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66 Cards in this Set

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how many electrons can orbitals hold?
who gives a fuck?

just kidding. 2.
Shell Model
First shell
Lowest energy
Holds 1 orbital with up to 2 electrons
Second shell
4 orbitals hold up to 8 electrons
Ionic Bonds
One atom loses electrons to become a positively charged ion
Another atom gains these electrons to become a negatively charged ion
The charge difference attracts the two ions to each other & keeps them together
Covalent Bonds
Atoms share a pair or pairs of electrons to fill the outermost shell
Nonpolar covalent bond
Atoms share electrons equally
Example: Hydrogen gas (H-H)
Polar covalent bond
Electrons spend more time near nucleus with most protons
Example: Water - electrons more attracted to O nucleus than to H nuclei
Hydrogen Bonds
Molecule held together by polar covalent bonds has no net charge
However, atoms of the molecule carry different charges
Atom in one polar covalent molecule can be attracted to oppositely charged atom in another such molecule
Free Radicals
molecules that lack a full complement of electrons in their outer shells
High capacity to oxidize
Can readily “steal” an electron from another, stable molecule
Antioxidant
chemicals that can give up an electron to a free radical before it damages cell
Some manufactured by the body (melatonin)
Others available in diet (vitamin C, vitamin E, carotenoids
Condensation reactions
form polymers from subunits; Enzymes remove -OH from one molecule, H from another; form bond between two molecules; discarded atoms can join to form water
Hydrolysis rxns
break polymers into smaller units; enzymes split molecules into two or more parts; an -OH group and an H atom derived from water are attached at exposed sites
Carbohydrates (sugars)
come in different forms (classes):
Monosaccharides (simple sugars)
Oligosaccharides (short-chain carbohydrates)
Polysaccharides (complex carbohydrates)
Most sugars are composed of carbon, hydrogen and oxygen atoms in a 1:2:1 ratio
Most abundant biological molecule
Lipids
Most include fatty acids: Fats; Phospholipids; Waxes
Sterols and their derivatives have no fatty acids
Tend to be insoluble in water
Proteins
A protein is a chain of amino acids linked by peptide bonds
Peptide bonds are covalent bonds that link amino groups of one amino acid with carboxyl groups of the next via condensation reactions
Protein Structure
Primary structure = sequence of amino acids; unique
Secondary structure = local regions of hydrogen bond formation between different parts of the peptide chain: helix or pleated sheet
Tertiary structure = final folding of secondary structures into a functional unit
Quaternary structure = multiple tertiary structures held together
cell theory
Every organism is composed of one or more cells
The cell is the smallest unit having properties of life
All cells come from pre-existing cells
3 common features of cells
A plasma membrane
An internal region where DNA is stored
Cytoplasm
advantages of small cells
Surface-to-volume ratio is important: the bigger a cell is, the less surface area there is per unit volume
Above a certain size, material cannot be moved in or out of cell fast enough; in this case the cell dies
plasma membrane (lipid bilayer)
the mediator of exchange
Gives membrane its fluid properties and determines function
Two layers of phospholipids: hydrophilic heads face outward and hydrophobic tails face the center
Structure: extremely thin; mosaic of proteins and lipids
Lipids give membrane its fluid quality
Proteins carry out most membrane functions
Transports, Receptors, Recognition proteins, Adhesion proteins
Nucleus
Keeps the DNA molecules of eukaryotic cells separated from metabolic machinery of cytoplasm
Makes it easier to organize DNA and to copy it before parent cells divide into daughter cells
Components: nuclear envelope, nucleoplasm, nucleolus
Chromatin: cell’s collection of DNA + associated proteins
A chromosome is one DNA molecule and its associated proteins; the appearance of chromosomes change as the cell divides
The Endomembrane System
Group of related organelles; assembles lipids; modifies new polypeptides; sorts and ships products to various destinations
Rough ER = sacs studded with ribosomes; protein modification
Smooth ER = interconnected tubules w/o ribosomes; lipid assembly; toxin inactivation
Golgi = finishes modifications to proteins + lipids; packages for transport within cell or to surface (vesicle trafficking)
Mitochondria
ATP-producing powerhouses
Carry out the most efficient energy-releasing reactions
Reactions require oxygen
