Final Exam Review Flashcards
(146 cards)
1
Q
What are the two main parts of a phospholipid?
A
Hydrophilic head and hydrophobic tails
2
Q
How do lipids arrage in an aqueous environment?
A
Hydrophilic heads face outward toward water, and hydrophobic tails face inward.
3
Q
What is the basic structure of biological membranes?
A
The lipid bilayer
4
Q
What does the lipid bilayer allow the formation of?
A
Vesicles, organelles, and cells
5
Q
Why is the lipid bilayer important for cellular functions?
A
It compartmentalizes cellular functions and creates boundaries
6
Q
What must a bacterium do to survive in a warmer environment?
A
Adjust its cell membrane to maintain fluidty
7
Q
How does increasing fatty acid saturation affect the membrane?
A
Its makes the membrane more rigid
8
Q
How does decreasing fatty acid chain length affect membrane fluidity?
A
It reduces excessive fluidity
9
Q
What role does cholesterol play in the membrane at higher temperatures?
A
It helps stabilize the membrane.
10
Q
Why is the membrane fluidity important for a bacterium in warm conditions?
A
To ensure the membrane remains functional and stable.
11
Q
What kind of amino acids are found in a single transmembrane domain?
A
Hydrophobic amino acids like valine, leucine, and phenylalanine.
12
Q
Identify the molecule in each pair that is more likely to diffuse through the lipid bilayer.
Amino acids or steroid hormones
Cl- or ethanol
Glycerol or RNA
H2O or O2
A
Steriod hormones; Ethanol; Glycerol; O2
13
Q
What are the three transport proteins involved in glucose transport?
A
- GLUTs (Facilitated Diffusion): Moves glucose down its concentration gradient; Conformational change from outward-facing to inward-facing after glucose binding, does NOT require energy
- SGLT (Secondary active transport): Moves glucose against its concentration gradient by coupling with sodium; sodium binding induces a conformational change that co-transports glucose into the cell; energy comes from the sodium gradient, maintained by the sodium-potassium pump
- GLUT2 (Bidirectional transport): Moves glucose in both directions, depending on the concentration gradient; conformational changes occurs upon glucose binding, facilitating its movement; found in the liver, pancreas, and kidney
14
Q
What is the normal function of CFTR protein in airway epithelial cells?
A
- CFTR is a chloride ion channel on airway epithelial cells
- Transport chloride out of cells, aiding in water movement and maintain thin mucus
15
Q
How do mutations in the CFTR gene affect the protein’s function?
A
- Mutations (F508) causes CFTR misfolding, preventing it from reaching the cell surface or functioning properly
- Impaired CFTR function limits chloride ion transport
16
Q
What are the consequences of impaired CFTR function on ion transport and mucus consistency?
A
- Disrupted chloride transport causes sodium retention inside cells and reduced water secretion
- Results in thick, sticky mucus in the airways, obstructing airflow and increasing infection risk
17
Q
How could a bacterium go from living in a cold environment to a warm environment (human intestine) if ingested?
A
- The bacterium must adjust its membrane to maintain fluidity at higher temperatures.
- Increase the saturation of fatty acids in membrane lipids to make the membrane more rigid.
- Decrease the length of fatty acid chains to reduce excessive fluidity.
- Increase cholesterol content to help stabilize the membrane.
- These adjustments maintain optimal membrane function and stability in warmer environments.
18
Q
General Functions of Proteins (List and Describe 3 Functions)
A
- Enzymatic Activity: Proteins that act as enzymes catalyze biochemical reactions, speeding up metabolic processes. Ex. Amylase breaking down starch into sugars
- Structural Support: Provide support and shape to cells, tissues, and organisms. Ex. Collagen strengthens connective tissues
- Transport: Proteins facilitate the movement of molecules across cell membranes or within the body. Ex. Hemoglobin transports oxygen in the blood.
19
Q
What is the primary structure of a protein?
A
- Linear sequence of amino acids in a polypeptide change
- Determined by the gene encoding it
- Stabilized by peptide bonds, which are covalent bonds formed between the carboxyl group of one of the amino acids and the amino group of the next
20
Q
What is the secondary structure of a protein?
