cells Flashcards
What is the basic structure of a plasma membrane?
It consists of a phospholipid bilayer with embedded proteins, allowing selective transport of substances.
What is the main function of the nucleus?
The nucleus contains genetic material (DNA) and controls the cell’s activities, including replication and transcription.
What are mitochondria responsible for?
Mitochondria are the site of aerobic respiration and ATP production.
Where does photosynthesis occur in plant cells?
Photosynthesis occurs in chloroplasts, specifically in the thylakoids for light-dependent reactions and the stroma for light-independent reactions.
What are ribosomes responsible for?
Ribosomes are the site of protein synthesis, translating mRNA into polypeptides.
What is the difference between rough and smooth endoplasmic reticulum?
Rough ER is covered with ribosomes and synthesizes proteins, while smooth ER synthesizes lipids and steroids.
What is the function of the Golgi apparatus?
The Golgi apparatus modifies, packages, and transports proteins and lipids from the ER into vesicles.
What do lysosomes do?
Lysosomes contain digestive enzymes that break down waste materials and cellular debris.
What is the role of the cell wall in plant cells?
The cell wall provides structural support and prevents the cell from bursting under osmotic pressure.
What is the function of the vacuole in plant cells?
The vacuole stores nutrients and waste products and helps maintain turgor pressure.
What is binary fission?
Binary fission is the process by which prokaryotic cells divide to form two genetically identical daughter cells.
How is mitosis different from meiosis?
Mitosis produces two genetically identical diploid cells, while meiosis produces four genetically varied haploid cells.
What is the purpose of mitosis?
Mitosis is for growth, tissue repair, and asexual reproduction in eukaryotic cells.
What are homologous chromosomes?
Homologous chromosomes are pairs of chromosomes, one inherited from each parent, with the same genes but possibly different alleles.
Describe the structure of the phospholipid bilayer.
It has hydrophilic phosphate heads facing outward and hydrophobic fatty acid tails facing inward, forming a barrier to water-soluble substances.
What is the role of channel proteins in the membrane?
Channel proteins facilitate the transport of charged or polar molecules across the cell membrane.
What is facilitated diffusion?
Facilitated diffusion is the passive movement of molecules across the membrane via specific carrier or channel proteins.
How does active transport differ from passive transport?
Active transport requires energy (ATP) to move molecules against a concentration gradient, while passive transport moves molecules down a concentration gradient without energy.
What is osmosis?
Osmosis is the diffusion of water molecules across a partially permeable membrane from a region of higher water potential to lower water potential.
What are the steps of cell fractionation?
- Homogenisation of cells, 2. Filtration to remove debris, 3. Ultracentrifugation to separate organelles based on density.
What is the mitotic index?
The mitotic index is the ratio of cells undergoing mitosis to the total number of cells in a sample.
What is the importance of cholesterol in membranes?
Cholesterol regulates membrane fluidity, making it more stable and less permeable to very small molecules.
How do temperature and ethanol affect membrane permeability?
Higher temperatures and ethanol increase membrane fluidity, disrupting the phospholipid bilayer and increasing permeability.
What is co-transport?
Co-transport involves the coupled transport of two molecules across the membrane via a carrier protein, one moving down its concentration gradient driving the movement of another against its gradient.
What is antigenic variability?
Antigenic variability is the ability of pathogens to alter their surface antigens to evade detection by the immune system.
What is the role of T cells in the immune response?
T cells are involved in cell-mediated immunity, with helper T cells activating other immune cells and cytotoxic T cells killing infected or cancerous cells.
What is the role of B cells in the immune response?
B cells are involved in humoral immunity, producing specific antibodies against pathogens.
What is the fluid mosaic model?
The fluid mosaic model describes the structure of the cell membrane, where proteins float in or on the fluid phospholipid bilayer.
What is the difference between TEM and SEM?
Transmission electron microscopes (TEM) provide 2D images of internal structures, while scanning electron microscopes (SEM) give 3D images of surface structures.
What is apoptosis?
Apoptosis is programmed cell death, preventing the division of damaged cells, which could lead to cancer.
What is the role of the nucleolus?
The nucleolus is responsible for producing ribosomal RNA (rRNA) and assembling ribosomes.
What is the structure and function of the nuclear envelope?
The nuclear envelope is a double membrane with pores that controls the passage of materials between the nucleus and the cytoplasm.
What is the function of the cristae in mitochondria?
Cristae increase the surface area for enzymes involved in ATP production during aerobic respiration.
What are thylakoids and their function?
Thylakoids are membrane-bound compartments inside chloroplasts, where light-dependent reactions of photosynthesis occur.
