Organelles and compartmentilization Flashcards
(90 cards)
1
Q
What are organelles?
A
Organelles are specialized structures within cells that perform distinct functions necessary for cellular operation and survival.
2
Q
Which structures are NOT considered organelles?
A
The cell wall, cytoskeleton, and cytoplasm are not considered organelles; they provide support and structure but do not have specific functions like organelles do.
3
Q
Which structures are considered organelles?
A
Nuclei, vesicles, ribosomes, and the plasma membrane are examples of structures that are classified as organelles.
4
Q
What is the function of the nucleus in a cell?
A
The nucleus serves as the control center of the cell, housing genetic material (DNA) and coordinating activities such as growth, metabolism, and reproduction.
5
Q
What is the role of ribosomes in cells?
A
Ribosomes are responsible for protein synthesis, translating messenger RNA (mRNA) into polypeptide chains that fold into functional proteins.
6
Q
How do vesicles function within a cell?
A
Vesicles transport materials within the cell, helping in processes such as secretion, endocytosis, and intracellular transport of proteins and lipids.
7
Q
Why is it important to understand the functions of different organelles?
A
Understanding organelle functions helps elucidate how cells operate, communicate, and maintain homeostasis, which is vital for overall organism health.
8
Q
How did advancements in technology contribute to the study of organelles?
A
The invention of ultracentrifuges enabled scientists to isolate and study individual organelles through cell fractionation, enhancing our understanding of their specific functions.
9
Q
What is cell fractionation?
A
Cell fractionation is a laboratory technique used to separate cellular components based on size and density, allowing for detailed study of individual organelles.
10
Q
Why is it significant that organelles are discrete subunits within cells?
A
The compartmentalization provided by organelles allows for specialized environments and conditions necessary for various biochemical processes to occur efficiently and simultaneously within the cell.
11
Q
What is the advantage of separating the nucleus and cytoplasm in eukaryotic cells?
A
The separation allows for distinct processes of gene transcription in the nucleus and translation in the cytoplasm, enhancing regulation and efficiency.
12
Q
What occurs during gene transcription?
A
Gene transcription is the process where DNA is transcribed into messenger RNA (mRNA) within the nucleus, preparing it for protein synthesis.
13
Q
How does post-transcriptional modification of mRNA occur?
A
After transcription, mRNA undergoes modifications such as capping, polyadenylation, and splicing before it exits the nucleus to meet ribosomes in the cytoplasm.
14
Q
Why is post-transcriptional modification important?
A
- mRNA Stability: The addition of a methylated cap to the 5’ end and a poly-A tail to the 3’ end of the pre-mRNA protects it from degradation by exonucleases. This increases the lifespan of the mRNA, allowing for more efficient protein synthesis.
- Efficient Translation: The 5’ cap and poly-A tail also assist in ribosome binding and facilitate the export of mature mRNA from the nucleus to the cytoplasm, where translation occurs.
- Proteome Diversity: RNA splicing, particularly alternative splicing, greatly enhances proteome diversity. By removing introns and joining exons in different combinations, a single gene can produce multiple protein isoforms, increasing the functional complexity of the organism without increasing genome size.These modifications ensure mRNA stability, facilitate its export from the nucleus, and enhance translation efficiency by preparing it for ribosomal recognition.
15
Q
How does this separation differ in prokaryotic cells?
A
In prokaryotes, transcription and translation occur simultaneously in the cytoplasm since there is no nuclear membrane, allowing mRNA to immediately associate with ribosomes.
16
Q
What are some consequences of simultaneous transcription and translation in prokaryotes?
A
This allows for rapid protein synthesis but limits the opportunity for mRNA processing and quality control that occurs in eukaryotic cells.
17
Q
How does compartmentalization benefit eukaryotic cells?
A
- Specialized Functions: Membrane-bound organelles allow for the segregation of specific biochemical reactions and processes within the cell. This enables organelles to perform specialized functions such as photosynthesis, energy production, and membrane construction.
