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Cell Structure and Function, Exams of Biology

Liberty University (LU)Biology

A comprehensive overview of the fundamental concepts and structures of cells, including the differences between prokaryotic and eukaryotic cells, the various organelles and their functions, and the key processes that occur within cells. It covers topics such as the cell theory, cell fractionation, the basic features of prokaryotes and eukaryotes, the structure and function of the nucleus, chromatin, ribosomes, the endoplasmic reticulum, the golgi apparatus, lysosomes, vacuoles, membrane-bound organelles, the cytoskeleton, and extracellular structures. The document also delves into the fluidity of membranes, membrane proteins, passive and active transport mechanisms, and the different types of endocytosis. This detailed information on cell biology would be highly valuable for students studying topics related to cell structure and function, as it provides a solid foundation for understanding the complex and intricate nature of cells, which are the basic units of life.

Typology: Exams

2024/2025

Available from 10/12/2024

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LSU Biol 1201 LiCata Exam 2 Fall 2024
Cell theory - -All organisms are made of cells
-The cell is the simplest collection of matter that can be alive
-Cells are near the middle of the biological size range
scanning electron microscope - Focus electrons onto the surface of a specimen,
providing images that look 3-D
Transmission Electron Microscopes - focus a beam of electrons through a
specimen
cell fractionation - Takes cells apart and separates the major organelles from one
another centrifuges fractionate cells into their component parts
Basic Features of all prokaryotes and Eukaryotes - -Plasma Membrane
-Semifluid substance called cytosol
-Chromosomes (carry genes)
-Ribosomes (make proteins)
Prokaryotic cells - -No nucleus
-DNA in an unbound region called the nucleoid
-No membrane bound organelles
Eukaryotic cells - -DNA in nucleus with a membrane
-Membrane-bound organelles
-Internal Membranes = the endomembrane system
-Generally much larger than prokaryotic cells
-Plant and Animal cells have most of the same organelles
Nucleus - -Contains most of the cell's genes
-nuclear envelope encloses the nucleus
-Nuclear membrane is a lipid bilayer
-Nuclear pores regulate the entry and exit of molecules
-the shape of the nucleus is maintained by the nuclear lamina, which is composed
of protein
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LSU Biol 1201 LiCata Exam 2 Fall 2024

Cell theory - - All organisms are made of cells

  • The cell is the simplest collection of matter that can be alive
  • Cells are near the middle of the biological size range scanning electron microscope - Focus electrons onto the surface of a specimen, providing images that look 3-D Transmission Electron Microscopes - focus a beam of electrons through a specimen cell fractionation - Takes cells apart and separates the major organelles from one another centrifuges fractionate cells into their component parts Basic Features of all prokaryotes and Eukaryotes - - Plasma Membrane
  • Semifluid substance called cytosol
  • Chromosomes (carry genes)
  • Ribosomes (make proteins) Prokaryotic cells - - No nucleus
  • DNA in an unbound region called the nucleoid
  • No membrane bound organelles Eukaryotic cells - - DNA in nucleus with a membrane
  • Membrane-bound organelles
  • Internal Membranes = the endomembrane system
  • Generally much larger than prokaryotic cells
  • Plant and Animal cells have most of the same organelles Nucleus - - Contains most of the cell's genes
  • nuclear envelope encloses the nucleus
  • Nuclear membrane is a lipid bilayer
  • Nuclear pores regulate the entry and exit of molecules
  • the shape of the nucleus is maintained by the nuclear lamina, which is composed of protein

