MCAT biology terms Flashcards
1
Q
Mast Cells
A
Immune cells in lungs covered with antibodies. Release inflammatory chemicals upon antigen binding to promote immune response. Responsible for respiratory allergic reactions due to reactions with things like pollen and molds.
2
Q
Bicarbonate Buffer System
A
Mechanism where respiratory system controls blood pH via controlling carbon dioxide concentrations. Less CO2 in blood = More Basic = Body responds with slower breathing to retain CO2. More CO2 in blood = More Acidic = Body increases breathing rate to remove CO2. Hyperventilation decreases CO2 levels in blood, making blood more basic. Body responds with trying to slow breathing rate.
3
Q
Intercostal Muscles
A
Layers of muscles between the ribs
4
Q
External Intercostal Muscles
A
contract upon inhalation to pull ribcage up and expand intrathoracic volume (chest cavity volume)
5
Q
internal Intercostal Muscles
A
contract upon forced exhalation only
6
Q
Surfactant
A
Detergeny covering alveoli to reduce surface tension and prevent alveolus from collapsing on itself. Premature babies do not have surfactant.
7
Q
“LAMB RAT”
A
- Left Atrium = (Mitral) Bicuspid Valve,
- Right Atrium, Tricuspid Valve
8
Q
Intercalated Discs
A
Connect muscle cells in the myocardium of the heart. Contain many gap junctions to connect the cytoplasm of adjacent cells and allowing for quicker signal propogation and coordinated ventricular contraction.
9
Q
Portal Systems
A
Transport systems where blood traveling through these systems goes through two capillary beds in series before returning to the heart. The three portal systems are the:
1) Hepatic (gut –> liver)
2) Hypophyseal (hyopthalamus –> anterior pituitary)
3) Renal (glomerulus -> vasa recta)
10
Q
Hematocrit
A
a measure of how many Red Blood Cells are in blood, given as a percentage of total cells in blood. Usually ~45%
11
Q
Hematopoietic Stem Cell
A
Stem cell which can differentiate to create Red Blood Cells, White Blood Cells, and Platelets.
12
Q
Rh Factor
A
Surface Protein expressed in red blood cells in the presence of allele called D. Leads to (+) or (-) blood type classifications. Dominant allele.
13
Q
Bohr Effect
A
a shifting of the oxyhemoglobin curve to the right, indicating a lower affinity of hemoglobin for oxygen so that oxygen can be transported from the RBC to tissues that need it. The Bohr Effect can be due to decreased pH and increasing the H+ concentration in the blood. H+ binds to hemoglobin allosterically and reduces affinity for oxygen. This allows more oxygen to be delivered to tissues that need it for aerobic production of ATP. Decreased pH can be caused by increased CO2 and lactic acid in blood. Right shift of curve can also be caused by increased temperature, and 2,3-bisphosphoglycerate (2,3-BPG).
14
Q
Fetal Hemoglobin
A
(HbF) has higher affinity for oxygen than adult hemoglobin (HbA), in order to pull oxygen from mother’s hemoglobin and onto fetal hemoglobin. Results in left shifted oxyhemoglobin dissociation curve
15
Q
Lysozyme
A
Enzyme able to attack petidoglycan walls of gram positive bacteria. Found in nasal cavity, tears, and saliva
16
Q
Humoral Immunity
A
Division of adaptive immunity that includes antibodies and B-cells which act within the blood rather than within cells.
17
Q
Thymus
A
Gland that matures T-cells. Located between the lungs, just above the heart. Adults don’t have
18
Q
Complement
A
Proteins that nonspecifically will punch holes in the cell membranes of bacteria, making them osmotically unstable. Can use the classical pathway which requires antibody binding, or alternative pathway which doesn’t)
19
Q
Interferon
A
Proteins produced by cell upon viral infection to block cellular and viral protein production. Decrease permeability of cell membrane and upregulate MHC class 1 and class 2 molecules on cell surface to signal immune system. Responsible for malaise, tiredness, muscle soreness, and fever during viral infections.
