Final Exam Cell Biology

Gardner-Webb University

Prokaryotic Cells

- Lack a nuclear envelope

- Significantly smaller

- No cytoplasmic bound organelles

- DNA as genetic material. Less base pairs than in Eukaryotic.

- Singular circular DNA molecule for chromosome

Eukaryotic Cells

- Have a nucleus that separates genetic material from cytoplasm.

-Larger in size

- Cytoplasmic membrane bound organelles.

- DNA as genetic material. More base pairs .

- Multiple linear DNA molecules for chromosomes.

The original genetic material was _____?

RNA

Genes

Segments of DNA that encode proteins or RNA.

Transcription

Nucleotide gene sequence is copied into RNA.

Translation

RNA sequence is used to specify the order of amino acids in a protein.

First cell

Enclosed in a phospholipid membrane.

Phospholipids are

amphipathic (hydrophilic head and hydrophobic tail). Spontaneously form a bilayer of H2O.

3 stages of glycolysis regarding the use of ATP

1) Glycolysis

2) Photosynthesis

3) Oxidative Metabolism

When did Glycolysis evolve?

When the earth's atmosphere was anaerobic.

The first photosynthesis molecules used

H2S to convert CO2 to organic molecules.

Photosynthesis may have allowed the evolution of

Oxidative metabolism.

This type of cell has rigid cell walls

Prokaryotic cells

Site of DNA replication/RNA synthesis in Eukaryotic cells

Nucleus

Lysosomes

Digest anything the cell needs to get rid of

Mitochondria

Powerhouse of the cell. Most ATP is made here. Energy is being converted to something the cell can use.

Cytoskeleton

Gives the cell shape and helps with organization of all things within the cell, also aids in movement of the entire cell.

Rough ER

Synthesis of proteins that will be secreted from cells. They are then transported to the golgi apparatus.

Golgi Apparatus

Organizes the proteins transported.

Smooth ER

Lipid synthesis. Different jobs depending on location of the cell in the body.

Centrioles

Part of the cytoskeleton that organizes the microtubules within the cell.

Peroxisomes

Detoxify hydrogen peroxide in cells

Nucleolus

Part of nucleus

Nucleus

Where everything happens.

Vacuole

Stores water

Cell wall

Provides structure

Endosymbiosis

Prokaryotic cells living inside of the ancestors of eukaryotic cells.

Robert Hooke (1665)

Coined the name cell. Looked at cork under a microscope. Holes looked like rooms called "cells".

Antony van Leeuwenhoek (1670's)

Observed a variety of cells (Sperm, RBC, Bacteria)

Cell Theory (TEST MATERIAL)

2 Parts:

- All organisms are composed of cells

- Cells only arise from division of pre-existing cells

Microscopy

Used to study cell and tissue morphology. Can also be used to study physiology.

Types of microscopy

Bright-field, phase contrast, DIC, Fluorescence, Electron.

Phase contrast & DIC Microscopy

- Used with living cells.

- The advantage is that it can see and understand cell behaviors.

- Disadvantage is that you cannot stain these living cells.

Fluorescence Microscopy

- Laser that operates at a specific wavelength. Fluorescent dye is added to inspected molecule. Filters detect emitted light providing image.

GFP

Jellyfish originated. Fused to any protein by using recombinant DNA. Highlights the protein. Way to locate & visualize molecules within a cell (specifically proteins) without staining/fixing the cells.

Fluorescence recovery after photo-bleaching (FRAP)

Cell regions with GFP-labeled proteins are bleached.

GFP labeled molecules move -> Fluorescence is restored.

Study rate of protein movement in living cells.

Use a laser to specifically point at a highlighted protein and study it

Fluorescence resonance energy transfer (FRET)

- 2 proteins are couples to different fluorescent dyes. This allows you to see if the different proteins interact.

- Excitation wavelength of the 2nd protein is the same as the emission wavelength of the first protein. Only when the proteins bind together.