A
- Refers to the localized folding or coiling within the polypeptide chain
- x-helices and b-pleated sheet
- Stabilized by hydrogen bonds between the oxygen of the carboxyl group (C=O) and the hydrogren of the amino group (N-H) in the protein backbone
21
Q
What is the tertiary structure of a protein?
A
- Refers to the 3D shape of a single polypeptide chain
- Stabilized by hydrogren bonds, ionic bonds, hydrophobic interactions, disulfide bridges between R-groups
22
Q
What is the quaternary structure of a protein?
A
- Arrangement of multiple polypeptide chains (called subunits) into a single functional protein complex.
- Similar interactions to tertiary structures; hydrogen bonds, ionic bonds, hydrophobic interactions, disulfide bridges (less common)
23
Q
How do hydrogen bonds contribute to protein folding?
A
Hydrogen bonds stabilize protein folding by forming between backbone atoms in secondary structures and between side chains in tertiary and quaternary structures
24
Q
How can pH changes affect protein folding?
A
pH changes alter the ionization states of amino acid side chains, disrupting hydrogen bonds and potentially leading to protein denaturation
25
How can a mutation in the PAH gene lead to PKU?
A mutation like A300Q changes the amino acid sequence, affecting PAH protein folding or active site, reducing its ability to break down phenylalanine, leading to PKU.
26
How does the A300Q mutation disrupt PAH function?
The A300Q mutation changes alanine to glutamine, disrupting protein folding, stability, or active site function, reducing PAH activity and causes phenylalanine accumulation (leads to PKU).
27
What is PKU (Phenylketonuria)?
- PKU is a genetic disorder by mutations in the PAH gene
- Leads to nonfunctional PAH enzyme, resulting in phenylalanine build-up, which can cause harm to the brain.
28
How do chaperone proteins assist mutant CFTR protein in Cystic Fibrosis?
Chaperone proteins attempt to refold the misfolded CFTR protein, preventing aggregation and helping it reach the membrane to function as a chloride channel.
29
What happens during the Unfolded Protein Resposne (UPR)?
- UPR is activated by the accumulation of misfolded proteins
- Enhances protein-folding capacity
- Inhibits protein Synthesis
- Promotes the degradation of faulty proteins
30
How does the proteasome degrade mutant CFTR protein?
- Mutant CFTR proteins that cannot fold properly are targeted for degradation by the proteasome.
- The process starts with ubiquitination, where ubiquitin molecules are attached to the misfolded protein.
- Multiple ubiquitin molecules serve as a tag for the proteasome to recognize the protein.
- The proteasome unfolds and translocates the protein into its core.
- The proteasome breaks down the protein into smaller peptides for further degradation.
31
What is an alternative mechanism for protein degradation aside from the proteasome?
- Lysosomal degradation via autophagy
- Damaged protein or organelles are enclosed in autophagosome
- Autophagosome fuse with a lysosome for degradation by digestive enzymes
32
What is the structure of a voltage-gated sodium channel?
Composed of a single polypeptide chain with 4 domains (I-IV), each containing 6 transmembrane segments (S1-S6)
33
What acts as the voltage sensor in a voltage-gated sodium channel?
The S4 segment in each domain acts as the voltage sensor
34
What forms the pore in the voltage-gated sodium channel?
The P-loop between S5 and S6 forms the pore, allowing selective sodium ion passage.
35
What controls sodium ion flow after the channel opens?
The inactivation gate between domain III and IV controls sodium flow after the channel opens.
36
What triggers the opening of voltage-gated sodium channels?
Membrane depolarization causes the S4 segments to shift, opening the channel.
37
How does the channel close to stop sodium influx?
The inactivation gate closes the channel shortly after it opens, halting sodium flow
38
What is the resting membrane potential of a neuron?
Around - 70 mV
39
What occurs during depolarization in an action potential?
Sodium channels open, allowing Na+ to enter the neuron, raising the membrane potential toward +30 mV
40
What causes repolarization in a neuron?
Voltage-gated potassium channels open, allowing K+ to exit, bringing the membrane potential back toward
41
What is hyperpolarization?
After repolarization, the membrane potential briefly becomes more negative than the resting potential.
