Cell Biology Quiz
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A scientist is studying a newly discovered unicellular organism. Initial observations reveal the absence of a membrane-bound nucleus. Based on this information, to which type of cell does this organism most likely belong?

  • Eukaryotic
  • Plant
  • Animal
  • Prokaryotic (correct)

    • Which of the following eukaryotic cell components is responsible for modifying and packaging proteins and lipids?

  • Mitochondria
  • Endoplasmic Reticulum
  • Lysosomes
  • Golgi Apparatus (correct)

    • Which structure is found in prokaryotic cells?

  • Golgi Apparatus
  • Mitochondria
  • Endoplasmic Reticulum
  • Nucleoid (correct)

    • Which of the following cell structures is primarily involved in the synthesis of proteins?

    <p>Ribosomes (B)</p> Signup and view all the answers

    A cell biologist is comparing the chemical composition of living organisms with that of non-living materials. What key distinction related to organic compounds would the biologist likely observe?

    <p>Organic compounds are exclusive to living organisms or their remains. (C)</p> Signup and view all the answers

    How does the cytoskeleton facilitate essential cell functions?

    <p>By enabling the cell to rearrange its internal components for growth, division, and adaptation. (C)</p> Signup and view all the answers

    Which type of protein filament primarily contributes to a cell's resistance to mechanical stress, such as stretching and crushing?

    <p>Intermediate filaments (C)</p> Signup and view all the answers

    What is the primary role of microtubules within a non-dividing cell, such as a neuron or myocyte?

    <p>To group together in a region called the centrosome. (C)</p> Signup and view all the answers

    A researcher observes a cell exhibiting fountain-like cytoplasmic movement. Which characteristic best describes this type of movement?

    <p>Cytoplasm flows around two vacuoles in opposite directions. (D)</p> Signup and view all the answers

    How would you describe the relationship between the sol and gel states of cytoplasm?

    <p>The sol is a liquid state, while the gel is a semi-solid state. (C)</p> Signup and view all the answers

    Which characteristic of the lysosome membrane is crucial for protecting the cell from its own digestive enzymes?

    <p>Resistance to the acid hydrolases contained within. (A)</p> Signup and view all the answers

    What is the primary difference between autophagy and autolysis in the context of autolysosome function?

    <p>Autophagy targets damaged organelles for destruction, while autolysis involves the digestion of the cell itself. (B)</p> Signup and view all the answers

    If a cell lacked the transmembrane H+ -ATPase in its lysosomes, what would be the most likely consequence?

    <p>Lysosomal enzymes would not be able to function effectively. (A)</p> Signup and view all the answers

    A researcher observes a vesicle fusing with a primary lysosome. The vesicle contains material that was brought into the cell. What type of lysosome is most likely being formed?

    <p>A heterolysosome. (D)</p> Signup and view all the answers

    Which of the following is NOT a component found in the granular matrix of peroxisomes?

    <p>Acid hydrolases. (D)</p> Signup and view all the answers

    Why is the categorization of endosomes important for understanding cellular processes?

    <p>Because it indicates the origin and type of material being processed by the lysosome. (B)</p> Signup and view all the answers

    Which cellular event relies on the activity of autolysosomes?

    <p>Breakdown of a malfunctioning mitochondrion. (C)</p> Signup and view all the answers

    A cell with a high number of peroxisomes is likely involved in which of the processes?

    <p>Breakdown of fatty acids. (B)</p> Signup and view all the answers

    Which of the following processes is NOT a primary function of enzymes found within peroxisomes?

    <p>Production of proteins for cellular repair. (B)</p> Signup and view all the answers

    What distinguishes de novo peroxisome formation from the division of pre-existing peroxisomes?

    <p>De novo peroxisome formation involves detachment of vesicles from the endoplasmic reticulum and mitochondria. (B)</p> Signup and view all the answers

    During the division of a pre-existing peroxisome, what structural change leads to the creation of two daughter structures?

    <p>The peroxisome forms a tube-like structure around which a tightening ring is formed. (B)</p> Signup and view all the answers

    A researcher observes a cell and notes the presence of two centrioles made of microtubules arranged in a cylinder shape. Which organelle is the researcher most likely observing?