Confocal Microscopy

Increases contrast & detail by analyzing fluorescence from a single point. Small point of light is focused on the specimen at a specific depth.

Emitted fluorescence is detected by video camera and provides us with the image.

Shows individual threads of microtubules around proteins.

Electron Microscopy

- Beam of electrons. Cell specimen will be stained with heavy metal salts.

- Resolution approximately 0.2 nm (normally 1-2). Better visually than light microscopy.

- Transmission EM and Scanning EM

Transmission Electron Microscopy (TEM)

- Specimen fixed and preserved with heavy metal salts.

- Beam of electrons is passed through the specimen and forms an image on a fluorescent screen.

- Contrast is from scattering electrons.

Scanning Electron Microscopy

Heavy metal salts as the stain but this time coats the cell.

- 3-D image of cell.

- Scans surface, S in SEM can stand for surface.

Steps of Subcellular fractionation:

1) Start out "blending" the cells. The spinning begins in a centrifuge. First is really slow. This collects the largest parts of cell (Nuclei)

2) Take just the buffer of the first spin and put it in a new tube and spin again faster this time. This spin will collect larger organelles such as the mitochondria, chloroplasts, etc.

3) Spin again, even faster, in a new tube and get things lysosomes, peroxisome sediment.

4) Fastest spin in centrifugation. Get fragments of the plasma membrane, ER settlement.

** Goes from largest to smallest, Slowest to fastest**

Vitro Culture

Study how cells grow, develop, differentiate, and perform genetic manipulations.

Adherent Cells

mostly animal cell types attach and grow on the plastic surface of petri dishes. Sticking cells

Non-adherent cells

Cells that grow in suspension, not stick.

Primary culture

Cells collected from tissue

Secondary Cultures

Cells that are replated multiple times, just at lower densities.

True of false? Most normal cells such as fibroblasts can be cultured indefinitely

False. They divide until they don't.

Cell lines

Scientist developed cells.

Embryonic stem cells/tumor cells are permanent and proliferate indefinitely in culture.

Can be thought of as immortal.

HeLa cells were the first cell lines that were created. Cervical cancer biopsy from Henrietta Lacks (1951).

Compare Electron & Light Microscopy. Which characteristics belong with which type of microscopy?

- Source Electron Gun: Electron

- Can view living electrons: Light

- Images in color: Light

- Source: Light bulb: Light

- Max magnification approx. 200,000x: Electron

- Organism must be dead: Electron

- Images in B&W: Electron

- Max magnification 1000X: Light

The cell obtains energy from

its environment.

Gibbs Free Energy (G)

Change in free energy of a reaction combines changes in enthalpy & entropy.

Water

- Most abundant molecule in Eukaryotic cells (70%).

- Polar molecule

- Hydrogen Bonding (molecular bonds)

Hydrophilic Molecule

Readily soluble in water.

Polar & Ions

Hydrophobic Molecule

- Cannot interact w/water

- Nonpolar molecules

4 classes of organic molecules

carbohydrates, lipids, proteins, nucleic acids

Monosaccharides

- Simple Sugars

- Major Nutrients of cells

- Glucose (G6H1206) is principle energy source for cells

- Linear forms, ring forms. (Alpha, Beta. Alpha has OH down position. Beta has OH up position.)

Glycosidic Bonds

Connect monosaccharides

The bond (Alpha or Beta) matters because it determines structure - linear/branched

Oligosaccharides

Polymers of a "few" sugars

Polysaccharides

Macromolecules; polymers of 100s or 1000s of sugars.

common polysaccharides

Glycogen: Stores glucose in animal cells

Starch: Stores glucose in plant cells

(Glycogen and Starch stores glucose in Alpha configuration)

Cellulose: Main structural component of plant cell walls.

Cellulose stores glucose in beta configuration).

Functions of Lipids

Energy storage, major component in cell membranes, Important in cell signaling.

