Great Ideas in Science PROV 301-001 (Spring 2017) Prof. Robert M. Hazen Office: East 202 Phone: x 32163 E-mail: rhazen@ciw.edu

Lecture 11 PROV301 – Great Ideas of Science The Living Cell Lecture 11 PROV301 – Great Ideas of Science Great Idea: Life is based on chemistry, and chemistry takes place in cells

Cells All living things are made of cells, which are like chemical factories. Every cell has an “inside” and an outside, separated by a cell membrane. Every cell uses raw materials and energy to produce new chemicals. Every cell must contain information on how to operate and how to make new cells.

Observing Cells: The Light Microscope

Observing Cells: The Electron Microscope

The Cell Theory Robert Hooke (1635-1702) – Discovery of cells, which are like small compartments. Matthais Scheiden (1838) – The cell theory: All living things are composed of cells. The cell is the fundamental unit of life. All cells arise from previous cells.

Two Kinds of Cells Prokaryotes (“before nucleus”): smaller Eukaryotes (“true nucleus”): bigger

Cellular Architecture Organelle: Any specialized structure in a cell. The cell membrane (or cell wall in plants) separates the inside from the outside. The nucleus is like the front office of a factory. Mitochondria and chloroplasts act like the power plants of cells.

Plant Cells

Animal Cells

Cell Membranes They isolate the cell from the outside. They separate the cell’s many parts on the inside.

Lipids

Cell Membranes Cell membranes incorporate receptors that recognize, bind to, encapsulate, and transport individual molecules.

The Nucleus Contains DNA

The Cytoskeleton: The cell’s inner conveyor belts and supports, formed by proteins.

How Is Energy Obtained? Plants – make sugar in the presence of the Sun by the process of photosynthesis Energy (light) + CO2 + H2O  Glucose + O2

Carbohydrates (sugars) Carbon Hydrogen Oxygen

Cellulose and Starch

Glucose splits into 2 pyruvic acids + ATP How Is Energy Obtained? Plants and animals convert sugar into small energy-rich molecules by the process of glycolysis. Glucose splits into 2 pyruvic acids + ATP ATP  ADP + PO4 + energy

Some animals obtain energy by the process of respiration: How Is Energy Obtained? Some animals obtain energy by the process of respiration: Glucose + O2  Energy + CO2 + H2O

The Final Stages of Respiration Glucose is broken down to CO2 plus H2O. 36 to 38 ATP molecules are produced to carry energy throughout the cell. This process is the reverse of photosynthesis!

How Is Energy Obtained? Many organisms obtain additional energy from pyruvic acid by the process of fermentation: Pyruvic Acid  small molecules + ATP Familiar products of fermentation include vinegar, alcohol, and carbonic acid

The Energy Organelles: Chloroplasts and Mitochondria Chloroplasts are in plant cells only; they contain chlorophyll. Mitochondria are in both plants and animals; they produce the cell’s ATP. These organelles have their own DNA!

Mitochondria ATP is manufactured in mitochondria. All mitochondria is inherited from your mother. You can trace DNA back along maternal lines. This connection leads to genetic anthropology.

Genetics: The Genetic Code KEY IDEA: All living things share the same genetic code. Classical genetics is based on observations of organisms. Cellular genetics is based on observations of cell division and chromosomes. Molecular genetics is based on the study of DNA and RNA.

Two great mysteries of life Like begets like. You begin life as a single cell.

Three Stages of Genetics Research 1. Classical Genetics 2. Cellular Genetics 3. Molecular Genetics

Gregor Mendel (1822-1884) Mendel conducted breeding experiments on pea plants. He identified two-characteristic variations and established pure-breeding stocks.

Gregor Mendel (1822-1884) Mendel conducted breeding experiments on pea plants. He identified two-characteristic variations and established pure-breeding stocks. Then he conducted cross- breeding experiments. He discovered that offspring traits are derived from their parents.

Classical Genetics “Mendel Laws” Genes exist (Mendel called them “atoms of inheritance”) Each parent contributes half of your genes. Some genes are dominant and some are recessive.

Classical Genetics Discovering Mendel’s Laws Results Do pea plant experiments by cross-breeding purebred plants to create hybrid plants. Results All first generation hybrid plants are tall.

If you cross a pure bred tall (TT) pea plant with a pure bred short (tt) pea plant, all offspring are tall. Mother T T Father t tT tT

Classical Genetics Discovering Mendel’s Laws Results Do pea plant experiments by cross-breeding purebred plants to create hybrid plants. Results All first generation hybrid plants are tall. In the next experiments, cross breed those hybrids with each other. The second generation is ¾ tall and ¼ short!

