9-1 Cellular growth

Déjà vu What are the 3 parts of the Cell Theory? All living things are made of one or more cells Cells are the smallest unit of living organisms Cells arise only from existing cells

Why are cells so small?

Cells grow until they reach their size limit, then they either stop growing or divide.

Cell Size Limitations Ratio of Surface Area to Volume Transport of Substances Cellular Communication

Cellular Reproduction As the cell grows, its volume increases much more rapidly than the surface area. Ratio of Surface Area to Volume Surface Area = the area covered by the plasma membrane Volume= the space taken up by the inner contents of the cell (organelles, cytoplasm, nucleus Back to Outline

Transport of Substances Substances move by diffusion or by motor proteins. Diffusion over large distances is slow and inefficient. Small cells maintain more efficient transport systems.

Transport of Substances So…The cell might have difficulty supplying nutrients and expelling enough waste products. (It gets harder to get the good stuff in and the bad stuff out)

Think About It… Back to Outline

Cellular Communications Cellular Reproduction Cellular Communications Cell size affects the ability of the cell to communicate instructions for cellular functions.

How do cells stay small?

Cell Cycle Cells reproduce by a cycle of growing and dividing Each time a cell goes through one complete cycle, it becomes two cells.

Cells go through different types of cell division depending on the organism and the reason for the cell dividing. Reasons for cell division: -Repair -growth -development -asexual reproduction -gamete formation About 2 trillion cells are produced by an adult human body every day. This is about 25 million new cells per second!

CHROMOSOMES “packages of DNA”

Eukaryotic Chromosomes

When genes are being used to make proteins, the DNA is stretched out so it can be easily read. This “relaxed” form of DNA is call chromatin. As a eukaryotic cell prepares to divide, the DNA associates itself with histone proteins. DNA coils tightly around the proteins and forms a beadlike structure called a nucleosome. Nucleosomes pack together to form thick fibers, forming a chromosome. The “X” chromosome that we are used to seeing is actually two exact copies of one chromosome, each one is called a chromatid. The two chromatids of a chromosome are attached at a point called a centromere.

DEMO

DNA Genes Proteins YARN = TAPE = CLOTHES PIN =

Explain the role of chromosomes during cell division. Journal Explain the role of chromosomes during cell division.

Cell Cycle Interphase is the stage during which the cell grows, carries out cellular functions, replicates DNA, and prepares for division. Mitosis is the stage of the cell cycle during which the cell’s nucleus and nuclear material divide. Cytokinesis is the method by which a cell’s cytoplasm divides, creating a new “daughter” cell with identical nuclei

Eukaryotic Cell Cycle

Think about it… How can we tell how much time the cell spends in each phase?

Thought Question How do you think cell division in eukaryotes compares to cell division in bacteria (binary fission)?

Prokaryotes vs. eukaryotes Cell Cycle is the process by which eukaryotic cells reproduce themselves Reproduce by a method called binary fission

Which is not a phase of the cell cycle? Chapter Diagnostic Questions Which is not a phase of the cell cycle? cytokinesis interphase apoptosis mitosis A B C D CDQ 3

Which can more efficiently supply nutrients and expel waste products? Section 1 Formative Questions Which can more efficiently supply nutrients and expel waste products? larger cells smaller cells cells with lower surface area to volume ratio cells shaped like a cube A B C D FQ 1

At what stage does a cell spend most of its life? Section 1 Formative Questions At what stage does a cell spend most of its life? cytokinesis interphase mitosis synthesis A B C D FQ 2

What happens in the cell during cytokinesis? Cellular Reproduction Section 1 Formative Questions What happens in the cell during cytokinesis? The cell grows and carries out normal functions. The cell copies its DNA and forms chromosomes. The cell’s nucleus and nuclear material divide. The cell’s cytoplasm divides. A B C D FQ 3

In what stage of the cell cycle does the Section 2 Formative Questions In what stage of the cell cycle does the cell’s replicated genetic material separate? cytokinesis interphase mitosis prophase A B C D FQ 4

C B A Which cell has the lowest ratio of surface area to volume? Standardized Test Practice Which cell has the lowest ratio of surface area to volume? A B C A B C STP 1

Standardized Test Practice At what stage of interphase does the cell take inventory and make sure it is ready for the division of its nucleus? G1 S G2 M A B C D STP 2

The Stages of Interphase G1 (Gap 1) -The cell is growing, carrying out normal cell functions, and preparing to replicate DNA. Nerve cells, muscle cells, and some other highly specialized cells do not leave the G1 phase, and therefore do not replicate in the body under normal conditions.

The Stages of Interphase S (Synthesis) -The cell copies its DNA in preparation for cell division.

The Stages of Interphase Cellular Reproduction The Stages of Interphase G2 (Gap 2) -The cell prepares for the division of its nucleus.

Surface Area : volume activity, page 245

Surface area lab Is the distance of diffusion the same for all blocks? Explain. List the cubes in order of size, from largest to smallest. Now list them in order of surface area:volume ratio, from largest to smallest. How do these lists compare? What is the relationship between surface area:volume ratio and diffusion in a cell? Are large organisms, such as redwood trees and elephants, large because they contain extra-large cells or just more regular sized cells?