Module 2 Cell Structure and Function Flashcards
(209 cards)
1
Q
What is the basic structure of the plasma membrane?
A
Phospholipid bilayer with hydrophilic heads facing outward and hydrophobic tails facing inward
2
Q
What are the six main functions of membrane proteins?
A
Transport, enzyme activity, signal transduction, cell recognition, cell junctions, and cell-matrix interactions
3
Q
What makes the plasma membrane ‘selectively permeable’?
A
It allows specific molecules to pass in and out of the cell while blocking others
4
Q
What is the primary purpose of the nuclear membrane?
A
To protect DNA and control the entry/exit of molecules through nuclear pores
5
Q
How is DNA packaged in the nucleus?
A
DNA wraps around histones → forms nucleosomes → creates chromatin fibers → forms chromatin loops → condenses into chromosomes
6
Q
What happens in the nucleolus?
A
Ribosomal RNA (rRNA) is produced and ribosome subunits are assembled and then leave through nuclear pores
7
Q
What is the endomembrane system?
A
A network of membrane-bound organelles that transport molecules (includes ER, Golgi, lysosomes)
8
Q
What are the two types of endoplasmic reticulum?
A
Rough ER (with ribosomes, makes proteins) and Smooth ER (makes lipids, no ribosomes)
9
Q
What is the primary function of the Golgi apparatus?
A
To modify, sort, and package proteins for transport or secretion
10
Q
What are the three types of cytoskeletal elements?
A
Microfilaments, intermediate filaments, and microtubules
11
Q
What makes microtubules unique?
A
They are dynamic, have a central lumen, and help move vesicles within the cell, they are assembled + disassembled as required. Made of tubulin dimers coiled to form a tube 25nm ((lumen 15nm diameter)) located in cytoskeleton of cell
12
Q
What are intermediate filaments characterized by?
A
They are the most stable and often made of keratin
13
Q
Do ribosomes have a membrane?
A
False. Ribosomes are not membrane-bound organelles.
14
Q
What is the key difference between Integral and Peripheral Proteins?
A
Integral proteins are embedded in the membrane, (eg: transmembrane intergral proteins spans the membrane) while Peripheral proteins are loosely associated with the membrane surface (not embedded in it).
15
Q
Describe the hydrophobic/hydrophilic components of Integral Proteins:
A
Integral proteins have both hydrophobic regions (to interact with membrane lipid tails) and hydrophilic regions (to interact with water inside/outside the cell)
16
Q
What is the Transport protein function?
A
Moves molecules across the membrane, either passively or using energy
17
Q
What is Signal Transduction?
A
Converts external signals into cellular responses by changing protein shape when a molecule binds (causing communication of information to inside the cell) RECEPTION> TRANSDUCTION > RESPONSE
18
Q
What is Cell Recognition function?
A
Allows cells to identify and interact with other cells using specific molecular markers
19
Q
What is the Enzyme function of membrane proteins?
A
Catalyzes chemical reactions at the membrane surface
20
Q
Describe the plasma membrane structure:
A
A mosaic of molecules bobbing in a fluid bilayer of phospholipids, which is dynamic and constantly changing
21
Q
What is the nuclear envelope of a eukaryotic cell?
A
A double membrane (also called nuclear envelope) with nuclear pores that selectively controls molecular entry and exit, protecting the DNA
22
Q
What is temporal and spatial control in a cell?
A
The ability to regulate when (temporal) and where (spatial) specific cellular functions occur, controlling molecule movement and activity
23
Q
Where are ribosomes commonly found?
A
Free in the cytoplasm and attached to the rough endoplasmic reticulum (rough ER)
24
Q
What happens when ribosomes are activated?
A
They come together (large and small subunits) to form a complete ribosome and begin protein synthesis
25
What is the main function of ribosomes?
Protein synthesis - translating messenger RNA (mRNA) into proteins
26
Where does glycolysis occur?
In the cytoplasm (outside the mitochondria)
27
What are the reactants and products of glycolysis?
Reactant: 1 glucose molecule
Products:
- 2 pyruvate molecules
- 2 net ATP
- 2 NADH electron carriers
28
Does glycolysis require oxygen?
