Chapter 10- Cell division and growth

Centromere

-Area near the center where a pair of chromatids of a chromosome are attached -They are usually located near the middle of chromatids, although some lie near the ends

Internal regulators

-Cyclin proteins that are internal regulators will respond to events that are inside the cell Example: 1) several regulatory proteins make sure that a cell does not enter mitosis until all its chromosomes have been replicated. 2) prevents a cell from entering anaphase until all its chromosomes are attached to the mitotic spindle.

Cytokinesis

-Cytoplasm is split into two and two new daughter cells are formed. -After mitosis is complete, the cell contains two nuclei--> as a result cytoplasm needs to be split--> cytokinesis -Happens at the same time as telophase

Prophase

-First and longest phase of mitosis 1) Chromosomes become visible 2) Centrioles move to opposite sides of the nucleus 3) Spindle is formed and connects to chromosomes 4) Nuclear membrane/envelope breaks down

Telophase

-Fourth and final phase of mitosis -The previously condensed chromosomes will begin to unwind and nuclear envelope re-forms around each cluster of chromosomes. -Spindle breaks apart -They are two attached cells -But cell division is not complete -After mitosis is complete, the cell contains two nuclei.

Chromatids

-Half of a chromosome -At the start of cell division each chromosome consists of two identical "sister" chromatids. -Each pair of chromatids is attached at an area called the centromere

Controls on cell division

-If you look at cells dividing on a petri dish, they will divide until they cover the whole bottom of the dish. If we take out some cells from the middle of the dish--> they will divide until the plate is completely covered again, at which point division will stop............................. Similar to how the body heals: When the body is cut, broken or bruised, cells at the edge of the injury will divide rapidly until the injury is healed. -Cells will also divide until they run out of resources (space, food, etc.)

Chromosomes

-In eukaryotic cells, the genetic information that is passed on from one generation of cells to the next is carried by chromosomes. -Made up of DNA (carries cell's coded genetic info) and proteins -Not visible in most cells except during cell division -During most of the cell cycle, the genetic material is in the form of chromatin. -At the start of cell division, the DNA that is spread throughout the nucleus condenses into chromosomes. -Before cell division, each chromosome is replicated -As a result, at the start of cell division each chromosome consists of two identical "sister" chromatids.

DNA "overload"

-Limits cell growth If a cell were to grow too large, there would not be enough DNA to sit all the needs of that larger cell. Like putting a small community library in NYC--> not enough books (DNA) for a big city (cell).

The ability to exchange materials across the cell membrane

-Limits cell growth The ability to exchange materials such as water, oxygen, food and waste is based on the relationship between volume and surface area. The volume of a cell increases much more rapidly than the surface area causing the ratio of surface area to volume to decrease. This decrease can cause major problems for the cell.--> Makes it harder for cells to do a good job of transferring things across the cell membrane.

External regulators

-Respond to events outside the cell -Direct cells to speed up or slow down the cell cycle and make sure neighboring tissues don't disrupt eachother For example: you have a cut, the external regulators make sure that the skin cells don't grow in the wrong places, such as your eye.

Metaphase

-Second phase of mitosis -Often only lasts a few minutes -During this phase, the chromosomes finish attaching to the spindle and line up across the center of the cell.

What are some different ways that human cells move through the cell cycle?

-Skin cells duplicate when you fall and heal an open wound -In the human body, most muscle and nerve cells don't divide at at once one they have developed (mature) while skin, blood, digestive, etc. grow and divide rapidly throughout life. Such cells may pass through a completely cycle every few hours. This process provides new cells to replace those that wear out or break down.

Anaphase

-Third phase of mitosis -During this phase, sister chromatids separate into individual chromosomes and are pulled apart -This phase ends when chromosomes stop moving

Why do cells divide rather than continue to grow indefinitely?

2 limits to cell growth: 1) DNA "overload" 2)The ability to exchange materials across the cell membrane [The larger the cell becomes, the more demands the cell places on its DNA and the more trouble the cell has moving enough nutrients and waste across the cell membrane]

What does a cell need to do before it divides? Why?

A cell needs to replicate its genetic information before it can divide.

Spindle

A fan-like micro-tubule structure that helps separate the chromosomes -Formed in prophase and connects the centrioles to the chromosomes.

Cell Division

Cell division: he process by which a cell divides into to daughter cells -Prokaryotic cell division is very simple..eukaryotic cells have a much more complex way of dividing.

Cyclin

Cyclin: cellular protein that regulates the cell cycle and stimulates mitosis to occur --There are many different types of cyclin proteins that are found mitotic cells; some are known as internal regulators, while other are known as external regulators. How and when it was discovered: -For many years, biologists searches for a substance that regulated the cell cycle....in 1980, scientists discovered that cells in mitosis contain a specific protein that stimulates mitosis to occur.......this protein= cyclin! -It is called cyclin because it controls the cell cycle -They did an experiment where they injected cyclin from the cells that were undergoing mitosis into non-dividing cells.....those non dividing cells began to undergo mitosis.

Chromatin

During the majority of the cell cycle, the genetic information will be in the form of chromatin

S Phase

During this phase, DNA (chromosomes) is replicated.

G1 Phase

During this phase, cells do most of their growing and make new proteins and organelles.

G2 Phase

During this phase, the cell prepares for cell division by preparing the organelles needed for division. -Cell also grows a little more -Usually the shortest of the three phases of interphase

How many chromosomes does a human body cell have at the start of cell division?

Human cells at the start of cell division have 46 chromosomes, each of which consists of two chromatids.

Volume

Length x Width x Height -The amount of space an object takes up (bigger cell--> takes up more space)

Surface area

Length x Width x number of sides

What is more efficient; two have many little cells or big cells?

Little cells

What is worse to tear a muscle or to break a bone? Why?

Most mustle and nerve cells don't divide while bone cells do.

Interphase

Period of growth in between cell divisions -Interphase is usually the longest part of the cell cycle -Interphase consists of three individual phases; G1 phase, S phase and the G2 phase

Mitosis

Process of cell division in eukaryotes -Depending on the type of cell, the four phases of mitosis can last anywhere from a few minutes to several days. -Consists of 4 parts (phases); 1) Prophase 2) Metaphase 3)Anaphase 4) Telophase

What happens right before [eukaryotic] cell division?

The DNA that is spread throughout the nucleus condenses into chromosomes. -Before cell division, each chromosome is replicated

Cell Cycle

The life cycle of a cell -During the cell cycle, the cell grows, prepares for division, and divides into 2 daughter cells, each of which will perform the cycle again. -2 parts of the cell cycle; interphase and mitosis/cell division

How do prokaryotic cell have cell division?

They very simply just copy the genetic information and split into two.

Centrioles

Two tiny structures located in the cytoplasm near the nuclear envelope -During this phase centrioles move to opposite sides of the nucleus and form a spindle

DNA

Where the information that controls a cell's function is stored When a cell is small, the information stored in DNA can meet all of the cell's needs..