Cell Biology and Cell Theory
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Questions and Answers

What is the primary component found in the outer mitochondrial membrane?

  • Phospholipids (correct)
  • Cardiolipin
  • Proteins
  • Cholesterol

What role does Porin play in the outer mitochondrial membrane?

  • It facilitates ATP production.
  • It assists in replication of mitochondrial DNA.
  • It synthesizes fatty acids.
  • It forms channels for diffusion of small molecules. (correct)

What is the lipid-protein ratio of the inner mitochondrial membrane?

  • 0.5:1
  • 1:1
  • 0.27:1 (correct)
  • 1:0.27

What is a significant characteristic of the inner mitochondrial membrane?

<p>Very resistant to polar and ionic molecules. (B)</p> Signup and view all the answers

What best describes the intermembrane space of the mitochondrion?

<p>Has a similar ionic composition to the cytosol. (B)</p> Signup and view all the answers

Which enzyme processes occur within the mitochondrial matrix?

<p>Citric acid cycle and fatty acid oxidation. (D)</p> Signup and view all the answers

What structures are formed by the folds of the inner mitochondrial membrane?

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

Which of the following is NOT found in the mitochondrial matrix?

<p>Porin proteins (C)</p> Signup and view all the answers

What is a key function of the rough endoplasmic reticulum?

<p>Modification and transport of proteins (B)</p> Signup and view all the answers

Which condition is associated with dysfunction in the endoplasmic reticulum?

<p>Alzheimer's disease (D)</p> Signup and view all the answers

What is unique about mitochondrial DNA?

<p>It is genetically semi-autonomous (B)</p> Signup and view all the answers

Which type of endoplasmic reticulum is responsible for lipid synthesis?

<p>Smooth endoplasmic reticulum (A)</p> Signup and view all the answers

Which organelle is involved in the detoxification of drugs within mammalian liver cells?

<p>Endoplasmic reticulum (A)</p> Signup and view all the answers

What is the role of cytochrome P450 in the endoplasmic reticulum?

<p>Drug hydroxylation (C)</p> Signup and view all the answers

How do free radicals affect mitochondrial DNA?

<p>They can damage it (B)</p> Signup and view all the answers

The Golgi complex is also known as what?

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

What is the optimal pH for lysosomal enzymes?

<p>5 (D)</p> Signup and view all the answers

Which enzyme is NOT associated with protein hydrolysis in lysosomes?

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

Which of the following processes does NOT involve lysosomes?

<p>Photosynthesis (D)</p> Signup and view all the answers

What role does acid phosphatase serve in relation to lysosomes?

<p>It is a lysosomal enzyme marker. (B)</p> Signup and view all the answers

In which type of cells are lysosomes NOT found?

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

What happens to lysosomal bodies during the autolysis of a cell?

<p>They release hydrolytic enzymes. (C)</p> Signup and view all the answers

Which of the following enzymes is primarily involved in lipid hydrolysis?

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

Which condition can result from lysosomal dysfunction?

<p>Allergic responses (A)</p> Signup and view all the answers

What is the primary consequence of urate crystal deposition around joints in gout?

<p>Phagocytosis causing lysosomal damage (C)</p> Signup and view all the answers

What characterizes I-cell disease?

<p>Deficiency of GlcNAc phosphotransferase (B)</p> Signup and view all the answers

What happens to lysosomal enzymes in I-cell disease?

<p>They are secreted into the plasma (B)</p> Signup and view all the answers

Which of the following is a common feature of inherited lysosomal disorders?

<p>Deficiency of key acid hydrolases (B)</p> Signup and view all the answers

What structure do peroxisomes share during their formation?

<p>Smooth endoplasmic reticulum (C)</p> Signup and view all the answers

Which of the following correctly describes the appearance of peroxisomes?

<p>Approximately 0.5 μm in diameter (D)</p> Signup and view all the answers

What is the outcome of the lysosomal enzymes lacking Mannose-6-P?

<p>High plasma levels and improper targeting (D)</p> Signup and view all the answers

How does the phagocytosis of urate crystals affect lysosomes?

<p>It causes their destruction (C)</p> Signup and view all the answers

What is produced during the oxidation reactions carried out by peroxisomes?

<p>Hydrogen peroxide (D)</p> Signup and view all the answers

Which of the following fatty acids can be oxidized by liver peroxisomes?

<p>Long-chain fatty acids (C 16 to 18 or &gt; C 18) (C)</p> Signup and view all the answers

What characterizes the cytoplasm (cytosol) of a cell?

