Origins + Biomolecules - Molecular and Cell Bio Exam 1

First cell

• 3.8 billion years ago

• Biomolecules form spontaneously as earth cools

Stanley Millar’s experiment

• replicated atmospheric conditions for first cell, researched the spontaneous formation of organic molecules

• Electric sparks interact w/ mixture of H2, CH4, NH3, and water vapor, cool it down, and it formed a variety of organic molecules, including amino acids

• Demonstrated possibility of spontaneous synthesis of organic molecules, with the basic materials in atmosphere, allowing first cell to exist

Evolution of cells

Small molecules → macromolecules → cells

RNA world hypothesis

First cell was a bit of self-replicating RNA enclosed in a phospholipid bilayer (forms spontaneously and can form enzymes). Original molecule of life, eventually evolved into DNA

Why did metabolism evolve?

Cells evolved to be more complex, so they needed another way to get energy other than the environment (which is what they mainly used before), and became dependent on ATP

Glycolysis

breaking down glucose for 2 ATP

Photosynthesis

Use sun’s energy, CO2, and water to create glucose and O2

Glycosidic linkage

the bond between carbohydrates

Oxidative metabolism

Break down glucose + oxygen → H2O + CO2, (38-38 ATP)

• Possible because of the buildup of oxygen in the atmosphere from photosynthesis

Endosymbiosis

One organism lives inside another organism

Eukaryotes

• arose from endosymbiosis, bacteria living inside archaea

• chloroplasts and mitochondria (from endosymbiosis), prokaryote sized, and have their own circular DNA and ribosomes

Prokaryotes

No nucleus, no organelles, single circular DNA, smaller, less DNA content

Eukaryotes

Nucleus, organelles present, larger + more DNA content, linear DNA

Covalent bonds

• share valence electrons

• strongest interactions (for biology)

• single, double, triple bonds

Ionic bonds

• held together by attraction of opposite charges

• electrons donated or taken

Hydrogen bonds

• bond between hydrogen (+) and oxygen or nitrogen (-)

• Singularly is weak, but strong w/ a lot of them

Hydrophilic

• forms hydrogen bonds w/ water and polar molecules

• surrounds charged ions

Lipophilic/hydrophobic

• molecules w/o charged groups

• poorly soluble in water, so associate closely w/ each other instead

Aphipathic

molecules that have moth hydrophilic and hydrophobic properties

Catabolic reactions

• breakdown complex molecules into simpler ones and releases energy.

• Downhill reactions

Anabolic reactions

• link simple molecules to form complex molecules and requires energy

• uphill reactions

Carbohydrate functions

• Energy

• cell walls and structure

• signaling

Lipid functions

• Membranes

• energy storage

• signaling

Nucleic acid functions

Information storage, energy storage, signaling

Protein functions

• Enzymes

• cytoskeleton and structure

• signaling

Dehydration reaction

• Two monomers bond together through loss of water molecule

• polymers formed by dehydration

Hydrolysis

• Uses a water molecule to break bond between monomers

• polymers broken by hydrolysis

Carbohydrate structure

• simple sugar, provides energy

• C_n (H₂O)_n

• Bonded by glycosidic linkage

Oligosaccharide

2-10 monomers

Polysaccharide

More than 10 monomers

Starch and Glycogen (carbohydrates, complex sugars)

• Energy storage, readily hydrolysable by enzymes

• can branch

• alpha(1→4 or 1→6) bonds

Cellulose (carbohydrates, complex sugars)

• for structure, not hydrolysable (bacteria can break it down)

• Forms beta(1→4) bonds, which causes cellulose to form long extended chains that pack side by side, forming mechanical strength by hydrogen bonds

Fatty acids

long hydrocarbon chains, carboxyl group is polar (which is at the head)

Triglycerides

• 3 fatty acids linked by glycerol, clumps together to form fat droplets

• insoluble in water

• efficient energy storage ****

Saturated fatty acid

All single bonds between H-C, can densely pack together

Unsaturated fatty acid

Some double bonds between H-C, results in a kink in the structure. Not able to densely pack together

Phospholipids

• main component of cell membranes

• 2 acyl (C-H) chains instead of 3, 3rd replaced by polar head group

• Acyl chains held together by glycerol (or serine… which is special)

• Amphipathic: important for membranes, fatty acid tails will clump together

What types of lipids are used for energy storage?

Fatty acids and triglycerides

What types of lipids are used for signaling?

Glycolipids and cholesterol

Glycolipids

• same structure as phospholipids, but head contains carbohydrate (no phosphate)

• Used for cellular recognition

Cholesterol

• C-H chain is formed into a multi-ring structure

• Used as hormones for signaling

What is the difference in function of DNA and RNA

• DNA is for long term information storage

• RNA is for short term information storage

Nucleotide

Contains: sugar molecule, nitrogenous base, and a phosphate group

• Adenine + guanine (purines), cytosine + thymine + uracil (pyrimidines)

Phosphidiester bonds

• The bond that holds nucleotides together

• Formed from dehydration reaction

• Bond between 5’ phosphate and 3’ hydroxyl

What are other functions of nucleotides?

• Energy (ATP)

• Signaling (cAMP)

Nucleoside

sugar molecule and nitrogenous base

Nucleic acid

large biomolecules composed of nucleotides