What is the stroma in chloroplasts?
The stroma is the fluid-filled space in chloroplasts where light-independent reactions (Calvin cycle) take place.
What is the role of the smooth endoplasmic reticulum (SER)?
The SER synthesizes lipids, steroids, and carbohydrates and is involved in detoxification.
What are lysosomes and their role in cell digestion?
Lysosomes are membrane-bound organelles containing hydrolytic enzymes that break down waste materials and cellular debris.
What is the function of plasmodesmata in plant cells?
Plasmodesmata are channels between plant cells that allow the transport of materials and communication between adjacent cells.
What is the function of vacuoles in animal cells?
In animal cells, vacuoles are small and temporary, often involved in the storage or transport of substances.
What is the tonoplast?
The tonoplast is the membrane surrounding the central vacuole in plant cells, controlling the exchange of substances.
What is a key function of the plant cell wall?
The plant cell wall provides structural support and prevents the cell from bursting due to osmotic pressure.
What is the function of 70S ribosomes in prokaryotes?
70S ribosomes are responsible for protein synthesis in prokaryotic cells.
What is the role of the capsule in prokaryotic cells?
The capsule provides protection against desiccation and helps prokaryotic cells evade the host immune system.
How do viruses replicate inside host cells?
Viruses attach to host cells, inject their genetic material, and use the host’s machinery to replicate viral components.
What is a key difference between prokaryotic and eukaryotic cells?
Prokaryotic cells lack membrane-bound organelles, such as a nucleus, while eukaryotic cells have membrane-bound organelles.
What is the resolution of a microscope?
Resolution is the ability to distinguish two points as separate entities in a microscopic image.
What is the difference between magnification and resolution?
Magnification refers to how much larger an image is compared to the actual object, while resolution refers to the clarity of detail in the image.
How does a transmission electron microscope (TEM) work?
TEM passes a beam of electrons through a thin specimen, providing detailed images of the internal structures of cells in 2D.
How does a scanning electron microscope (SEM) work?
SEM scans a beam of electrons across the surface of a specimen to produce detailed 3D images of the surface structure.
What is cell fractionation?
Cell fractionation is the process of breaking open cells and separating organelles by size and density through centrifugation.
What is homogenization in cell fractionation?
Homogenization is the breaking open of cells, often using a blender, to release organelles.
What is the purpose of ultracentrifugation?
Ultracentrifugation is used to separate cell components by spinning samples at high speeds, causing the heaviest organelles to form pellets.
What are the steps of mitosis?
The steps of mitosis are prophase, metaphase, anaphase, and telophase.
What happens during prophase in mitosis?
During prophase, chromosomes condense, the nuclear envelope breaks down, and spindle fibers form.
What happens during metaphase in mitosis?
In metaphase, chromosomes align along the metaphase plate, attached to spindle fibers by their centromeres.
What happens during anaphase in mitosis?
In anaphase, sister chromatids are pulled apart to opposite poles of the cell by spindle fibers.
What happens during telophase in mitosis?
During telophase, the nuclear envelope reforms around separated chromosomes, which begin to uncoil.
What is cytokinesis?
Cytokinesis is the division of the cytoplasm, resulting in two genetically identical daughter cells.
What is the mitotic index formula?
The mitotic index is calculated as: (Number of cells in mitosis / Total number of cells) x 100.
What is the significance of a high mitotic index?
A high mitotic index indicates active cell division, which can be a sign of tissue growth or cancer.
How do cancer treatments target the cell cycle?
Cancer treatments often disrupt the cell cycle by inhibiting DNA replication, mitosis, or spindle fiber formation, slowing tumor growth.
What is binary fission?
Binary fission is the process of prokaryotic cell division, where the circular DNA replicates and the cell splits into two daughter cells.
How is ATP used in active transport?
ATP provides energy to carrier proteins, allowing them to move molecules against a concentration gradient.
What is the role of carrier proteins in active transport?
Carrier proteins change shape to transport specific molecules across membranes using energy from ATP.
What is co-transport?
Co-transport is the simultaneous transport of two molecules through a membrane, with one moving down its concentration gradient to drive the other against its gradient.
What is the definition of water potential?
Water potential is the tendency of water to move from one area to another, typically measured in kilopascals (kPa).
How does osmosis differ from diffusion?
Osmosis is the movement of water across a partially permeable membrane, whereas diffusion is the movement of solutes.
What is plasmolysis?
Plasmolysis is the process where plant cells lose water in a hypertonic solution, causing the cell membrane to pull away from the cell wall.
What is the function of aquaporins?
Aquaporins are specialized channel proteins that facilitate the rapid transport of water across cell membranes.