No, can occur in aerobic and anaerobic conditions
29
How many ATP are net produced in glycolysis?
2 net ATP per glucose molecule (4 ATP produced, 2 ATP invested)
30
What step of cellular respiration is pyruvate oxidation?
Considered the 'link step' between glycolysis and the citric acid cycle
31
Where does pyruvate oxidation occur?
Mitochondrial matrix
32
What happens during pyruvate oxidation?
- Converts pyruvate to acetyl-CoA
- Releases CO2
- Produces NADH
- Prepares molecules for citric acid cycle
33
What step of cellular respiration is the citric acid cycle?
Third step of cellular respiration, occurring after pyruvate oxidation
34
Where does the citric acid cycle occur?
Mitochondrial matrix
35
What are the products of the citric acid cycle?
Per glucose molecule:
- 2 ATP
- Multiple NADH
- Multiple FADH2
- CO2
36
Why is the citric acid cycle important beyond energy production?
Produces intermediate molecules used in:
- Amino acid synthesis
- Neurotransmitter production
- Other metabolic pathways
37
What step of cellular respiration is oxidative phosphorylation?
Final step of cellular respiration, occurring after the citric acid cycle
38
Where does oxidative phosphorylation occur?
Inner mitochondrial membrane
39
What are the key components of oxidative phosphorylation?
- Occurs in the inner mitochondrial membrane of mitochondria
- Electrons from NADH and FADH₂ pass through the ETC, pumping protons (H⁺) into the intermembrane space, creating a proton gradient.
- Electron transport chain (complexes 1-4)
- Proton gradient
- ATP synthase
- Oxygen as final electron acceptor
- Requires Oxygen
40
How many ATP are produced in oxidative phosphorylation?
26-28 ATP per glucose molecule
41
What is the final product when oxygen accepts electrons?
Water (H2O)
42
How do NADH and FADH2 contribute to ATP production?
They transfer electrons to the electron transport chain, which:
- Moves electrons through protein complexes
- Pumps hydrogen ions across the inner mitochondrial membrane
- Creates a proton (hydrogen ion) concentration gradient
43
What is a proton gradient?
A difference in hydrogen ion concentration between the mitochondrial matrix and intermembrane space
- Created by electron transport chain complexes
- Provides potential energy for ATP synthesis
44
How does the proton gradient generate ATP?
- Hydrogen ions flow through ATP synthase
- Causes ATP synthase to rotate like a turbine
- Drives conversion of ADP to ATP through chemiosmosis
45
What is substrate-level phosphorylation?
Type of ATP production w/o ETC and O2
-Direct enzyme-catalyzed transfer of phosphate from a substrate to ADP forming ATP
46
Where and when does substrate-level phosphorylation occur?
During glycolysis (cytoplasm) and citric acid cycle (mitochondrial matrix)
47
How efficient is substrate-level phosphorylation?
Less efficient, produces fewer ATP molecules compared to oxidative phosphorylation
48
What is oxidative phosphorylation?
ATP production using energy from electron transport chain and proton gradient
49
How efficient is oxidative phosphorylation?
Highly efficient, produces majority of cellular ATP (26-28 ATP per glucose)
50
How many total ATP are produced from one glucose molecule?
30-32 ATP (2 from glycolysis, 2 from citric acid cycle, 26-28 from oxidative phosphorylation)
51
What are pancreatic islets?
Clusters of hormone-producing cells in the pancreas (Islets of Langerhans)
52
Are pancreatic islets endocrine or exocrine?
Endocrine glands (secrete hormones directly into bloodstream)
53
What are beta cells?
Cells in pancreatic islets that produce and secrete insulin
54
When do beta cells release insulin?
When blood glucose levels are high (after eating)
55
What are alpha cells?
Cells in pancreatic islets that produce and secrete glucagon
56
When do alpha cells release glucagon?
When blood glucose levels are low (between meals, during fasting)
57
What characterizes Type 1 Diabetes?
- Insufficient insulin production
- Autoimmune destruction of pancreatic β-cells
- Requires insulin replacement
- Less common form of diabetes
58
What characterizes Type 2 Diabetes?