- Increased Efficiency: By concentrating enzymes and substrates in specific compartments, cells can increase the rate and efficiency of chemical reactions. This localization minimizes the risk of conflicting side reactions and accidental enzyme inhibition by substrates from other biochemical pathways.
- Optimized Environments: Different organelles can maintain distinct internal environments suited to their specific functions. For instance, lysosomes maintain an acidic pH necessary for their digestive enzymes to function properly.
18
Q
What role do ribosomes play after mRNA exits the nucleus?
A
Ribosomes translate the processed mRNA into proteins, synthesizing polypeptides based on the genetic code carried by the mRNA.
19
Q
Why is it significant that eukaryotic cells can modify mRNA before translation?
A
It provides an additional layer of regulation, allowing cells to control gene expression and respond to environmental changes more effectively.
20
Q
How does understanding compartmentalization contribute to biology?
A
Understanding how compartmentalization functions helps explain cellular organization, regulation of metabolic processes, and evolutionary advantages in complex organisms.
21
Q
What is compartmentalization in cells?
A
Compartmentalization refers to the division of the cytoplasm into distinct areas or organelles, each specialized for specific biochemical processes.
22
Q
What is one advantage of compartmentalization regarding metabolite concentration?
A
Compartmentalization allows for the concentration of metabolites and enzymes in specific areas, enhancing the efficiency and speed of biochemical reactions.
23
Q
How does compartmentalization separate incompatible biochemical processes?
A
By isolating different reactions in distinct compartments, cells can prevent harmful interactions between incompatible processes, ensuring that they can occur simultaneously without interference.
24
Q
What role do lysosomes play in cellular compartmentalization?
A
- Isolation of Degradative Enzymes: Lysosomes contain hydrolytic enzymes that break down various biomolecules. By confining these enzymes within a membrane-bound compartment, the cell protects its other components from unintended degradation.
- Maintenance of Optimal Conditions: Lysosomes maintain an acidic pH (4.5-5.0) that is essential for the optimal activity of their enzymes. This acidic environment is separate from the slightly basic cytosol (pH 7.2).
- Cellular Defense: During endocytosis, phagocytic vacuoles form around potentially harmful substances like bacteria. These vacuoles then fuse with lysosomes, allowing for the safe digestion of the material without exposing the rest of the cell to potential toxins.
- Waste Disposal System: Lysosomes act as the cell’s waste disposal system, breaking down various cellular debris and recycling materials. This function helps maintain cellular homeostasis and efficiency.
25
How do phagocytic vacuoles exemplify compartmentalization?
Phagocytic vacuoles form when a cell engulfs external particles or pathogens, creating a separate compartment where these materials can be digested without affecting the rest of the cell.
26
Why is it important for enzymes to be concentrated in specific compartments?
Concentrating enzymes in specific compartments increases the likelihood of substrate interaction, facilitating faster reaction rates and more effective metabolic pathways.
27
How does compartmentalization contribute to cellular organization?
Compartmentalization organizes cellular functions into distinct areas, allowing for better regulation and coordination of metabolic activities within the cell.
28
What happens if biochemical processes are not compartmentalized?
Without compartmentalization, conflicting reactions could occur simultaneously, leading to inefficiencies and potential damage to cellular structures due to unwanted interactions.
29
How does understanding compartmentalization enhance our knowledge of cell biology?
Understanding compartmentalization helps explain how cells maintain homeostasis, respond to environmental changes, and carry out complex biochemical processes effectively.
30
Why is compartmentalization considered an evolutionary advantage?
Compartmentalization allows for greater complexity in cellular functions, enabling organisms to adapt to diverse environments and perform specialized tasks that support survival and growth.
31
What is the primary function of mitochondria?
The primary function of mitochondria is to produce adenosine triphosphate (ATP), which serves as the main energy currency of the cell. This process occurs through cellular respiration, where mitochondria break down glucose and other molecules to release energy
32
How does the double membrane structure of mitochondria benefit ATP production?