20
Q
Major Histocompatibility Complex
A
(MHC) binds to pathogenic peptides (antigens) and carries it to cell surface where it can be recognized by other immune cells. Produced by virally infected cells via interferons. Also produced by macrophages. MHC-1 is produced by all cells except RBC’s and carries many proteins to cell surface; platelets also have MHC–1. When foreign proteins are presented, immune cells know that the presenting cell is infected and needs to be destroyed. Called endogenous pathway. MHC-2 are mainly displayed by professional antigen presenting cells like macrophages, dendritic cells, and some B-cells. Takes antigens from environment, processes them inside the cell, then displays them to activate the rest of the immune system. Called exogenous pathway.
21
Q
MHC I
A
- can present self OR non-self antigens
- they are found in every cell of the body EXCEPT for red blood cells.
- bind to CD8 Cells, aka cytotoxic T cells
22
Q
MHC II
A
only present non-self antigens
* they are found on only Antigen-Presenting Cells (APC’s)
* bind to CD4 Cells, aka helper T cells
23
Q
Pattern recognition receptors
A
(PRR) able to recognize category of invaders (bateria, virus, fungus, parasite) in order to initiate appropriate cytokine response. These receptors are presented on macrophages and dendritic cells.
24
Q
Natural Killer Cells
A
Detect and destroy cells with downregulated MHC; they basically poke holes in the cell’s membrane, which prevents that cell from keeping a stable membrane potential and therefore it dies. Includes cancer cells and some virally infected cells
25
Neutrophils
Most abundant type of white blood cells in the body. They are quicker to respond than macrophages because they "come in hot with guns-a-blazing and ask questions later". Short lived (5 days). Dead neutrophils are responsible for formation of pus. Follow bacteria via chemotaxis and phagocytize them. Can also destroy opsonized cells.
26
Eosinophils
Release large amounts of histamine upon activation for inflammation. Contain bright, red-orange ganules in a typical histological stain.
27
Histamine
Released by Eosinophils and Basophils. Cause inflammation by inducing vasodilation and increased leakiness of blood vessels so additional immune cells can enter tissue.
28
Basophils
Have large, purple granules in a typical histological stain. Least populus leukocyte. Produce large amount of histamine in response to allergens. Closely related to mast cells.
29
Plasma Cells
(Effector B-Cells)
"antibody creating factories"
30
Memory B Cells
stick around longer than Plasma Cells; their main function is to make proliferation easier (more rapid and more prolonged proliferation) for the NEXT time you encounter a certain antigen
31
Salivary Amylase (ptyalin)
Enzyme in saliva capable of hydrolyzing starch into smaller sugars.
32
Lipase
Enzyme in saliva that catalyzes the hydrolysis of lipids.
33
Epiglottis
Cartilaginous structure that folds down to cover larynx during swallowing, so food doesn't enter and lead to choking.
34
Peristalsis
Involuntary, rhythmic contraction of smooth muscle that propels food down digestive tract. Can be reversed during emesis (vomiting) to move contents from the stomach, out the mouth.
35
Stomach Anatomy
Consists of the Fundus (top), Body (middle), Pylorus (bottom), and Antrum (exit). Lesser curvature is the inside curve, Greater Curvature is the outside curve. Rugae is the internal, folded lining of the stomach.
36
Gastric Glands
Dominant glands in the Fundus and Body. Stimulated by the Vagus Nerve of the Parasympathetic Nervous System. Contain three main cell types: Mucous Cells, Chief Cells, and Parietal Cells.
37
Mucous Cells
secretes bicarbonate-rich mucous that protects the inner lining of the stomach from the harshly acidic pH environment.
38
Chief Cells
secretes pepsinogen in the stomach, the inactivated form of pepsin; digests proteins once the persinogen is activated by H+
39
Pepsin
Enzyme produced from pepsinogen being cleaved by hydrogen ions in the stomach. Cleaves peptide bonds near aromatic amino acids, resulting in short, peptide fragments. Uniquely most active at low pH.
40
Parietal Cells
secretes HCl and intrinsic factor. The HCl decreases pH so that the H+ ions can cleave pepsinogen into pepsin. The low pH also helps kill most harmful bacteria and denature proteins and break down some intramolecular bonds that hold food together. Intrinsic factor aids in the absorption of vitamin B12
41
Intrinsic Factor
Glycoprotein secreted by the parietal cells in the gastric glands in the stomach. It is involved in the absorption of vitamin B12
42
G-Cells
Cells in the pyloric glands of the stomach that secrete Gastrin
43
Gastrin
Peptide Hormone that induces the parietal cells in the stomach to secrete more HCl and also signals the stomach to contract. Secreted by G-cells
44
Pyloric Glands
Dominant glands in the Antrum and Pylorus sections of the stomach. Contain G-cells that secrete gastrin.