<p>It has a high protein content and ribosomal RNA. (C)</p> Signup and view all the answers

What is the primary function of the plasma membrane?

<p>To separate cell contents from the outer environment (D)</p> Signup and view all the answers

Which component typically makes up about 60 percent of the dry weight of membranes?

<p>Proteins (D)</p> Signup and view all the answers

What does selective permeability of the plasma membrane allow?

<p>Controlled flow of molecules and ions into and out of the cell (B)</p> Signup and view all the answers

Which inherited disorder is associated with the absence of peroxisomes?

<p>Zellweger’s syndrome (A)</p> Signup and view all the answers

How are all membrane carbohydrates typically attached?

<p>Covalently attached to proteins or lipids (D)</p> Signup and view all the answers

What component of lipids makes the polar head hydrophilic?

<p>Glycerol-3-P (C)</p> Signup and view all the answers

Which types of lipids are specifically mentioned as being part of cell membranes?

<p>Glycerophospholipids and Sphingolipids (D)</p> Signup and view all the answers

How does the degree of unsaturation affect cell membranes?

<p>It determines fluidity (A)</p> Signup and view all the answers

Which of the following fatty acids is NOT a common unsaturated fatty acid found in membrane lipids?

<p>Palmitic acid (D)</p> Signup and view all the answers

What are the three types of sphingolipids mentioned?

<p>Sphingomyelin, Cerebrosides, Gangliosides (C)</p> Signup and view all the answers

Approximately what percentage of fatty acid groups in membrane lipids are saturated?

<p>50% (C)</p> Signup and view all the answers

Which fatty acid is the most abundant unsaturated fatty acid found in animal membrane lipids?

<p>Oleic acid (A)</p> Signup and view all the answers

What characteristic do lipids possess due to their structure?

<p>They are amphipathic (A)</p> Signup and view all the answers

Flashcards

Outer mitochondrial membrane composition

Mostly phospholipids and cholesterol; contains porin proteins.

Porin protein function

Forms channels allowing small molecules (<10,000 Da) to pass freely through the outer membrane.

Inner mitochondrial membrane composition

High protein content (with a low lipid-protein ratio); rich in cardiolipin; resists the passage of polar/ionic molecules.

Cristae

Highly folded inner mitochondrial membrane.

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Intermembrane space composition

Similar ionic composition to the cytosol, due to outer membrane permeability

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Mitochondrial matrix location

The space enclosed by the inner mitochondrial membrane.

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Mitochondrial matrix composition

Contains enzymes for citric acid cycle and fatty acid oxidation, DNA, ribosomes, required proteins.

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Inner mitochondrial membrane function

Highly selective barrier; regulates passage of molecules into the matrix; houses electron transport chain proteins

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Mitochondrial function

Mitochondria are involved in energy production (ATP) and have their own DNA.

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Mitochondrial DNA

Specific DNA that is responsible for mitochondrial protein production.

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Endoplasmic Reticulum (ER)

A network of membranes in the cell involved in protein and lipid synthesis, transport, and modification.

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Rough ER

ER with ribosomes; synthesizes proteins.

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Smooth ER

ER without ribosomes; synthesizes and modifies lipids.

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Golgi apparatus

Modifies, sorts, and packages proteins and lipids for transport.

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Mitochondrial diseases

Disorders related to impaired mitochondrial function affecting energy production.

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ER dysfunction

Disorders related to malfunctions in the endoplasmic reticulum (ER) affecting protein/lipid processing.

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Lysosome Function

Lysosomes are organelles that break down waste materials and cellular debris. They contain enzymes that digest various molecules, such as proteins, lipids, and carbohydrates.

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Lysosome Location

Lysosomes are found in animal cells, excluding red blood cells (erythrocytes). Their numbers and types vary.

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Lysosomal pH

The pH inside lysosomes is lower than the surrounding cytoplasm (cytosol).

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Lysosomal Enzymes

Lysosomes contain enzymes that are optimized to work optimally at an acidic pH (around 5). These break down various biomolecules.

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Acid Phosphatase Function

Acid phosphatase is an enzyme used to identify lysosomes because it's highly concentrated in them.

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Lysosomal Autophagy

Damaged organelles, like mitochondria and the endoplasmic reticulum, can be digested inside lysosomes during the process of autophagy.

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Lysosomal Autolysis

During cell death, lysosomal membranes break open, releasing their enzymes into the cell. This causes cell self-digestion.

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Acrosome and Sperm

The acrosome, a specialized lysosome, is part of the sperm and may play a role in fertilizing an egg.

