The blue whale is the largest mammal in the world. The pygmy shrew is 1 of the smallest mammals in the world. How does the size of an average cell compare between the two?
A. the average cell of a blue whale is smallerthen the average cell of a pygmy shrew. B. the average cell of a blue whale is largerthen the average cell of a pygmy shrew.C. the average cell of a blue whale is about the same size as the average cell of a pygmy shrew.
Cell Growth • When an organism grows, the number of cells increase, but the size of each cell remains small!
Limits on Cell Growth • DNA “Overload”: the larger a cell becomes, the more demands the cell places on its DNA • When a cell is small, DNA can easily control the cell’s functions & meet its needs. • When a cell is large, it still only has 1 copy of the DNA, so it’s more difficult for the cell to perform its functions.
Limits on Cell Growth • Exchanging Materials: large cells have more trouble moving substances across the cell membrane • If a cell is too large, it’s difficult to get enough oxygen & nutrients in & waste products out.
Cell Division • When a cell gets too large, it: • Makes a copy of its DNA (replication), then… • Divides to form 2 “daughter” cells
The Cell Cycle • The series of events that a cell goes through as it grows & divides
A Basic Overview of the Cell Cycle • The cell grows. • The cell prepares for division. • The cell divides into 2 daughter cells. • The cycle begins again in the new daughter cells.
The Cell Cycle Cell Growth
The Cell Cycle Cell Growth DNA Replication
The Cell Cycle Cell Growth DNA Replication Preparation for Mitosis
The Cell Cycle Interphase is the phase of the cell cycle that occurs before the cell begins dividing!
The Cell Cycle G1 Phase = Cell Growth S Phase = DNA Rep. G2 Phase = Prepare for Mitosis G1 + S + G2 = Interphase
The Cell Cycle – Interphase • All the time in the cycle when the cell is not dividing Cells are in interphase 90% of the time – it is the longest phase!
Interphase • Interphase has 3 parts: • G1 Phase • S Phase • G2 Phase
Interphase – G1 Phase • Cells grow • Cells increase in size • Cells synthesize (make) new proteins & organelles What would happen if cells divided without going through this phase?
Interphase – S Phase • DNA is replicated What would happen if cells divided without going through this phase?
Interphase – G2 Phase • Cells produce organelles & molecules that are required for cell division What would happen if cells divided without going through this phase?
Which of the following is not part of interphase? • G1 • S • G2 • M Phase M Phase!
Which part of interphase does the cell do most of its growing? • G1 • S • G2 • Equal G1!
Which part of interphase does the cell produce centrioles? • G1 • S • G2 • What are those? G2!
Cell Division – the M Phase • 2 stages of eukaryotic cell division • Mitosis: division of the cell nucleus • Cytokinesis: division of the cell cytoplasm
Remember! The M Phase occurs AFTER interphase!
Mitosis • Mitosis (division of the cell nucleus) is made of 4 parts: • Prophase • Metaphase • Anaphase • Telophase
G1 phase M phase S phase G2 phase
Remember! • Every somatic (body) cell contains identical genetic information! • DNA is passed from the parent cell to the daughter cells through DNA Replication!
Chromatin & Chromosomes • Chromatin consists of DNA & the proteins it is wrapped around. (DNA + Proteins = Chromatin) • Chromosomes are made of condensed chromatin.
Which of the following is not a somatic cell? • Cheek Cell • Nerve Cell • Egg Cell • Heart Cell Egg cell!
Chromosomes • The cells of every organism have a specific number of chromosomes. • Humans have 46 chromosomes in each cell (23 from mom & 23 from dad)! Down Syndrome is caused by an extra chromosome #21!
Chromosomes are only visible during cell division, when they are condensed. • The rest of the time, the chromatin is spread throughout the nucleus!
Before cell division begins, each chromosome is replicated. • When a chromosome is replicated, it consists of 2 identical “sister” chromatids. • Sister chromatids are attached to each other at the spot called the centromere. Chromosomes
Remember! Mitosis is the division of the nucleus! What are some reasons that cells undergo mitosis? • Growth • Repair • Maintenance • Asexual Reproduction
Asexual Reproduction • A single-celled organism reproduces by itself. • Two types: • Binary Fission: organism replicates its DNA & divides in half, producing 2 identical daughter cells (bacteria) • Budding: asexual process by which yeast increase in number Budding Binary Fission