Structure: two compartments
Outer membrane faces cytoplasm
Inner membrane folds back on itself
ATP-making machinery is embedded in the inner mitochondrial membrane
Cytoskeleton
Basis for cell shape and internal organization
Enables organelle movement within cells and, in some cases, cell motility
Main elements are microtubules (spatial organization), microfilaments (cell rearrangements), and intermediate filaments (strong anchors)
Selective Permeability
PM controls movement
Diffusion: net movement of like molecules or ions down a concentration gradient
Osmosis = diffusion of water
Tonicity
Diffusion + Osmosis = no energy
Transport Proteins + Transport
Transport proteins span the lipid bilayer
Interior is able to open to both sides
Change shape when they interact with solute
Play roles in passive and active transport
Passive transport = flow of solutes through the interior of passive transport proteins down their concentration gradients; no energy needed
Active transport = net diffusion of solute is against concentration gradient; transport protein must be activated
ATP gives up phosphate to activate protein
Binding of ATP changes protein shape and affinity for solute
Exocytosis and endocytosis also occur (PM vesicles)
Enzyme Structure + Function
Enzymes speed the rate at which certain reactions occur
An enzyme recognizes and binds to only certain substrates (Induced-Fit Model)
Reactions do not alter or use up enzyme molecules
Enzyme-substrate complexes are short lived and reversible
Factors influencing activity
Temperature, pH, salt concentration, coenzymes + cofactors
Toxins will also affect
Aerobic Respiration
Aerobic respiration converts glucose to CO2 + H2O, in the process allowing for the production of ATP
Glycolysis: glucose to 2 pyruvate in cytoplasm
Glycolysis has 2 overall steps: one uses energy to prime the system, the other produces energy (yield: 2ATP + 2NADH)
NADH = electron carrier
Pyruvate enters mitochondria  Krebs Cycle
Preparatory reactions occur prior to entrance to Krebs
Products: Coenzyme A; 2 CO2; 3 NADH; FADH2; ATP
NADH, FADH2 need to be oxidized (reset) and their electrons converted to ATP  Electron Transport Chain (ETC)
ETC passes electrons to the final electron acceptor: oxygen
As electrons move, H+ is moved from inner to outer compartment; flow back across membrane drives ATP synthesis
Glucose Utilization
When glucose is present, it is absorbed into the blood
Pancreas releases insulin that stimulates glucose uptake by cells
Cells convert glucose to glucose-6-phosphate, trapping glucose in the cytoplasm where it can be used for glycolysis
If glucose intake is higher than what is needed, glucose-6-phosphate is diverted into glycogen synthesis for storage (in liver and muscle)
When glucose levels in the blood drop, the pancreas releases glucagon which stimulates liver cells to convert glycogen back to glucose and to release it to the blood (muscle cells do not release their stored glycogen)
Glycogen makes up only about 1% of the body’s energy reserves; proteins make up 21% of energy reserves; fats make up the bulk of reserves (78%)
Energy from Fats + Proteins
Most stored fats are triglycerides
Triglycerides are broken down to glycerol and fatty acids
Glycerol is converted to PGAL, an intermediate of glycolysis
Fatty acids are broken down and converted to acetyl-CoA, which enters Krebs cycle
Proteins are broken down to amino acids
Amino acids are broken apart
Amino group is removed; ammonia forms, is converted to urea, and is excreted
Carbon backbones can enter the Krebs cycle or its preparatory reactions
Reproduction + Cell Division
Parents produce a new generation of cells or multi-celled individuals like themselves
Parents must provide daughter cells with hereditary instructions, encoded in DNA, and enough metabolic machinery to start up their own operation
Mitosis, division of cytoplasm
Body growth and tissue repair
Meiosis, division of cytoplasm
Formation of gametes, sexual reproduction
Chromosomes
Chromosomes are DNA molecules & attached proteins
Chromosome Number = the sum total of chromosomes within a given cell type
Somatic cells
Chromosome number is diploid (2n; 46 for humans)
Two of each type of chromosome (2 sets of 23; one set from father, one set from mother)
Gametes
Chromosome number is haploid (n; 23 for humans)
One of each chromosome type
Chromosomes are duplicated in preparation for mitosis
Cell Cycle
Cycle starts when a new cell forms
During cycle, cell increases in mass and duplicates its chromosomes
Cycle ends when the new cell divides
Interphase is the longest phase and includes G1, S, G2
Mitosis involves division and encompasses 4 stages followed by physical division
