Chapter 3 - The Molecules of Cells Flashcards
What are valence electrons?
Electrons in the outermost shell of an atom that are available for chemical bonding.
What is a stable number of electrons in a valence shell?
Most stable when full. Most of the elements important in biology need eight electrons in their outermost shell.
Why is carbon the backbone of so many biologically relevant molecules (4 reasons)?
It’s abundant; it can form four covalent bonds; can easily form and break bonds with oxygen and other carbons (important for respiration/ photosynthesis, carbon chains are useful). Carbon is super versatile (length, double bonds, branching, rings).
How many valence electrons does carbon have? How many bonds does it want?
Carbon has four electrons in the outer valence shell, and can form four covalent bonds.
What is the basic formula for a hydrocarbon?
Contains only hydrogen and carbon. Carbon forms the skeleton or backbone.
What is the basic formula for a carbohydrate? Hydrophobic/philic?What are they used for?
Hydrated Carbon – they all contain C and H2O. Contains hydroxyl groups (OH) & carbonyl groups (C=O).
Tend to be hydrophilic due to many OH groups. Used for energy storage (sugars/starches).
What is the basic formula for a protein?
Polymers made from various combinations of 20 amino acids. A carbon backbones with a carboxyl (COOH) and amino group (NH2). The carboxyl and amino groups of different molecules are joined to create proteins.
What are nucleic acids?
What is their basic formula?
Are macromolecules including Ribonucleic Acid (RNA) and Deoxyribonucleic Acids (DNA). Made of monomers called nucleotides (made of 5C sugar, a phosphate group PO4, and a nitrogen base).
Dehydration synthesis joins nucleotides: sugar to phosphate.
What are lipids? What are two common properties between lipids?
Includes compounds commonly known as fats, oils, and waxes. Includes fats (triglycerides), phospholipids and steroids. They are not huge macromolecules. Vary a lot in structure and function but are all hydrophobic.
What are the 6 primary functional groups that can be added to carbon skeletons?
Hydroxyl Group OH
Carbonyl Group C=O
Carboxyl Group COOH
Amino Group NH2
Phosphate Group PO4
Methyl Group CH3
Remember N and O are polar and hydrophilic.
What is an isomer? What are the three types?
Organic compounds with the same molecular formula, but different structures. They differ in chemical properties despite having the same basic chemistry.
Structural (branching)
Geometric (cis/trans, functional groups around a double bond)
Enantiomers (mirror image)
What is a monomer?
A subunit (molecule) that serves as a building block for a polymer (mono = 1)
What is a polymer?
A large molecule consisting of many identical or similar monomers (poly = many)
What is a macromolecule?
A very large molecule important to biological processes, such as a protein or nucleic acid. (Macro = big)
Polymers are macromolecules.
What chemical reaction is used to “stick” monomers together to make polymers?
Dehydration synthesis!
The formation of larger molecules from smaller reactants accompanied by the loss of a water molecule.
What is a catalyst?
A substance that increases the rate of a chemical reaction without being permanently changed. It’s reusable!
What is the definition of hydrolysis?
How is this related to polymers and monomers?
The reverse of dehydration synthesis.
(Hydro = water, lysis = loosen, dissolve)
Adding water and breaking a bond (and breaking the water into H and OH).
Can break polymers back into monomers.
What are monosaccharides? Example?
A class of carbohydrates. Single unit sugars (monomers), basic ratio of 1:2:1 for C:H:O; (i.e., CH2O). Most common is glucose – C6H12O6 (often in a ring structure).
How are monosaccharides structured and names?
Open or ring forms with 3 to 7 carbon. Usually end in “ose”. Generally named based on number of carbon (3C = triose).
What’s the difference between an aldose and ketose sugar?
If C=O is at the end of the molecule its an aldose sugar.
if it is not at the end it’s a ketose sugar.
What is a disaccharide? Example?
A class of carbohydrates. 2 monosaccharides joined via dehydration synthesis. i.e. Maltose, Sucrose (NRG transport in plants), Lactose.
What is a polysaccharide? Example?
A class of carbohydrates. Very long chains of monosaccharides linked together via dehydration synthesis. i.e. Starch (plant); Glycogen (animal); Cellulose (plant) and Chitin (animal).
What is starch? What is it used for?
The simplest polysaccharide, used as an energy storage molecule in plants. Consists entirely of glucose molecules “stuck” together via dehydration synthesis. Animals have enzymes to break starch into glucose.
What is a glycogen?
A storage polysaccharide of animals, highly branched, most often found in muscle and liver cells.
What is chitin? What’s it used for?
A modified polysaccharide that contains N and an important structural material in the exoskeletons of insects, crabs, and lobsters
How are glycogen and starch different?
Starch: energy storage in plants, straight (amylose) or branched (amylopectin).
Glycogen: energy storage in animals, highly branched.
What is cellulose?
How is it different from starch or glycogen?
Principal component of plant cell walls; most abundant organic molecule on earth; a polysaccharide whose linkages cannot be broken down by most animals; source of insoluble fibre.
What’s the structure of an amino acid?
Central carbon (the alpha C) is bonded to an amino group (NH2), a carboxyl group (COOH), a hydrogen and a functional R group.
