Topic 3A Part D Flashcards
Explain the importance of eukaryotic organelles
Eukaryotic organelles are crucial because they compartmentalize the cell, allowing specific processes to occur efficiently and simultaneously. (Each organelle performs specific functions, such as energy production or protein synthesis. By compartmentalizing, the cell can carry out various processes at the same time, without interference, and more efficiently.)
For example:
- Nucleus: Stores genetic material and controls cellular activities.
- Mitochondria: Generate energy (ATP) through respiration.
- Chloroplasts (in plants): Conduct photosynthesis.
- Endoplasmic Reticulum: Synthesizes proteins (rough ER) and lipids (smooth ER).
- Golgi Apparatus: Modifies, packages, and transports proteins and lipids.
- Lysosomes: Break down waste and recycle cellular components.
These specialized functions ensure the cell operates in an organized and efficient manner.
Why is it important that apoptosis does not occur more or less than it should? Investigate examples of diseases that are caused at least in part by apoptosis
It is important that apoptosis (programmed cell death) occurs at the right level because it maintains a balance between cell survival and death. Disruption in apoptosis can lead to diseases:
Excessive apoptosis can cause the loss of healthy cells, leading to tissue damage and degenerative diseases.
Examples:
1. Alzheimer’s Disease: Excessive apoptosis in neurons leads to brain atrophy and cognitive decline.
2. Parkinson’s Disease: Overactive apoptosis contributes to the death of dopamine-producing neurons in the brain.
3. AIDS: The virus triggers apoptosis in immune cells, weakening the immune system.
Inhibited apoptosis allows damaged or mutated cells to survive, which can lead to uncontrolled cell growth.
Examples:
1. Cancer: Defective apoptosis pathways prevent the elimination of abnormal cells, allowing tumors to grow and spread. For instance, mutations in the p53 gene, a regulator of apoptosis, are common in cancers.
2. Autoimmune Diseases: Failure to remove self-reactive immune cells can lead to conditions like lupus or rheumatoid arthritis.
In summary, apoptosis ensures proper development, immune function, and removal of damaged cells. Imbalances can result in severe diseases, highlighting the importance of its regulation.
Define term subunit
A subunit is a smaller, individual part of a larger structure or molecule. In biology, it often refers to a single polypeptide chain within a protein that combines with other subunits to form a functional protein complex. For example, hemoglobin has four subunits, each contributing to its overall function.
How are AIDS caused?
AIDS (Acquired Immunodeficiency Syndrome) is caused by the HIV (Human Immunodeficiency Virus). Here’s how it develops:
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HIV Infection:
- HIV infects and destroys key immune cells called CD4 T cells (a type of white blood cell crucial for fighting infections).
- The virus integrates its genetic material into the host cell, replicates, and spreads to other CD4 cells.
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Immune System Weakening:
- Over time, the destruction of CD4 cells weakens the immune system.
- The body becomes less able to fight off infections and diseases.
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Development of AIDS:
- If untreated, HIV progresses to AIDS.
- AIDS is diagnosed when CD4 cell counts drop below 200 cells/mm³ (normal is 500–1,500) or when the person develops opportunistic infections or cancers, like tuberculosis, pneumonia, or Kaposi’s sarcoma.
Transmission: HIV spreads through:
- Unprotected sex
- Sharing needles
- Blood transfusions (rare with modern screening)
- Mother-to-child transmission during childbirth or breastfeeding.
Prevention and Treatment:
- Prevention: Safe sex, clean needles, and regular testing.
- Treatment: Antiretroviral therapy (ART) helps control the virus, preventing it from progressing to AIDS.
What are the advantages of using transmission and scanning electron microscopes’ images of cell membranes, ribosomes, centrioles, nuclei, mitochondria, and lysosomes in animal cells? And give examples where each would be most appropriate to use.
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Transmission Electron Microscope (TEM):
- Advantages: Provides detailed, high-resolution images of internal structures within cells, such as organelles like ribosomes, nuclei, and mitochondria.
- Example: TEM is ideal for studying the ultrastructure of mitochondria to analyze the inner membrane or cristae for energy production.
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Scanning Electron Microscope (SEM):
- Advantages: Produces 3D images of cell surfaces, allowing detailed visualization of external features such as the cell membrane or surface textures of organelles.
- Example: SEM is most appropriate for examining the surface structure of lysosomes or the shape of centrioles in three dimensions.
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Cell Membranes:
- Use TEM to observe the bilayer structure and embedded proteins.
- Use SEM to view the surface features or projections like microvilli.
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Ribosomes:
- TEM is best for visualizing the small size and distribution of ribosomes in the cytoplasm or attached to the rough ER.
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Centrioles:
- SEM is excellent for 3D imaging of the cylindrical structure of centrioles.
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Nuclei:
- Use TEM to study the nuclear envelope, nucleoplasm, and chromatin in high detail.