    <p>Centrosome (B)</p> Signup and view all the answers

    Before cell division, what key event occurs involving the centrosome?

    <p>The centrosome duplicates, and the two centrosomes move to opposite poles of the cell. (A)</p> Signup and view all the answers

    Which component is exclusive to plant cells when compared to animal cells?

    <p>Cell wall (C)</p> Signup and view all the answers

    What is the origin of all plastids in plant cells?

    <p>They originate from plastid precursors known as proplastids. (C)</p> Signup and view all the answers

    If a cell is actively synthesizing plasmalogens, which are essential components of the myelin sheath in neurons, which organelle is most likely playing a significant role?

    <p>Peroxisome (B)</p> Signup and view all the answers

    How does the protein production differ between free ribosomes and ribosomes associated with the endoplasmic reticulum in eukaryotes?

    <p>Free ribosomes produce proteins that function in the cytosol, while ER-associated ribosomes produce proteins that undergo post-translational modification and are exported from the cell. (B)</p> Signup and view all the answers

    What distinguishes the ribosomes found in mitochondria and chloroplasts from those found in the eukaryotic cytoplasm?

    <p>Mitochondria and chloroplasts contain ribosomes that are smaller and more closely resemble those found in bacteria. (C)</p> Signup and view all the answers

    A plant cell's firmness is directly maintained by which component of the cell?

    <p>The consistent turgor pressure within the vacuole. (D)</p> Signup and view all the answers

    If a cell requires a significant amount of energy, which of the following mitochondrial characteristics would you expect to observe?

    <p>A higher number of mitochondria and increased infoldings of the inner membrane (cristae). (B)</p> Signup and view all the answers

    If a plant cell's vacuole had a compromised membrane, which of the following functions would be most immediately affected?

    <p>The storage of reserve materials and metabolic byproducts. (A)</p> Signup and view all the answers

    How does the structure of the mitochondrial membrane facilitate its function in energy production?

    <p>The inner membrane's selective permeability and cristae maximize the surface area for the electron transport chain. (C)</p> Signup and view all the answers

    Which evidence most strongly supports the endosymbiotic theory regarding the origin of mitochondria and chloroplasts?

    <p>The similarity in size and structure between bacterial DNA and the DNA found in mitochondria and chloroplasts. (C)</p> Signup and view all the answers

    What is the primary role of mitochondrial DNA (mtDNA) within the mitochondrion?

    <p>To provide the genetic material for a small number of proteins essential for ATP production. (A)</p> Signup and view all the answers

    According to the endosymbiotic theory, what is the evolutionary origin of eukaryotic organelles like mitochondria and chloroplasts?

    <p>They are believed to have evolved from engulfed prokaryotic cells. (B)</p> Signup and view all the answers

    How does the distribution of ATP generated by mitochondria relate to their mobility within the cell?

    <p>Mitochondria move to areas of high ATP demand, ensuring localized energy supply. (D)</p> Signup and view all the answers

    Which of the following characteristics of mitochondria and chloroplasts provides evidence for the endosymbiotic theory?

    <p>Their replication process involving binary fission, similar to bacteria. (C)</p> Signup and view all the answers

    How does mitochondrial division contribute to maintaining cellular energy requirements?

    <p>Mitochondrial division increases the number of mitochondria in response to increased energy demand. (B)</p> Signup and view all the answers

    A scientist is studying a newly discovered organelle in a eukaryotic cell. The organelle contains its own DNA, which is circular, and its ribosomes resemble those found in bacteria. Additionally, the organelle's proteins start with N-formylmethionine. Which evolutionary theory do these findings support?

    <p>Endosymbiotic theory. (C)</p> Signup and view all the answers

    Where do vesicles with substrates intended for product processing enter the golgi apparatus?

    <p>Cis cisterna. (D)</p> Signup and view all the answers

    In cellular metabolism, what distinguishes anabolic processes from catabolic processes?

    <p>Anabolic processes consume energy to build complex molecules, while catabolic processes release energy by breaking them down. (B)</p> Signup and view all the answers

    What structural feature is characteristic of the Golgi apparatus?