45
Chyme
Acidic, semifuild mixture in the stomach resulting from the digestion of solid food.
46
Cardiac Sphincter
Sphincter that controls the movement of the bolus from the esophagus into the stomach
47
Pyloric Sphincter
Sphincter that controls movement of chyme from the stomach to duodenum
48
Small Intestine
Responsible for continued digestion and absorption of nutrients. Approximately 7 meters long. Consists of three segments: Duodenum, Jejunum, and Ileum. The majority of chemical digestion takes place in the duodenum while the majority of absorption takes place in the jejunum and ileum.
49
Duodenum
Site of chemical digestion in the small intestine. Releases tons of enzymes such as brush border enzymes, secretin, and cholecystokinin.
50
Brush Border Enzymes
Enzymes present on the inside surface of cells lining the duodenum that are released in the presence of chyme. These enymes break down dimers and trimers of biomolecules into absorbable monomers. Include disaccharidases and peptidases
51
Lack of Digestive Enzyme
Intestines can't cleave disaccharaide for digestion. This increases osmolarity and pulls water into the intestines to form diarrhea. Bacteria in the small intestine are able to break down disaccharides, but result in methane gas as a biproduct, resulting in farts.
52
Bile
Complex fluid of bile salts, pigments, and cholesterol. Produced by the liver and stored in the gallbladder before secretion into the small intestine.
53
Bile Salts
Have hydrophobic and hydrophilic regions to act as an emulsifier in the duodenum to allow fats and cholesterol to form micelles and giving access to pancreatic lipase digestion (a water soluble enzyme). The creation of micells increases surface area of fats for aided digestion by lipases. Formation of micelles is a form of mechanical digestion.
54
Pancreatic Juices
Secreted by pancreas into duodenum due to stimulation by cholecystokinin (CCK). Complex mixture of ezymes in bicarbonate-rich solution. This basic solution neutralizes chyme to allow for ideal pH for enzymatic digestion (most active around pH 8.5). Contains enzymes to digest carbohydrates, fats, and proteins.
55
Acinar Cells
Cells that make up the bulk of the pancreas and participate in its exocrine functions. Produce pancreatic juices.
56
Pancreatic Enzymes
Secreated by Acinar Cells.
Pancreatic Amylase: Digests carbohydrates.
Trypsinogen: Activated by Enteropeptidase (produced in Duodenum) to form trypsin, which then activates chymotrypsinogen. Procarboxypeptidases A and B to protein digestion.
Pacreatic Lipase: Breaks down fats into free fatty acids and glycerol
57
Duodenal Papillae
Secretion point of pancreatic juices into duodenum from pancreatic ducts.There is a major and a minor duodenal papilla.
58
Liver
* Regulates blood sugar via glyogenesis, glycogenolysis, gluconeogenesis, and the storage and release of fats.
* Converts Ammonia (waste product of amino acid metabolism) into Urea
* Detoxifies chemicals such as drugs and alcohol
* Produces Bile
* Synthesizes albumin and clotting factors
59
bilirubin
Major pigment in Bile, which is the byproduct of the breakdown of hemoglobin. Inability to process or excrete bilirubin results in Jaundice.
60
Gallbladder
Stores and concentrates bile. CCK stimulates the gallbladder to contract and push bile into the billiary tree, which merges with the pancreatic duct before entering the duodenum via the duodenal papillae. Gallbladder stones made of cholesterol or bilirubin can cause inflammation of the gallbladder and blockage of both the biliary tree and pancreatic ducts.
61
Villi
Small, fingerlike projections from the epithelial lining of the small intestine. Each villus is covered in microvilli. This greatly increases surface area for absorption. Each villus contains a capillary bed for absorption of water soluble nutrients and small fatty acids into the blood and a lacteal to transport fats into the lymphatic system
62
Lacteal
Lymphatic channel that takes up fats in the form of milky fluid chylomicron for transport into the lymphatic system. Located in the Villi.
