Animal Cell Structure and Physiology

Flashcards on Animal Cell Structure and Physiology

Animal Cell

A eukaryotic cell externally limited by a plasma membrane containing membrane-bound nucleus and organelles, known as the basic, living, functional unit of life.

Cytology

The scientific study of cells; also known as Cell biology.

Organelle

Minuscule, specialized structures within a cell that carry out specific functions essential for the cell's survival and optimal operation.

Endosymbiotic Theory

A hypothesis suggesting a large archaeal-like prokaryotic cell engulfed a smaller aerobic bacterium, forming a symbiotic relationship, leading to the rise of eukaryotic cells.

Robert Hooke

English physicist who coined the term “cell” after observing dead plant cells in 1665.

Anton van Leeuwenhoek

Dutch microbiologist and the Father of Microbiology who observed living cells using single-lens microscopes in 1674.

Robert Brown

Scottish botanist who discovered and identified the nucleus in plant cells in 1831.

Matthias Jakob Schleiden

German botanist and co-founder of the cell theory, who defined the cell as the basic unit of plant structure in 1838.

Theodor Schwann

German physiologist and co-founder of the cell theory, who defined the cell as the basic unit of animal structure.

Rudolf Virchow

German pathologist and physician who stated omnis cellula e cellula (all cells arise from pre-existing cells), refuting spontaneous generation.

Nucleus

A prominent organelle that serves as the control center of the cell, containing the majority of the cell's DNA and where DNA transcription into RNA occurs.

Nuclear Membrane

A double-layered barrier made up of lipid bilayers that separates the contents of the nucleus from the cytoplasm.

Nucleopore

Regulate the dynamic process of protein and nucleic acid transport into and out of the nucleus.

Nucleoplasm

A highly viscous gel-like substance within the nucleus where the chromatin and nucleolus are suspended.

Nucleolus

Contains RNA and protein; Preassembly point for ribosomes.

Genes

Hereditary units which regulate the majority of cellular structure and function.

Chromosome

A long single molecule of DNA coiled together with several proteins.

Chromatin

A complex of DNA, proteins, and a few RNA within the nucleus.

Plasma Membrane

A flexible, semi-permeable membrane composed of a phospholipid bilayer that serves as a selective barrier, separating the cell’s internal environment from its external surroundings.

Fluid Mosaic Model

A molecular arrangement where the plasma membrane resembles a continually moving sea of fluid lipids that contains a mosaic of many different proteins.

Glycoprotein

Proteins with carbohydrate groups covalently attached, typically on the extracellular surface of the plasma membrane.

Glycocalyx

A sugar-rich, extracellular coat; Molecular “signature” enabling cell-to-cell recognition.

Microvilli

Nonmotile, microscopic projections of the plasma membrane that increase surface area to enhance absorption.

Cytoplasm

The cellular material outside the nucleus and inside the plasma membrane, consisting of all the cellular contents.

Cytosol

A semitransparent, aqueous fluid that suspends organelles and contains dissolved nutrients, ions, and various solutes within the cytoplasm.

Inclusions

Chemical substances that vary by cell type, typically serving as stored nutrients or cell products, such as lipid droplets, glycogen granules, pigments, secretory materials, and crystals.

Mitochondria

A double membrane-bound organelle responsible for converting glucose into ATP through aerobic respiration.

Mitochondrial Cristae

Shelf-like folds of the inner mitochondrial membrane that increase surface area to enhance the efficiency of aerobic respiration.

Mitochondrial Matrix

The central, fluid-filled compartment enclosed by the inner mitochondrial membrane, containing enzymes, mitochondrial DNA, and substrates essential for cellular respiration.

Ribosomes

Small, bilobed structures composed of two subunits made of ribosomal RNA and proteins; Function as the site of protein synthesis.

Endoplasmic Reticulum

A membranous network of flattened sacs or tubules, forming a system of fluid-filled canals that coil and twist through the cytoplasm.

Rough ER

A membrane-bound organelle studded with ribosomes, responsible for the synthesis, folding, and post-translational modification of proteins.

Smooth ER

Responsible for the synthesis of lipids and steroid hormones, the breakdown of cholesterol and fats, and the detoxification of organic molecules.

Golgi Apparatus

A stack of disk-shaped membranes that modifies, stores, packages, and transports protein and lipid molecules.