    <p>Highly flattened, arched cisternae. (A)</p> Signup and view all the answers

    Which of the subsequent statements correctly describes the energy dynamics of anabolic reactions?

    <p>Anabolic reactions require an input of energy, which is then stored in the chemical bonds of the products. (C)</p> Signup and view all the answers

    Considering the structure of the Golgi apparatus, what is the functional significance of the cis, medial, and trans cisternae?

    <p>They represent sequential stages of substrate processing and modification. (A)</p> Signup and view all the answers

    Flashcards

    Cytology

    The study of cells, their structure and function.

    Cell Division

    The process by which cells reproduce by dividing into daughter cells.

    Prokaryotic Cells

    Simple cells without a nucleus; includes bacteria.

    Eukaryotic Cells

    Complex cells with a nucleus; includes animals and plants.

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    Cell Components

    Structures within a cell that perform specific functions, such as nucleus, mitochondria.

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    Cytoplasm states

    Cytoplasm exists in two forms: semi-liquid (sol) and semi-solid (gel).

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    Cytoplasmic movement types

    Cytoplasm moves in four ways: rotationally, circulating, pulsating, and fountaining.

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    Cytoskeleton purpose

    Cytoskeleton provides support and helps rearrange internal components in cells.

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    Intermediate filaments

    A type of cytoskeletal filament that provides mechanical support and helps maintain cell shape.

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    Microtubules functions

    Microtubules assist in cell transport, form centrioles, and create cilia and flagella.

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    Lysosome

    An organelle that contains hydrolytic enzymes for digestion.

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    Hydrolytic enzymes

    Enzymes in lysosomes that catalyze intracellular digestion.

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    Low pH

    An acidic environment created by the H+-ATPase in lysosomes.

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    Primary lysosomes

    Lysosomes formed in the rER and bud from the Golgi apparatus.

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    Secondary lysosomes

    Formed from the fusion of primary lysosomes with endosomes or autophagosomes.

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    Autolysosomes

    Secondary lysosomes that digest damaged organelles and dead cells.

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    Heterolysosomes

    Formed by the fusion of primary lysosomes with vesicles from endocytosis.

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    Peroxisomes

    Organelles that break down fatty acids and detoxify harmful substances.

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    Free Ribosomes

    Ribosomes that float in the cytoplasm, producing proteins for the cytosol.

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    Ribosomes with ER

    Ribosomes associated with the endoplasmic reticulum, producing proteins for export.

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    Ribosome Subunits

    Each ribosome consists of two subunits: small and large.

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    Prokaryotic Ribosomes

    Small ribosomes found in prokaryotes, often referred to as 70s.

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    Eukaryotic Ribosomes

    Larger ribosomes found in eukaryotes, commonly known as 80s.

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    Mitochondria Functions

    Mitochondria perform aerobic respiration and ATP production.

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    Mitochondrial Structure

    Mitochondria have a double membrane with an inner matrix and cristae.

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    Mitochondrial DNA

    Mitochondria contain circular mitochondrial DNA (mtDNA) for their functions.

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    Golgi Apparatus

    An organelle composed of cisternae for processing and packaging proteins.

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    Cisternae Types in Golgi

    The Golgi apparatus has cis, medial, and trans cisternae for different processing stages.

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    Detoxification

    The process of breaking down toxic substances like ethanol in peroxisomes.

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    β-Oxidation

    A process that oxidizes fatty acids to produce acetyl-CoA.

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    α-Oxidation

    Oxidation process for branched fatty acids into linear chains.

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    Formation of Peroxisomes

    Peroxisomes form from preperoxisomes or by division of existing ones.

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    Plasmalogen synthesis

    Creation of plasmalogens, important for neuron myelin sheath.

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    Centrosome

    Structure consisting of two centrioles, important for cell division.

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    Plastids

    Double-membrane organelles with their own DNA and ribosomes.

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    Cell Sap Components

    Cell sap is mainly composed of water, ions, proteins, sugars, and organic acids.

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    Vacuole Functions

    Vacuoles help maintain turgor pressure, store materials, and gather waste products in cells.

