Biology Chapter 10
Terms in this set (40)
What are some of the difficulties a cell faces as it increases in size?
The larger a cell becomes the more demands the cell places on its DNA. In addition a larger cell is less efficient in moving nutrients and waste materials across the cell membrane.
DNA cell size difficulties
Living cell store critical information in DNA
AS a cell grows that information is used to build the molecules needed for cell growth
As size increases the demands on that information grow as well. If a cell were to grow without limit an information crisis would occur
A growing cell makes greater demands on its genetic library. If the cell gets too big the DNA would not be able to serve the needs of the growing cell.
Membrane cell difficulties
Food oxygen and water enter a cell through the cell membrane. Waster products leave in the same way
The rate at which this exchange occurs depends on surface area of the cell
The rate at which food and oxygen are used up and waster products are produced depends on the cells volume
Surface area to volume ration
If a cell gets to large the surface area of the cell is not large enough to get enough oxygen and nutrients in and waste out.
Before a cell grows too large it divide into a new cell in a process called cell division
Before cell division the cell copies its entire DNA
In then divides into 2 cells. Each new cell receives the same DNA
Cell division reduces cell volume. It also results in an increased ratio of surface area to volume ratio for each new cell
Offspring produced by sexual reproduction inherit some of their genetic information from each parent.
In multicellular organisms cell division leads to growth. It also enables and organisms to repair and maintain its human body
In single celled organisms cell division is a form of reproduction
Asexual reproduction is reproduction that involves a single parent producing an offspring. The offspring produced are in most cases genetically identical to the single cell that produced them
Asexual reproduction is simple efficient and effective for organisms to produce a large number of offspring
Both prokaryotic and eukaryotic single celled organisms and many multicellular organisms can reproduce asexually.
In sexual reproduction offspring are produced by the fusion of two sex cells one from each of two parents. These fuse into a single cell before the offspring can grow
The offspring produced inherit some genetic information from both parents
Most animals and plants and many single celled organisms reproduce sexually.
Role of chromosomes in cell division
Chromosomes make it possible to spate DNA precisely during cell division
The genetic information that is passed on from one generation of cells to the next is carried by chromosomes
Every cell must copy its genetic information before cell division begins.
Each daughter gets its own copy of the DNA
Each organisms has a set number of chromosomes
chromosmes in prokaryotes
Prokaryotic cells lack nuclei instead their DNA molecules are found in the cytoplasm
Most Prokaryotes contain a single circular DNA molecule or Chromosome that contain most of the cells genetic information
chromosmes in eukaryotes
In eukaryotic cells chromosomes are located in the nucleus and are made up of chromatin
Main events of cell cylce
During the cell cycle a cell grows, prepares for division and divides to form two new daughter cells
The prokaryotic cell cycle is a regular pattern of growth DNA replication and cell division
Most prokaryotic cells begin to replicate or copy their DNA once they have grown to a certain size
When DNA replication is complete the cells divide through a process called binary fission
Binary fission is a form of asexual reproduction during which two genetically identical cells are produced
phases of cell divison
Interphase is the time between cell divisions. It is a period of growth that consists of the G1, S, G2 The M phase is the part with cell division
What happens in theis phases
In the G1 phase cells increase in size and synthesize new proteins and organelles
In the S or synthesis phase new DNA is synthesized when the chromosomes are replicated
In the G2 phase many of the organelles and molecules required for cell division are produced
In eukaryotes cell division occurs in two stages mitosis and cytokinesis
Mitosis is the division of the cell nucleus
each strands of a duplicated chromosome
Centromere there area where each pair of chromatids is joined
Centrioles tiny structures located in the cytoplasm of animal cells that help organize the spindle
Spindle a fanlike microtubule stature that helps spate the chromatids
During prophase the first phase of mitosis the duplicated chromosome condenses and becomes visible
The centrioles move to the opposite side of the nucleus and help organize the spindle
The spindle form DNA strands attach at a point called centromere
The nucleolus disappears and nuclear envelope breaks down.
During the metaphase the second phase of mitosis the centromeres of the duplicated chromosomes line up across the center of the cell
Spindle fibers connect the centromere of the centreomere of each chromosome to the two poles of the spindle
During anaphase the third phase of mitosis the centromeres are pulled apart and the chromatids separate to become individual chromosomes
The chromosomes separate into two groups near the poles of the spindle
During telophase the fourth and final phase of mitosis the chromosomes spread out into a tangle of chromatin
A nuclear envelope re-forms around each cluster of chromosomes
The spindle breaks apart and a nucleolus becomes visible in each daughter nucleus
Cytokinesis complete the process of cell division it splits the cell into two.