- Insulin resistance
- Body produces insulin but cells don't respond effectively
- Often related to lifestyle and obesity
- More common form of diabetes
59
What happens to glucose in untreated diabetes?
- Glucose accumulates in bloodstream
- Cannot enter cells effectively
- Leads to high blood sugar (hyperglycemia)
60
What are two contradictory symptoms of untreated diabetes?
- Increased hunger
- Unexplained weight loss
61
What are the main function of histones?
To package and organise DNA into chromatin
62
Can you label this diagram?
63
What is Paracrine Signaling?
Local signaling where molecules are released from one cell and act on nearby target cells. Example: Fibroblast growth factor during blood clotting.
64
What is Synaptic Signaling?
Communication between neurons or between neurons and muscle cells through neurotransmitters.
## Footnote
Example: Acetylcholine release at neuromuscular junctions.
65
What is Endocrine Signaling?
Long-distance signaling where hormones are released into the bloodstream, traveling throughout the body to reach target cells.
## Footnote
Example: Insulin released from pancreas affecting cells across the body.
66
What types of secreted signals are local and long distance signaling?
Local Signals: Paracrine and Synaptic (short-range). Distant Signals: Endocrine (long-range via bloodstream).
67
What are the 3 steps of cell signalling?
1. Reception: Ligand binds to specific receptor
2. Transduction: Signal is converted and relayed through the cell (often via phosphorylation, aka phosphorylation cascade)
3. Response: Cellular action is triggered (e.g., gene expression, protein activation)
68
What are two other common names for a signaling molecule?
1. Ligand
2. First messenger
69
Fill in the blanks: Receptors for water soluble molecules 1. (are/not) 2. _________ bound
1. Are 2. Membrane
70
Fill in the blanks: Receptors for lipid soluble molecules 1. (are/not) 2. _________ bound
1. (are) Not 2. Membrane
71
What is a G-protein coupled receptor (GPCR)?
A transmembrane protein that spans the membrane 7 times and binds to G proteins as molecular switches.
72
What happens when a ligand binds to a GPCR?
It can activate different enzymes and initiates signal transduction pathways.
73
What are the characteristic features of GPCRs?
They have 7 transmembrane domains, allow specific ligand binding, and are a target for about 1/3 of modern drugs.
74
What occurs to a GPCR when it is activated?
It changes shape (conformationally), exposing new protein interactions, and GTP displaces GDP, but the enzyme remains inactive; can then interact with enzyme as G protein dissociates from receptor. Then lastly G protein has GTPase activity promoting its release form the enzyme and back to its resting form.
75
Which body system relies heavily on ligand gated ion channels?
The nervous system: released neurotransmitters bind as ligands to ion channels on target cells to propagate action potentials
76
What is a ligand-gated ion channel receptor?
Back:
- Protein receptor with a gate that opens/closes when specific ligand binds
- When ligand is NOT bound: gate is closed
- When ligand binds: gate opens, allowing specific ions to flow through
- Characteristics:
* Allows specific ions (e.g., sodium, potassium, calcium, chloride) to pass
* Highly important in nervous system
* Changes protein conformation when ligand binds
- Example: Acetylcholine receptor in muscle cells that triggers muscle contraction
- Crucial for processes like action potentials and muscle contractions
77
What is a typical phosphorylation cascade?
Relay race-like process of passing a phosphate group between proteins. Inactive protein kinases are activated by receiving a phosphate. Each protein kinase transfers phosphate to the next protein. Allows for signal amplification. Involves multiple steps from initial signal to final cellular response. Phosphate transferred from ATP to specific amino acids (typically serine or threonine), phosphotases removes the phosphate groups. NO energy is made, only spent.
78
True or False: Phosphorylation always activates the subsequent protein
False. Phosphorylation can SOMETIMES activate a protein. In some cases, phosphorylation may inactivate or modify protein function. Context and specific protein determine the effect of phosphorylation.
79
What is the role of phosphatases in a phosphorylation cascade?