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    Endosymbiotic Theory

    Proposes that eukaryotic organelles originated from prokaryotic cells merging.

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    Circular DNA in Organelles

    Mitochondria and chloroplasts contain circular DNA similar to bacteria.

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    Division of Organelles

    Mitochondria and chloroplasts replicate by division, not created anew.

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    Ribosomes in Organelles

    Mitochondria and chloroplasts have ribosomes that resemble bacterial ribosomes.

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    Cell Metabolism

    The total of all biochemical reactions in cells, essential for growth and reproduction.

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    Anabolism

    Anabolic processes synthesize complex molecules from simple ones; require energy.

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    Study Notes

    Cell Composition and Structure

    • Dr. Michelle Kuzma and Dr. Danuta Mielżyńska-Švach are the lecturers.
    • The slides cover molecular biology in 2024/2025.
    • Cell composition and structure are studied in different domains (cytology, cytochemistry, cytophysiology, cytopathology, cytogenetics).

    Areas of Cell Study

    • Cytology is a main area of study.
    • Cytochemistry, cytophysiology, cytopathology, and cytogenetics are sub-areas of study.

    The Cell

    • Cells are the smallest structural and functional unit in all organisms.
    • Cells are formed by the division of other cells (cell division).
    • Cells contain genetic information passed on to daughter cells during cell division.
    • All cells are made of the same chemical compounds.

    Types of Cells

    • Cells are categorized as prokaryotic or eukaryotic.
    • Prokaryotic cells (e.g., bacteria) have a simpler structure, lacking a defined nucleus and other membrane-bound organelles.
    • Eukaryotic cells (e.g., animals and plants) are more complex with a defined nucleus and other membrane-bound organelles.

    Types of Cells (Classification)

    • The slide displays a branching diagram of Bacteria, Archaea, and Eukaryota.
    • The various branches are further subdivided into different groups of organisms (e.g., Spirochetes, Proteobacteria, Cyanobacteria, etc).

    Eukaryotic Organisms

    • Eukaryotic organisms can be single-celled or multi-celled.
    • Single-celled eukaryotes include protozoa, some algae, and some fungi.
    • Multi-celled eukaryotes include plants, fungi, and animals.

    Prokaryotic Cell Components

    • Cell surface components: cell membrane, cell wall, capsule (mucus), flagella, cilia, pili, fimbriae.
    • Cell interior components: cytosol, nucleoid (equivalent of the cell nucleus), ribosomes, plasmids.

    Eukaryotic Animal Cell

    • A eukaryotic animal cell includes cytoplasm (cytoplasmic matrix), cytoskeleton, nucleus, endoplasmic reticulum, mitochondria, Golgi apparatus, lysosomes, and peroxisomes.

    Cell Components

    • All organisms are composed of inorganic and organic chemicals.
    • Inorganic compounds are mainly found in non-living matter.
    • Organic compounds are predominantly found in living organisms or their remnants.

    Inorganic Components

    • Chemical elements: macroelements (at least 0.01% of cell mass), microelements (between 0.01-0.00001% of cell mass), trace elements (µg/g range), and ultratrace elements (µg/g range).
    • Water makes up approximately 70% of the cell.

    Chemical Elements (Macromolecules and Microelements)

    • Macroelements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Sulfur (S), Potassium (K), Sodium (Na), Magnesium (Mg).
    • Microelements: Iron (Fe), Silicon (Si), Copper (Cu), Manganese (Mn), Fluorine (F), Iodine (I), Boron (B), Molybdenum (MI), Zinc (Zn).
    • Ultraelements: Radium (Ra), Silver (Ag), and Gold (Au).

    Water

    • Water is the major component of every organism (approximately 70-80% of the content of a living cell).
    • It is essential for proper body function, acting as a solvent for many chemical compounds and an environment for reactions.

    Water Molecule Structure

    • Water molecules consist of one oxygen and two hydrogen atoms.
    • A hydrogen bond forms between the oxygen and hydrogen atoms due to differences in electronegativity.
    • Uneven charge distribution makes the water molecule dipolar.
    • The attraction between hydrogen and oxygen atoms causes water molecules to associate into larger groups.

