Materials move through cells by diffusion. Oxygen and food move into cells, while waste products move out of cells. How does the size of a cell affect how efficiently materials get to all parts of a cell? Work with a partner to complete this activity 1. On your bell work, make a drawing of a cell that has the following dimensions: 5 cm x 5 cm x 5 cm. Your partner should draw another cell about one half the size of your cell on their own bell work paper. 2. Compare your drawings. How much longer do you think it would take to get from the cell membrane to the center of the big cell than from the cell membrane to the center of the smaller cell? 3.What is the advantage of cells being small? It would take twice the amount of time. If cells are small, materials can be distributed to all parts of the cell quickly.

Image from: Image by Riedell CELL GROWTH & DIVISION 10-1 & 10-2

Cell Reproduction Cell Theory states that all cells come from pre-existing cells Cells reproduce by cell division Cells are constantly wearing out and are replaced by cell division

2 Reasons why cells divide 1. _____________________ As cell grows bigger demand on DNA “genetic library” becomes too great Ex: Small town library has 1000 books. As town grows and more people borrow books, there may be a waiting list to read the most popular titles DNA OVERLOAD

2 Reasons why cells divide 2. _____________________ As cell grows bigger demand for transport across membrane is too great Material exchange can’t keep up

Ability to transport of oxygen, food, waste across cell membrane depends on _______________ Need for these depends on ___________ SURFACE AREA CELL VOLUME As cell grows these DON’T increase at the same rate See relationship between volume and SA

Go to Section: Cell Size Surface Area (length x width x 6) Volume (length x width x height) Ratio of Surface Area to Volume Ratio of Surface Area to Volume in Cells Section 10-1

BIGGER CELLS NEED MORE FOOD and OXYGEN, but CAN’T TRANSPORT IT FAST ENOUGH or IN BIG ENOUGH QUANTITIES!

Multicellular organisms grow mainly by increasing cell number Image from: Image by Riedell

Reproduction: Not as simple as it looks.

Reproduction presents a major problem for cells and organisms: (how can information be transmitted faithfully to progeny) I II III IV = one bit of genetic information

= one bit of genetic information The information transfer problem becomes more challenging as more bits of information are incorporated into the organism

One of life’s solutions to this challenge: “Package” the bits of information into single units called chromosomes = one bit of genetic information

Fig 2.4 The structure of a highly condensed, replicated chromosome. © 2003 John Wiley and Sons Publishers

SPREAD OUT IN NON-DIVIDING CELLS SCRUNCHED UP IN DIVIDING CELLS CHROMATIN CHROMOSOMES DNA CAN BE:

chromosomes Packaging of genetic material in prokaryotes and eukaryotes prokaryote cell eukaryote cell

DNA in PROKARYOTES BACTERIAL DNA is CIRCULAR HAVE ONE CHROMOSOME NO NUCLEUS; ATTACHED TO CELL MEMBRANE

CELL DIVISION in PROKARYOTES Bacteria reproduce using __________________________________ BINARY FISSION

DNA in EUKARYOTES (Plants & Animals) DNA is ROD-SHAPED CHROMOSOMES MANY PAIRS FOUND IN NUCLEUS

______________ = a series of events that cells go through as they grow and develop; Cell Cycle takes hours CELL CYCLE

Organs which need to produce new cells continuously have the highest turnover. For example:- Bone marrow- producing replacement blood cells The testes - producing semen

The cell cycle. © 2003 John Wiley and Sons Publishers

Go to Section: M phase G 2 phase S phase G 1 phase Figure 10–4 The Cell Cycle Section 10-2

CELL CYCLE INTERPHASE – non-dividing phase G 1 - Grow bigger Cell is “doing its job” DNA is spread out as chromatin S - Synthesis (copy DNA) & chromosomal proteins G 2 - Grow bigger, make organelles & molecules needed for cell division

CELL DIVISION M Stage = MITOSIS = Nuclear division Prophase Metaphase Anaphase Telophase Cytokinesis = Cytoplasm divides G 0 – cell stops dividing (Ex: nerve cell)

INTERPHASE (G 1 - S - G 2 ) In between divisions Cells are in this phase most of the time Can see nucleus or chromosomes DNA spread out as chromatin… DNA gets copied Organelles get copied

PROPHASE =1st dividing phase Spindle fibers form & attach to chromosomes Nuclear membrane & nucleolus disappear DNA scrunches into chromosomes Centrioles appear in centrosome region & move to poles Pearson Education Inc publishing as Pearson Prentice Hall

The Spindle A spindle is a web type structure made up of microtubule fibres. It is essential for mitosis because it arranges the chromosomes into their correct positions in preparation for cell division. Mitotic centre Microtubul e A cell at metaphase a spindle

________ region organizes spindle Spindle MICROTUBULES are part of cytoskeleton CENTROSOME

METAPHASE Chromosomes line up in ___________ middle Images from: Pearson Eduction Ince; Publishing as Pearson Prentice Hall

ANAPHASE Centromeres split Centrioles pull chromatids_______ apart Images from: Pearson Eduction Ince; Publishing as Pearson Prentice Hall

TELOPHASE (reverse prophase steps) See ______ nuclei Nuclear membrane & nucleolus return Chromosomes spread out as chromatin Centrioles disappear Spindle fibers disappear two Images from: Pearson Eduction Ince; Publishing as Pearson Prentice Hall

CYTOKINESIS = division of the cytoplasm to create 2 cells *ANIMAL CELLS pinch cytoplasm in two with a ______________________ CLEAVAGE FURROW

*PLANT CELLS can’t pinch because they have a sturdy ____________ *Plant cells separate cytoplasm by growing a _______________ down the middle. CELL PLATE CELL WALL

Go to Section: Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Section 10-2 Figure 10–5 Mitosis and Cytokinesis

Go to Section: Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Section 10-2 Figure 10–5 Mitosis and Cytokinesis

Go to Section: Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Section 10-2 Figure 10–5 Mitosis and Cytokinesis

Go to Section: Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Section 10-2 Figure 10–5 Mitosis and Cytokinesis

Go to Section: Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Section 10-2 Figure 10–5 Mitosis and Cytokinesis

Go to Section: Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Section 10-2 Figure 10–5 Mitosis and Cytokinesis

Go to Section: REMEMBER! I Interphase P Prophase M Metaphase A Anaphase T Telophase IPMAT

Go to Section: includes is divided into Concept Map Section 10-2 Cell Cycle

Go to Section: includes is divided into Concept Map Section 10-2 Cell Cycle M phase (Mitosis) Interphase G 1 phase S phaseProphaseG 2 phaseMetaphaseTelophaseAnaphase