The double membrane creates distinct compartments, with the inner membrane housing the electron transport chain and ATP synthase, optimizing conditions for ATP production.
33
What is the significance of a small volume of intermembrane space in mitochondria?
A small intermembrane space allows for rapid accumulation of protons (H⁺ ions) during electron transport, creating a strong electrochemical gradient essential for ATP synthesis.
34
How do the cristae enhance mitochondrial function?
The large surface area of the cristae (folds of the inner membrane) increases the number of embedded proteins and enzymes involved in the electron transport chain and ATP synthesis.
35
What role does compartmentalization play in mitochondrial function?
Compartmentalization allows for the separation of different metabolic processes, such as the Krebs cycle occurring in the matrix and oxidative phosphorylation occurring across the inner membrane.
36
What occurs in the mitochondrial matrix?
The matrix contains enzymes necessary for the Krebs cycle (citric acid cycle), where acetyl-CoA is oxidized to produce NADH and FADH₂, which are crucial for ATP production.
37
How does the structure of mitochondria relate to their efficiency in energy production?
The combination of a double membrane, extensive cristae, and compartmentalization maximizes surface area and creates optimal conditions for efficient ATP generation.
38
Why is aerobic respiration more efficient than anaerobic processes?
Aerobic respiration produces significantly more ATP per glucose molecule than anaerobic processes, due to complete oxidation of glucose in mitochondria.
39
What adaptations do mitochondria have for high-energy demanding cells?
Cells with high energy demands, such as muscle cells, have more mitochondria and larger cristae to support increased ATP production required for their functions.
40
How does understanding mitochondrial adaptations contribute to biology?
Understanding these adaptations helps explain how cells meet their energy needs, adapt to different metabolic demands, and how dysfunctions in mitochondria can lead to various diseases.
41
What is the primary function of chloroplasts?
The primary function of chloroplasts is to conduct photosynthesis in plant and algal cells. Chloroplasts capture light energy from the sun and convert it into chemical energy in the form of glucose through a two-step process: light dependent and light independent.
42
How does the large surface area of thylakoid membranes benefit photosynthesis?
The extensive surface area of thylakoid membranes allows for a greater number of photosystems and electron transport proteins, enhancing the efficiency of light absorption and energy conversion.
43
What are thylakoids?
Thylakoids are membrane-bound structures within chloroplasts that contain chlorophyll and other pigments, where the light-dependent reactions of photosynthesis occur.
44
Why is a small volume of fluid inside thylakoids advantageous?
A small volume allows for rapid accumulation of protons (H⁺ ions) during the light-dependent reactions, creating a strong proton gradient essential for ATP synthesis through chemiosmosis.
45
What is the role of the Calvin cycle in photosynthesis?
The Calvin cycle, occurring in the stroma of chloroplasts, uses ATP and NADPH generated from light-dependent reactions to convert carbon dioxide into glucose.
46
How does compartmentalization benefit chloroplast function?
Compartmentalization allows distinct environments for light-dependent reactions in thylakoids and the Calvin cycle in the stroma, optimizing conditions for each process.
47
What are photosystems?
Photosystems are complexes of proteins and pigments embedded in thylakoid membranes that capture light energy and initiate the process of electron transport during photosynthesis.
48
How do adaptations in chloroplasts enhance overall photosynthetic efficiency?
The combination of large surface area, small thylakoid volume, and compartmentalization allows chloroplasts to maximize light capture and optimize biochemical reactions necessary for glucose production.
49
Why is understanding chloroplast adaptations important in biology?
Understanding these adaptations helps explain how plants efficiently convert solar energy into chemical energy, which is fundamental to life on Earth and impacts ecological systems.
50
How do chloroplasts illustrate the concept of compartmentalization in cells?
Chloroplasts demonstrate compartmentalization by having distinct structures (thylakoids and stroma) that segregate different stages of photosynthesis, allowing for specialized functions within a single organelle.
51
What is the primary structure of the nuclear envelope?
The nuclear envelope consists of a double membrane that surrounds the nucleus, separating it from the cytoplasm.