Fatty Acids

- Long hydrocarbon chains: 16-18 carbons w/ carboxyl group.

- Saturated single bonds - straight chain

- Unsaturated double bonds - makes kink in chain

Triglycerols (Triglycerides)

- 3 fatty acids linked to a glycerol.

- Insoluble in water. (fat droplets in cytoplasm)

- Efficient energy storage

Phospholipids

- 2 fatty acids joined to a polar head group (phosphate)

- Glycerol phospholipid: 3rd carbon bound to phosphate group. Can have another polar group.

- Exception is Sphingomyelin. Only non-glycerol phospholipid in cell membranes. Serine polar head group.

Glycolipids

Two hydrocarbon chains & a carbohydrate polar head group

Cholesterol

4 hydrophobic hydrocarbon rings ad a polar hydroxyl (OH) group.

Makes cholesterol amphipathic

Steroid Hormones such as ______, ________ act as chemical messengers.

Testosterone, Estradiol.

Examples of nucleic acids

DNA and RNA

- Messenger RNA, Ribosomal RNA, Transfer RNA.

Purine bases

Adenine and Guanine

Pyrimidine Bases

Cytosine, Thymine, Uracil

NucleoSide

Nitrogenous base and sugar

NucleoTide

Nitrogenous base, sugar, AND a phosphate group.

Phosphodiester Bonds TEST MATERIAL

5' phosphate to 3' hydroxyl of another.

Polynucleotides have a sense of direction

- Terminates in a 5' phosphate group and 3' hydroxyl group

- Always synthesized in the 5' to 3' direction

Double stranded molecule & base pairs

DNA. A-T. C-G. One strand is a template for the other - self replication.

Protein structure

- Polymers of amino acids

- Four levels of structure

Protein Function

- Structural components

- Transport & Storage of small molecules (ex. O2)

- Transmit info between cells (hormones)

- Defense against infection (antibodies)

- Enzymes ( catalyzing reaction in cell)

Amino Acids

Carbon bonded to a

- Carboxyl group (COO-)

- An amino group (NH3+)

- A hydrogen

- A distinctive side chain

Chemical nature of side chain

- Nonpolar

- Basic

-Polar

- Acidic

Disulfide bond

Covalent bond between two cysteines

Polypeptides

Chains of amino acids

What are the ends of nucleic acids?

N Terminus and C Terminus

What are the 4 levels of structure?

primary structure, secondary structure, tertiary structure, quaternary structure

Primary Structures

- amino acid sequence

- Frederick Sanger identified insulin sequence.

Protein 3-D conformations

Christian Anfinsen.

- Denatured proteins by dif. temps (ex. Heat)

- Mild treatment, proteins restored back to normal stage.

X-ray crystallography

Analyze proteins structure. John Kendrew looked at the structure of myoglobin.

Secondary Structures

- Amino acid arrangement in localized regions

- H bonds between the CO and NH groups of peptide bonds.

Tertiary structure

- Folding of one polypeptide chain

- amino acids in different regions interact

Quaternary structure

Interactions between different polypeptide chains within the same protein

- Hemoglobin (split into 4 parts)

2 Fundamental properties of enzymes IMPORTANT

1) Increase rate of chemical reactions without themselves bein consumed/permanently altered

2) Increase reaction rates without altering the chemical equilibrium between reactants and products.

Activation energy

Energy required to reach the transition state. This is reduced by enzyme.

Enzymes bind to

substrates. Creates Enzyme-Substrate complex (ES)

S binds to the

Active site

S converted to P

P released

Reactions often involve ___ or more substrates

2

Lock and Key model

Substrate fits precisely into active site

Induced fit model (more accurate)

Conformation of both the enzyme and the substrate. Both modified.

Coenzymes

Small organic molecules that work with enzymes to enhance reaction rates.

- not altered by the reaction

- NAD+ electron carrier

Allosteric Regulation

Enzyme activity is controlled by binding small molecules to regular sites.