Enzymes that dephosphorylate proteins
Remove phosphate groups from activated proteins
Inactivate the protein by removing the phosphate
Allows proteins to return to their original inactive state
Enables proteins to be reactivated if:
* Ligand is still present
* More relay molecules are available
* New signal triggers the cascade again
Provides a mechanism to turn off cellular responses
Ensures signaling is not active longer than necessary
80
Calcium as a Second Messenger
- Concentration 1000 times higher outside the cell
- Stored in:
* Outside cell
* Smooth ER
* Mitochondrial matrix
- Moves from ER to cytosol when triggered
- Activated by IP3(also second messenger) receptor/channel
- Can activate multiple proteins
- Critical in muscle contraction
- Excitotoxic when levels become too high
- Regulated by ATP-dependent pumps
-Can be really potent
81
Cyclic AMP (cAMP) as a Second Messenger
- Small molecule, never made of protein
- Formed by enzyme adenyl cyclase
- Converts ATP to cyclic AMP
- Powerful messenger used across cell signaling systems
- Activated by G-protein coupled receptors
- Can activate protein kinase A
- Broken down by phosphodiesterase (PDE)
## Footnote
Example of drug interaction: Caffeine blocks PDE, keeping cAMP active longer
82
Muscles use what ion to contract?
Ca^+ (Calcium ions)
83
What is the main purpose of massive amplification in cell signaling?
- Allows a single molecule (e.g., adrenaline) to trigger a massive cellular response
- Example: One adrenaline molecule can generate 10^8 molecules of response
- Provides rapid and powerful cellular reactions
- Useful in emergency situations (e.g., fight or flight response)
- Enables quick energy generation
- Allows for:
* Rapid glucose release from glycogen
* Quick ATP production
* Fast cellular activation
- Demonstrates efficiency of multi-step signaling pathways
- Provides multiple control points for cellular response
84
What are the 3 steps of gene expression?
1. Transcription (in nucleus)
2. Processing (in nucleus)
3. Translation (in cytoplasm)
85
What is DNA?
Hereditary material that stores and transmits genetic information using nucleotides, composed of two strands that can be used as a template for making RNA and proteins
86
What is RNA?
A nucleic acid that acts as a messenger, carrying genetic information from DNA to ribosomes for protein synthesis; less stable than DNA
87
What are the 3 main steps of transcription?
1. Initiation: RNA polymerase binds to promoter
2. Elongation: RNA polymerase moves downstream, creating RNA
3. Termination: RNA polymerase detaches at termination signal
88
What do 'upstream' and 'downstream' mean in gene expression?
Upstream: Region before a gene (includes promoter)
Downstream: Region after a gene (includes terminator)
Significance: Helps control where gene expression starts and stops
89
What are the base pairings in DNA and RNA?
DNA: A pairs with T, C pairs with G
RNA: A pairs with U, C pairs with G
90
Which is single-stranded: DNA or RNA?
RNA is single-stranded; DNA is double-stranded
91
What happens during transcription initiation?
- TATA box (TBP) creates DNA bend
- Allows assembly of transcription factors
- RNA polymerase II binds to promoter region
- Prepares for RNA synthesis
92
What's the difference between template and non-template strands?
Template strand (3' to 5'): Used to create RNA
Non-template/Coding strand (5' to 3'): Complementary to RNA
5' end: Phosphate group
3' end: Hydroxyl group
93
What happens during elongation of transcription?
Elongation:
- RNA polymerase moves downstream
- Hydrogen bonds form between DNA template and RNA nucleotides
- Phosphodiester bonds connect RNA nucleotides
- DNA temporarily unwinds in 'transcription bubble'
94
What occurs during termination?
- Polymerase reaches polyadenylation signal (string of A's)
- Pre-mRNA is released
- Limited proofreading occurs
- RNA is less precisely proofread compared to DNA replication
95
Where does mRNA processing occur?
In the nucleus
96
What is splicing?
Removing introns (non-coding regions) and joining exons
- Performed by spliceosome
- Allows for alternative splicing and protein diversity
97
What is mRNA capping and tailing?
Capping: Modified nucleotide added to 5' end
Tailing: Poly-A tail added to 3' end
Purpose: Stabilize mRNA and facilitate translation
98
What are UTR regions?