    Carbon Atom Structure

    • The carbon atom's nucleus contains 6 protons and 6 neutrons.
    • It has two electron shells: K shell (contains 2 electrons) and L shell (contains 4 electrons).
    • A carbon atom has four valence electrons and four vacancies for electrons from other elements.

    Carbon Atom Structure (continued)

    • Carbon's ability to form strong covalent bonds with other carbon atoms allows for the formation of chains, branched structures, and rings.
    • Organic compounds consist of carbon atoms bonded to at least one other element (e.g., hydrogen, oxygen, nitrogen, sulfur, phosphorus).

    Organic Components

    • Cells contain four major families of small organic molecules: carbohydrates, fatty acids, amino acids, and nucleotides.
    • These molecules are predominantly found in solution in the cytosol.
    • Monomer subunits construct the macromolecules of the cell (polymers).

    Organic Components (Categories)

    • Small organic building blocks of the cell include sugars, fatty acids, amino acids, and nucleotides.
    • Larger organic molecules of the cell include polysaccharides (e.g., glycogen, starch), fats and membrane lipids, proteins, and nucleic acids.

    Carbohydrates

    • Carbohydrates are composed primarily of carbon, hydrogen, and oxygen.
    • Monosaccharides (e.g., glucose, fructose), disaccharides (e.g., sucrose, lactose), oligosaccharides (e.g., raffinose), and polysaccharides (e.g., cellulose, starch) are various forms of carbohydrates.
    • The longer the carbon chain, the less soluble the carbohydrate is in water.

    Carbohydrate Function

    • Energy storage/production: glycogen in animals, starch in plants.
    • Structure: cellulose (plant cell walls), chitin (fungi cell walls), ribose and deoxyribose sugars in DNA and RNA.
    • They modify proteins.
    • Transport: glucose in animals and humans, sucrose in plants.

    Fatty Acids

    • Fatty acids typically contain an even number of carbon atoms (14 to 24).
    • They have a carboxyl group attached to a hydrocarbon chain.
    • Saturated fatty acids only contain single bonds.
    • Unsaturated fatty acids contain one or more double bonds.

    Lipids

    • Lipids are esters of fatty acids bonded to alcohols.
    • Examples include glycerol, sphingosine, and higher monohydric alcohols.
    • Lipids are insoluble in water due to their low ability to polarize under water's influence, a characteristic property.

    Types of Lipids

    • Simple lipids (e.g., fats and oils (triglycerides) and waxes (esters with non-glycerol alcohols)).
    • Complex lipids (e.g., phosphoric acid (phospholipids) and carbohydrate (glycolipids)).
    • Steroids (e.g., cholesterol).

    Lipid Functions

    • Structural: building blocks of biological membranes.
    • Energy storage: in animals as subcutaneous tissue and in hibernators' tissues. Plant lipids are found in seeds, fruits, and roots.
    • Signaling: steroid hormones, vitamins A and D.
    • Protection: protects from mechanical injuries. Protects leaves, fruits, and marine mammals from excessive water loss.

    Cell Composition (Summary)

    • Water (~70%) and small inorganic chemicals (~30%) build cells.
    • Macromolecules (protein ~15%, polysaccharide ~2%, DNA ~1%, RNA ~6%) make up the remaining part of the cell.

    Cell Structure

    • The internal cell environment is enclosed within a cell membrane (plasma membrane) which separates it from external environments.
    • For some cells, like bacteria and plant cells, there is an additional cell wall surrounding the cell membrane.
    • The internal environment is called cytoplasm; it has cytosol and organelles.
    • Organelles are either membrane-bound or non-membrane bound.

    Cell Structure: Cell Membrane

    • Cells and their organelles are bordered by cell membranes (plasma membrane).
    • Cell membranes of both extra and intracellular cells consist of: lipids, proteins, and sugars as components.
    • Membrane functions include protection, reaction to stimuli, enzymatic catalysis, substance transport, and regulation of osmotic pressure.