52
What is the significance of having a double membrane in the nucleus?
The double membrane provides a barrier that protects genetic material and regulates the exchange of substances between the nucleus and cytoplasm.
53
Why are nuclear pores essential in the nuclear membrane?
Nuclear pores allow for selective transport of molecules such as RNA and proteins between the nucleus and cytoplasm, facilitating communication and regulation.
54
How do nuclear pores function?
Nuclear pores are large protein complexes that form channels through which molecules can pass, allowing small molecules to diffuse freely while regulating larger macromolecules.
55
What is one advantage of compartmentalizing transcription and translation?
Compartmentalization allows for post-transcriptional modifications of mRNA in the nucleus before it is exported to the cytoplasm for translation, enhancing gene expression regulation.
56
How does the nuclear envelope contribute to cell division?
During mitosis and meiosis, the nuclear envelope breaks down into vesicles, allowing chromosomes to segregate properly and ensuring accurate distribution to daughter cells.
57
What happens to the nuclear membrane during cell division?
The nuclear membrane disassembles into vesicles, which helps facilitate the separation of duplicated chromosomes during cell division processes.
58
Why is it important for mRNA to be modified before reaching ribosomes?
Modifying mRNA (e.g., capping, polyadenylation, splicing) ensures stability and proper recognition by ribosomes, optimizing translation efficiency.
59
How does the double membrane structure enhance nuclear function?
The double membrane allows for distinct environments within the nucleus and cytoplasm, enabling specialized processes like transcription in the nucleus and translation in the cytoplasm.
60
Why is understanding the structure and function of the nuclear envelope important in biology?
Understanding the nuclear envelope's role in protecting genetic material and regulating gene expression provides insights into cellular function, development, and disease mechanisms.
61
What are free ribosomes?
Free ribosomes are ribosomes that float freely in the cytoplasm and synthesize proteins that are typically retained within the cell.
62
What types of proteins do free ribosomes produce?
Free ribosomes primarily produce proteins for use within the cell, such as enzymes and structural proteins.
63
What is the rough endoplasmic reticulum (RER)?
The rough endoplasmic reticulum is a membrane-bound organelle studded with ribosomes on its cytoplasmic surface, involved in the synthesis of proteins destined for secretion or for use in membranes.
64
How do membrane-bound ribosomes on the RER differ from free ribosomes?
Membrane-bound ribosomes synthesize proteins that are either secreted from the cell or incorporated into cellular membranes, while free ribosomes synthesize proteins that remain in the cytoplasm.
65
What is the significance of the rough appearance of the RER?
The rough appearance is due to the presence of ribosomes on its surface, which are actively engaged in protein synthesis.
66
How do proteins synthesized on free ribosomes enter cellular functions?
Proteins synthesized on free ribosomes can function directly in metabolic processes, serve as enzymes, or contribute to cellular structure without leaving the cytoplasm.
67
What happens to proteins synthesized by membrane-bound ribosomes?
Proteins synthesized by membrane-bound ribosomes enter the lumen of the RER, where they undergo folding and post-translational modifications before being transported to their final destinations.
68
Why is compartmentalization important in protein synthesis?
Compartmentalization allows for specialized environments for protein synthesis, folding, and modification, enhancing efficiency and accuracy in producing functional proteins.
69
What role does the RER play in protein quality control?
The RER assists in ensuring that only properly folded and modified proteins proceed to their next destinations, preventing misfolded proteins from being secreted or incorporated into membranes.
70
How does understanding the functions of free ribosomes and the rough endoplasmic reticulum contribute to cell biology?
Understanding these structures helps elucidate how cells produce and manage proteins, which is essential for maintaining cellular function and responding to environmental changes.
71
What is the primary function of the Golgi apparatus?
The Golgi apparatus is responsible for processing, modifying, and packaging proteins and lipids for secretion or delivery to other organelles.
72
How does the Golgi apparatus receive proteins?
