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MCAT > Biological Sciences > Flashcards

Biological Sciences Flashcards

1
Q

What is inside of a micelle?

A

Fatty Acids and Cholesterol

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2
Q

What happens once inside an enterocyte during lipid digestion?

A

There is no micelle inside an enterocyte. The fatty acids and cholesterol combine with an apolipoprotein.

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3
Q

Where are micelles found?

A

lumen of the small intestine

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4
Q

What is the purpose of an apolipo protein?

A

An apolipo protein acts as a ligand for receptors on liver cells and adipose tissue cells. It is how lipids are absorbed into the liver and fat.

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5
Q

What is the difference between lipid absorption and carbohydrate/protein absorption?

A

Carbohydrates and proteins go to the liver first via the blood.

Lipids go to the heart first via lymph.

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6
Q

What is the purpose of a chylomicron?

A

The purpose of a chylomicron is to transport fatty acids and cholesterol through lymph and blood, i.e. aqueous environments.

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7
Q

What type of molecule is a chylomicron? Is it hydrophobic or hydrophilic?

A

Both- it is amphipathic.

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8
Q

Desribe the path of lipid absorption.

A

Lacteals → Lymph Vessels → Thoracic Duct → Heart

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9
Q

What happens in the mouth during protein digestion?

A

Nothing

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10
Q

What happens in the stomach during protein digestion?

A

Chief cells of the stomach make pepsinogen.

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11
Q

Zymogen

A

Inactive form of an enzyme (any enzyme that ends with -inogen).

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12
Q

How is pepsinogen activated in the stomach?

A

HCl activates pepsinogen.

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13
Q

Where is HCl made and what is its purpose?

A

Parietal cells of the stomach make HCl which activates pepsinogen to pepsin.

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14
Q

What does pepsin do?

A

Pepsin breaks peptide bonds to make smaller polypeptides in the stomach.

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15
Q

Name the 5 Proteases

A

Pepsin

Trypsin

Chymotrypsin

Carboxypeptidase

Aminopeptidase

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16
Q

What happens during protein digestion in the small intestine?

A

Pancreas releases trypsin and chymotrypsin into the small intestine.

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17
Q

What is the purpose of enterokinase?

A

In the small intestine, enterokinase activates trypsin and chymotrypsin.

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18
Q

How do trypsin and chymotrypsin digest proteins?

A

They break peptide bonds at specific “R” groups.

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19
Q

How does carboxypeptidase digest proteins?

A

Carboxypeptidase removes an amino from the carboxy terminus.

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20
Q

How does aminopeptidase digest proteins?

A

Aminopeptidase removes an amino from the amino terminus.

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21
Q

How are peptides (mono, di, and tri) absorbed?

A

Via Secondary Active Transport

Similar to monosaccharides

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22
Q

How is stomach acid neutralized in the small intestine?

A

Bicarb from the pancreas neutralizes acid in the stomach.

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23
Q

What neutralizes the acidic chyme in the small intestine?

A

Bicarb

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24
Q

5 Pancreatic Enyzymes

A

Trypsin

Chymotrypsin

Carboxypeptidase

Amylase

Lipase

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25
Q

5 Brush Border Enzymes of the Small Intestine

A

Enterokinase

Aminopeptidase

Sucrase

Maltase

Lactase

(last three are disaccharases)

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26
Q

What is the initial stimulus for digestive juice release?

A

G-cells of the stomach sense pressure of food.

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27
Q

What activates gastrin?

A

pressure on baro-receptor of stomach

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28
Q

Gastrin Mechanism

A
  • released on basolateral side of stomach
  • enters blood and travels through body back to the stomach
  • binds parietal cells which make HCl (to activate pepsin from pepsinogen)
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29
Q

Gastrin Origin

A

Pyloric Gastric Cells

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30
Q

Gastrin Result

A

Gastrin causes parietal cells to release HCl to convert pepsinogen to pepsin so pepsin can break peptide bonds.

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31
Q

To where are pancreatic juices released? How are they released?

A

The first part of the duodenum senses the acidic chyme. This causes the release of secretin basolaterally into the blood. Secretin then travels to the pancreas stimulating the release of digestive juice.

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32
Q

Secretin Stimulus

A

Acidic chyme in the first part of the duodenum

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33
Q

Secretin Mechanism

A

Secretin is released basolaterally to the blood to the pancrease to stimulate the release of pancreatic enzymes.

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34
Q

Secretin Origin

A

First part of the duodenum (because pancreas joins at second part)

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35
Q

Secretin Result

A

Release of pancreatic juice into the second part of the duodenum through the pancreatic duct.

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36
Q

Where is bile made?

Where is bile stored?

A

Made in the liver.

Stored in the gallbladder.

