Wrong - Bio/Biochem

MCAT Mistakes Made

Oxidation Number Rule 1

1. Assign 0 to elements in their pure form.

Oxidation Number Rule 2

1. Assign the ion’s charge to monoatomic ions.

Oxidation Number Rule 3

1. Assign +1 to Group 1 metals and +2 to Group 2 metals.

Oxidation Number Rule 4

1. Assign –1 to fluorine.

Oxidation Number Rule 5

1. Assign +1 to hydrogen, or –1 in metal hydrides.

Oxidation Number Rule 6

1. Assign –2 to oxygen, or –1 in peroxides

Oxidation Number Rule 7

1. Assign –1 to halogens, unless bonded to oxygen.

Oxidation Number Rule 8

1. Ensure the sum of oxidation numbers equals 0 for neutral compounds or the ion’s charge for polyatomic ions.

Astrocyte Function in Brain

Maintain blood-brain barrier

Oligodendrocyte function in brain

Myelinate axons in CNS

Ependymal Cells in Brain Function

Line ventricles/produce CSF (cerebrospinal fluid)

Function of Prolactin and Produced Where?

Produced: Anterior Pituitary

Function: Produce breast milk

Regulation: Inhibited by dopamine secretion by hypothalamus

Function of Aldosterone and Produced Where?

Produced: Adrenal Cortex

Function: Regulates blood pressure, fluid balance, and electrolyte levels. Increases when blood volume is low, decreases when blood volume is high.

Regulation: Regulated by renin-angiotensin-aldosterone system (RAAS) and plasma potassium levels

Function of Calcitonin and Produced Where?

Produced: Thyroid Gland

Function: Lowers calcium levels in blood

Regulation: High calcium levels in blood

Function of Vasopressin and Produced Where?

Produced: Posterior Pituitary (Direct from Hypothalamus)

Function: Blood pressure/water retention

Function of Oxytocin and Produced Where?

Produced: Posterior Pituitary (Direct from Hypothalamus)

Function: Lactation and Labor

Fluidity of trans vs cis double bonds in cell membrane

cis double bonds increase fluidity more than trans double bonds

Detruscor Muscle

Smooth muscle lining the bladder

Relaxed when bladder filling up with urine, contracts when time to pee

Involuntary

Internal Urethral Sphincter

Smooth muscle allowing urine out of bladder

Involuntary, must relax to allow urine out of bladder, contracts when bladder filling up thus not allowing urine to escape

External Urethral Sphincter

Skeletal muscle. Must relax to allow urine out of bladder, contracts to prevent urine from escaping. Voluntary.

Sliding Filament Model of Muscle Contraction Step 1

Nerve signals release a chemical called acetylcholine to start muscle contraction.

Sliding Filament Model of Muscle Contraction Step 2

Acetylcholine causes calcium ions to be released from storage in the muscle.

Sliding Filament Model of Muscle Contraction Step 3

Calcium ions attach to troponin, moving tropomyosin aside and exposing binding sites on actin.

Sliding Filament Model of Muscle Contraction Step 4

Myosin heads grab onto the exposed actin sites, forming connections.

Sliding Filament Model of Muscle Contraction Step 5

Myosin heads pull the actin filaments toward the center of the muscle, which is powered by the release of ADP and Pi. (Power Stroke)

Sliding Filament Model of Muscle Contraction Step 6

A new ATP molecule attaches to myosin, causing it to let go of actin.

Sliding Filament Model of Muscle Contraction Step 7

ATP is used to reset the myosin head for the next cycle.

T-state of Hemoglobin

Low oxygen affinity 0-20 pO2

T-R state of Hemoglobin

Positive cooperativity 20-50 pO2

R-state of Hemoglobin

High oxygen affinity 50+ pO2

Right shift on oxygen dissociation curve

Decreased affinity for oxygen

Causes:

• Greater CO2

• Greater [H] (more acidic)

• Greater temp

• Greater 2,3-bisphosphoglycerate

Left shift on oxygen dissociation curve

Increased affinity for oxygen

Causes:

• Decrease CO2

• Decrease [H] (more basic)

• Decreased temp

• Greater 1,3-bisphosphoglycerate

Glucose

Fructose

Mannose

Xylose

Ribose

Sugar L or D?

Anomeric carbon is made as 1. Count to highest number carbon.

• If R then D

• If S then L

Sugar alpha or beta?