63
Hepatic Portal System
Portal system in which blood first travels through capillaries in the villi of the small intestine to absorb nutrients, then again through the capillaries in the liver for nutrients to be processed and for toxins to be removed.
64
Chylomicrons
Packaged triglycerides and esterified cholesterol that gets transferred from the mucosal cells of the villi of the small intestine into the lacteal for insertion into the lymphatic system
65
Fat Soluble Vitamins
Vitamins A, D, E, and K. Easily dissolve into chylomicrons to enter body. Failure to digest or absorb fat may lead to deficiencies in fat soluble vitamins.
66
Water Soluble Vitamins
Vitamin B complexes and C. Absorb directly from small intestine into blood plasma.
67
Cecum
Outpocketing of the Large Intestine that accepts fluid exiting the small intestine through the ileocecal valve and is the site of attachment of the appendix. Home to many aerobic bacteria that produce a symbiotic relationship that helps produce vitamin K and biotin (vitamin B7).
68
Appendix
Originally thought to be vestigial, but now thought to aid in warding off bacterial infections and repopulating the large intestine with normal flora after diarrhea.
69
colon
A part of the large intestine that's main function is to absorb water and salts from indigested material left over from the small intestine. Absorbs less water than the small intestine, but still aids in formation of feces. Too much or too little absorption causes constipation or diarrhea respectively.
70
Internal and External Anal Sphincters
Seperate the rectum from the outside. Internal sphincter is involuntary. External is voluntary.
71
Vasa Recta
Capillaries that surround the loop of Henle as the second capillary be in the renal portal system (the first being the glomeruli)
72
Bowman's Capsule
Cuplike structure around glomerulus that leads to the proximal convoluted tubule.
* It is the pressure difference in Bowman's Capsule that causes intitial filtration in the kidneys
73
Detrusor Muscle
Muscular lining of the bladder which contracts after stimulation from the parasympathetic nervous system.
74
Micturition reflex
When stretch receptors in bladder recognize that it is full, they fire parasympathetic neurons to the detrusor musccle and internal urethral sphincter causing them to contract and relax respectively.
75
Starling Forces
Forces that govern the movement of fluid into the Bowmen's Capsule from the Glomerulus. This is a result of the hydrostatic and oncotic forces of the Bowman's Space and Glomerulus capillaries.
76
Countercurrent Multiplier System
The system in which the Vasa Recta and Nephron flow in opposite directions, allowing more hypertonic blood (high osmolarity) to be exposed to the loop of Henle, allowing for maximum water absorption.
77
Loop of Henle
Descending Loop: Only permeable to water. Water leaves the loop, creating an increasingly concentrated solution at the end of the loop.
Ascending Loop: Only permeable to salts. This allows the highly concentrated fluid at the end of the loop to be reabsorbed by the vasa recta, decreasing concentration by the time the fluid gets to the distal convoluted tubules.
78
Diluting Segment
Thicker portion of the ascending loop of Henle with larger cells due to more mitochondria in these cells to facilitate active transport. These cells are pushing out salts against their concentration gradient, since the fluid inside the loop of Henle has become hypotonic compared to the interstitium. This is the only portion of the nephron that can produce urine more dilute than blood.
79
Proximal Convoluted Tubule
Proceeds the Bowmans Capsule. Amino Acids, Salts, Glucose, Water Soluble Vitamins reabsorbed into the Vasa Recta along with water. About 70% of the filtered sodium is reabsorbed here. H+, Urea, NH3,and K+ (aka "HUNK") are all secreted here.
80
Distal Convoluted Tubule
Responds to Aldosterone, which promotes sodium reabsorption. Water will follow the sodium, concentrating the urine and decreasing its volume. Waste products are also secreted here.
81
Collecting Duct
Final concentration of urine largely dependent on permability of collecting duct, which is affected by ADH and Aldosterone to increase water absorption and concentrate urine output. Water travels to Vasa Recta, where it reenters blood stream.
82
Osmotic vs Oncotic Pressure
Osmotic Pressure = "Sucking" pressure that draws water into blood
Oncotic Pressure = Osmotic Pressure specifically caused by Proteins
83
Renal Bicarbonate Buffer System
When pH is too high, kidneys can selectively excrete more bicarbonate and reabsorb more H+. When pH is too low, kidneys exctrete more H+ and reabsorb more bicarbonate.