    Cell Structure: Cytoplasm

    • Cytoplasm is a colloidal solution. Dissolved particles are too small to settle under gravity but are too large to fully dissolve in water.
    • Two phases: the dispersive (water - approximately 90% of the cytoplasmic volume) and the dispersed (substances suspended in water - 9% organic compounds, and 1% mineral compounds).

    Cell Structure: Cytoplasm (Continued)

    • Cytoplasm functions: fills the cell and shapes it, provides an environment for suspending cell organelles, site of metabolic reactions, and facilitates the movement of organelles and transport of substances.
    • Cytoplasm can move in multiple ways: rotationally, circulating, pulsating, and fountaining.

    Cell Structure: Cytoskeleton

    • Cytoskeleton is a filament system that rearranges, as cells grow, divide, and adapt; necessary for cells' spatial and mechanical functions.
    • Three families of protein filaments: intermediate filaments (8-10 nm), microtubules (25 nm), and actin filaments (7 nm).

    Cytoskeleton (intermediate filaments)

    • Intermediate filaments are formed from tissue-specific proteins (keratin, vimentin, etc.).
    • Intermediate filaments provide mechanical support giving resistance against stretching and crushing and maintain cell shape.

    Cytoskeleton (microtubules)

    • Microtubules are a type of cytoskeletal filaments composed of tubulin (a globular protein).
    • Microtubules build centrioles, the mitotic spindle, and facilitate cell transport.
    • Microtubules form cilia and flagella and organize in a region called the centrosome in cells that don't divide.

    Cytoskeleton (actin filaments)

    • Actin filaments (microfilaments) are made up of actin.
    • Actin filaments provide mechanical support for the cell and various organelles.
    • They are involved in cytoplasm and organelle movement, enable creeping movement and cell shape change, and participate in the contraction of muscle cells.

    Cell Organelles (Eukaryotic, Animal)

    • Cell organelles include: lysosome, nuclear envelope, transport vesicle, mitochondrion, peroxisome, Golgi apparatus, endoplasmic reticulum, and plasma membrane .

    Cell Structure: Organelles

    • Membrane-bound organelles: double membrane-bound (nucleus, mitochondria, chloroplasts) and single membrane-bound (Golgi apparatus, lysosomes, peroxisomes, endoplasmic reticulum, and vacuoles).

    Cell Structure: Organelles (single membrane)

    • Golgi apparatus modifies proteins, secretes various substances.
    • Lysosomes contain digestive enzymes and are associated with decomposition processes (e.g., breakdown of peroxides).
    • Peroxisomes contribute to breakdown reactions (e.g., decomposition/reduction of toxic chemicals).

    Cell Structure: Organelles (Non-Membrane Bound)

    • Cell wall: a non-membrane-bound organelle, the outer covering of some non-animal cells.
    • Cytoskeleton: provides cell structure.
    • Ribosomes: site of protein synthesis.
    • Centrosome/Microtubule Organizing Centre: contains centrioles and microtubules important in cell division.
    • Centriole: a cylindrical organelle involved in spindle fiber creation during cell division.

    Nucleus

    • Amount per human cell varies (e.g., monokaryocytes, bikaryocytes, polykaryocytes vs. erythrocytes, cells of stratum corneum).
    • Size/shape depends on cell type, age, and functionality (spherical, elliptical, fragmented).
    • Nucleus occupies about ~10% of mammalian cell volume.
    • Position: typically in the center of the cell or along the cell membrane.

    States of the Nucleus

    • Interphase: between or in preparation for cell division.
    • Mitotic: during cell division.
    • Metabolic: in resting cells (Go phase); directs metabolic processes.

    Nucleus Structure during Interphase

    • Nuclear envelope (membrane), nuclear matrix (nucleoplasm), nucleolus.
    • Chromatin (types: condensed (heterochromatin) and dispersed (euchromatin)).

    Nucleolus

    • The nucleus usually contains one nucleolus, which is not separated from the nucleoplasm.
    • Nucleolus has fragments of 5 chromosomes, contains DNA which is responsible for rRNA and ribosomal subunits.
    • Nucleolus functions as a nucleolar organizer (NORs). In humans, there are 10 NORs on chromosome pairs 13, 14, 15, 21, and 22.