T t T TT Tt t tT tt If you cross two hybrid (Tt) pea plants, ¾ will be tall and ¼ will be short. T t T TT Tt t tT tt

Classical Genetics “Mendel Laws” Genes exist (Mendel called them “atoms of inheritance”) Each parent contributes half of your genes. Some genes are dominant and some are recessive.

Cellular Genetics Use a microscope to observe cells dividing. You will see chromosomes, which are elongated objects that can be dyed with bright colors.

Cellular Genetics Use a microscope to observe cells dividing. You will see two kinds of cell division: In Mitosis one cell becomes two. Most cellular division in your body is mitosis. In Meiosis one cell becomes 4 sex cells (either sperm or egg).

Mitosis Mitosis is cell division—not sexual reproduction. Observe chromosomes undergo a multi-step process: 1. Copy the chromosomes. 2. Form spindle fibers. 3. Migrate the chromosomes. 4. A new membrane forms and two cells result.

Mitosis

Meiosis Meiosis is sexual reproduction in which one cell forms 4 sex cells (sperm or egg), each of which is genetically unique. Steps in the process: 1. Copy the chromosomes. 2. “Cross over” to switch sections of genes.

Meiosis Meiosis is sexual reproduction in which one cell forms 4 sex cells (sperm or egg), each of which is genetically unique. Steps in the process include: 1. Copy the chromosomes. 2. “Cross over” to switch genes. 3. Divide the chromosomes. 4. Divide chromosomes again. The result is 4 daughter cells, each with ½ the normal number of chromosomes, and each chromosome is unique!

Meiosis Meiosis begins just like mitosis by doubling chromosomes, but crossing over and switching genes gives unique sex cells with half of the normal numbers of chromosomes.

Molecular Genetics: The big questions What chemical carries the genetic message? How is that molecular message translated into the chemicals of life?

The Discovery of DNA by Oswald Avery (1877-1955) DNA is composed of 3 kinds of molecules: (1) a sugar called deoxyribose; (2) a phosphate group; and (3) one of 4 bases, called A, T, G, or C. Avery found that the amounts of sugar, of phosphate, and base are exactly equal. Also, the amount of A = T and C = G.

Nucleotides: The Building Blocks of Nucleic Acids Nucleotides are made of three kinds of molecules: A sugar A phosphate group One of 4 different bases: A, T, G, & C

DNA’s Double Helix Nucleotides: Nucleotides are the individual building blocks in DNA and RNA—the “nucleic acids”. Each nucleotide has a phosphate linked to a sugar linked to a base Nucleotides link to each other in two important ways.

DNA Structure Nucleotides link along each helix by alternating phosphate and sugar. Nucleotides also link two helices by pairs of base molecules, either A-T or C-G.

DNA Base Pairing: The “rungs” of the DNA ladder A-T C-G

DNA replication occurs before mitosis & meiosis. The Replication of DNA DNA replication occurs before mitosis & meiosis. The molecular process is: 1. The DNA double helix splits in two down the middle. 2. New bases bond to the newly exposed bases. 3. This process results in two identical DNA strands!

What does DNA do?

DNA Makes Proteins = Enzymes

Proteins form from 20 amino acids Every amino acid has: An amino group, A carboxyl group, And one of 20 different side-groups.

Protein – sequence of amino acids The primary structure is a chain of amino acids. The secondary structure is a folded chain. The tertiary structure involves more folds. HOW DOES DNA MAKE PROTEINS???

How Does DNA Make Protein? 1. Chromosomes (DNA) carry the genetic message 2. Messenger RNA copies the genetic message 3. Transfer RNA holds an amino acid 4. Ribosomal RNA assembles a protein

RNA Structure 1. RNA has a single strand of nucleotides. 2. The sugar is ribose. 3. Uracil (U) replaces thymine (T); U binds to A to form A-U pairs.

How does DNA make Proteins How does DNA make Proteins? Step 1: Transcription of DNA Messenger RNA (mRNA)

How does DNA make proteins How does DNA make proteins? Step 2: Match tRNA to mRNA Transfer RNA (tRNA)

The Ribosome

The Genetic Code: Every living thing uses the exact same genetic code, which matches 3 genetic letters with an amino acid. Thus a sequence of DNA corrsponds to a string of amino acids, which is a protein!