UTA BIOL3301 Cell Physiology Dr. Charles

First life estimate to have emerged

3.8 billion years ago

What molecule is believed to be the initial genetic system?

RNA

First cell was speculated to have arisen from _ sequester in the _ _.

RNA

Phospholipid bilayer

As cells got larger and more evolved, needs changed. What is this called?

Adaptation

DNA replaced RNA as genetic material. This is known as

Central Dogma of Molecular Biology

Gene Expression

DNA - RNA- Protein

All cells use _ as their source of metabolic energy

ATP

Prokaryotic cells

Only found in Bacteria and Archaea:

Simpler in structure

Smaller size

Lack membrane-bound organelles

No internal membranes

DNA structure is circular

No true nucleus

Eukaryotic cells

In all other organisms:

Complex structure

Larger in size

Contains membrane-bound organelles

Contain internal structures

DNA exists in linear strands that are coiled

Experimental organisms include

Chickens

Frogs

Model Organisms include

Bees, nematodes

HeLa Cells

human epithelial cells of a strain maintained in tissue culture since 1951 and used in research, especially in virology.

Light Microscopy

Visible light passes through the cell.

Resolve details as small as 0.2 um in biological specimens

Light microscopy limitations

Resolution decreases as magnification increases

Fluorescence microscopy

uses a fluorescent dye to label molecule of interest

Dye absorbs 1 wavelength of light while emitting a different wavelength.

Confocal Microscopy

Special microscope that uses image deconvolution

Images obtained from different depths of focus combined -> Sharper image

Transmission Electron Microscopy

A beam of electrons passes through thin slice of specimen

2D image

Resolve details as small as 1nm

Scanning Electron Microscopy

Beam of electrons bounces off surface of cell to

Provide a 3D image of cell surface

Resolve details as small as 3-20nm.

First Eukaryotic cells engulfed a primative bacteria, this is known as the

Endosymbiotic theory

What is comnposed of atoms and is smaller subunits of all substances?

Matter

Protons

Positively charged particles- nucleus

Neutrons

no charge, in nucleus

Electrons

negative charge, outside nucleus (orbitals)

Smallest unit of matter

Atoms

An atom is very stable when its

Outer most shell is entirely filled

Electrons determine

chemical behavior, stability

When atoms are partially filled electrons tend to

interact with other atoms resulting in chemical bonds

Covalent bond

A chemical bond formed when two atoms share electrons

Ionic bond

Atoms give electrons to another (ELECTRON TRANSFER)

There are _ types of covalent bonds

2

Nonpolar covalent bond

a covalent bond in which the electrons are shared equally by the two atoms

Polar covalent bond

unequal electron sharing, different electronegativities

Usually mix well with water via hydrogen bonds

Hydrogen bonds

Very weak bonds; occurs when a hydrogen atom in one molecule is attracted to the electrostatic atom in another molecule

Hydrophobic inbteractions

isolate themselves

Nonpolar molecules associate with one another

Important role in protein folding and lipid bilayer formation

Van der Walls interactions

Transient interactions occur when molecules are in close proximity.

Weak <1/2 strength of hydrogen bonds, can occur between any atoms

Bonds strongest to weakest

Covalent bonds

Ionic bonds

Hydrogen bonds

Molecules can be either

Organic or Inorganic

Organic molecules

usually exist as polymers

Carbohydrates

Lipids

Nucleic Acids

Proteins

Carbohydrates

Sugars and starches

Monosaccharides

Simple sugars

Main monosaccharide

Glucose

carbohydrates- Disaccharides

2 monomers

Can join via dehydration synthesis

Sucrose, lactose, maltose

Carbohydrates- Polysaccharides

Long monomer chains

Starch

Glycogen

Starch

Storage molecule of plants

Glycogen

Storage molecules of humans

Carbohydrates are considered __ __ energy source

Short term

Lipids

Do not dissolve in water

Function of lipids

Store long-term energy

Protect vital organs

Insulation

Help absorb lipid-soluble vitamins and minerals

Make up cell membrane

3 important types of lipids

triglycerides, phospholipids, steroids

Fatty acids

Chains of carbon atoms bonded to hydrogen group COOH

Triglycerides are classified as

Saturated and unsaturated

Saturated

contain single covalent bonds linking carbon atoms (saturated with hydrogens)

Unsaturated

Contains one or more double bonds between carbon atoms

Phospolipids

made up of one glycerol bonded to two fatty acid chains and one negatively charged phosphate group.

Glycolipids

Two fatty acid chains are attached to a polar head linked to a sugar.