    Functions of the Nucleus

    • DNA synthesis (replication): before nuclear division.
    • RNA synthesis from DNA (transcription).
    • Site of ribosome formation (for protein synthesis/translation).

    The Endoplasmic Reticulum

    • A system of single-layered membranes forming a network of cisternae, channels, and vesicles.
    • Function: enlarges internal surface area of the cell, divides cytoplasm into compartments, and determines the route of transport.
    • Two types: rough and smooth ER.

    The Endoplasmic Reticulum (Rough ER)

    • Contains ribosomes for protein synthesis, modification, and quality control.
    • Connects the outer nuclear membrane with cell and organelle membranes.

    The Endoplasmic Reticulum (Smooth ER)

    • Lacks ribosomes.
    • Involved in lipid and steroid synthesis, detoxification of substances, and internal transport.

    Ribosomes

    • Ribosomes are made of rRNA and proteins.
    • Two types: free ribosomes (produce proteins for use in the cytoplasm) and ribosomes associated with the endoplasmic reticulum (produce proteins exported from the cell).
    • Ribosomes in mitochondria and chloroplasts are similar to bacterial ribosomes. Ribosomes are in eukaryotic cells

    Mitochondria

    • Number in a single cell depends on the organism, cell type, and energy requirements.
    • Size and shape can vary (filamentous, granular, branched).
    • Mitochondria are formed by division of existing ones.
    • Number of mitochondria per various cell types, such as epidermal, sperm, liver, skeletal muscle, nerve, and ova.

    Mitochondrial Structure

    • Two-layer membrane: outer (smooth) and inner (with folds called cristae).
    • Intermembrane space between the membranes.
    • Inner membrane allows selected compounds to pass through (facilitated diffusion).
    • Mitochondria have matrix, mitochondrial DNA (mtDNA), ribosomes (70S), and enzymes (necessary for ATP production inside a mitochondrion). Multiple mtDNA molecules (4-10/human mitochondrion) are packed into nucleoids within the matrix (ellipsoidal shape).

    Mitochondrial Functions

    • Aerobic respiration (Krebs cycle and electron transport chain).
    • ATP (adenosine triphosphate) production; ATP is a chemical energy carrier used in cell metabolism.
    • ATP delivery to other cell parts or cytoplasm.

    Golgi Apparatus

    • Highly flattened, arched cisternae (3-20).
    • Separating vesicles.
    • Cis, medial, and trans cisternae.
    • Receives components from the perinuclear endoplasmic reticulum, the cell membrane, and endosomes.
    • Modifies and transports proteins and lipids, links carbohydrates to proteins, fats, and nucleosides, sulfates proteins, and recycles cell membrane substances after endocytosis.

    Lysosomes

    • Varying shapes & sizes depending on the cell type and function (e.g., macrophages, hepatocytes, neurons).
    • Spherical or oval vesicles surrounded by a single membrane.
    • Number and location may differ even in cells of the same tissue.
    • Contain about 40 hydrolytic enzymes (acid hydrolases) catalyzing intracellular digestion reactions.

    Lysosomes (Continued)

    • Low pH environment (pH 5) created by transmembrane H+ ATPase/proton pump.
    • Lysosome membranes resistant to acid hydrolases due to unique proteins.
    • Two types of lysosomes: primary (formed in endoplasmic reticulum and Golgi apparatus) & secondary (formed after primary lysosomes fuse with endosomes or autophagosomes). Secondary lysosomes can further be categorized into autolysosomes and heterolysosomes depending on the material taken in by endocytosis (endosomes). Endosomes categorized into phagosomes (material taken in by phagocytosis) or pinosomes (material taken in by pinocytosis). Decomposition products into the cytosol (simple sugars, amino acids, nucleotides) of secondary lysosomes.

    Peroxisomes

    • Oval or spherical organelles surrounded by a single cell membrane.
    • Diameter between 0.2-1.8 µm.
    • Abundance varies by tissue (liver, kidney, nervous tissue).
    • Matrix may contain a crystalline core (nucleoid) with various forms.