Chromatin - - DNA associated with proteins in the nucleus

  • It condenses to chromosomes as a cell prepares to divide
  • Each chromosome is a single DNA molecule associated with proteins Nucleolus - Located within the nucleus and is the site of ribosomal RNA (rRNA) synthesis Ribosomes - - Particles made of ribosomal RNA and protein
  • Ribosomes carry out protein synthesis Endoplasmic Reticulum - - More than half of the total membrane in the cell
  • The ER membrane is continuous with the nuclear envelope
  • Two distinct regions of ER consisting of smooth ER (w/o ribosomes) and rough ER (w/ ribosomes) Smooth ER - - Synthesizes lipids
  • Metabolizes carbohydrates
  • Detoxifies drugs and poisons
  • Stores Calcium ions Rough ER - - Has ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates)
  • Distributes transport vesicles
  • Is a membrane factory for the cell Golgi apparatus - - Flattened membrane sacs called cisternae
  • Modifies products of the ER
  • Manufactures certain macromolecules
  • Sorts and packages materials into transport vesicles Lysosomes - - A membranous sac of enzymes that can digest macromolecules
  • Lysomal enzymes work best in the acidic environment inside the lysosome Phagocytosis - - Engulfing food particles or other cells
  • Fuse with lysosomes
  • Microfilaments
  • Intermediate filaments Microtubules - - Part of cytoskeleton
  • Thickest fibers, made of Alpha and Beta tubulin Microfilaments - - Part of cytoskeleton
  • Thinnest fibers, made of actin, also called actin filaments intermediate filaments - - Part of the cytoskeleton
  • intermediate sized, made of a variety of proteins Centrosomes and Centrioles - - In many cells microtubules grow out from a centrosome near the nucleus
  • the centrosome is a "microtubule-organising center"
  • in animal cells the centrosome has a pair of centrioles each with nine triplets of microtubules arranged in a ring cilia and flagella - - microtubules control the beating of cilia and flagella, locomotor appendages of some cells
  • cilia and flagella differ in beating patterns cilia and flagella structure - - A core of microtubules sheathed by the plasma membrane
  • A basal body that anchors it
  • A motor protein called dynein which drives the bending movements Actin and Myosin - - Microfilaments that function in cellular motility use myosin in addition to actin
  • in muscle cells thicker filaments composed of myosin interdigitate with the thinner actin fibers
  • They drive amoeboid movement via Pseudopodia (cellular extensions)
  • Cytoplasmic streaming = a circular flow of cytoplasm within cells, is also aactin- myosin driven Extracellular structures - - Cell walls of plants
  • The extracellular matrix (ECM) of animals
  • Intercellular junctions cell walls of plants - - Extracellular structure that distinguishes plant cells from animal cells
  • Prokaryotes, fungi, and some protists also have cell walls
  • Protects the plant cell, maintains shape, and prevents excessive uptake of water
  • Made of cellulose fibers along with other polysaccharides and protein Extracellular Matrix (ECM) of animal cells - - Animal cells lack cell walls but are covered by elaborate (ECM)
  • Made up of glycoproteins such as collagen, proteoglycans, and fibronectin
  • ECM proteins bind to receptor proteins in the plasma membrane called integrins
  • Functions of ECM= support, adhesion, movement, regulation cell junctions - - Neighboring cells often adhere, interact, and communicate Cell junction types - - Plasmodesmata= plants only, transport of material* between cells
  • Tight junctions= Hold cells together
  • Desmosomes- hold cells together
  • Gap Junctions= transport material between cells Materials=*(water, ions, small molecules, rarely macromolecules) fluidity of membranes - - Higher temp= more fluid
  • More unsaturated fatty acids= more fluid
  • more saturated fatty acids= less fluid
  • Ability to change lipid compositions in response to temp evolved in organisms tat live where temps vary
  • Cholestrerol= allows for quick responses to temp in cells Membrane proteins - - Proteins determine most of the membrane's functions
  • Membranes have distinct outside and inside faces mostly due to proteins
  • Peripheral proteins= are bound to the surface of the membrane
  • Integral proteins= penetrate the hydrophobic core(If they span the mebrane then they are transmembrane proteins)
  • Each type of transport protein is highly specific for one type of transported molecule Channel proteins - - have a hydrophilic channel that molecules pass through
  • Chanel proteins called aquaporins facilitate the passage of water
  • Provide corridors that allow a specific molecule or ion to cross the membrane
  • Solutes still move from high to low concentrations Carrier Proteins - - Actively "shuttle" molecules across the membrane
  • Undergo a change in shape that translocates the solute-binding site across the membrane
  • Solutes still move from high to low concentration Ion Pumps - - Use ATP energy for transport
  • Create membrane potentials= the voltage difference across a membrane (stored energy)
  • Voltage is created by differences in the distribution of positive and negative ions across a membrane facilitated diffusion - - Transport proteins speed the passive transport of molecules across the plasma membrane
  • Solutes still move from high to low concentration
  • Carrier & Channel proteins active transport - - Moves substances against their concentration gradients
  • Requires energy usually ATP
  • Performed by specific membrane proteins
  • Allows cells to maintain solute concentrations that differ from their surroundings cotransport - - When active transport of one solute indirectly drives transport of other solutes bulk transport - - requires energy
  • Exocytosis= transport vesicles fuse with membrane and release their contents
  • Endocytosis=The cell takes in macromolecules by forming vesicles from the plasma membrane