The Golgi apparatus receives proteins from the rough endoplasmic reticulum (RER) via transport vesicles that bud off from the RER.
73
What modifications occur to proteins in the Golgi apparatus?
Glycosylation: The most significant modification is the addition and modification of sugar molecules to proteins. This includes:
- Trimming of mannose residues from N-linked oligosaccharides
- Addition of new sugars like N-acetylglucosamine, galactose, and sialic acid
- O-linked glycosylation, where sugars are added to serine or threonine residues
Proteoglycan formation: The Golgi apparatus adds long glycosaminoglycan chains to core proteins, creating proteoglycans.
Sulfation: Sugars in proteoglycans and some tyrosine residues on proteins are sulfated, adding negative charges.
Phosphorylation: Some proteins undergo phosphorylation in the Golgi.
Proteolytic cleavage: Certain proteins, like proinsulin, are cleaved into their active forms.
74
How does the structure of the Golgi apparatus facilitate its function?
The Golgi apparatus consists of stacked membrane-bound sacs (cisternae) that provide a large surface area for enzymatic reactions and modifications of proteins.
75
What is the significance of compartmentalization within the Golgi apparatus?
Compartmentalization allows different enzymes to act on proteins in specific regions, ensuring efficient processing and sorting of proteins based on their final destinations.
76
What happens to proteins after they are processed in the Golgi apparatus?
After processing, proteins are packaged into vesicles that transport them to their designated locations, such as secretion outside the cell or delivery to lysosomes.
77
How does the Golgi apparatus play a role in secretion?
The Golgi apparatus packages proteins into secretory vesicles that fuse with the plasma membrane, releasing their contents outside the cell through exocytosis.
78
Why is proper functioning of the Golgi apparatus crucial for cells?
Proper functioning ensures that proteins are correctly modified and sorted, which is vital for maintaining cellular functions and responding to environmental signals.
79
What can happen if there are defects in the Golgi apparatus?
Defects in the Golgi apparatus can lead to improper protein processing, resulting in diseases such as congenital disorders, metabolic syndromes, and certain neurodegenerative diseases.
80
How does understanding the structure and function of the Golgi apparatus contribute to cell biology?
Understanding its role in protein processing and secretion helps clarify how cells communicate, maintain homeostasis, and respond to changes in their environment.
81
What are vesicles?
Vesicles are small, membrane-bound sacs within cells that transport and store substances, facilitating communication and transport between different cellular compartments.
82
What is the primary function of vesicles in cells?
Vesicles play a crucial role in transporting proteins, lipids, and other molecules to their destinations, including secretion outside the cell or delivery to organelles.
83
How are vesicles formed?
Vesicles can form by budding off from membranes of organelles such as the endoplasmic reticulum or Golgi apparatus, or during processes like endocytosis.
84
What role does clathrin play in vesicle formation?
Clathrin is a protein that coats the cytoplasmic side of the membrane during vesicle formation, helping to shape the membrane into a bud and facilitating the budding process.
85
How does clathrin contribute to the specificity of vesicle transport?
Clathrin-coated vesicles are involved in specific transport pathways, ensuring that the correct cargo is selected and packaged for transport to designated locations within or outside the cell.
86
What happens to clathrin after vesicle formation?
After vesicle budding, clathrin is often removed once the vesicle is formed, allowing it to be recycled for future vesicle formation.
87
What types of substances can be transported by vesicles?
Vesicles can transport a variety of substances, including proteins, lipids, neurotransmitters, hormones, and waste products.
87
Why is compartmentalization important for vesicle function?
Compartmentalization allows for the separation of different biochemical processes and prevents unwanted interactions between incompatible substances during transport.
88
How do vesicles facilitate communication between organelles?
Vesicles enable the transfer of proteins and lipids between organelles, allowing them to communicate and coordinate their functions effectively.
89
Why is understanding vesicle structure and function important in biology?
Understanding vesicles is crucial for comprehending cellular processes such as secretion, endocytosis, and intracellular transport, which are vital for maintaining cellular homeostasis and function.