42
What triggers neurotransmitter release to the synapse?
An action potential reaching the axon terminal causes voltage-gated calcium channels to open, allowing Ca2+ influx
43
How do synaptic vesicles release neurotransmitters?
Calcium influx triggers vesicle fusion with the presynaptic membrane facilitated by SNARE proteins, leading to exocytosis of neurotransmitters.
44
What happens after neurotransmitters are released into the synaptic cleft?
They bind to receptors on the postsynaptic membrane, continuing the signal transmission
45
How do proteins destined for organelles enter the ER?
A signal peptide on the protein's N-terminus is recognized by an SRP, guiding the ribosome to the ER membrane for protein insertion
46
What happens after a protein enters the ER?
- The signal peptide is cleaved
- The protein is released into the ER lumen or intergrated into the membrane
47
How are proteins directed from the ER to the Golgi?
Proteins have sorting signals, are packed into vesicles, and transported to the cis-Golgi network
48
What tag directs lysosomal proteins from the ER to the Golgi?
Mannose-6-phosphate (M6P) tag
49
How are lysosomal proteins modified in the cis-Golgi?
Phosphotransferase adds the mannose-6-phosphate (M6P) tag to lysosomal proteins
50
What is the role of the M6P (mannose-6-phosphate) tag?
It directs lysosomal proteins to their final destination by being recognized by receptors
51
How do lysosomal proteins move from the trans-Golgi to the endosomes?
- M6P-tagged proteins are recognized by M6P receptors in the trans-Golgi
- Clathrin-coated vesicles then bud off, transporting the protein-receptor complexes to the early endosome
52
What happens to lysosomal proteins and their receptors in the endosome?
Lysosomal proteins are sent to the late endosome, while M6P receptors dissociate and are recycled back to the trans-Golgi
53
How does the endosome mature into a late endosome?
The endosome becomes more acidic, its protein composiition changes, and it fuses with the lysosome for enzyme activation and degradation.
54
What is the function of storage polysaccharides?
Storage polysaccharides store energy for future use
55
Give examples of storage polysaccharides
Starch (plants) and glycogen (animals)
56
Describe the structure of starch.
Starch consist of amylose (unbranched) and amylopectin (branched), allowing for easy breakdown into glucose
57
Describe the structure of glycogen.
Glycogen is a highly branched glucose polymer, mainly found in the liver and muscles, enabling rapid glucose release
58
How do the structures of starch and glycogen relate to their function?
Their alpha-glycosidic bonds make them soluble and easy to break down for quick energy release; branches in glycogen allow for faster breakdown
59
What is the function of structural polysaccharides?
Provide mechanical support, strength, and protection to cells and organisms.
60
Give examples of structural polysaccharides
Cellulose (plants) and chitin (arthopods and fungi)
61
Describe the structure of cellulose.
Cellulose is a linear polymer of glucose connected by beta-glycosidic bonds, forming strong fibers for rigidity
62
Describe the structure of chitin.
Chitin is similar to cellulose but has nitrogen-containing acetyl groups, providing strength to exoskeletons and fungal cell wells
63
How do the structures of cellulose and chitin relate to their function?
Beta-glycosidic bonds form long, straight chains that create strong, rigid fibers, ideal for providing structural integrity.
64
What are the key differences between storage and structural polysaccharides?
- Storage polysaccharides (starch, glycogen) are branched and used for energy storage
- Structural polysaccharides (cellulose, chitin) are linear and provide strength and support
65
How is ATP used by cells to drive endergonic reactions?
ATP provides energy through hydrolysis, which powers endergonic reactions by energy coupling
66
What is energy coupling?
Energy coupling is when energy from an exergonic reaction (ATP hydrolysis) drives and endergonic reaction.
67
Provide an example of energy coupling in cells
In protein synthesis, ATP activates amino acids and powers ribosomes to form peptide bonds.
68
What is ATP hydrolysis?
ATP is broken down into ADP and inorganic phosphate (Pi), releasing energy
69
What are endergonic reactions?
Endergonic reactions require energy input; products have more energy than reactants (photosynthesis)
70
What are exergonic reactions?