    Peroxisome Structure

    • Peroxisome has matrix, a crystalline core (nucleoid), and cell membrane.

    Peroxisome Functions

    • Responsible for over 60 catabolic and anabolic processes.
    • Involved in detoxification, β-oxidation (long-chain molecules), and α-oxidation (branched fatty acids) reactions.
    • Synthesizes and produces cholesterol, bile acids, and plasmalogens.
    • Byproduct of fatty acid oxidation is hydrogen peroxide (H₂O₂), broken down by catalase or peroxidases.

    Peroxisome Formation

    • Two ways: de novo from preperoxisomes or as a result of division from pre-existing peroxisomes.
    • Preperoxisomes recruit enzymes, peroxins, and integral membrane proteins to fuse into mature peroxisomes.

    Centrosome

    • The centrosome (diplosome) is a structure near the nucleus and Golgi apparatus.
    • It consists of two centrioles composed of microtubules arranged in the form of cylinders.
    • Duplicates itself to form two centrosomes during cell division (each with two centrioles) that move to opposite cell poles.

    Plant Cells

    • Plant cells have a cell wall (cellulose and lignin) and a large vacuole in addition to other organelles found in animal cells.
    • Plastids are present in plant cells, which are oval-shaped organelles with a double cell membrane, plastid DNA, and ribosomes.
    • Examples of plastids include chloroplasts, chromoplasts, amyloplasts, and leucoplasts.

    Chloroplast Structure

    • Chloroplasts have lamellae, grana, thylakoids, and stroma.
    • Chloroplast DNA is in the stroma.
    • Chloroplasts have an inner and outer membrane.

    Cell Wall

    • Plant cells have a multi-layered cell wall made of cellulose and/or chitin.
    • Cellulose is a glucose polymer.
    • Chitin is a N-acetylglucosamine polymer.
    • Two types: primary (cellulose and pectin) and secondary (cellulose and lignin).

    Plant Vacuole

    • Vacuole is surrounded by a single membrane (tonoplast).
    • Interior filled with cell sap (water, ions, proteins, sugars, organic acids).

    Vacuole Functions

    • Maintain constant cell firmness (turgor pressure).
    • Store reserve materials.
    • Gather unnecessary metabolic products.

    Comparison (Plant vs. Animal Cells)

    • Plant cells have a cell wall and chloroplasts; animal cells do not.
    • Plant cells have a large vacuole, while animal cells have smaller, less prominent ones.

    Endosymbiotic Theory

    • Explains the origin of mitochondria and chloroplasts in eukaryotic cells.
    • This theory assumes that eukaryotic organelles evolved from prokaryotic cells.
    • Mitochondria and chloroplasts have their own DNA and ribosomes similar to bacteria.

    Endosymbiotic Theory (Evidence)

    • Mitochondria and chloroplasts have circular DNA similar to bacterial DNA.
    • Both are formed by division (from existing ones), not created de novo by the cell.
    • Mitochondrial and chloroplast ribosomes are similar to bacterial ribosomes.

    Cell Metabolism

    • Metabolism encompasses all biochemical reactions in living organisms' cells.
    • It involves the circulation of matter, energy, and information.
    • Maintains organisms' reception of stimuli, growth, movement, reproduction, and metabolic changes.

    Cell Metabolism (Directions)

    • Anabolism: synthesis of complex organic compounds from simpler ones (requires energy input).
    • Catabolism: breakdown of complex organic compounds into simpler ones (releases energy or chemical energy in bonds).

    Cellular Respiration

    • The breakdown of organic compounds into inorganic compounds (CO₂ and H₂O) to release energy.
    • Occurs in two main stages:
    • glycolysis (in the cytoplasm, breaking glucose down to pyruvic acid).
    • Further oxidation in the mitochondria.

    Intracellular Respiration (Steps)

    • Glycolysis (in cytoplasm): Glucose to pyruvate, and producing NADH.
    • Krebs Cycle (in mitochondria): Pyruvate (intermediate) to produce 2 cycles per glucose molecule, NADH, and FADH2.
    • Electron Transport (in mitochondria): NADH and FADH2 transfer electrons to create ATP.

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