• Alpha if anomeric carbon substituent and highest number carbon substituent opposite

• Beta if anomeric carbon substituent and highest number carbon substituent same

Molar mass of glucose?

180g/mol

Protein aggregates are formed between secondary structures, what bonds does this involve?

Hydrogen bonds and hydrophobic core

Phosphate backbones are … charged and need to be buffered by … charges to bind to nucleotides that are also … charged

negatively, positive, negatively

A nucleoside is…

A nucleotide without phosphate group

Hypotension

Low blood pressure, volume decrease in blood vessels. Counteracted by aldosterone.

Hypertension

High blood pressure, increase in volume in blood vessels

Osteoclast

Cells that breakdown bones to release calcium in blood. Increased activity by PTH

Osteoblast

Cells that build up bones by taking calcium from blood.

Phospholipid Structure

Ceramide Stucture

Sphingomyelin Structure

Concentration Cell

Galvanic cell with same metal so overall cell potential of 0 V

Somatotropin (Growth Hormone)

• Secreted by pituitary gland

• Promotes release of fatty acids from adipose tissue in bloodstream

Loop of Henle Form and Function

• Hairpin tube in nephron of kidney

• Generates concentrated urine to conserve body water

Loop of Henle Thin Descending Limb

• Very permeable to water

• Impermeable to salts

• Water filters out to concentrate waste

Loop of Henle Thin Ascending Limb

• Impermeable to water

• Permeable to salts

• Allow salts to be reabsorbed

Loop of Henle Thick Ascending Limb

• Impermeable to water

• Pumps out electrolytes

How is the hypertonicity (higher concentration) of the medulla maintained?

High NaCl and Urea concentration outside of the medulla so that water flows out of the collecting ducts to be reabsorbed by the body.

1 amino acid weight?

110 Daltons

Heterochromatin

• Deacytelated histones

• Tightly bound to DNA

• Positively charged lysines sticking out

Euchromatin

• Acetylated histones

• DNA accessible

• Neutralized lysines

Small intestine order

Duodenum, Jejunum, Ileum

Large intestine order

Colon, Cecum, Rectum

Bulburethral gland

Precum, alkaline to handle acidity of vagina

Configuration of amino acids

All amino acids are L confi naturally

All amino acids S naturally EXCEPT CYSTEIN WHICH IS R

Starvation Response

• Low Glucose

• Glucagon release

• Glycogenolysis

• Break down of triacylglycerols to glycerol and fatty acids in liver

• Glycerol to G3P for gluconeogensis

• Fatty acids oxidized to acetyl-coa for TCA energy production

• Excess acetyl-coa turned to ketone bodies

Complex 2 Key Facts

• Also known as succinate dehydrogenase

• Runs parallel to complex 1

• Uses succinate to convert FAD to FADH2 in TCA cycle

• Complex 2 then turns FADH2 to FAD, takes the electrons and passes them to complex 3

Glucogenic amino acids function

Converted into glucose precursors such as

• pyruvate

• α-ketoglutarate

• Succinyl-CoA

• Fumarate

• Oxaloacetate

Glucogenic amino acids list?

• Alanine

• Arginine

• Asparagine

• Aspartic acid

• Cysteine

• Glutamic acid

• Glutamine

• Glycine

• Histidine

• Methionine

• Proline

• Serine

• Valine

Ketogenic amino acids function

Broken down into acetyl-Coa or acetoacetyl-CoA

Ketogenic amino acids list?

• Leucine

• Lysine

Both ketogenic and glucogenic amino acids?

• Isoleucine

• Phenylalanine

• Threonine

• Tryptophan

• Tyrosine

Menstruation occurs?

When FSH and LH are at their lowest

Ovulation occurs?

During LH spike.

ADH (antidiuretic hormone) does what?

• Less peeing

• Increased water reabsorbtion

• Increases permeability of water in collecting duct

• Increases blood volume and thus pressure because more water will return to blood

The carnitine shuttle

Moves fatty acids into mitochondrion for beta oxidation

The malate-aspartate shuttle

Interconverts malate and aspartate in both the mitochondria and the cytosol. NADH in cytosol is consumed to generate NADH in mitchondrion

The citrate shuttle

Moves fatty acids out of mitochondrion for fatty acid synthesis

The glycerol-3-phosphate shuttle

Transports electrons from NADH in cytosol to FADH2 in mitochondrion.