What is the purpose of the sodium-potassium pump?
The sodium-potassium pump moves sodium out of cells and potassium into cells, maintaining an electrochemical gradient across the membrane.
What is antigenic variability?
Antigenic variability occurs when pathogens alter their surface antigens to evade detection by the immune system.
What is a monoclonal antibody?
A monoclonal antibody is an antibody produced from a single clone of B cells, designed to target a specific antigen.
What is the purpose of vaccinations?
Vaccinations introduce weakened or inactive forms of pathogens to stimulate the production of memory cells without causing disease.
What is herd immunity?
Herd immunity occurs when a high percentage of a population is vaccinated, reducing the spread of disease and protecting unvaccinated individuals.
What is the purpose of a control in an experiment?
A control is used as a standard for comparison to check the reliability and validity of the results.
What are the main stages of the cell cycle?
The main stages of the cell cycle are interphase, mitosis, and cytokinesis.
What is the role of the G1 phase in the cell cycle?
In the G1 phase, the cell grows and synthesizes proteins and organelles needed for DNA replication.
What happens during the S phase of the cell cycle?
During the S phase, DNA replication occurs, resulting in each chromosome consisting of two sister chromatids.
What is the function of the G2 phase in the cell cycle?
In the G2 phase, the cell continues to grow and prepares for mitosis by synthesizing proteins needed for chromosome movement.
What is the role of spindle fibers during mitosis?
Spindle fibers attach to the centromeres of chromosomes and help separate the sister chromatids during cell division.
How do cancer cells differ from normal cells?
Cancer cells divide uncontrollably, bypassing the normal checkpoints of the cell cycle and forming tumors.
What is the significance of programmed cell death (apoptosis)?
Apoptosis eliminates damaged or unnecessary cells in a controlled manner to maintain tissue health.
What is the role of the centromere in cell division?
The centromere holds sister chromatids together and attaches them to spindle fibers during mitosis.
How does binary fission occur in bacteria?
In binary fission, the bacterial DNA replicates, the cell elongates, and the plasma membrane pinches in to divide the cell into two daughter cells.
What is the function of telomerase?
Telomerase is an enzyme that extends the telomeres at the ends of chromosomes, allowing cells to divide without losing essential DNA.
What are telomeres and their function?
Telomeres are repetitive DNA sequences at the ends of chromosomes that protect the genetic material from degradation during replication.
What is a stem cell?
A stem cell is an undifferentiated cell capable of dividing and giving rise to specialized cells for tissue growth and repair.
What is differentiation in cells?
Differentiation is the process by which a stem cell becomes specialized to perform a specific function.
How are tissues formed in multicellular organisms?
Tissues are formed by the aggregation of similar specialized cells that perform a common function.
What is the role of epithelial tissue?
Epithelial tissue forms protective layers that cover the surfaces of organs and structures in the body.
What is the function of connective tissue?
Connective tissue provides support, binds structures together, and helps transport nutrients.
What are the two main types of immune responses?
The two main immune responses are the non-specific (innate) and specific (adaptive) immune responses.
What are antigens?
Antigens are foreign molecules that trigger an immune response by stimulating the production of antibodies.
What are antibodies?
Antibodies are proteins produced by B cells that bind specifically to antigens, marking them for destruction by the immune system.
What are B memory cells?
B memory cells are long-lived cells that remember a specific pathogen and enable a faster immune response upon subsequent exposure.
How does the body protect itself from pathogens in the non-specific immune response?
The non-specific immune response includes barriers like skin, mucus, and phagocytic cells like neutrophils and macrophages.
What is the role of T helper cells in the immune response?
T helper cells activate B cells to produce antibodies and help activate cytotoxic T cells to kill infected cells.
What is the role of cytotoxic T cells?
Cytotoxic T cells kill infected cells by releasing perforin, which creates pores in the target cell membrane.
What is the purpose of a vaccine booster shot?
A vaccine booster shot stimulates the immune system to produce more memory cells, enhancing long-term immunity.
What is clonal selection in the immune response?
Clonal selection is the process where a specific B or T cell is activated by an antigen and proliferates to form clones of identical cells.
What is passive immunity?
Passive immunity occurs when antibodies are transferred from one individual to another, such as from mother to baby or via antibody injections.
How does active immunity differ from passive immunity?
Active immunity involves the body’s own immune response to an antigen, while passive immunity involves receiving antibodies from another source.
What is the ELISA test used for?
The ELISA test detects the presence of specific antigens or antibodies in a sample, often used for disease diagnosis.
How do monoclonal antibodies work in cancer treatment?