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Lysosome function in gout

When urate crystals are engulfed by lysosomes, they damage the lysosome, releasing enzymes that trigger inflammation and arthritis.

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Inherited lysosomal diseases

Genetic disorders causing accumulation of lipids or sugars in cells, due to missing key lysosomal enzymes.

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I-Cell disease cause

I-cell disease lacks the enzyme GlcNAc phosphotransferase, preventing proper tagging of lysosomal enzymes for delivery to lysosomes.

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I-Cell disease effect

Missing lysosomal enzymes in I-cell disease cause buildup of molecules leading to severe physical and mental problems.

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Lysosomal enzyme transport

Properly functioning lysosomal enzymes are tagged with Mannose-6-phosphate, directed to lysosomes for waste breakdown.

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Peroxisome characteristics

Small organelles, approximately 0.5 μm in diameter, likely formed from the smooth endoplasmic reticulum, lacking electron transport systems.

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Lysosome deficiency symptom

Abnormal accumulation of molecules causes progressive physical and mental delays, with death often within the first decade of life (in I-cell disease).

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Microbodies

Another name for peroxisomes.

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What are peroxisomes?

Small, membrane-bound organelles involved in oxidation reactions, producing and breaking down hydrogen peroxide.

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What's a key function of peroxisomes?

They break down long-chain fatty acids, especially those containing more than 18 carbon atoms.

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What is cytosol?

The fluid inside a cell, excluding organelles. It's where many metabolic reactions occur.

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What are plasma membranes?

The outer boundary of a cell, separating the inside from the outside environment.

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What does selective permeability mean?

The ability of a membrane to control which molecules pass through, allowing some while blocking others.

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What are the main components of cell membranes?

Lipids (like fats), proteins (for various jobs), and carbohydrates (for cell recognition).

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What is the purpose of internal membrane systems?

They surround organelles and help them carry out their specific functions.

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How does the carbohydrate content of membranes vary?

The amount of carbohydrates attached to proteins and lipids can differ between types of membranes.

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Lipid Structure

Lipids have a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail. This makes them amphipathic, meaning they have both polar and nonpolar properties.

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Fatty Acids in Membranes

Fatty acids are major components of membrane lipids. They have long chains and can be saturated (no double bonds) or unsaturated (one or more double bonds).

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What impacts membrane fluidity?

The degree of unsaturation in fatty acids affects membrane fluidity. More unsaturated fatty acids lead to greater fluidity.

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Glycerophospholipids

Glycerophospholipids are important membrane lipids. Examples include phosphatidylcholine (lecithin) and phosphatidylserine.

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Sphingolipids

Sphingolipids are another type of membrane lipid, especially found in nerve tissues. There are three types: sphingomyelin, cerebrosides, and gangliosides.

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Why are lipids important for membranes?

Lipids form the structural basis of cell membranes. Their amphipathic nature allows them to create a barrier that controls the passage of molecules.

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Lipid Roles

Lipids are not just structural components; they also serve as energy storage, signaling molecules, and insulation.

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Lipid Diversity

There are many different types of lipids, each with specific functions. This diversity is crucial for various biological processes.

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Study Notes

Cell Theory

  • Each organism is composed of cells.
  • All cells arise from pre-existing cells.
  • The genetic code is passed down from one generation to the next.
  • Metabolism encompasses anabolism and catabolism, chemical reactions within the cell.

Types of Cells

  • Two main types: prokaryotic and eukaryotic.

Prokaryotic Cells

  • Smaller in size, minimal internal organization.
  • Lack membrane-bound organelles.
  • Genetic material (DNA) is not enclosed by a nuclear membrane.
  • DNA is not complexed with histones.
  • Respiratory system is closely associated with the plasma membrane.
  • Reproduction does not involve mitosis or meiosis.
  • Examples: Bacteria and Cyanobacteria.

Eukaryotic Cells

  • Larger size, complex internal structure.
  • Contain membrane-bound organelles.
  • Genetic material (DNA) is enclosed within a nuclear membrane.
  • DNA is complexed with histones.
  • Respiratory system is in the mitochondria.
  • Reproduction involves mitosis and meiosis.
  • Examples: Fungi, plants, and animals (including humans).