Exergonic reactions release energy; products have less energy than reactants (cellular respiration)
71
How do insulin and glucagon maintain blood glucose levels?
- Insulin lowers blood glucose by promoting glucose uptake
- Glucagon raises it by stimulating glucose release from glycogen
72
When is insulin released, and what is its effect?
Insulin is released when blood glucose is high (after eating) and promotes glucose storage, lowering blood glucose
73
When is glucagon released, and what is its effect?
Glucagon is released when blood glucose is low (fasting) and stimulates glycogen breakdown, raising blood glucose.
74
What are isoenzymes?
Isoenzymes are different forms of the same enzyme that catalyze the same reaction but function in different tissues or conditions
75
How does a deficiency in aldolase B lead to hereditary fructose intolerance (HFI)?
Without aldolase B, fructose cannot break down in the liver, causing toxic intermediates and disrupting glucose metabolism.
76
Why does ingesting fructose cause low blood glucose in HFI?
Fructose ingestin disrupts glucose metabolism, impairing glucose production and utilization, leading to low blood sugar levels
77
What is feedback inhibition in metabolic pathways?
Feedback inhibition is when the end product of a pathway inhibits an earlier enzyme, preventing overproduction of that product.
78
Provide an example of feedbackm inhibition.
In isoleucine synthesis, high levels of isoleucine inhibit threonine dehydratase, the first enzyme in the pathway
79
Why is feedback inhibition important?
It prevents wasteful overproduction of molecules and helps maintain cellular homeostasis
80
What is fermentation?
Anaerobic process that regenerates NAD+ by converting pyruvate into products like lactic acid or ethanol
81
Why is NAD+ regeneration important to cells?
NAD+ is required for glycolysis to continue; without it, glycolysis would stop, halting ATP production
82
Give an example of fermentation.
Lactic acid fermentation occurs in muscle cells during anaerobic conditions converting pyruvates into lactic acid to regenerate NAD+
83
Why are the electron transport chain (ETC) and ATP synthase considered coupled processes?
The ETC creates a proton gradient that provides the energy needed for ATP synthase to produce ATP
84
How does the proton gradient drive ATP synthase?
The proton gradient creates potential energy that is harnessed by ATP synthase to convert ADP and Pi into ATP
85
What is DNP and how does it illustrate the connection between ETC and ATP synthase?
DNP uncouples the processes by allowing protons to leak across the membrane, preventing ATP synthesis even though the ETC remains active
86
How many ATP are produced from one glucose molecule during cellular respiration?
36-38 ATP are produced from one glucose molecule
87
What is the ATP yield of glycolysis?
2 ATP and 2 NADH
88
What is the ATP yield of the citric acid cycle?
2 ATP, 6 NADH, and 2 FADH2
89
How do NADH and FADH2 contribute to ATP production?
NADH and FADH2 donate electrons to the ETC, driving proton pumping to establish a gradient that ATP synthase uses to produce 28 ATP
90
What are the base pairing rules in DNA?
A - T: Adenine with Thymine through two hydrogen bonds
C - G: Cytosine with Guanine through three hydrogen bonds
91
What are the base pairing rules in RNA?
In RNA,
A - U: Adenine with Uracil
C - G: Cytosine still with Guanine
92
Why is base pairing important?
Base pairing ensures accurate DNA replication and RNA transcription, maintain genetic integrity
93
Where does DNA replication begin?
Begins at specific sites called Origin Of Replication
94
How are replication forks formed?
Helicase unwinds DNA, forming replication forks at the origin of replication
95
How does DNA replication proceed from the origin?
Replication proceeds bidirectionally, with two replication forks moving in opposite directions
96
What is the difference between the leading and lagging strand in DNA replication?
- Leading strand is synthesized continously in the direction of the replication fork
- Lagging strand is synthesized discontinously in short Ozarki fragments
97
How are Okazaki fragments joined together?
DNA ligase joins the Okazaki fragments on the lagging strand after DNA polymerase I replaces RNA primers with DNA nucleotides
98
Why is DNA replication bidirectional?
Bidirectional replication ensures that both DNA strands are replicated simultaeously and efficiently
99
What role does helicase play in DNA replication?