Monoclonal antibodies can be designed to target cancer cells specifically, delivering drugs or stimulating the immune system to attack the cancer.
What is HIV and how does it affect the immune system?
HIV is a virus that infects and destroys helper T cells, weakening the immune system and leading to AIDS.
How does reverse transcriptase function in HIV?
Reverse transcriptase is an enzyme in HIV that converts its RNA genome into DNA, allowing it to integrate into the host cell’s DNA.
How does the immune system respond to a viral infection?
The immune system produces antibodies to neutralize the virus and cytotoxic T cells to destroy infected cells.
Why are antibiotics ineffective against viruses?
Antibiotics target bacterial cell structures like the cell wall, which viruses lack, making them ineffective against viral infections.
What are the differences between innate and adaptive immunity?
Innate immunity provides immediate, non-specific defense, while adaptive immunity targets specific pathogens and provides long-lasting protection.
What are phagocytes and their role?
Phagocytes, such as macrophages, engulf and digest pathogens as part of the body’s non-specific immune defense.
What are cytokines?
Cytokines are signaling proteins released by immune cells that regulate inflammation, immune responses, and cell communication.
What is the primary function of lymphocytes?
Lymphocytes (B and T cells) are responsible for recognizing specific antigens and coordinating the adaptive immune response.
What are the stages of the humoral immune response?
The stages are: antigen recognition, clonal selection, production of antibodies by plasma cells, and formation of memory B cells.
What is the function of histamines in the immune response?
Histamines are chemicals released by mast cells that increase blood flow and permeability during inflammation.
How do vaccines stimulate immunity?
Vaccines introduce a weakened or inactive pathogen, prompting the immune system to produce antibodies and memory cells without causing illness.
What is the role of helper T cells in HIV infection?
Helper T cells coordinate the immune response by activating other immune cells, but HIV specifically targets and destroys these cells.
What is meant by ‘antigen-antibody complex’?
An antigen-antibody complex forms when an antibody binds to its specific antigen, marking it for destruction by immune cells.
How do monoclonal antibodies work in diagnostic tests?
In diagnostic tests, monoclonal antibodies bind to specific antigens, indicating the presence of a substance, such as in pregnancy or COVID-19 tests.
Why do some pathogens change their surface antigens?
Pathogens may change surface antigens (antigenic variation) to avoid detection by the host’s immune system.
What is the role of ribosomal RNA (rRNA)?
rRNA forms part of the ribosome and catalyzes the assembly of amino acids into protein chains during translation.
What is the significance of circular DNA in prokaryotes?
Circular DNA in prokaryotes contains the essential genetic information needed for the cell’s functions and reproduction.
What are plasmids in bacterial cells?
Plasmids are small, circular DNA molecules that replicate independently of chromosomal DNA and often carry genes for antibiotic resistance.
What is the function of a bacterial capsule?
The capsule protects bacteria from phagocytosis and desiccation, and it can help the bacteria adhere to surfaces.
What are pili in bacterial cells?
Pili are hair-like structures that help bacteria attach to surfaces and facilitate conjugation (DNA transfer between cells).
What are the key features of a virus?
Viruses have a protein coat (capsid), genetic material (DNA or RNA), and sometimes an envelope derived from the host cell membrane.
How do viruses replicate inside host cells?
Viruses attach to host cells, inject their genetic material, and hijack the host’s machinery to replicate and assemble new virus particles.
What is the role of reverse transcriptase in retroviruses?
Reverse transcriptase converts viral RNA into DNA, allowing the retrovirus to integrate into the host genome.
What is the function of the Golgi vesicles?
Golgi vesicles transport modified proteins and lipids from the Golgi apparatus to their final destination, either inside or outside the cell.
What is the structure of the fluid mosaic model?
The fluid mosaic model describes a membrane as a flexible phospholipid bilayer with embedded proteins, allowing for fluidity and varied functions.
How does cholesterol affect membrane fluidity?
Cholesterol decreases membrane fluidity by restricting the movement of phospholipids, providing stability especially in animal cells.
What is simple diffusion?
Simple diffusion is the passive movement of molecules from an area of high concentration to low concentration across a membrane without energy.
What factors affect the rate of diffusion?
The rate of diffusion is influenced by temperature, concentration gradient, surface area, distance, and the size of molecules.
How do carrier proteins function in facilitated diffusion?
Carrier proteins bind to specific molecules, change shape, and transport the molecules across the membrane down their concentration gradient.
What is the difference between endocytosis and exocytosis?
Endocytosis involves the uptake of substances into the cell via vesicles, while exocytosis involves the release of substances out of the cell.
What is phagocytosis?