- SEM could provide a 3D perspective of the nucleus surface.
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Mitochondria:
- TEM is ideal for analyzing the internal structure (cristae) and its role in respiration.
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Lysosomes:
- TEM allows for detailed observation of enzymatic contents within lysosomes.
By combining TEM and SEM, researchers can gain both internal and external structural insights into organelles.
Why does too much apoptosis cause aids
Too much apoptosis contributes to AIDS because HIV triggers excessive programmed cell death in critical immune cells, weakening the immune system. Here’s how it happens:
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Direct Infection of CD4 T Cells:
- HIV infects CD4 T cells, integrates its genetic material, and replicates.
- Infected cells undergo apoptosis due to the stress caused by viral replication.
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Bystander Effect:
- HIV can cause nearby, uninfected CD4 T cells to undergo apoptosis. This happens due to signals from infected cells or viral proteins like gp120, which bind to receptors on uninfected cells and trigger self-destruction.
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Chronic Immune Activation:
- HIV infection causes constant immune activation, leading to overproduction of cytokines (inflammatory signals).
- This prolonged activation induces apoptosis in both CD4 and other immune cells.
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Loss of CD4 T Cells:
- Excessive apoptosis results in a massive reduction of CD4 cells, which are essential for coordinating the immune response.
- Without these cells, the body cannot fight off opportunistic infections or cancers, leading to the immune collapse characteristic of AIDS.
Thus, the virus not only replicates but also accelerates the death of immune cells, leaving the body vulnerable to life-threatening diseases.
What are the differences between prokaryotes and eukaryotes
- Nucleus: Prokaryotes lack a nucleus; eukaryotes have a nucleus.
- Organelles: Prokaryotes have no membrane-bound organelles; eukaryotes have them (e.g., mitochondria).
- Size: Prokaryotes are smaller (1-5 µm); eukaryotes are larger (10-100 µm).
- DNA: Prokaryotes have circular DNA; eukaryotes have linear chromosomes.
- Cell Division: Prokaryotes use binary fission; eukaryotes use mitosis or meiosis.
- Examples: Prokaryotes include bacteria; eukaryotes include animals, plants, and fungi.
Q: What are the structural differences between Gram-positive and Gram-negative bacteria?
- Cell Wall Thickness:
Gram-positive bacteria have a thick peptidoglycan layer.
Gram-negative bacteria have a thin peptidoglycan layer.
- Outer Membrane:
Gram-positive bacteria lack an outer membrane.
Gram-negative bacteria have an outer membrane containing lipopolysaccharides (LPS).
- Teichoic Acids:
- Present in Gram-positive bacteria.
- Absent in Gram-negative bacteria. - Periplasmic Space:
- Absent or minimal in Gram-positive bacteria.
- Present in Gram-negative bacteria between the inner and outer membranes. - Stain Retention:
- Gram-positive bacteria retain crystal violet and appear purple after Gram staining.
- Gram-negative bacteria lose crystal violet and appear pink after counterstaining.
Q: What are specialised cells?
A: Specialised cells are cells that have specific structures and functions, adapted to perform a particular role in an organism (e.g., red blood cells transport oxygen).
Q: What are undifferentiated cells?
A: Undifferentiated cells, also known as stem cells, are cells that have not yet developed a specific function and can divide to produce more stem cells or differentiate into specialised cells.
Q: What is differentiation?
A: Differentiation is the process by which an undifferentiated cell, such as a stem cell, becomes specialised to perform a specific function in an organism.
Q: What are the characteristics of bacteria, and which features are found in all bacteria?
Features found in all bacteria:
Cell wall: made of peptidoglycan (provides structure).
Cytoplasm: Contains enzymes and ribosomes.
Ribosomes: For protein synthesis (70S ribosomes).
Cell membrane: Controls the movement of substances in and out.
Circular DNA: Found in the nucleoid, containing genetic information.
What are the features that are only found in some bacteria?
Features found in some bacteria:
Plasmids: Small circular DNA molecules, separate from the main DNA.
Flagella: Tail-like structures for movement.
Pili: Hair-like structures for attachment or DNA exchange.
Capsule: A protective outer layer for defense against the immune system.
Endospores: Resistant structures formed in harsh conditions.
Photosynthetic pigments: Found in some bacteria for photosynthesis.
Q: Are all bacteria pathogens?
A: No, not all bacteria are pathogens. Most bacteria are harmless or beneficial, while only some cause diseases.
Q: What are examples of pathogenic and non-pathogenic bacteria?
Pathogenic bacteria (cause disease):
- Escherichia coli (certain strains cause food poisoning).
- Mycobacterium tuberculosis (causes tuberculosis).
- Vibrio cholerae (causes cholera).
** Non-pathogenic bacteria (harmless or beneficial):**
- Lactobacillus acidophilus (used in yoghurt production).
- Rhizobium (fixes nitrogen in plant roots).
- Bifidobacterium (supports gut health).