Helicase unwinds the DNA double helix, creating replication forks
100
What is the function of primase in DNA replication?
Primase adds RNA primers to provide a starting point for DNA synthesis
101
What does DNA polymerase III do during replication?
DNA polymerase III synthesizes new DNA strands in the 5' to 3' direction, continuously on the leading strand and discontinuously on the lagging strand
102
How does DNA ligase contribute to DNA replication?
DNA ligase seals the gaps between Okazaki fragments on the lagging strand, forming a continuous strand
103
What is the cell checking for at the G2-M checkpoint?
The cell checks for DNA damage, ensures DNA replication is complete, and verifies that the cell has enough resources for mitosis
104
Why si the G2-M checkpoint important?
It ensures the integrity of the genome before the cell enters mitosis, preventing the divsion of cells with damaged or incomplete DNA
105
What are the key molecules involved in the G2-M checkpoint?
Cyclin B, CDK1 (Cyclin dependent kinase 1), and Wee1 kinase.
Cyclin B-CDK1 complex is required for mitosis
Wee1 kinase inhibits CDK1 to delay entry into mitosis if issues are detected
106
What role does the Cyclin B-CDK1 complex play at the G2-M checkpoint?
It drives the cell into mitosis by phosphorylating proteins that initiate mitotic events
107
What is the first stage of mitosis?
Prophase:
- Chromatin condenses into chromosomes
- The mitotic spindle forms
- The nuclear envelope begins to break down
108
How does the G2-M checkpoint facilitate the transition to prophase?
Once the G2-M checkpoint is passed, the activation of Cyclin B-CDK1 triggers the molecular events that initiate prophase
109
What is the cell checking for at the Metaphase-Anaphase checkpoint?
The cell ensures that all chromosomes are properly attached to the mitotic spindle and alighed at the metaphase plate (center)
110
What key molecules are involved in the Metaphase-Anaphase checkpoint?
The Anaphase Promoting Complex/Cyclosome (APC/C) and securin. APC/C activates separase by degrading securin, allowing the sister chromatids to separate
111
Why is the Metaphase-Ananphase checkpoint important?
It prevents the premature separation of sister chromatids, ensuring accurate chromosome segregation
112
How does the cell exit mitosis?
After the chromatids are separated, the APC/C targets Cyclin B for degradation, leading to deactivation of CDK1, and the cell progresses into cytokinesis, completeing mitosis
113
What is the cell checking for in G1-S checkpoint?
The cell checks for DNA damage, assesses cell size, and ensures that sufficient nutrients and growth signals are present to support DNA replication
114
Why is the G1-S checkpoint important?
It ensures that the cell only proceeds to DNA replication when conditions are optimal, preventing the replication of damaged DNA
115
What are the key molecules involved in teh G1-S checkpoint?
Cyclin D, CDK4/6, Rb protein, and E2F transcription factors
The Cyclin D-CDK4/6 complex phosphorylates Rb, releasing E2F to initiate S-phase gene transcription
116
How does the cell enter the S phase?
The phosphorylation of Rb by Cyclin D-CDK4/6 allows E2F to activate the transcription of genes required for DNA replication, enabling entry into the S phase
117
What is apoptois and why is it important in cellular biology?
- Programmed cell death
- Important for removing damaged, infected, or unnecessary cells
- Maintains tissue health and prevents cancer
118
What are the key molecular players in apoptosis?
Caspases (initiator and executioner caspases) execute apoptosis
119
How do caspases contribute to apoptosis?
Initiator caspases activate excutioner caspases which cleave cellular components, leading to cell death
120
Why is p53 called the "guardian of the genome?"
p53 responds to DNA damage by halting the cell cycle, allowing for repair or triggerig apoptosis if damage is irreparable, thus protecting the genome from mutations
121
What role does p53 play in the cell cycle and apoptosis?
p53 activates genes that stop the cell cycle at checkpoints and can induce apoptosis by actiating pro-apoptotic proteins like Bax
122
How do mutations in the p53 contribute to cancer?
Mutations in p53 prevent it from stopping the cell cycle or inducing apoptosis, allowing damaged cells to proliferate and accumulate mutations, leading to cancer.