Cytokinesis is the division of cytoplasm
The process of cytokinesis is different in plant and animal cells
The cell membrane is drawn in until the cytoplasm is pinched into two equal parts
Each part contains its own nucleus and organelles
In plants the cell membrane is not flexible enough to draw inward because of the rigid cell wall
Instead a cell plate forms between the divided nuclei that develops into a cell membrane
A cell wall then forms in between the two new membranes
How is the cell cycle regulated
The cell cycle is controlled by regulatory proteins both inside and outside the cell
Cyclins are a family of proteins that regulate the timing of the cell in eukaryotic cells
Internal regulators are proteins that respond to events inside a cell. They allow the cell to proceed only once certain processes have happened inside the cell
External regulaors are proteins that respond to events outside the cell. They direct cells to speed up or slow down the cell cycle
Growth factors are external regulators that stimulate the growth and division of cells. They are important during embryonic development and wound healing.
Apoptosis is a process of programmed cell death.
Apoptosis plays a role in development by shaping the structure of tissues and organs in plants and animals.
How do cancer cells differ from other cells
Cancer cells do not respond to the signals that regulate growth of most cells. As a result the cells divide uncontrollably
Cancer is a disorder in which body cells loses the ability to control cell growth.
Cancer cells divide uncontrollably to form a mass of cells called a tumor.
A benign tumor is noncancerous. It does not spread to surrounding healthy tissue
A malignant tumor is cancerous. It invades and destroys surrounding healthy tissue and can spread to other parts of the body. The spread of cancer is called metastasis. Cancer cells absorb nutrients needed by other cells, block nerve connections and prevent organs from functioning.
Cancers are caused by defects in genes that regulate cell growth and division
Some sources of gene defects are smoking tobacco, radiation exposure defective genes and viral infection
A damage or defective p53 gene is common in cancer cells. It causes cells to lose the information needed to respond to cell growth signals.
Some localized tumors can be removed by surgery
Many tumors can be treated with targeted radiation
Chemotherapy is the use of compounds that kill or slow the growth of cancer cells.
How do cell become specialized for different functions
During the development of an organism cells differentiate into different types of cells
All organisms start life as just one cell
Most multicellular organisms pass through an early stage of development called an embryo which gradually develops into an adult organism
During development an organism cells become more differentiated and specialized for particular functions
The process by which cells become specialized is called differentiation
During development cells differentiate into many different types and become specialized to perform certain tasks
Differentiated cells carry out jobs that multicellular organism need to stay alive.
In some organisms a cells role is determined at a specific point in development
In the worm C elegans, daughter cells from each cell division follow a specific path toward a role as a particular kind of cell
Cell differntiation in mammals
Cell differentiation in mammals is controlled by a number of interacting factors in the embryo.
Adult cells generally reach a point at which their differentiation is complete and they can no longer become other types of cells
The unspecialized cells from which differentiated cells develop are known as stem cells
One of the most important questions in biology is own the entire specialized differentiated cell types in the body are formed by just a single cell
Biologists say that such a cells is totipotent, literally able to do everything to form all tissues in the body
Only the fertilized egg and the cells produced by the first few cell division of embryotic development are truly totipotent
After four days of development a human embryo forms into a blastocyst a hollow ball of cells with a cluster of cells inside known as the inner cell mass
The cells of the inner cell mass are said to be pluripotent which that they are capable of developing into many but not all of the bodies cell types
Embryonic stem cells
Embryonic stem cells are found in the inner cell mass of the early embryo
Embryonic stem cells are pluripotent
Researchers have grown stem cells isolated form human embryos in the culture their experiments have confirmed that embryonic stem cells have the capacity to produce most cell types in human bodies
Adult stem cells
Adult organisms contain some types of stem cells
Adult stem cells are multipotent. They can produce many types of differentiated cells
Adult stem cells of a given organ or tissue typical produce only the types of cells that are unique to that tissue
Stem cell benifits
Stem cells offer the potential benefit of using undifferentiated cells to repair or replace badly damaged cells and tissues.
Stem cell research may lead to new ways to repair the cellular damage that results from heart attack stroke and spinal cord injuries
Stem cell controversial
Most techniques of harvesting or gathering embryonic stem cells cause destruction of the embryo
Government funding of embryotic stem cell research is an important political issue
Groups seeking to protect embryos oppose such research as unethical
Other groups support this research as essential to saving human lives and so view it as unethical to restrict the research.
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