84
Langerhans cells
Special macrophages that reside within the stratum spinosum of the epidermis. Capable of presenting antigens to T-cells to activate the immune system.
85
Red Fibers
Slow twitch fibers, high myoglobin content and derive energy aerobically. Lots of Mitochondria
86
Islets of Langerhans
Pancreatic bundles of cells that release hormones. Include alpha, beta, and delta cells, which release glucagon, insulin, and somatostatin respectively.
87
Vagus Nerve
Mostly Parasympathetic Nerve that slows down heart rate when activated. Originates in Medulla Oblongata.
88
White Fibers
Fast twitch fibers. Less myoglobin. Contract rapidly, but fatigue more quickly.
89
Tropomyosin
Protein that spirals around actin in muscles, covering the myosin binding sites.
90
Troponin
Protein on tropomyosin. Has a Ca2+ binding site. When activated by calcium binding, troponin causes tropomyosin to undergo conformational change, exposing myosin binding sites
91
Myosin
Motor protein in muscles. Binds to Actin filaments in the cocked position, with ADP + Pi bound. This happens only when actin filaments have exposed myosin binding sites after Ca2+ is bound to troponin.
After myosin-actin binding, ADP + Pi dissociate from myosin, causing the power stroke. This contracts the sarcomere. ATP then binds to myosin, freeing it from actin. ATP is hydrolyzed to ADP + Pi, recocking the myosin (which is unbound from actin).
92
Tetanus
When muscle contracts do not get the chance to relax at all due to constant stimulation at a high frequency. E.g. after a tough workout, your muscles are still tense, even though you aren't flexing.
93
Harversion Systems
Structural Unit of Bone, also called Osteons. Have Harversian and Volkmann's Canals (longitudinal and transverse canals) that allow blood vessels, nerves, and lymph vessels to maintain bone health.
94
Endochondral Ossification
Process of hardening cartilage into bone. Responsible for formation of most of the long bones of the body.
95
Synovial Fluid
Lubricates the movements of structures in the joint space. Secreted by soft tissue called the synovium, which is enclosed inside of the joint cavity by the synovial capsule.
96
Flat Bones
Contains red bone marrow, indicating that high RBC production occurs here; usually provide protective functions and are found in areas associated with little movement, such as skull bones, ribs, and vertebrae.
97
Long Bones
Contains yellow bone marrow, indicating that low RBC production occurs here; found in areas associated with physical movement such as the arms, legs, hands, and feet.
98
Penetrance
The proportion of individuals in the populations carrying an allele who actually express the phenotype.
* ex: 100% penetrance means that if you have the genes for being smart, then you'll definitely be smart! Less than 100% penetrance means that you may have the genes for being smart, but you may not actually be smart.
99
Expressivity
Is the degree to which a certain penetrant gene is expressed. Different manifestations of the same genotype across the population. Constant expressivity means all individuals with a given genotype experience same phenotype.
* ex: Constant expressivity means that if your genes for being smart manages to penetrate (show up as a trait), then your IQ is 120. Variable expressivity means that your IQ doesn't have to be 120, it could be somewhat lower or somewhat higher.
100
Mendel's First Law (Law of Segregation)
Genes exist in alleles, of which each person has two of (one from each parent). Gametes only carry one allele due to separation during meiosis of the alleles. Only one allele will be fully expressed if two alleles are different, while one is silent (except for codominance and incomplete dominance)
101
Mendel's Second Law (Law of Independent Assortment)
Inheriting one gene does not affect the inheritance of another gene. This was later explained by recombination during meiosis. Problematic when linked genes were discovered.
102
gene pool
all of the alleles in a population
103
Where are your mitochondria inherited from?
from your mother
104
Hardy-Weinberg Equations
* p + q = 1
* p^2 + 2pq + q^2 = 1
Equations show the frequency of alleles in a population and also the frequency of a given genotype or in the population. There will always be twice as many alleles as individuals in a population.
105
Inclusive Fitness
Measure of an organism's success in the population. Based on number of offspring, ability to support offspring, and ability of the offspring to support others. Promotes altruism since sacrificing oneself, commonly for offspring, can ensure passing of genes to future generations
106
Punctuated Equilibrium
Some species have "Explosions" of evolutionary change that occur in rapid bursts, rather than slowly over a long period of time.