Untranslated regions at 5' and 3' ends of mRNA
- Part of exons
- Do not code for protein
- Involved in mRNA regulation
99
Where does translation occur?
In the cytoplasm on ribosomes
100
What is a codon?
Three-nucleotide sequence in mRNA that codes for a specific amino acid
101
What is a ribosome?
Cellular machine that reads mRNA and assembles proteins
- Consists of small and large subunits
- Has A, P, and E sites for tRNA movement
102
What is an anticodon?
Three-nucleotide sequence on tRNA that matches mRNA codon
Allows specific amino acid placement during translation
103
What is tRNA's role?
Transfers specific amino acids to ribosome
- Carries amino acids
- Has anticodon for specific matching
104
What is the role of GTP in translation?
Provides energy for:
- Initiating translation
- Moving tRNAs
- Protein synthesis processes
105
Fill in the blanks: a) ____ is the physical link between mRNA and b) ____ ____ sequence of proteins
a) tRNA
b) amino acids
106
What happens during translation initiation?
- Met-tRNA binds to start codon (AUG)
- Small ribosomal subunit scans mRNA
- Hydrogen bonds form between anticodon and codon
- Initiation complex forms
- Large ribosomal subunit joins
- Requires GTP energy
107
What are the steps of translation elongation?
1. Codon Recognition
- Incoming tRNA matches mRNA codon
- Hydrogen bonds form between anticodon and codon
2. Peptide Bond Formation
- Amino acid added to growing polypeptide chain
- Peptide bond forms between amino acids
3. Translocation
- Ribosome shifts
- tRNAs move through A, P, E sites
- Requires energy (GTP)
108
What happens during translation termination?
- Stop codon (UAA, UAG, UGA) reached
- Release factor binds without an amino acid
- Polypeptide is released from ribosome
- Ribosome undergoes hydrolysis
- Ribosomal subunits separate
- Polypeptide begins folding
109
Fill in the blank: Gene expression is a) _____ regulated
a) tightly
110
What are the main characteristics of housekeeping proteins?
- Produced continuously
- Always present in cell
- Long half-life
- Essential for basic cellular functions
- Examples: Tubulin, some metabolic enzymes
111
What are the characteristics of stimulus-responsive proteins?
- Produced only when specific signal is received
- Short-lived
- Quickly activated and deactivated
- Respond to cellular needs
- Function during specific conditions or processes
112
What is the N-terminus?
- The beginning of a protein/polypeptide chain
- Contains the amino group (-NH2)
- Corresponds to the first amino acid added during translation
- Relates to the 5' end of the mRNA
113
What is the C-terminus?
- The end of a protein/polypeptide chain
- Contains the carboxyl group (-COOH)
- Last amino acid added during translation
- Corresponds to the 3' end of the mRNA
114
What is the key difference between N-terminus and C-terminus?
- N-terminus: Starts with amino group
- C-terminus: Ends with carboxyl group
- N-terminus is added first during protein synthesis
- C-terminus is added last during protein synthesis
115
Why are N and C termini important?
- Determine protein folding
- Influence protein interactions
- Critical for protein structure and function
- Help in protein identification and characterization
116
Label this diagram
A:
117
Label this diagram of a ribosome in translation of gene expression:
A:
118
What is the central dogma of gene expression?
DNA > RNA > Protein
119
What is primary protein structure?
- The order of amino acids in a protein
- Directly determined by DNA sequence
- Like a chain of amino acids linked together
- Has a beginning (N-terminus) and end (C-terminus)
120
What are the two main types of secondary structure mentioned?
- Alpha helices
- Beta pleated sheets
- Basic folding patterns within the protein chain
- Formed by how amino acids interact with each other
121
What is tertiary structure?
- The overall 3D shape of a single protein
- How the protein folds into its final shape
- Determines how the protein will work
122
What is quaternary structure?
- When multiple protein pieces come together
- Not all proteins have this structure
- Creates more complex protein structures
123
Why is protein structure important?