The difference between different amino acids is the R group.
What do we mean by primary, secondary, tertiary, and quaternary structure of a protein?
Primary: Amino acids connected by peptide bonds (a long chain).
Secondary: Spirals (Alpha helix) or pleated sheets made by hydrogen bonds.
Tertiary: The overall 3D shape stabilized by interactions between R groups.
Quaternary: 2 or more 3D tertiary proteins and “sticking” them together to form a larger protein.
What holds the secondary structure of proteins together?
Hydrogen bonds between atoms in the protein’s backbone. (hydrogen bonds with the electronegative nitrogen and oxygen).
What holds the tertiary structure of proteins together?
Interactions between the R groups in the protein. Different groups can form ionic, covalent and hydrogen bonds with each other.
What happens when a protein becomes denatured? Why does this happen?
They lose their 3-D shape and their function. Can be caused by acids (pH changes), salts or heat and may be reversible.
What do we call the bond that forms between the carboxyl group of one amino acid with the amino group of another?
Amino acids are linked via dehydration synthesis. The bond that forms is called a peptide bond.
What are some of the functions of proteins (7)?
Enzymes (catalyze/regulate chemical reactions); Transport (across cell membrane); Defensive; Signal (hormones); Receptor (in cell membrane); Contractile (muscle cells); Structural (connective tissues).
What are the 4 nitrogenous bases in DNA?
The four bases in DNA are adenine (A), cytosine (C), guanine (G), and thymine (T).
What are the 4 nitrogenous bases in RNA?
Adenine (A), cytosine (C), uracil (U), and guanine (G).
What is complimentary base pairing? Which bases pair together?
Pairs are joined by hydrogen bonds between the bases.
In DNA:
Adenine (A) and thymine (T) pair.
Cytosine (C) and guanine (G) pair.
RNA, adenine pairs with uracil.
What does hydrophobic and hydrophilic mean?
Hydrophobic – “water-fearing”
Hydrophilic – “water-loving”
Are lipids hydrophobic or hydrophilic?
Hydrophobic.
What class of molecules did we look at that are not considered polymers?
Triglycerides (?)
Fats are not huge macromolecules.
What’s a triglyceride composed of? What type of bond holds it together?
A glycerol (a 3C alcohol) and 3 long-chain fatty acids. Attached by dehydration synthesis forming an ester bond.
What is the primary function of fats/triglycerides?
Long-term concentrated energy storage, cushions organs, insulates body, needed for cell membranes.
What do we mean when we say fatty acids are saturated? What are they saturated with? Example?
Saturated fats have no double bonds in their fatty acids. This allows them to be saturated with hydrogens.
Mostly animal fats, pack tightly, tend to be solid at room temp.
What do we mean when we say fatty acids are unsaturated? Or polyunsaturated?
There are one or more double bonds. The fatty acid may be kinked, pack more loosely, tend to be liquid at room temp.
Several C=C double bonds makes it polyunsaturated.
Why do double bonds make fats more likely to be a liquid at room temperature?
The double bond causes a bend or a “kink” that prevents the fatty acids from packing tightly.
What is the name of the bond that forms between the carboxyl group of a fatty acid and the hydroxyl group of the glycerol molecule?
An ester bond which is created through dehydration synthesis.
What is the name of the chemical reaction that joins molecules together? What version of this reaction have we focused on?
Synthesis reactions. This class has focused on dehydration synthesis: the formation of larger molecules from smaller reactants accompanied by the loss of a water molecule.
How are phospholipids different from triglycerides? How do they react with water?
They only have 2 hydrogen/carbon tails and add one phosphate (PO4) group.
Has a hydrophilic head and two hydrophobic tails.
Why do phospholipids automatically form bilayers or micelles in aqueous solutions? What shape are these formations?
Because of the hydrophilic head and two hydrophobic tails. This is important to cell membranes.
Micelles are round. Bilayers are sheets.
A type of lipid where the carbon skeleton contains 4 fused rings is called a ___________.
Steroid.
What is cholesterol?
A type of steroid (and therefore a lipid) and an important building block of cell membranes and steroids, including sex hormones etc.
Is cholesterol soluble in water?
No, cholesterol is hydrophobic.
How is cholesterol transported in the body?
Cholesterol is packaged for transport in lipoproteins (fat-proteins).
More protein than fat = high density lipoproteins (HDL).
Less protein than fat = low density lipoproteins (LDL).
What’s the difference between HDL or LDL? Which is better?
LDL (low-density lipoprotein) leaves more sticky cholesterol build up in arteries while HDL (high-density lipoprotein) can remove build up…if it hasn’t hardened too much.
When plaques from excess cholesterol in the blood builds up in artery walls it is called ______.
Atherosclerosis
When plaques becomes hardened by fibrous tissue and calcification it is called ___________.
Arteriosclerosis
What is the primary cause of a heart attack?
Coronary artery disease (arteriosclerosis in the heart’s arteries). Also trans fats can increase the risk of heart disease.
What is the primary cause of a stroke?
The arteries of the brain (cerebral arteries) being affected by arteriosclerosis.