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37
Q

What causes the gallbladder to contract and release bile into the small intestine?

A

CCK

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38
Q

CCK Mechanism

A

Secreted basolaterally

Goes to gallbladder to cause contraction

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39
Q

CCK Stimulus

A

CCK release is stimulated by fatty acids entering the small intesting (from just enough churning of the stomach).

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40
Q

CCK Origin

A

Enterocytes in 1st part of duodenum

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41
Q

CCK Result

A

Gallbladder contracts and squeezes out bile (to emulsify fats)

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42
Q

What is the purpose of bile?

A

Bile emuslifies fats in order to increase lipid surface area for lipase to work.

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43
Q

Enterokinase Stimulus

A

pressure on baro-receptor

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44
Q

Enterokinase Mechanism

A

Exocrine (into duct)

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45
Q

Enterokinase Origin

A

Enterocyte of 1st part of duodenum

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46
Q

Enterokinase Result

A

activation of trypsin from trypsinogen

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47
Q

Product of Meiosis I

A

2 different haploid cells (since homologs are different)

48
Q

What is on the plate in Metaphase I?

A

23 tetrads on the plate

(actually 46 chromosomes; 92 chromatids)

49
Q

What is a tetrad?

A

2 homologs stuck together

50
Q

In Meiosis I, how many chromosomes migrate to each pole?

A

23 chromosomes migrate to each pole in Meiosis I (with different alleles)

51
Q

In Meiosis II, how many chromosomes are on the plate?

A

23 chromosomes line up on plate but each chromosome has 2 sister chromatids which need to separate.

52
Q

How many chromosomes in Anaphase II?

A

46 chromosomes (diploid)- sister chromatids separate and each gets its own centromere

(same in Telophase II)

53
Q

Name of male specific meiosis.

A

Spermatogenesis

54
Q

In Spermatogenesis, the first diploid cell before the S-phase is called?

A

Spermatogonium

55
Q

What happens to the spermatogonium? What does it become?

A

The spermatogonium undergoes the S-phase to become a Primary Spermatocyte

56
Q

What forms inside of a Primary Spermatocyte? Is a Primary Spermatocyte haploid or diploid?

A

Tetrads form in the Primary Spermatocyte.

Diploid.

57
Q

What is the product of Spermatogenesis I (Meiosis I)?

A

Two Secondary Spermatocytes- both are haploid (with extra sister chromatids)

58
Q

What is the product of Spermatogenesis II (Meiosis II)?

A

Two Spermatids

59
Q

What is the product of Spermatogenesis?

A

4 Spermatids (2 of which are identical to each other)

60
Q

What becomes of spermatids?

A

Spermatids become Spermatazoa which then grow tails to become Sperm.

61
Q

Where does Spermatogenesis occur?

A

S seminiferous tubules

E epidydimis (storage)

V vas deferens

E ejaculatory duct

N

U urethra

P

SEVEN UP

62
Q

Female Specific Meiosis

A

Oogenesis

63
Q

In what stage is oogenesis at birth?

A

At birth, oogenesis is frozen in Prophase I.

Oogonium in fetus.

Born with Primary oocytes.

64
Q

When and what becomes of the Primary Oocyte?

Is it haploid or diploid?

A

Starting around age 13, the primary oocyte turns into a secondary oocyte.

Primary oocyte is diploid.

Secondary oocyte is haploid.

65
Q

Path of Secondary Oocyte

A

Abdominal Cavity → Fallopian Tubes

66
Q

Where does fertilization occur?

A

Fallopian Tubes

67
Q

In what phase is the secondary oocyte arrested?

A

Prophase II

68
Q

What happens if the sperm encounters the secondary oocyte?

A

Secondary oocyte completes Meiosis II and yields an ovum

69
Q

Where does zygote formation occur?

A

2/3 of the way down the Fallopian Tubes

70
Q

What becomes of the zygote?

A

The zygote beecomes the Morulla.

71
Q

How many cells is the Morulla?

A

16-32 cells

72
Q

What becomes of the Morulla? Where does it happen?

A

The Morulla becomes the Blastula where the Fallopian Tubes join the uterus.

73
Q

4 Importances of Blastula

A
  1. Hollows out
  2. Produces HCG (pregnancy test)
  3. Implants in Endometrium (uterine lining)
  4. Totipotent (cells can become anything)
74
Q

When does implantation occur?

A

3-5 days after fertilization

75
Q

When does the blastula differentiate?

A

Immediately after implantation

76
Q

When is HCG detectable in the mother’s blood?

A

HCG is detectable 10 days after fertilization because the mother’s placental cells fuse with the baby’s cells.

77
Q

What follows the Blastula stage?

A

Gastrulation

78
Q

What happens during Gastrulation?