- The shape determines how the protein works
- If the shape changes, the protein might not function
- Structure is critical for the protein's job in the cell
124
What is phosphorylation?
Adding a phosphate group to a protein
- Can activate or deactivate proteins
- Controlled by specific enzymes
- Important in cell signaling
125
What does a kinase do?
Enzyme that adds phosphate groups to proteins
- Typically activates the protein it phosphorylates
- Part of signal transduction process
- Requires energy (usually from ATP)
126
What is a phosphorylation cascade?
Series of protein activation through phosphorylation
- Each kinase activates the next protein
- Creates an amplification of the original signal
- Allows for quick and widespread cellular response
127
What does a phosphatase do?
Removes phosphate groups from proteins
- Often deactivates or resets the protein
- Opposite action of kinase
- Helps control and stop cellular signals
128
How does a phosphorylation cascade work?
Initial signal triggers first kinase
- First kinase phosphorylates and activates next protein
- Process continues down a chain of proteins
- Allows small signal to create large cellular response
129
In a phosphorylation cascade, how do kinases and phosphatases interact?
In a phosphorylation cascade, protein kinases ACTIVATE proteins by PHOSPHORYLATING them, while phosphatases INACTIVATE proteins by DEPHOSPHORYLATING them.
130
Why does phosphorylation occur?
Allows quick cellular response to signals
- Changes protein shape/activity
- Turns proteins 'on' or 'off'
- Helps regulate:
* Enzyme activity
* Protein-protein interactions
* Cellular processes
* Signal transmission
- Provides a fast molecular switch mechanism
- Enables cells to respond rapidly to external and internal signals
131
What does diploid mean in cell division?
Having two complete sets of chromosomes (2n); in humans, this means 46 chromosomes (23 pairs)
132
What does haploid mean in cell division?
Having a single set of chromosomes (n); in humans, this means 23 chromosomes, typically found in gametes
133
What is somatic cell division?
Cell division that occurs in non-reproductive body cells, using mitosis to create genetically identical daughter cells
134
How does somatic cell division differ from reproductive cell division?
Somatic division (mitosis) produces identical diploid cells with no genetic variation, while reproductive division (meiosis) creates genetically unique haploid cells
135
What is the purpose of somatic cell division?
Growth, repair, and replacement of body tissues; maintains diploid chromosome number
136
What is the purpose of the G1 phase?
Cell growth, preparation for DNA replication, and centrosome replication begins
137
What occurs during the S phase of Interphase?
DNA replication takes place, doubling the cell's DNA content. DNA strands are separated, and new DNA is synthesized opposite each of the old strands
138
Do all somatic cells divide?
No, many but not all somatic cells divide. Most spend time in interphase performing their specific cellular functions
139
What type of cells typically stay in G1 or exit to G0 phase?
Neuronal/nerve cells typically do not divide after initial development, remaining in G1 or exiting to G0
140
What occurs during the G2 phase in terms of cell preparation?
Cell checks if organelles are sufficient for division, completes centrosome replication, and verifies biosynthetic readiness
141
What characterizes early prophase?
Nuclear membrane is still intact, chromosomes begin to condense from uncondensed chromatin, cell remains diploid, mitotic spindle starts forming
142
What defines late prophase?
Nuclear membrane breaks down, chromosomes are fully condensed, mitotic spindle is fully formed, cell remains diploid
143
Describe Anaphase.
Sister chromatids separate and move to opposite poles of the cell, pulled apart by mitotic spindle microtubules shortening, with organization centres located at opposite cell poles
144
Why are chromosomes condensed during cell division?
To facilitate easier organization and separation of genetic material, prevent tangling, and ensure accurate chromosome segregation during cell division
145
What are the three stages of Interphase?
G1 (growth), S (synthesis), G2 (checking)
146
What are the four phases of Mitosis (PMAT)?
Prophase, Metaphase, Anaphase, Telophase
147
What happens in Metaphase?
Chromosomes align at the cell's equatorial plane
148
What characterizes Telophase?
Nuclear envelopes reform, chromosomes decondense, cell prepares for cytokinesis
149
What is the primary purpose of Mitosis?
