goes through a sequence of events:

3. Nucleus gets fragmented.

APOPTOSIS Cell goes through a sequence of events:

4. Cell debris (or broken cell parts) removed by macrophages

Mutagen:

is a substance or agent that courses DNA impairment that result in the alternation of DNA sequence.

e.g. bacteria, virous, and UV

carcinogens:

Carcinogens are mutations that cause cancer, as damaged cells fail to meet checkpoint requirements, causing rapid cell division and tumor formation.

Tumor:

are large masses of cancerous cell. Cancerous cells evade the cell cycle checkpoint and divide rapidly coursing tumor.

Two types of genes control the cell cycle:

proto-oncogenes: which initiate cell division.

Two types of genes control the cell cycle:

tumor-suppressor genes: which prevent division in response to DNA or cell damage.

Two types of genes control the cell cycle:

proto-oncogenes and tumor-suppressor genes.

oncogenes:

Mutations in genes regulating cell cycle can lead to negative consequences, such as oncogenes causing uncontrollable cell division and tumor-suppressor genes initiating most human cancers.

STEM CELLS:

are undifferentiated cells found in multicellular organisms. they are characterized by the properties of self-renewal and potency. they are unspecialized cells that can divide repeatedly while remaining unspecialized.

the two properties of stem cells are:

self-renewal and potency.

self-renewal:

have the ability to divide many times while maintaining an unspecialized states.

potency:

the ability to differentiate (transom) into specialized cells, there are different potency that depends on the type of stem cell.

EMBRYONIC STEM CELS:

are derived from the inner mass of blastocyst. cells derived from the inner cell mass are pluripotent meaning they can become any cell of the body with the exception of placental cells.

Totipotent stem cells, (high or most potency)

found in zygotes, can differentiate into any cell in an organism.

Pluripotent stem cells: (high potency)

can divide into most, or all, cell types in an organism, but cannot develop into an entire organism on their own.their ability to form all three of the basic body layers (ectoderm/endoderm/mesoderm) and even germ cells.

Adult stem cells: Multipotent least potency

Adult stem cells are undifferentiated cells found in several types of tissues like the brain and bones, that can differentiate into a small number of cell types usually related to the tissues or organs, as they are multipotent

Germ layers:

After the blastocyst implants, it forms a 'Gastrula', which undergoes changes to form germ layers, where stem cells differentiate into specific types.