Chapter 6 Cell Function: Cell cycle & Introduction to Genes

Cellular Functions 1.Transport across membranes 2.Energy Conversion & use – Energy Production; Plants Only 3.Reproduction – Molecule Synthesis 2 The activities of a cell can be split into 3 main main activities:

Review 3 ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ Mitochondria Cell Membrane Chloroplasts Central Vacuole Nucleus (DNA) Ribosomes Golgi Rough Endoplasmic Reticulum

Introduction to Genetics DNA Review Chromosomes The Cell Cycle 4

5 All cells in a multicellular organism are genetically identical The cell cycle is the process of creating new cells, has two main steps: – Replication (Synthesis) – Growth Every cells arises from a pre- existing cell – Plant cells arise from plant cells – Animal cells from animal cells

The Cell Cycle Original cell  two __________ cells 6 Identical Different

DNA: A Review 4 different nucleotides Form bonds creating sugar phosphate backbones – “Handrails” Hydrogen bonds between nucleotides 7

DNA: A Review 8

(A) to (T) (C) to (G) 9

DNA: A Review Create a strand of nucleotides (polynucleotides) called a nucleic acid chain DNA – has two sugar phosphate “handrails” RNA – has only one sugar phosphate “handrail” 10

DNA vs. RNA DNA nucleotides: A, T, G, C RNA nucleotides: A, U, G, C 11

Cell Replication DNA stores genetic information Genetic information must be duplicated when a new cell is formed – And then the copy must be transferred to the new cell To do this efficiently DNA must be condensed after duplication – Forming chromosomes 12

DNA Replication Cellular replication (Mitosis) – A series of events Cell copy and equally disperse DNA – In to two new IDENTICAL cells 13

DNA Replication 1.Original strand of DNA unwound 2.The two complementary strand separate 3.Each is used to create a new complementary strand 4.DNA has been duplicated 14

Eukaryotic DNA Normally loosely packed as chromatin in the nucleus Readily able to be read and copied as needed 15

What is a Chromosome? 16 DNA is “Supercoiled” to condense in an organized manner, creating chromosomes

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What is a Chromosome? Condensed DNA is able to move more easily – Structural stability 18

Chromatin or chromosomes? academy.asd20.org/kadets/lundberg/ethics/1.html \

Genetic Division DNA is duplicated and the identical copies of chromosomes remain connected at the centromere This prepares the two copies (sister chromatids) for cellular division 20

Cellular division 1.DNA is replicated 2.The DNA is equally divided (Mitosis) 3.The remainder of the cell is divided 4.Two new identical cells (Daughter cells) exist 21

The Cell Cycle Cells spend 90% of their time in Interphase 22 Events: – Cell Growth – Synthesis – Mitosis

Control System Checkpoints exist to prevent the cell from proceeding if it is not ready 3 major checkpoints in eukaryotic cell cycle 23

Control System Checkpoints G 1 G 2 M 24

Molecular Control System If the cell meets the requirements of a checkpoint – allowed to pass 25

Molecular Control System If a cell does not meet requirements – remains at that stage until ready Cell enters the G 0 phase – A non-replicating state – However may re-enter the cell cycle later 26

Cell Replacement Some cells are frequently undergoing mitosis to replace cells Others stop mitosis at adulthood, and never replace cells 27

Normal rates of replacement Skin cells – 35 days Red blood cells – 120 days Skeletal & Fat cells – 10 years Heart Cells (Cardiomyocytes) – about 50% over a lifetime Cerebral Neurons - Never 28

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Liver & Skin cells Constantly replicating, replace warn out cells Liver – removes toxins from the blood – Taxing on the cells, so must constantly replenish – This is why doctors can take part of your liver for a transplant (but not part of a kidney) Skin – exposed to the environment – Including your digestive system lining 31

Scar tissue 32

Neurons – love the ones you got Neurons stop replicating at ~14-15 years of age – Enter G 0 and remain there indefinitely – Researchers trying to figure out why these cells stop replicating Reverse the process so that brain cells can re-generate Paralysis – severed neurons – Can Re-attached limbs regain function? Why can we not re-grow limbs? But can regrow/replace skin? 33

Alzheimer's and Parkinson's Degradation of neurons in Adults – Why is this bad? 34

Density Dependence Cells will signal each other when maximum density is reached – stop replicating 35

Cancerous Cells A series of mutations – Cause the loss of normal cell cycle controls – Such as Density dependence 36 Cells continually divide, never leave the cell cycle

Cancerous Cells Form a mass of rapidly dividing cells – Tumor 37 Eventually cells can leave the mass – entering the lymph or blood systems – spreading throughout the body.

Programed Cell Death Signals within the cell – Similar to reproductive signals – Start a response that cause the cells to die Example: limb formation Apoptosis 38

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Questions 1.What are Chromosomes? 2.What are the steps a cell must go through to replicate? 40 – What happens if those steps are not completed? 3.What kinds of cells do not replicate in humans? – What kind replicate quickly?

Questions 1.Condensed DNA 2.Growth Phases, and DNA Synthesis – Growth phases increase cell size – Synthesis replciates DNA – Then Mitosis (the act of cells dividing) 41

Questions 42 3.Brain cells stop replication – However skin and liver cells, which are exposed to the outside environment divide rapidly. – Most other cells in our body dive at slower rates.