To create genetically identical daughter cells for growth and repair
150
Can you label this diagram about cell division?
Answers:
151
What is a sister chromatid?
Two identical copies of a chromosome, attached at the centromere, created during DNA replication before cell division, containing the same genetic information
152
At what points in cell division are there haploid cells?
Haploid cells are produced at the end of meiosis II, resulting in four haploid gametes (egg or sperm cells)
153
What is cytokinesis?
The physical process of cell division where the cytoplasm of a single cell is divided into two daughter cells, typically occurring after nuclear division (mitosis or meiosis)
154
What are the key checkpoints in the mitotic cell cycle?
- G1 Checkpoint: Checks if DNA is undamaged and cell is healthy enough to divide
- G2 Checkpoint: Ensures DNA replication is complete and no DNA damage exists
- M Checkpoint (Mitotic Checkpoint): Verifies all chromosomes are properly attached to the mitotic spindle and aligned correctly before separation
155
How many stages of meiosis are there?
Two stages of meiosis:
- Meiosis I: Homologous chromosomes separate
- Meiosis II: Sister chromatids separate (similar to mitosis)
156
What are homologous chromosomes?
Chromosomes that pair up during meiosis, one from the maternal parent and one from the paternal parent, containing genes for the same traits at the same locations but potentially different alleles
157
What is a tetrad of chromosomes?
A structure formed during prophase I of meiosis, consisting of four chromatids - two sister chromatids from each of the two homologous chromosomes that have paired up
158
What unique events occur during Prophase I of Meiosis?
Homologous chromosomes pair up, form tetrads, undergo crossing over at points called chiasmata, and exchange genetic material between non-sister chromatids
159
What happens during Metaphase I of Meiosis?
Homologous chromosome pairs (tetrads) align
160
What is the primary purpose of Meiosis I?
To separate homologous chromosomes and create genetic variation through crossing over and independent assortment
161
Describe Anaphase I in Meiosis
Homologous chromosomes separate and move to opposite poles of the cell, with each chromosome still containing sister chromatids
162
What characterizes Telophase I of Meiosis?
Two daughter cells form, each with half the original number of chromosomes (haploid), each chromosome still contains sister chromatids, cleavage furrow
163
What happens during Prophase II of Meiosis?
Chromosomes condense, and the nuclear envelope breaks down, similar to mitosis, but now in haploid cells
164
Describe Metaphase II in Meiosis
Chromosomes align at the cell's equator, with sister chromatids facing opposite poles
165
What occurs during Anaphase II of Meiosis?
Sister chromatids separate and move to opposite poles of the cell, creating four unique haploid cells
166
What is the final result of Meiosis II?
Four genetically unique haploid cells, each with a single set of chromosomes, ready to function as gametes
167
What are the key similarities between mitosis and meiosis?
Both involve chromosome condensation, use similar cellular machinery, involve spindle formation, separate chromosomes/chromatids, and occur in eukaryotic cells.
168
What is the purpose of mitosis?
Growth, repair, asexual reproduction.
169
What is the purpose of meiosis?
Sexual reproduction, genetic variation.
170
How many divisions occur in mitosis?
One division.
171
How many divisions occur in meiosis?
Two sequential divisions.
172
What is the chromosome number produced by mitosis?
Produces two diploid, identical cells.
173
What is the chromosome number produced by meiosis?
Produces four haploid, genetically unique cells.
174
Is there genetic variation in mitosis?
No genetic recombination.
175
Is there genetic variation in meiosis?
Genetic recombination through crossing over and independent assortment.
176
In which cells does mitosis occur?
Somatic cells.
177
In which cells does meiosis occur?
Reproductive cells (gonads).
178
What structural difference between RNA and DNA contributes to RNA's relative instability, and how does this affect their functions in the cell?
-RNA has a hydroxyl group (-OH) at the 2' position in the sugar ring, which DNA lacks. This makes RNA more reactive and less stable than DNA. RNA's instability suits its temporary tasks like transmitting genetic information from DNA and protein synthesis, while DNA's stability allows for long-term genetic information storage.
179
What type of proteins do free ribosomes make compared to attached?
