Notes – Limits to Cell Growth and the Cell Cycle
There are two main reasons why cells divide instead of continue to grow:
1. The larger a cell becomes, the more demands the cell places on its _________.
2. The cell has more trouble moving enough _____________________ and
___________________ across the cell membrane.
DNA “Overload”
-
Information that controls a cell’s function is stored in a molecule known as
___________.
In eukaryotic cells, DNA is found in the _______________.
When a cell is_____________, the information stored in DNA is able to meet all of the
cell’s needs.
If a cell was too _________ an “information crisis” would occur and the cell would not
function properly.
EXAMPLE: Small library in a big town.
Exchanging Materials
-
Food, water, and nutrients enter a cell through its _______ __________________
___________ products leave in the same way
The relationship between a cell’s ______________ and its _________________
_______ is the key to understanding why cells must divide as they grow!
Cell Division
In eukaryotes, cell division occurs in ________ major stages:
1. The division of the cell nucleus is called _________.
2. The division of the cell cytoplasm is called ___________.
I. Chromosomes
Genetic information is passed from one _________________ to the next on
chromosomes. Before cell division, each chromosome is ____________ or copied.
Chromosomes are made up of ________molecules.
Each chromosome consists of 2 identical _________ chromatids. Each pair is
attached at an area called the ________________.
When the cell divides, the chromatids ____________ and each new cell gets one
chromatid.
II.The Cell Cycle
A series of events that cells go through as they _______
& __________.
Interphase-period of ___________ that occurs between cell divisions.
Key Concepts:
During the cell cycle…….
-a cell ________
-prepares for ______________
-divides to form ____ daughter cells
III. Phases of the cell cycle:
1.
2.
3.
4.
5.
G1 (first gap phase)
S phase
G2 (second gap phase)
M phase
G0 (resting phase)
G1 Phase- the cell _________ in size and synthesizes new ________
and ________________.
S Phase- chromosomes are _____________ and DNA synthesis takes
place; the rest of the cell cycle is usually completed
G2 Phase- organelles and molecules _________ for cell division are
produced. The cell is ready to start ____ phase.
Mitosis (occurs in 4 phases)
1. Prophase- It is the first and ____________ phase of mitosis. The
_____________ separate and take up position on opposite sides of the
nucleus. The __________ is forming and the paired chromosomes are
visible.
* the centrosome helps to organize the spindle which is a fanlike microtubule
that helps separate the chromosomes.
*Chromatin ___________ into chromosomes
*Nuclear envelope _________ down.
2. Metaphase- The chromosomes line up across the _________ of the cell.
Microtubules _________ the centromere of the each chromosome to the
poles of the spindle.
3. Anaphase- The sister chromatids _________ into individual chromosomes
and they continue to move until they have separated into _______ groups.
4. Telophase- Chromosomes gather at ___________ ends of the cell and lose
their distinct shape. A new ________ envelope forms around each cluster of
chromosomes.
Cytokinesis
The cytoplasm _________ in half and each daughter cell has an identical set
of duplicate chromosomes. In plants, a structure known as the ______
______ forms midway between the individual nuclei
G0 Phase- the cell leaves the cell cycle and quits ___________.
This may be a temporary _________ period or more permanent.
Ex: _________ cells and heart ___________ cells no longer divide
after reaching maturity.