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What is the basis for building large and diverse organic compounds?
Carbon’s ability to bond with four other atoms
What do carbon chains form?
the backbones of most organic molecules
What are isomers?
the same molecular formula but different structures
What are hydrocarbons composed of?
only carbon and hydrogen
What do organic compound’s properties depend on?
size and shape of its carbon backbone and atom attached to that skeleton
What do hydrophilic functional groups give?
organic molecules specific chemical properties
What do the four classes of biological molecules contain?
very large molecules
What are the very large molecules contained in the four classes of biological molecules often called?
macromolecules because of their size and polymers because they are made from identical or similar building blocks strung together.
What is a monomer?
building block for polymers
How are monomers linked to formed polymers?
through dehydration reactions
How are polymers broken apart?
through hydrolysis
What mediates dehydration reaction and hydrolysis?
enzymes
What do carbohydrates range from?
small sugar molecules (monomers) to large polysaccharides
What are sugar monomers?
monosaccharides
What is the formula of a monosaccharide?
has multiple of CH2O and contains hydroxyl groups and a carbonyl group
What is formed when two monosaccharides (monomers) bond?
a disaccharide (through dehydration reaction)
What are lipids?
diverse hydrophobic compounds composed largely of carbon and hydrogen.
What do fats (triglycerides) consist of?
glycerol linked to three fatty acids
How are unsaturated fatty acids formed?
when some fatty acids contain one or more double bonds
How are saturated fatty acids formed?
when fats have the maximum number of hydrogens. (Saturated fatty acids are found in animal fats)
What is hydrogenated vegetable oils an example of?
unsaturated fats that have been converted to saturated fats by adding hydrogen.
This hydrogenation (Hydrogenated vegetable oil) creates what?
trans fats, (which are associated with health risks)
What are phospholipids?
components of cell membrane
What does steroids include?
cholesterol and some hormones
What is cholesterol?
common component in animal cell membranes and is also the precursor for making other steroids, including sex hormones
What are anabolic steroids?
synthetic variants of the male hormone testosterone that are abused by some athletes with serious consequences
Proteins are what?
involved in nearly every dynamic function in your body and are very diverse.
What do proteins function as?
enzymes, transport proteins embedded in cell membranes, defensive proteins (such as antibodies), signal proteins (such as hormones), receptor proteins, contractile proteins (found within muscle cells), structural proteins (such as collagen), and storage proteins
What is protein diversity based on?
different sequences of amino acids. monomers that contain:
an amino group, a carboxyl group, an H atom, and an R group, all attached to a central carbon.
What do R groups do?
distinguish 20 amino acids, each with specific properties.
How are amino acid monomers linked?
in a dehydration reaction
joining the carboxyl group of one amino acid to the amino group of the next amino acid, and creating a peptide bond.
Additionally, amino acids can be what?
added by the same process to create a chain of amino acids called a polypeptide.
What are phages?
bacterial viruses
What do DNA and RNA (nucleic acids) consist of?
long chains (polymers) of chemical units (monomers) called nucleotides
What is a DNA polynucleotide?
one of the two strands of DNA, a nucleotide polymer (chain)
What is a nucleotide composed of?
nitrogenous base, five-carbon sugar, and phosphate group
How are nucleotides joined to one another?
by a sugar-phosphate backbone
What are the different types of nitrogen-containing bases in DNA?
adenine (A), cytosine (C), thymine (T), and guanine (G)
What is the full name for DNA?
deoxyribonucleic acid, with nucleic referring to DNA’s location in the nuclei of eukaryotic cells.
How does RNA (ribonucleic acid) differ to DNA?
RNA uses the sugar ribose (instead of deoxyribose in DNA) and has a nitrogenous base uracil (U) instead of thymine
What does DNA replication start with?
the separation of DNA strands
What do enzymes use?
each strand as a template to assemble new nucleotides into a complementary strand.
What happens when DNA replication follows a semiconservative model?
The two DNA strands separate. Each strand then becomes a template for the assembly of a complementary strand from a supply of free nucleotides. Each new DNA helix has one old strand with one new strand.
What happens when using the enzyme DNA polymerase?
the cell synthesizes one daughter strand as a continuous piece. The other strand is synthesized as a series of short pieces, which are then connected by the enzyme DNA ligase.
What is DNA of a gene - a linear sequence of many nucleotides - transcribed to?
into a RNA, which is translate into a polypeptide.
What is transcription?
the synthesis of RNA under the direction of DNA
What is translation?
the synthesis of proteins under the direction of RNA
How can a gene that is defined as a region of DNA be expressed?
expressed to produce a functional product that is either a polypeptide or an RNA molecule.
What does the sequence of nucleotides in DNA provide?
a code for constructing a protein
What does translation requires?
the conversion of the nucleic acid language to the polypeptide language
What happens during translation?
there is a change in language from the nucleotide sequence of the RNA to the amino acid sequence of the polypeptide
What is the genetic code?
the set of rules that dictates the amino acid translations of each of the mRNA nucleotide triplets.
What do nearly all organisms use?
an identical genetic code to convert the mRNA codons transcribed from a gene to the amino acids sequence of a polypeptide
What happens in the nucleus after the DNA helix unzips?