Free: Proteins used inside the cell Attached: Proteins used outside the cell
180
What is a codon and what role does it play in protein synthesis?
Answer: A codon is a sequence of three nucleotides in mRNA that corresponds to a specific amino acid or stop signal during protein synthesis. It's the basic unit of the genetic code, guiding the assembly of amino acids into proteins
181
Which is more likely to impact the final protein? A mutation within a coding region, or a mutation within an intron?
A mutation within a coding region; because the coding region is what determines what amino acids will be coded for whereas in an intron usually will be spliced out.
182
Determine what these two words are by their definitions: a) Altered DNA sequence ___ line: passed on to future progeny. b) _____: occurs during cell division, not whole body local effects
a) germ line
b) local/somatic
183
What can small scale mutations be? (2 types with its own sub-types)
Substitutions, Insertions/Deletions (AKA Indels)
184
What are the sub-types of Substitution mutations?
Silent, Missense, Non-sense
185
What are the sub-types of Indel (Insertion or Deletion) mutations?
1 or 2 Nucleotide Indel, 3 Indel (No frameshift)
186
What is a Substitution type- silent mutation?
When there is a change in the nucleotide pair but the change still codes for the same amino acid (eg: GGA > GGC still both code for Glycerin)
## Footnote
Example: GGA > GGC still both code for Glycerin
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What is a missense mutation?
Where the substitution of a nucleotide causes a new amino acid to be made, can especially be a problem if the amino acids have different hydrophilicity/hydrophobicity.
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What is a nonsense mutation?
When substitution of a nucleotide results in premature codon for a STOP amino acid.
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What is a frameshift mutation via insertion or deletion?
Insertion adds extra nucleotides, shifting the frame forward. Deletion removes nucleotides, shifting the frame backward; effectively changing the amino acids downstream of the mutation.
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In a 3 nucleotide-pair insertion/deletion what occurs?
There is no frameshift; however, with insertion of nucleotides there will be an extra amino acid (this is how Huntington’s can occur with the CAG codon).
## Footnote
Example: Huntington’s can occur with the CAG codon.
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What is sickle cell anemia in regards to DNA mutations?
Sickle cell anemia is a result of a missense substitution mutation in the DNA sequence coding for hemoglobin. This changes one of the amino acids in the hemoglobin protein, altering its structure. Consequently, the red blood cells containing this abnormal hemoglobin become sickle-shaped and rigid, leading to difficulties in gas exchange in capillaries and transportation of nutrients to tissues in the body.
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What could be the potential consequences of overproduction or insufficient levels of cyclin and Cdk in a cell?
Overproduction of cyclin or Cdk might push the cell to divide prematurely, potentially leading to errors in chromosome separation and contributing to the development of cancer. Insufficient levels of cyclin or Cdk could prevent MPF activation, stopping the cell cycle and preventing cell division.
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What could be the potential consequences of a malfunction at the G2 checkpoint?
A malfunction at the G2 checkpoint can allow cells with DNA damage or incomplete replication to proceed to mitosis, leading to the formation of abnormal daughter cells. This can result in genomic instability and potentially contribute to diseases such as cancer.
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How can these cancer-causing mutations arise?
1. Genetic predisposition: in all cells of the body 2. Acquired, locally in one cell initially (eg: UV damage, smoking, etc).
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What are Proto-oncogenes?
Proto-oncogenes are normal genes that promote cell growth and division. However, when these genes are altered or mutated, they can become oncogenes that contribute to uncontrolled cell growth, leading to cancer.
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What is Tumour suppressor genes?
These genes typically produce proteins that slow down cell division, repair DNA mistakes, or tell cells when to die. When these genes don't work properly, cells can grow out of control and may eventually form a tumor.
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What is the Role of cAMP as a second messenger
cAMP is produced when a hormone or neurotransmitter activates adenylate cyclase. cAMP then activates protein kinases, leading to protein phosphorylation and a cellular response.
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What is the Role of Ca2+ as a second messenger
Ca2+ is stored in the ER. Upon receiving a signal, Ca2+ is released into the cytoplasm, where it activates enzymes and proteins, leading to a cellular response.
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