123
What are oncogenes, and how do they contribute to cancer?
Oncogenes are mutated forms of proto-oncogenes that drive uncontrolled cell growth and division, contributing to cancer development
124
What are tumor suppressor genes, and how do they function?
Tumor suppressor genes (p53, Rb) regulate cell division and prevent excessive growth. Mutations in these gens disables these controls, allowing cancerous growth
125
How can mutations in oncogenes and tumor suppressor genes lead to cancer?
Mutations in oncogenes can cause excessive cell proliferation, while loss-of-function mutation in tumor suppressors genes remove growth regulation, both contributing to tumor development.
126
What are six key hallmarks of cancer?
- Sustaining proliferative signaling
- Evading growth suppressors
- Resisting cell death
- Enablig replicative immortality
- Inducing angiogenesis
- Activating invasion and metastasis
127
What does sustaining proliferative signaling mean in cancer?
Cancer cells maintain uncontrolled cell division by constantly activating growth factor signaling pathways, even in the absence of external signals
128
What molecular mechanisms allow cancer cells to sustain proliferative signaling?
Cancer cells may:
- Produce their own growth factors (autocrine signaliing)
- Overexpress growth factor receptors (EGFR)
- Mutate downstream signaling proteins (Ras, PI3K)
129
How can sustaining proliferative signaling be targeted for cancer therapy?
- EGFR inhibitors
- Tyrosine kinase inhibitor
- Ras pathway inhibitors
130
What is meant by evading growth suppressors in cancer?
Cancer cells bypass mechanisms that normally inhibit cell proliferation, such as tumor suppressor proteins
131
What molecular mechanisms do cancer cells use to evade growth suppressors?
- Inactivation of tumor suppressor genes (TP53, RB1)
- Loss of contact inhibition
132
What therapies target the evasion of growth suppressors?
- Restoring tumor suppressor function
- CDK inhibitors
133
How do cancer cells resist cell death?
Cancer cells avoid apoptosis by altering apoptotic pathways
134
What molecular mechanisms help cancer cells resist apoptosis?
- Upregulating anti-apoptotic proteins (Bcl-2)
- Downregulating pro-apoptotic proteins (Bax)
- Mutations in p53
135
What therapies target cancer cells resistance to cell death?
Bcl-2 inhibitors
136
What is replicative immortality in cancer cells?
Cancer cells can divide indefinitely by maintain telomere length
137
What molecular mechanisms enable replicative immortality?
Cancer cells often reactivate the enzyme telomerase, which prevents telomere shortening
138
How can replicative immortality be targeted in cancer therapy?
Telomerase inhibitors
139
What is angiogenesis and why is it important for cancer?
Angiogenesis is the formation of new blood vessels, which cancer cells induce to supply themselves with oxygen and nutrients
140
What molecular mechanisms induce angiogenesis in cancer?
Cancer cells overexpress pro-angiogenic factors such as VEGF (vascular endothelial growth factor)
141
What are therapuctic strategies to inhibit angiogenesis?
- VEGF inhibitors
- Tyrosine kinase inhibitor targeting VEGF receptors
142
How do cancer cells activate invasion and metastasis?
Cancer cells gain the ability to invade surrounding tissues and spread to distant sites (metastasis)
143
What molecular changes enable cancer invasion and metastasis?
- Epithelial-to-mesenchymal transition (EMT)
- Degradation of extracellular matrix by proteases (MMPs)
144
What therapies target cancer invasion and metastasis?
- MMP inhibitors to block tissue invasion
- Therapies targeting EMT pathways
145
How do current cancer therapies target multiple hallmarks of cancer?
Combination therapies often target multiple hallmarks at once, such as using VEGF inhibitors alongside chemotherapy to target angiogenesis and cell proliferation
146
What are some examples of therapies designed to disrupt cancer hallmarks?
- EGFR inhibitors (proliferative signaling)
- CDK inhibitors (evading growth suppressors)
- Apoptosis-inducing agents (resisting cell death)
- Telomerase inhibitor (replicative mortality)
- VEGF inhibitor (angiogenesis)
- EMT pathway inhibitors (invasion and metastasis)