DNA helix unzips, RNA nucleotides line up and RNA polymerase joins them along one strand of the DNA, following the base-pairing rules
What is a promoter and what does it do?
a specific nucleotide sequence that acts as a binding site for RNA polymerase and determines where transcription starts.
What does RNA polymerase add?
RNA nucleotides until it reaches a sequence of DNA base called the terminator, which signals the end of the gene
What happens in Initiation?
RNA synthesis begins after RNA polymerase attached to the promoter
What happens in Elongation?
newly formed RNA strand grows
What happens in termination?
RNA synthesis ends when RNA polymerase reaches the terminator DNA sequence.
What is messenger RNA (mRNA)
The kind of RNA that encodes amino acids. It is called this because it conveys genetic messages from DNA to the translation machinery of the cell.
What happens before leaving the nucleus as mRNA?
Eukaryotic transcripts undergo RNA splicing, in which
introns (noncoding segments of RNA) are spliced out
exons (the parts of a gene that are expressed) are spliced together, and
a cap and tail are added to the ends of the mRNA
Where does translation take place?
in the cytoplasm
A ribosomes attaches to the mRNA and translate its message into a specific polypeptide, aided by what?
transfer RNAs (tRNA)
How is an anticodon formed?
each tRNA is a folded molecule bearing a base triple, on one end and a specific amino acid attachment site at the other end.
What are the three phases that translation can be divided into (Hint: it’s the same as transcription)
initiation, elongation, and termination
What does initiation bring together?
mRNA, a tRNA bearing the first amino acid, and the two subunits of a ribosome
What happens in elongation?
amino acids are added to the polypeptide chain until a stop codon terminates translation
When does elongation stop?
it continues until a stop codon reaches the ribosome’s A site
How does a polypeptide chain grow in elongation?
as mRNA moves one codon at a time relative to the ribosome, a tRNA with a complementary anticodon pairs with each codon, adding its amino acid to the growing polypeptide chain.
What does the sequence of codons in DNA spell out?
via the sequence of codons in mRNA, spells out the primary structure of a polypeptide.
What are mutations?
changes in the genetic information of a cell or virus, caused by errors in DNA replication or recombination, or by physical or chemical agents called mutagens
What alters a gene?
substituting, inserting, or deleting nucleotides alters this, with varying effects
What is a virus?
it is an infectious particle consisting of little more than “genes” in a bit of nucleic acid wrapped in a protein coat called a capsid and, in some, cases, a membrane envelope
What happens when phage DNA enters a lytic cycle?
it is replicated, transcribed, and translated
What assembles into new phages?
the new viral DNA and protein molecules, which burst from the host cell
What happens in the lysogenic cycle?
phage DNA inserts into the host chromosomes and is passed on to generations of daughter cells
What happens when the phage DNA is inserted into the lysogenic cycle?
the phage DNA is referred to as a prophage, and most of its genes are inactive. Later it may initiate phage production
What do flu viruses and most plant viruses have?
RNA rather than DNA as their genetic material
What do some animal viruses steal?
a bit of host cell membrane as protective envelope
What are emerging viruses?
ones that seem to burst on to the scene, becoming apparent to the medical community quite suddenly.
What are prions?
infectious proteins that can cause brain diseases in animals
What happens when the prion gets into a cell.
containing the normal for of the protein, the prion somehow converts normal protein molecules to misfolded versions
What are the three mechanisms bacteria use to move genes from cell to cell?
transformation - the uptake of DNA from the surrounding environment
Transduction - gene transfer by phages
Conjugation - the transfer of DNA from a donor to a recipient bacterial cell
What happens when DNA gets into a bacterial cell?
part of it may then integrate into the recipient’s chromosomes
What is heredity?
it is the transmission of traits from on generation to the next.
When did genetics begin?
Genetics (the scientific study of heredity) began with Gregor Mendel’s experiments.
What did Mendel cross?
Mendel crossed pea plants and trace traits from generation to generation.
What did Mendel hypothesize?
He hypothesized that there are alternative versions of genes (alleles), the units that determine heritable traits.
What did Mendel develop?
Mendel developed four hypotheses, described below using modern terminology
What is Mendel’s first hypothesis?
There are alternative versions of genes (called alleles) that account for variations in inherited characters.
What is Mendel’s second hypothesis?
For each character, an organism inherits two alleles of a gene, one from each parent.
What is homozygous?
An organism that has two identical alleles for a gene
What is heterozygous
An organism that has two different alleles for a gene
What is Mendel’s third hypothesis?
If the two alleles of an inherited pair differ, then one determines the organism’s appearance and is called the dominant alleles and other has no noticeable effect of the organism’s appearance and is called the recessive allele
What is Mendel’s fourth hypothesis?
A sperm or egg carriers only one allele for each inherited character because allele pairs separate (segregate) from each other during the production of gametes. This statement is called the law of segregation.
What does Mendel’s hypotheses explain?
It also explains the 3:1 ratio observed in the F2 generation
What do the F1 hybrids all have?
They all have a Pp genotype
What does the punnett square show?
It shows the four possible combinations of alleles that could occur when these gametes combine
What does every diploid cell have?
It has pairs of homologous chromosomes
What do the chromosomes in a homologous pair carry?
They carry alleles of the same genes at the same locations
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