Cisternae

A series of 3-20 small, flattened, sac-like structures within the Golgi apparatus that contain specific enzymes for protein modification.

Golgi Vesicles

Membranous sacs that contain proteins processed and packaged by the Golgi apparatus.

Secretory Vesicle

Specialized Golgi vesicles that transport proteins to the plasma membrane for release into the extracellular fluid via exocytosis.

Lysosomes

Membrane-bound vesicles containing up to 60 distinct digestive and hydrolytic enzymes.

Peroxisomes

Membranous sacs containing powerful oxidases, enzymes that use molecular oxygen to carry out oxidative reactions.

Cytoskeleton

An elaborate network of protein structures that extends throughout the cytoplasm, providing an internal framework that determines cell shape, supports other organelles, and provides the machinery for intracellular transport and various types of cellular movements.

Microfilaments

The thinnest cytoskeletal elements, composed of actin and myosin, concentrated at the cell periphery to support movement and maintain mechanical stability.

Intermediate Filaments

Composed of fibrous proteins, thicker than microfilaments but thinner than microtubules, providing mechanical support and stabilizing the positions of organelles.

Microtubules

Composed of hollow tubes made from tubulin subunits, originating from the centrosome and extending toward the cell periphery, playing a key role in determining cell shape, organizing organelles, and facilitating movement.

Centrioles

Cylindrical bodies lying close to the nucleus at right angles to each other, consisting of a pinwheel array of nine triplets of fine microtubules; primarily known for their role in generating microtubules and directing the formation of the mitotic spindle during cell division.

Centrosome

Collective term for pair of centrioles.

Cilia

Numerous, short, hairlike projections extending from the cell surface involved in moving substances along the cell surface.

Flagella

Typically longer than cilia, responsible for the locomotion of an entire cell.

Membrane Proteins

Proteins that are found attached to or embedded in the membrane of cells or organelles.

Integral Protein

Extend into or through the phospholipid bilayer and are firmly embedded in it.

Peripheral Protein

Noncovalently associated with membrane components and are located on either the inner or outer surface of the membrane, rather than being firmly embedded within it.

Channels

Facilitate simple or quasi-simple diffusion of solutes in aqueous solution, as well as osmosis of water across membrane.

Transporters

Selectively facilitate the movement of specific polar molecules or ions by binding to them noncovalently and reversibly, enabling their intact passage across the membrane.

Receptors

Function as cellular recognition sites, each specifically recognizing and binding noncovalently to a particular signaling molecule (Ligand), thereby triggering cellular responses.

Enzymes

Catalyze specific chemical reactions at either the internal or external surface of the cell membrane, facilitating the formation or breaking of covalent bonds.

Linkers

Anchor membrane proteins to the cytoskeleton within the cell, to the extracellular matrix, or to proteins in the plasma membranes of neighboring cells.

Cell-identity markers

Enable a cell to recognize other cells of the same type during tissue formation or recognize and respond to potentially dangerous foreign cells.

Solvent

Substance present in the greatest amount and serves as the medium in which other substances are dissolved.

Solute

Substance present in a smaller amount and is dissolved in the solvent.

Intracellular Fluid (ICF)

The fluid contained within cells.

Extracellular fluid (ECF)

The fluid found outside cells

Interstitial Fluid

The portion of ECF that surrounds and bathes tissue cells.

Passive Transport

Substance moves down its concentration or electrical gradient to cross the membrane using only its own kinetic energy.

Active transport

Cellular energy is used to drive the substance “uphill” against its concentration gradient.

Diffusion

The process by which molecules and ions move away from regions of higher concentration to regions of lower concentration, following their concentration gradient.

Simple Diffusion

A passive process in which substances move freely across the lipid bilayer of the plasma membrane without the assistance of membrane transport proteins.

Facilitated Diffusion

A passive process that enables polar or highly charged solutes to cross the plasma membrane with the assistance of integral membrane proteins.

Channel-mediated FD

Solutes move down their concentration gradient across the lipid bilayer through integral membrane protein channels.

Carrier-mediated FD

Solutes move down their concentration gradient across the plasma membrane via specific carrier proteins.

Osmosis

The net movement of a solvent across a selectively permeable membrane from an area of lower solute concentration to higher solute concentration.