Cell Organelles: Nucleus

  • Contains over 95% of the cell's DNA, the control center of the eukaryotic cell.
  • Nuclear envelope: A double membrane structure separating the nucleus from the cytoplasm.
  • Nuclear pore complexes: Embedded in the nuclear envelope, regulating protein and RNA movement.
  • Chromatin: Coiled DNA within the nucleus.
  • Nucleolus: A dense mass associated with the inner nuclear envelope involved in ribosome subunit assembly and rRNA synthesis.
  • Nucleoplasm: The nucleus's contents including enzymes like DNA and RNA polymerases, which play roles in mRNA and tRNA synthesis.
  • DNA replication and RNA transcription of DNA occur in the nucleus.

Cell Organelles: Mitochondria

  • The powerhouse of the cell.
  • Number: Varies greatly between cells.
  • Size: Typically 0.2-0.8 µm in diameter.
  • Shape: Assumes various shapes based on metabolic conditions.
  • Mitochondria contain an outer and inner membrane.
    • Outer membrane: Mostly phospholipid, cholesterol, and contains Porin proteins.
    • Inner membrane: Abundant in proteins and cardiolipin, highly folded (cristae), resistant to the passage of polar and ionic molecules; facilitates the passage of polar and ionic molecules through transport proteins.
  • Intermembrane space: The space between the outer and inner membranes. Has a similar ionic composition to the cytosol.
  • Mitochondrial matrix: The region enclosed by the inner membrane, containing the enzymes of the citric acid cycle and fatty acid oxidation. Contains circular DNA, ribosomes, and enzymes required for protein synthesis encoded in the mitochondrial genome. The mitochondrion is partly independent genetically.

Cell Organelles: Ribosomes

  • Small organelles responsible for protein synthesis.

Cell Organelles: Endoplasmic Reticulum

  • Extensive network of membranes extending throughout the cell.
  • Rough ER: Studded with ribosomes, synthesizes membrane-bound and secretory proteins, modifies and transports proteins. Modified and transported through the cell.
  • Smooth ER: Lacks ribosomes; Involved in lipid synthesis, steroid hormone production, and detoxification of drugs and poisons.

Cell Organelles: Golgi Complex/Golgi Apparatus

  • Stacked, flattened, membrane-bound sacs in eukaryotic cells.
  • Modifies, sorts, packages, and transports proteins and lipids from the ER.
  • Has a proximal (cis), medial, and distal (trans) section.
  • Receives proteins from the ER via transfer vesicles.
  • Post- translational modifications occur in the lumen.
  • Carbohydrates and lipid precursors are added to proteins to form glycoproteins and lipoproteins.
  • Secretory proteins are released via vesicles.

Cell Organelles: Lysosomes

  • Cellular organelles containing digestive enzymes.
  • Involved in intracellular digestion, breaking down waste materials and cellular debris.
  • Optimal pH is around 5.
  • Common in all animal cells (except red blood cells).
  • Important for autophagic processes and cellular autolysis.
  • The Enzymes in lysosmes are Hydrolytic enzymes, which are responsible for breaking down complex molecules. Enzymes include; proteolytic enzymes, nucleic acid hydrolyzing enzymes, lipid hydrolyzing enzymes, carbohydrate splitting enzymes, and other enzymes.
  • Lysosomal dysfunction may cause allergic responses, arthritic conditions, gout, inherited disorders, and I-cell disease.

Cell Organelles: Peroxisomes

  • Small organelles ("microbodies") containing enzymes involved in oxidation reactions.
  • Produce hydrogen peroxide, then destroy it
  • Oxidizes long-chain fatty acids.
  • May be absent in some inherited disorders, like Zellweger's syndrome. Enzyme within the microbody/peroxisome is catalase.

Cell Organelles: Cytosol/Cytoplasm

  • The contents of a cell outside the nucleus.
  • Organelle-free sap.
  • High protein content and rRNA.
  • Metabolic reactions occur here.

Biological Membranes

  • Plasma membrane: Prototype cell membrane; separates the cell content from the outer environment.
  • Components: Lipids (40-60% of the dry weight), proteins (60-40% of the dry weight), carbohydrates (1-10% of the dry weight).
    • Phospholipids: Head groups (attached to polar head group ) and tails (non-polar-hydrophobic).
    • Integral proteins: Deeply embedded in the membrane; contact with the hydrophobic area.
    • Peripheral proteins: Weakly adhered to the phospholipid membrane; interact with the ionic heads.
  • Membranes are involved in many life processes; including cellular communication, regulation of cell growth, cell division, etc..

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Description

Explore the fundamental principles of cell theory and the distinctions between prokaryotic and eukaryotic cells. Understand the structure, reproduction, and genetic characteristics that differentiate these cell types. This quiz will enhance your knowledge of cellular biology concepts.

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