Sexual Reproduction
Chromosomes are duplicated in germ cells
Germ cells undergo meiosis and cytoplasmic division
Cellular descendants of germ cells become gametes
Gametes meet at fertilization
Meiosis involves 2 consecutive divisions to reduce the number of chromosomes
Random Alignment
During transition between prophase I and metaphase I, microtubules from spindle poles attach to kinetochores of chromosomes
Initial contacts between microtubules and chromosomes are random
Either the maternal or paternal member of a homologous pair can end up at either pole
The chromosomes in a gamete are a mix of chromosomes from the two parents
Fertilization
Male and female gametes unite and nuclei fuse
Fusion of two haploid nuclei produces diploid nucleus in the zygote
Which two gametes unite is random
Adds to variation among offspring
Mitosis
Mitosis
Functions
Asexual reproduction
Growth, repair
Occurs in somatic cells
Two diploid cells are produced, each identical to the parent (produces clones)
Meiosis
Function
Sexual reproduction
Occurs in germ cells
Produces variable offspring
Four haploid cells are produced, each different from the parent and from one another
Alleles
different forms of the same gene
Dominant allele masks a recessive allele that is paired with it
Homozygous = two identical alleles (AA or aa) at same locus
Heterozygous = two different alleles (Aa) at same locus
Alleles form the genotype (unseen); phenotype = the expression of the genotype (observed)
Genes
basic units of information about specific traits (genes are DNA)
Principle of Gene Segregation
An individual inherits a unit of information (allele) about a trait from each parent
During gamete formation, the alleles segregate from each other
Homozygous parents produce gametes of same type alleles
Heterozygous parents would produce 2 games of each allele type
Predictable patterns of segregation
Genetic Probabilities
the chance that each outcome of a given event will occur is proportional to the number of ways that event can be reached
For heterozygous parents, 4 events are possible
“C” = dominant
“c” = recessive
3/4 chance of dominant
Probabilities are the same for each child
Dihybrid Cross
Complexity rises when look at multiple loci
Parents CCDD x ccdd will produce F1 generation that is all CcDd
Parents CcDd x CcDd produce 4 outcomes in the F2 generation
Again, genes assort independently
Pleiotropy
Alleles at a single locus may have effects on two or more traits
Classic example is the effects of the mutant allele at the beta-globin locus that gives rise to sickle-cell anemia
Two alleles: HbA (encodes normal beta-hemoglobin chain) and HbS (mutant allele encodes defective chain)
HbS homozygotes produce only the defective hemoglobin; suffer from sickle-cell anemia
Sickle cell anemia:
At low oxygen levels, cells with only HbS hemoglobin “sickle” and stick together
This impedes oxygen delivery and blood flow
Over time, it causes damage throughout the body
Homologous Chromosomes
Homologous autosomes are identical in length, size, shape, and gene sequence
Sex chromosomes are non-identical but are still considered homologous
Homologous chromosomes interact, then segregate from one another during meiosis
Alleles on homologous chromosomes may be same or different
Sex Determination
Human X and Y chromosomes function as homologues during meiosis
The X chromosome carries more than 2,300 genes, most genes deal with nonsexual traits
Genes on X chromosome can be expressed in both males and females
The Y chromosome has fewer than two dozen genes identified, one of which is the master gene for male sex determination
SRY gene (sex-determining region of Y)
SRY present, testes form
SRY absent, ovaries form
X Chromosome Inactivation
Mammalian females have two X chromosomes per cell
One X is inactivated per cell – produces a Barr Body
Condensed X chromosome that is visible but so tightly packed it cannot be expressed
Inactivation is random – it can be either the maternal or paternal X chromosome
Gene Linkage
Genes on the same chromosome are “linked”
Crossing over can rearrange linked genes
Farther apart two genes are on chromosome, the more they are to be rearranged by crossing over
Human Genetic Analysis
Pedigrees allow for the tracking of genes through families
Knowledge of probability and Mendelian patterns used to suggest basis of a trait
Can be used to track genetic abnormalities (rare, uncommon versions of traits) or genetic disorders (inherited conditions causing mild to severe diseases)
Abnormality: polydactyly (extra fingers and/or toes)
Disorder: Huntington disease
Why do genetic disorders continue if harmful?