Phagocytosis is a type of endocytosis where large particles, such as pathogens or debris, are engulfed by the cell and enclosed in a vesicle.
What is pinocytosis?
Pinocytosis is the process by which cells engulf extracellular fluid and its dissolved solutes into vesicles, commonly referred to as ‘cell drinking.’
How does the sodium-potassium pump work?
The sodium-potassium pump actively transports sodium ions out of the cell and potassium ions into the cell, using ATP to maintain a concentration gradient.
What is the purpose of osmosis in cells?
Osmosis regulates water movement, maintaining cell turgidity, or preventing excessive swelling or shrinking due to changes in water potential.
What is an isotonic solution?
An isotonic solution has the same water potential as the cell, so no net movement of water occurs across the cell membrane.
What is a hypertonic solution?
A hypertonic solution has a lower water potential (more solutes) than the cell, causing water to move out of the cell, leading to shrinkage.
What is a hypotonic solution?
A hypotonic solution has a higher water potential (fewer solutes) than the cell, causing water to move into the cell, leading to swelling or bursting.
How do aquaporins function in osmosis?
Aquaporins are specialized membrane channels that facilitate the rapid movement of water molecules across the cell membrane.
What is the role of the cell wall in osmoregulation in plants?
The cell wall provides structural support, preventing plant cells from bursting in hypotonic environments by maintaining turgor pressure.
What is water potential?
Water potential is the measure of the tendency of water to move from one area to another, influenced by solute concentration and pressure.
What is plasmolysis in plant cells?
Plasmolysis occurs when plant cells lose water in a hypertonic solution, causing the cell membrane to pull away from the cell wall.
What is meant by incipient plasmolysis?
Incipient plasmolysis refers to the point at which the cell membrane just begins to pull away from the cell wall due to water loss.
What are glycoproteins and their function in membranes?
Glycoproteins are proteins with attached carbohydrate chains that play roles in cell recognition, adhesion, and immune responses.
What are glycolipids and their function in membranes?
Glycolipids are lipids with attached carbohydrate chains that help maintain membrane stability and facilitate cell-to-cell communication.
What is the role of membrane receptors?
Membrane receptors detect external signals (like hormones or neurotransmitters) and initiate a cellular response.
How do pathogens evade the immune system through antigenic variation?
Pathogens change their surface antigens to avoid recognition by the host immune system, making it harder for memory cells to respond.
What is the purpose of memory cells in the immune system?
Memory cells ‘remember’ a specific pathogen, enabling a faster and stronger immune response upon re-infection.
What are cytokines and their role in the immune response?
Cytokines are signaling proteins that regulate immune responses, inflammation, and communication between immune cells.
What is the difference between innate and adaptive immunity?
Innate immunity is the body’s immediate, non-specific defense against pathogens, while adaptive immunity is a targeted, specific response involving B and T cells.
What is the function of antigen-presenting cells (APCs)?
APCs, such as macrophages, display foreign antigens on their surface to activate T cells in the adaptive immune response.
What is the structure of an antibody?
An antibody is Y-shaped with two antigen-binding sites, a variable region that binds to a specific antigen, and a constant region that interacts with immune cells.
What is the role of cytotoxic T cells in immune defense?
Cytotoxic T cells destroy infected or abnormal cells by releasing perforin, which creates pores in the target cell membrane, leading to cell death.
How does the body respond to a bacterial infection?
The immune system responds by recognizing bacterial antigens, activating B cells to produce antibodies, and triggering phagocytosis by macrophages.
What are monoclonal antibodies?
Monoclonal antibodies are identical antibodies produced by a single clone of B cells, designed to target a specific antigen for medical or diagnostic use.
What is the ELISA test used for in diagnostics?
The ELISA test detects the presence of specific antigens or antibodies in a sample, commonly used for diagnosing infections and immune responses.
How do vaccinations help prevent disease?
Vaccinations introduce antigens from weakened or dead pathogens, stimulating the immune system to produce memory cells for long-term immunity.
What is herd immunity?
Herd immunity occurs when a large proportion of a population is immune to a disease, reducing its spread and protecting unvaccinated individuals.
What is the role of helper T cells in the immune response?
Helper T cells activate B cells to produce antibodies and cytotoxic T cells to attack infected cells, coordinating the immune response.
What is the difference between passive and active immunity?
Passive immunity involves receiving antibodies from an external source, while active immunity involves the body’s own production of antibodies in response to an antigen.
What are the ethical concerns surrounding the use of monoclonal antibodies?
Ethical concerns include the use of animals in their production, the potential for severe side effects in patients, and the high cost of treatment.