three types of endocytosis - - Phagocytosis= "Cellular eating", food particles

  • Pinocytosis= "Cellular drinking", fluid gulping
  • receptor-mediated endocytosis= specific moleucles Metabolism - - The totality of an organsim's chemical reactions
  • Follows the laws of thermodynamics Metabolic pathway - - Begins with a specific molecule and ends with a product
  • Each step is catalyzed by a specific enzyme Catobolic pathways - - Release energy by breaking down molecules
  • Catabolism is cellular respiration (breakdown of glucose) Anabolic Pathways - Consume energy to build complex molecules first law of thermodynamics - - Energy in the universe is constant (Can be transferred and transformed, but not created or destroyed)
  • Also called the law of conservation of energy
  • Allows the ability to track energy leaving and entering the system second law of thermodynamics - - The entropy of the universe is increasing
  • The entropy of a closed system is >= 0
  • Entropy is a primary driving force for all physical processes Entropy - - Delta S (+) is favorable
  • Delta S (-) is unfavorable
  • An individual reaction (system) can have +Delta S or - Delta S
  • Entropy of the universe (system + surroundings) always increases (+delta S) for spontaneous reactions Free Energy - - A living system's free energy is energy that can do work
  • Delta G is the most basic form of energy currency in the cell Delta G - - Lower Delta G is more stable
  • Negative is favorable, releases energy
  • positive is unfavorable, requires energy
  • Noncompetitive= bind away from active site and decrease activity by changing the shape of the enzyme Regulation of Enzyme Activity - - Switching on or off genes that encode specific enzymes
  • Regulating enzyme activity= Through either Allosteric regulation or Cooperativity
  • Feedback regulation
  • Enzyme localization Allosteric Regulation - - May either inhibit or stimulate an enzyme's activity
  • Has a regulatory molecule bind to a protein at one site and affect the protein's function at another site Cooperativity - - A specific form of allosteric regulation
  • One substrate molecule primes an enzyme to bind additional substrates tighter or weaker
  • One active site affects a different active site Feedback inhibiton - - The end product of a metabolic pathway regulates the pathway
  • Prevents cell from wasting chemical resources Localization of enzymes - - Keeps all the enzymes for one process in the area where that process takes place
  • Ex. enzymes for cellular respiration are only in mitochondria catabolic pathways - - Oxidative breakdown of organic molecules
  • is exergonic Aerobic respiration - - consumes organic molecules and O2 and yields ATP Fermentation - - A partial degradation of sugars that occur without O
  • Anaerobic respiration is similar to aerobic respiration but uses compounds other than O
  • Glycolysis plus reactions that rregenerate NAD+
  • Two common types are alcohol and lactic acid fermentation
  • Produces 2 ATP per glucose

Obligate anaerobes - - cannot survive in the presence of O

  • carry out fermentation or anaerobic respiration Facultative anaerobes - - Include yeast and some bacteria Pyruvate - - A fork in the metabolic road that leads to two alternate catabolic routes (either fermentation or aerobic respiration)
  • Decided based on whether O2 is present in the mitochondrion Redox Reactions - - chemical reaction that transfer electrons
  • Often H atoms move along with the electron
  • Oxidation and reduction are both redox reactions Oxidation - - A substance loses electrons, or is oxidized Reduction - - A substance gains electrons, or is reduced (the amount of positive charge is reduced) NAD+ - - Is an electron acceptor and coenzyme
  • It gains 2 electrons and a hydrogen when it is reduced (NADH)
  • NADH represents stored energy that is used to synthesize ATP Three phases of the catabolism of glucose - - Glycolysis (Glucose into 2 molecules of pyruvate)
  • Citric Acid Cycle (pyruvate to CO2)
  • Oxidative phosphorylation (accounts for most of the ATP synthesis) Products from one Glucose - CO2 + water and 32-38 molecules of ATP Glycolysis - - Accounts for less than 10% of ATP
  • Uses 2 ATP to get started
  • Forms 2 pyruvate and 2 H20 from one glucose
  • Creates 4 ATP for a net total of 2 ATP
  • Creates 2 NADH and 2 H+
  • Does not require oxygen