A

During Gastrulation, the germ cell lines form. The cells are no longer totipotent.

79
Q

3 Germ Cell Lines

A

Mesoderm

Endoderm

Ectoderm

80
Q

Mesoderm

A

Means to Reproduce: gonads and uterus

Means to Move: bone and muscle

Means to Circulate: circulatory system, spleen, kidneys, heart, and blood vessels

81
Q

Ectoderm

A

Attracto-derm

eyes, hairs, nails, brain, PNS, and CNS

82
Q

Endoderm

A

Internal-Derm

pancreas, gallbladder, adrenal cortex, intestines

83
Q

Parthenogenesis

A

sexual reproduction without intercourse (lizards, whales…)

84
Q

How do cells differentiate?

A

Position and Environment

affect gene expression

tadpole experiment

85
Q

What breaks down carbohydrates in the mouth?

A

Sailvary Amylase

86
Q

How does salivary amylase digest carbohydrates?

A

Salivary Amylase breaks glycosidic bonds

Breaks down carbs into disaccharides and monosaccharides

87
Q

What happens to carbs in the stomach?

A

Carbs are not broken down any further in the stomach except for mechanical digestion.

88
Q

What happens to carbs in the duodenum?

A

Pancreatic Amylase breaks more glycosidic bonds.

89
Q

What level of carbohydrates does the body absorb?

A

The body can only absorb monosaccharides.

90
Q

3 Disaccharides

A

Sucrose

Maltose

Lactose

91
Q

Lactose

A

Glucose and Galactose

92
Q

Maltose

A

Glucose and Glucose

93
Q

Sucrose

A

Glucose and Fructose

94
Q

Names of 3 Disaccharases

A

Lactase

Sucrase

Maltase

95
Q

Purpose and Location of 3 Disaccharases

A

Break down disaccharides into monosaccharides in the small intestine.

96
Q

Where and how are monosaccharides absorbed?

A

Small Intestine

Across Enterocyte via Secondary Active Transport (coupled to sodium)

97
Q

Describe Secondary Active Transport for Carb Absorption

A

Mono’s are couple to sodium and enter apical side of enterocyte via Facilitated Diffusion.

Sodium pumped out on basolateral side of enterocyte to set up sodium gradient.

Sodium gradient is set up via ATP.

98
Q

Path of Monosaccharide after absorption

A

Blood → HPV → Liver

99
Q

What happens to the monosaccharide in the liver if blood glucose is high?

A

Glucokinase will process it and store it

100
Q

What happens to the monosaccharide in the liver if blood glucose is low?

A

The liver will send it out via

HPV → Inferior Vena Cava → Heart → Body

101
Q

Describe lipid digestion in the mouth and stomach.

A

only mechanical

102
Q

Describe lipid digestion in the small intestine.

A

Bile emulsifies lipids by destroying hydrophobic interactions between fatty acids.

This exposes Ester bonds.

Lipase breaks 2 of 3 Ester bonds to form Micelle.

103
Q

What type of molecule is a Micelle?

A

Amphipathic

Philic on outside (hydroxy’s)

Phobic on inside (fatty acids and cholesterol)

104
Q

What is the purpose of a Micelle?

A

Traverse mucous layer of intestine (philic)

Micelle breaks apart when it hits the mucous layer and ejects fatty acids into the enterocyte

105
Q

What happens in the S-phase of Mitosis?

A
  • DNA is made
  • making sister chromatids via semi-conservative replication
  • has major checkpoints
106
Q

What is after the S-phase?

A

G2

(PMAT)

107
Q

In mitosis, how many chromosomes line up during Metaphase?

How many chromatids line up?

A

46 Chromosomes

(each has a sister chromatid)

(looks like an “X”)

92 Chromatids

108
Q

In Anaphase, how many chromosomes are on each side after splitting?

A

46 chromosomes on each side (each with its own centromere)

Actually tetraploidy because 92 chromosomes in total.

109
Q

In Mitosis, when is the cell tetraploid?

A

anaphase and telophase (92 chromosomes)

110
Q

What pinches the two cells in telophase?

A

Actin

111
Q

How can the number of chromosomes always be determined?

A

by counting the centromeres

112
Q

When do you gain a new centromere?

A

A new centromere is gained in Anaphase when the sister chromatids split from each other.

113
Q

Explain Homologs.

A

2 different chromosomes with exactly the same genes but different alleles.

Ex: hair genes and color alleles

Different Genotype

114
Q

Importance of Prophase I of Meiosis

A

Tetrad Formation

Trying to distribute each homolog to a different cell

115
Q

Describe Tetrads (Meiosis)

A

2 homologs stuck together

(each with 2 sister chromatids)

MCAT (7 decks)

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