Amphipathic

Stabilizes plasma membrane involved in cell-to-cell interactions.

Amphipathic

having both a hydrophilic region and a hydrophobic region

Cholesterol (other lipids)

*4 carbon rings attached to other molecules

*Amphipathic

*Stabilize membrane, control fluidity

*Serves as a base for steroid hormones.

Nucleic Acids

Main information molecules of the cell

Polymers made up of monomer subunits called nucleotides.

Types of nucelic acids

DNA and RNA

DNA

Sugar: Deoxyribose

Bases: A, G, T, C

Double-stranded Helix

RNA

Sugar: Ribose

Bases: A, G, C, U

Single stranded

Proteins (macromolecule)

Composed of one or more chains of amino acids --> polypeptide chain

Amino Acids

Building blocks of proteins

Protein- function

Structural support

Transport

Movement

Regulation of chemical reactions

Enzymes

Hormones

You can _ have random bases binding

NEVER

Non-polar covalent are

hydrophobic

Not very reactive

Good for structure

Polar bonds will have a

Group with a charge, reactive, hydrogen bond to other Amino Acids.

Basic indicates that H2O can

accept or bond to hydrogen

Acidic indicates that H2O will

release a hydrogen ion

Levels of protein structures

primary, secondary, tertiary, quaternary

Primary structure of proteins

A linear chain of amino acids (only exists in the early stage of the protein being made. Cant do anything in this form)

Secondary structure of proteins

alpha helix and beta-sheet

Noncovalent interactions help polypeptides fold and maintain shape.

Hydrophobic forces also play a role

Tertiary structure of proteins

further interactions between the alpha helix and beta sheets connected by large regions. 3D structure

Final conformation for protein with only one subunit

Quaternary structure

Final conformation for protein with more than one subunit

2 polypeptides

Enzymes

specialized proteins that catalyze biological reactions

Speed up the rate of chemical reactions by lowering the activation energy of the reaction.

enzymes cant act until _ binds to active site

Substrate

Substrates binding produces a _ change in the enzyme

Conformational

Coenzymes

*small organic molecules that participate in specific enzymatic reactions.

*Recycled after use and can participate in multiple chemical reactions.

Enzymes have three types of regulations

Feedback inhibition

Allosteric regulations

Phosphorylation

Enzymatic Feedback inhibition

control over a biochemical process by its products, altering protein activity in a signaling pathway.

Enzymatic Allosteric regulation

Molecule other than a substrate binds at a regulatory site, altering protein activity

Binding sites on an enzyme

Active site

Allosteric site

Enzymatic Phosphorylation

is. a common modification that involves additions of phosphate groups

Plasma Membrane

All cells are surrounded by a plasma membrane

Bilayer of phospholipids- 5 nm (50 atoms) thick

Lipid bilayer

Phospholipids assemble into bilayer due to their amphipathic nature

Lipid bilayer has

Hydrophilic heads interact with aqueous environments

Hydrophobic tails shielded from water

Phospholipids are not restricted to one seat in the bilayer.

Behaves as a 2D fluid --> Function and membrane integrity

Bilayer Fluidity

Length of hydrocarbon tails

Number of double bonds in hydrocarbon tails.

Membrane Fluidity

is determined by how easily phospholipids move

Bilayer fluidity- Cholesterol

Molecules also help maintain membrane fluidity. Fills in gaps between unsaturated hydrocarbon tails --> more rigid

Bilayer Fluidity allows membrane proteins to _ into bilayer rapidly

diffuse

Nearly _ % of plasma membranes mass is protein

50%

Integral proteins

are embedded in the phospholipid layer

Peripheral proteins

Associate with the membrane indirectly

Transmembrane proteins

*Amphipathic must satisfy both hydrophobic and hydrophilic characteristics.

*Unlike side chains, peptide bonds are polar --> Backbone wants to H-bond

*Most transmembrane proteins cross the bilayer as alpha helix

Membrane transport

Properties of the phospholipid bilayer make for a selectively-permeable membrane

Channel Proteins

form pores through the membrane that allows the passage of specific molecules

*often regulated by size

* not permanently open --> Extracellular signal opens them.

Ion channels are usually

closed

Carrier proteins

selectively bind and transport specific molecules

Passive processes in membrane transport

Do not require energy

Depends on substances moving down a concentration gradient

Move from the area of more substance to an area of less

Two types: diffusion, osmosis

Active process in membrane transport

Require energy

Substances must be moved up their concentration gradient

Membrane-bound vesicles must be released.

Catabolism

Breakdown into smaller molecules, generating ATP