Mutation introduces new rare alleles
In heterozygotes, harmful allele is masked, so it can still be passed on to offspring
Autosomal-Recessive Inheritance
If parents are both heterozygous, child will have a 25% chance of being affected, and a 50% chance of being a carrier
Examples:
Cystic fibrosis
Phenylketonuria (PKU)
Tay-Sachs disease
Autosomal-Dominant Inheritance
Trait typically appears in every generation (carriers in this case show disease)
Examples:
Huntington disorder
Achondroplasia
Familial hyper-cholesterolemia
X-Linked Recessive Inheritance
Males show disorder more than females
Son cannot inherit disorder from his father
X-linked recessive
Red/green color blindness
Hemophilia A
Duchenne muscular dystrophy (DMD)
X-linked dominant
Faulty enamel trait
Changes to Chromosome Structure
Deletions:
permanent loss of part of a chromosome and its genes; may occur sponataneously, or be due to a virus, irradiation, or other environmental factors. Most are lethal or cause serious disease
Changes to Chromosome Structure
permanent loss of part of a chromosome and its genes; may occur sponataneously, or be due to a virus, irradiation, or other environmental factors. Most are lethal or cause serious disease
Changes to Chromosome Structure
Duplications
gene sequence is repeated several to hundreds of times; occur in normal chromosomes and may have an adaptive advantage
Translocation:
A piece of one chromosome becomes attached to another non-homologous chromosome; usually reciprocal
Aneuploidy:
individuals have one extra or less chromosome (2n + 1 or 2n - 1)
Major cause of human reproductive failure; most human miscarriages are aneuploids
Polyploidy:
individuals have three or more of each type of chromosome (3n, 4n)
Lethal for humans: 99% die before birth, newborns die soon after birth
Down Syndrome:
Trisomy 21; mother’s age = risk factor
Mental impairment and a variety of additional defects
Turner Syndrome: (XO; 98% spontaneous abortion)
Survivors are short, infertile females with no functional ovaries, secondary sexual traits reduced, may be treated with hormones, surgery
Klinefelter Syndrome: XXY condition
Results mainly from nondisjunction in mother (67%)
Phenotype is tall males; sterile or nearly so; feminized traits (sparse facial hair, somewhat enlarged breasts); treated with testosterone injections
XYY Condition
Taller-than-average males; most otherwise phenotypically normal; once thought to be predisposed to criminal behavior, but studies now discredit
Watson-Crick Model
Experiments in the 1950s showed that DNA is the hereditary material – scientists then raced to determine the structure of DNA
1953 - Watson and Crick proposed that DNA is a double helix DNA consists of two nucleotide strands
Strands run in opposite directions
Strands are held together by hydrogen bonds between bases
A binds with T, C with G
Molecule is a double helix
DNA to RNA to Proteins
DNA is a storage mechanism and represents the blueprint of the cell. Cells, however, are built from proteins and other molecules.
To make these “parts”, DNA is transcribed into RNA which serves as a “pattern” for fabricating new parts.
RNA is translated (fabricated) into protein.
RNA uses ribose sugars and Uracil [U] instead of Thymine
Messenger RNA (mRNA):
carries instructions (pattern)
Ribosomal RNA (rRNA):
major component of ribosomes (factory)
Transfer RNA (tRNA):
delivers amino acids to ribosomes (worker)