Cell Biology Quiz on Cytoskeleton and Organelles

Cell Composition and Structure

• The study of cell composition and structure involves several related areas like Cytology, Cytochemistry, Cytophysiology, Cytopathology, and Cytogenetics.
• Cells are the basic structural and functional units of all organisms.
• All cells originate from pre-existing cells through cell division.
• All cells contain genetic information passed to daughter cells during division.
• Cells are made of the same chemical compounds.
• All metabolic processes required for life occur within cells.

Types of Cells

• Prokaryotic cells lack a nucleus and membrane-bound organelles.
  • Bacterial cells are an example of prokaryotic cells
    • Parts of a bacterial cell include: pili, cytoplasm, capsule, cell wall, plasma membrane, nucleoid (DNA), plasmids, ribosomes, and flagella.
• Eukaryotic cells have a nucleus and membrane-bound organelles.
  • Eukaryotic cells can be single-celled (e.g., protozoa, some algae, some fungi) or multicellular (e.g., plants, animals, fungi).

Cell Components

• All organisms are composed of inorganic and organic compounds.
  • Inorganic compounds primarily make up non-living matter (e.g., water).
  • Organic compounds form the components of living organisms (e.g., carbohydrates, lipids, proteins, and nucleic acids).
• Inorganic components include:
  • Elements: macroelements (e.g., C, H, O, N, P, K, Na, Mg), microelements, trace elements, and ultratrace elements.
  • Water (~70% of a living cell).
• Chemical elements involved:
  • Macroelements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Sulphur (S), Potassium (K), Sodium (Na), Magnesium (Mg).
  • Microelements: Iron (Fe), Silicon (Si), Copper (Cu), Manganese (Mn), Fluorine (F), Iodine (I), Boron (B), Molybdenum (Mo), Zinc (Zn)
  • Ultraelements: Radium (Ra), silver (Ag), gold (Au)

Water

• Water is a crucial component of all living organisms, typically making up 70-80% of a living cell's content.
• Water acts as a solvent for many chemical compounds.
• Water is essential for a wide range of biological processes and reactions.
• Water's properties are due to its chemical structure.

The Structure and Properties of Atoms and Molecules

• Water is composed of one oxygen atom and two hydrogen atoms held by covalent bonds.
  • Oxygen is more electronegative than hydrogen.
  • The uneven sharing of electrons causes an uneven distribution of electrical charge.
  • Water molecules have a partially positive (δ+) and partially negative (δ-) side.
• Carbon atoms have four valence electrons which are highly flexible with many other atoms and elements.

Organic Components

• Cells contain four major families of small organic molecules:
  • Saccharides (sugars)
  • Fatty acids
  • Amino acids
  • Nucleotides

Carbohydrates

• Carbohydrates are composed of carbon, hydrogen, and oxygen.
• Carbohydrates include:
  • Monosaccharides (single sugar units, e.g., glucose, fructose).
  • Disaccharides (two sugar units, e.g., sucrose, lactose, maltose).
  • Oligosaccharides (several sugar units, e.g., raffinose).
  • Polysaccharides (many sugar units, e.g., cellulose, starch, glycogen).

Carbohydrate Function

• Storage and production of energy (e.g., glycogen in animals, starch in plants).
• Structure (e.g., cellulose in plant cell walls, chitin in fungal cell walls).
• Transport (e.g., glucose in animals, sucrose in plants).

Lipids (Fats)

• Lipids are esters of fatty acids and bonded to alcohols (e.g., glycerol and sphingosine).
• Lipids are insoluble in water.
• Lipids consist of various types, including simple and complex lipids.
• Examples:
  • simple lipids: fats and oils (triglycerides), and waxes
  • complex lipids: phospholipids and glycolipids
• Fatty acids contain an even number of carbon atoms (14-24) and a carboxyl group linked to a hydrocarbon chain.
• Saturated fatty acids contain only single bonds between carbon atoms.
• Unsaturated fatty acids have at least one double bond between carbon atoms.

Lipid Functions

• Structural components of biological membranes (e.g., phospholipid bilayer).
• Energy storage (e.g., subcutaneous tissue in animals, seeds in plants.
• Signaling molecules (e.g., steroid hormones, vitamins A and D).
• Protection (e.g., for organs, mechanical protection for plants).

Cell Structure: Organelles (Eukaryotic/Animal Cells)

• Cytoplasm (cytoplasmic matrix): includes cytosol and organelles.
• Cytoskeleton: includes microtubules, intermediate filaments, and actin filaments.
  • Functions include maintaining cell shape, providing mechanical support for organelles, cell movement and shape change, and facilitating muscle cell contraction.
• Nucleus: contains genetic information (DNA) and nucleolus.
• Endoplasmic reticulum: a network of membranes.
  • Rough ER has ribosomes attached and is involved in protein synthesis.
  • Smooth ER lacks ribosomes and is involved in lipid synthesis, detoxification, and transport of substances throughout the cell.
• Mitochondria: responsible for cellular respiration and energy production.
  • Structure includes outer and inner membranes, intermembrane space, matrix, cristae, mtDNA and ribosomes.
• Golgi apparatus: modifies proteins and other molecules, sorts them, transports them to other cellular destinations.
• Lysosomes: contain digestive enzymes involved in intracellular digestion and breakdown of cellular waste materials.
  • Types include: Primary, secondary, heterolysosomes (endosomes), autolysosomes.
• Peroxisomes: contain enzymes involved in specific metabolic reactions, such as oxidation of fatty acids, amino acids, and detoxification
• Centrosome: a structure that helps to organize microtubules in the cell, especially during cell division.

Cell Structure: Organelles (Plant Cells)

• Similar to animal cells except for additional features:
  • Cell wall: rigid outer covering around the plasma membrane made of cellulose (plants) and chitin (fungi). Functions include maintaining shape and providing protection.
  • Vacuole(s): large fluid-filled sacs within the cytoplasm. Functions include maintaining turgor pressure (internal water pressure), storing reserves, and gathering/storage/excretion of metabolic byproducts.
  • Plastids: double membrane-bound organelles; often involved with storage, photosynthesis, pigment synthesis (e.g. chloroplasts, chromoplasts, leucoplasts, amyloplasts, elaioplasts, proteinoplasts).

Cell Metabolism

• Metabolism broadly refers to all chemical reactions happening in a cell.

Anabolism

• Anabolism is the synthesis of complex molecules from smaller ones.
• Uses energy (requires energy input).

Catabolism

• Catabolism breaks down complex molecules into simpler ones.
• Releases energy.