Hydrostatic Pressure

The pressure exerted by the accumulating fluid against the membrane, opposing further water entry as the pressure increases.

Osmotic Pressure

The pressure exerted by non-permeable solute particles, drawing water toward the area of higher solute concentration; it is directly proportional to solute concentration.

Tonicity

Refers to a solution’s ability to alter cell volume by affecting water movement across the plasma membrane.

Isotonic Solution

The solute concentration is equal inside and outside the cell; no net water movement occurs.

Hypotonic Solution

The solute concentration is lower outside the cell, causing water to enter the cell, which may lead to lysis.

Hypertonic Solution

The solute concentration is higher outside the cell, drawing water out and resulting in crenation.

Primary Active Transport

Directly uses cellular energy, typically in the form of ATP, to transport molecules.

Secondary Active Transport

Utilizes energy stored in ionic concentration gradients

Symporters

Two substances move in the same direction

Antiporters

Move in opposite directions

Vesicular Transport

Involves ATP to facilitate the movement of substances into or out of the cell in bulk via small, membrane-bound sacs called vesicles.

Exocytosis

An active process by which cells secrete substances such as hormones, mucus, or waste products.

Endocytosis

An ATP-dependent process in which the cell engulfs extracellular substances by enclosing them within a vesicle that forms from the plasma membrane.

Phagocytosis

The cell engulfs large solid particles, such as worn-out cells, whole bacteria, or viruses.

Pinocytosis

The cell engulfs small volumes of extracellular fluid containing dissolved substances such as proteins or fats.

Receptor-mediated Endocytosis

A highly selective form of endocytosis in which receptor proteins on the cell surface bind to specific target molecules (ligands) and facilitate their internalization into the cell.

Transcytosis

A two-part vesicular transport process in which substances are internalized through endocytosis on one side of the cell, transported across the cytoplasm in vesicles, and then secreted via exocytosis on the opposite side.

Cell Junction

Specialized structures that serve as contact points between the plasma membranes of adjacent tissue cells.

Tight Junctions

Impermeable junctions that encircle the epithelial cells and bind them together into leakproof sheets.

Adherens Junctions

Contain plaque, a dense layer of proteins located on the inner surface of the plasma membrane, that attaches both to membrane proteins and to microfilaments of the cytoskeleton.

Desmosomes

Contain plaque that anchors to intermediate filaments—primarily composed of keratin—which extend across the cytosol to connect desmosomes on opposite sides of the cell, forming a strong internal network of protein filaments.

Hemidesmosomes

Resemble desmosomes in structure but differ in function, as they do not link adjacent cells but instead anchor cells to the basement membrane.

Gap Junctions

Specialized intercellular connections that facilitate direct communication between adjacent cells facilitated by connexons

Cellular Respiration

A catabolic metabolic pathway that converts biochemical energy from nutrients—mainly glucose—into ATP (Adenosine triphosphate), the main energy currency of the cell.

Aerobic Respiration

A metabolic process that utilizes oxygen to convert glucose and other nutrients into energy, primarily in the form of ATP, while producing carbon dioxide and water as byproducts.

Glycolysis

The sequence of 10-enzyme catalyzed reactions that converts glucose into pyruvate with simultaneous production of ATP.

Energy Investing Phase (Glycolysis)

Two ATP molecules invested energy to phosphorylate glucose molecules forming a six- carbon sugar diphosphate (Fructose-1,6-biphosphate). This molecule is then cleaved into two three-carbon sugars, glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP).

Energy Harvesting Phase (Glycolysis)

ATP and high-energy electrons are extracted from glucose intermediates, with hydrogen atoms transferred to NAD+ forming NADH. 4 ATP molecules are formed via substrate-level phosphorylation, with a net gain of 2 ATP per glucose molecule.

Lactate Fermentation

Also referred to as Lactic acid fermentation, is an anaerobic process that enables cells to regenerate NAD⁺ allowing glycolysis to proceed in the absence of oxygen.

Citric Acid Cycle (Krebs Cycle)

A series of reactions catalyzed by eight enzymes occuring in the matric of Mitochondrion

Preparatory Stage (Citric Acid Cycle)

Each pyruvate, derived from Glycolysis,undergoes oxidative decarboxylation, resulting in the formation of acetyl-CoA. This process releases one molecule of CO₂ and produces one molecule of NADH per pyruvate.