107
Polymorphism
Natually occuring differences in form between members of the same population, such as light and dark coloration in the same species of butterfly.
108
Adaptive Radiation
Rapid rise of a number of different species from a common anscestor. These species differ as a result of geographic differences in habitat.
109
Alternative Splicing
different ways of cutting up the RNA and rejoining exon pieces make different isoforms of the final RNA products.
110
Spliceosomes
are responsible for removing introns from pre-mRNA after it is synthesized. Different isoforms of a gene are a result of alternative splicing.
111
Start Codons
The ribosome begins translation at the RNA sequence containing AUG (which codes for the amino acid Methionine)
mnemonic: the classroom met in AUGust
112
Stop Codons
When the ribosome encounters any of these 3 RNA sequences during translation, it falls off the mRNA and translation ends.
* UAA
* UGA
* UAG
mnemonic:
U Are Annoying
U Go Away
U Are Gone
113
p53
is the classic example of a tumor suppressor. Tumor suppressors are "good" because they are involved in slowing down or controlling cell division when they are cancerous. In other words, if the cancer-producing oncogene is the "bad guy" gene, then tumor suppressors are the "good" genes. If something happens to p53 that causes it to no longer function, then a cell may become cancerous
114
Open Mitosis
mitosis that occurs in the cytoplasm because the nuclear envelope has degraded
115
Closed Mitosis
mitosis that occurs in the nucleus that occurs in some unicellular eukaryotes
116
Taq polyermase
used in PCR
117
Southern Blot
used to analyze DNA
118
Northern blot
used to analyze RNA
119
Western Blot
used to analyze Proteins (and anything associated with proteins such as posttranslational modificaiton of proteins via histone acetylation)
120
Phagolysosome
when a macrophage ingest a foreign material, the material initially becomes trapped in a phagosome. The phagosome then fuses with a lysosome to form a phagolysosome. Inside the phagolysosome, enzymes digest the foreign object.
121
Co-dominance
when two phenotypes are simultaneously expressed
* ex: blood type antigens: Type AB blood expresses both the A and B receptors simulataneously and is thus an example of codominance
122
Incomplete Dominance
when there is a mixing (or in between) of two phenotypes
* ex: red flower + white flower = pink flower
* ex: tall + short = medium height
123
Aspartate Transanimase
enzyme that transfers an amino group to α-ketoglutarate to form Glutamate and Oxaloacetate
124
2,4-dinitrophenol (DNP)
a lethal uncoupling agent that binds protons in the intermembrane space and transfers them across the inner mitochondrial membrane, thus dissapating the proton gradient and blocking ATP synthesis from occuring because protons will not cross down its concentration gradient to power ATP Synthase.
125
Pentose Phosphate Pathway
primary purpose is to regenerate NADPH, which is used as a reducing equivalent with glutathione for biosynthesis. Occurs in the cytoplasm. Rate limiting enzyme is glucose-6-phosphate dehydrogenase, which is inactivated by NADP+ and insulin. Inhibited by sufficient levels of NADPH of course
126
cytochrome p450
enzyme used in drug detoxification in the liver; sometimes coincidentally it can also inadvertently activate carcinogenic compounds that are not otherwise harmful
127
Heterozygote Advantage
the tendency for a carrier of a dangerous condition to have a survival advantage
(e.g. heterozygotes for sickle cell anemia are protected against malaria)
128
Binary Fission
the process of cell replication by prokaryotes (bacteria such as E.coli) where the new copy of DNA is attacted to the cell membrane and then the cell splits in half between the two copies of DNA
129
Directional Selection
occurs when individuals with only a certain more extreme form of a trait has greater fitness than an individual with an average form of the trait
(e.g. dark color moths have better advantage because of camoflauge than light color moths and are thus more fit for survival)
130
Stablizing Selection
occurs when individuals with the average form of a trait have the highest fitness
(e.g. when laying a medium number of eggs is better than: laying too little eggs--not enough to ensure survival of generations, or too many eggs---too many offpsring to feed with scarce resources)
131
Disruptive Selection
occurs when individuals with either extreme variation of a trait have greater fitness than the individual with the average form of the trait.
(e.g. small fish and large fish have better fit than medium sized fish because small are faster to run away and large are better fighters)
132
Divergent evolution
two or more species diverge from a common ancestor
(e.g. dog, wolf, and fox; elephant and whooly mammoth)
- hint: to "diverge" means to separate from the same point
133
Convergent evolution
two or more species share traits but are NOT due to a common ancester.
(e.g. birds, bats, and butterflys share the similar trait of wings but they do not share a common ancestor)
- hint: things that "converge" mean that they are coming closer together even though they never touch
134
Gram-Positive Cell Walls
* dyes purple
* contain a THICK peptidoglycan layer
135
Gram-Negative Cell Walls
* dyes pink
* contain a thinner peptidoglycan layer
* has a lipopolysaccharide layer, that can can set off an immune response
136
Obligate Aerobes
need oxygen in order to live
* "obligated to be only aerobic"
137
Obligate Anaerobes
are killed in the presence of oxygen
* "obligated to be only anaerobic"
138
Facultative Anaerobes
do not necessarily need oxygen, but they can grow better if oxygen is present
* "anaerobics but life is facilitated by being aerobic"
139
Aerotolerant Anaerobes
can live without oxygen and ignore oxygen regarless whether it is present or not
* "anaerobics that can tolerate oyxgen"
140
Ribozyme
an RNA molecule that is capable of catalyzing reactions. It is composed of RNA and is therefore susceptible to phosphodiesterases since it has phosphodiester bonds in the ribose phosphate backbond
141
Organogenesis
weeks 4-9 of prenatal development where production and development of the organs begin. Chemical or radiation exposure during this time is more likely to cause abnormalities that compromise viability of the embryo
142
Transformation
occurs when a bacterium acquires a piece of genetic material from the environment and integrates that piece of genetic material into the host cell genome. This is a common method by which antibiotic resistance can be acquired
143
Transduction
occurs when a bacteriophage acquires genetic information from a host cell. Sometimes, when the new virions are assembled in a host cell, some of the genetic material from the host cell is packaged along with the viral genetic material. Then, the bacteriophage infects another bacterium, resulting in transfer of bacterial genetic material.
144
Conjugation
is the bacterial form of MATING (sexual reproduction). It involves two cells forming a cytoplasmic bridge between them that allows for the transfer of genetic material. The transfer is ONE-way, from the donor male (+) to the recipient female (–). The bridge is made from appendages called sex pili that are found on the donor male. To form the pilus, bacteria must contain plasmids known as sex factors.
145
Splicing
occurs ONLY in eukaryotes. Splicing is the 1st of the 3 post-transciptional modifications that occur to the pre-mRNA before it becomes mature mRNA to exit the nucleus.
During splicing, introns are removed and the remaining pieces (exons) are joined together to form the mature mRNA from the pre-mRNA that was initially transcribed from the DNA; this process is done by Spliceosomes.
146
mRNA 5' G Cap
After splicing occurs, a Guanine is added on the 5' end of the pre-mRNA. Now, the "pre-mRNA" is finished with any post-transcriptional modifications and is refered to as mature "mRNA".
* This protects the mRNA from degrative enzymes as it travels from the nucleus to the cytoplasm.
147
What is the difference between prokaryotic mRNA and eukaryotic mRNA, regarding post-transcriptional modification?
Prokaryotic mRNA requires NO additional processing, unlike eukarotic mRNA (aka, splicing, addition of 5' Guanine Cap, and addition of 3' PolyAdenosine Tail do NOT occur in prokaryotes).
Because transcription in prokaryotes occurs in the cytoplasm (as opposed to in the nucleus for eukaryotes), the prokaryotic ribosomes are allowed to bind to the mRNA and begin translation even before transcription is complete.
148
Why might there be an initial lag in bacterial colony growth before increasing growth, after there is a change to their environment, such as the addition of a new polysaccharide?
the lag may to due to a period in which bacteria are regulating their gene expression (of enzymes). The regulation of gene expression is one method by which bacteria respond to changes in their environment, in this case the new addition of something that would aid in their growth. Before this addition, the bacteria lacked any enzymes to facilitate this growth because the genes for these enzymes were not yet expressed. However upon addition to a new polysaccharide to their environment, they increase gene expression of the necessary enzymes in order to use it as fuel. The growth of the colony occurs when these genes have been expressed and thus they are able to digest the polysaccharide for fuel.
149
150
