Cell Structure and Function Practice Flashcards

Flashcards covering cell biology concepts including structure, organelles, membrane transport, metabolic pathways (photosynthesis and respiration), and enzyme kinetics.

Cell

The fundamental structural, functional, and biological unit of all living organisms.

Cell membrane (plasma membrane)

A selectively permeable boundary that separates the interior of the cell from the outside environment and regulates the movement of substances into and out of the cell.

Cytoplasm

The internal fluid of a cell in which cellular components are suspended; in eukaryotes, it consists of the cytosol and organelles.

Cytosol

A gel-like substance made up of more than 80% water, containing ions, salts, and organic molecules.

Prokaryote

A microscopic, single-celled organism belonging to the domains Bacteria or Archaea that lacks a membrane-bound nucleus and specialized membrane-bound organelles.

Eukaryote

An organism consisting of one or more cells that contain a distinct, membrane-bound nucleus and specialized organelles.

Genophore

A single, circular chromosome containing the DNA in prokaryotic cells.

Nucleoid

An irregularly shaped region of the cytoplasm in prokaryotes that contains the cell’s genetic material and is not enclosed by a nuclear membrane.

Capsule

An outer protective layer found outside the cell wall in many bacteria that protects against damage, dehydration, and engulfment while assisting in adhesion.

Flagellum

A tail-like structure that enables movement in some cells, often in response to stimuli.

Plasmid

A small ring of double-stranded DNA found in many prokaryotic cells that carries extra genes, such as those for antibiotic resistance.

Mesosome

An infolding of the prokaryotic cell membrane, historically thought to aid respiration but now considered an artefact of cell preparation.

Cell wall

A rigid outer layer surrounding the cell membrane that provides structural support and protection; in plants, it is mainly composed of cellulose.

Pili

Small hair-like projections on the surface of many prokaryotic cells that assist in movement and DNA transfer.

Peptidoglycan

A polymer used to build bacterial cell walls.

Gram-positive Bacteria

Bacteria with a thick layer of peptidoglycan that dehydrates and absorbs crystal violet stain, resulting in a purple result.

Gram-negative Bacteria

Bacteria with an outer lipid membrane that dissolves during staining, failing to absorb the purple dye and resulting in a pink result.

Methanogenesis

A unique metabolic process that only Archaea are able to undergo.

Chloroplast

A double-membraned organelle containing chlorophyll and DNA, responsible for photosynthesis using light energy, $CO_2$, and $H_2O$ to produce glucose.

Thylakoids

Disc-shaped sacs forming compartments within the chloroplast where light-dependent reactions occur.

Grana

Stacks of thylakoids that increase the surface area for light absorption in the chloroplast.

Stroma

The fluid-filled space surrounding the grana in a chloroplast, containing enzymes for the light-independent Calvin cycle.

Tonoplast

The membrane surrounding the single, large, permanent vacuole found in plant cells.

Golgi apparatus

A stack of unconnected, flattened membrane sacs (cisternae) that modifies, sorts, and packages proteins and lipids.

Rough Endoplasmic Reticulum

A network of membranous sacs with ribosomes attached, primarily involved in processing and modifying proteins.

Smooth Endoplasmic Reticulum

A network involved in the synthesis of non-protein molecules such as lipids, phospholipids, and steroids.

Lysosome

A membrane-bound vesicle containing digestive enzymes to break down cellular waste and foreign matter.

Nucleolus

A structure inside the nucleus composed of proteins, DNA, and RNA where ribosomes are assembled.

Centrioles

Cytoplasmic structures consisting of microtubules involved in cell division and the formation of flagella and cilia.

Cytoskeleton

A network of microtubules, actin, and intermediate filaments that provides structural scaffolding and enables transport.

Mitochondrion

A double-membraned organelle that produces ATP through aerobic respiration and contains its own DNA.

Fluid Mosaic Model

A model of the cell membrane representing the arrangement of hydrophilic heads facing outwards and hydrophobic tails facing inwards.

Carrier Proteins

Proteins that bind to specific substances and change shape to move them across the membrane, used in both facilitated diffusion and active transport.

Channel Proteins

Membrane proteins that form continuous, hydrophilic pores allowing specific ions to pass through rapidly.

Aquaporins

Tiny channel proteins that facilitate the movement of water across the cell membrane.

Glycoprotein

Recognition proteins protruding from the cell membrane that act as ID tags for the immune system.

Peripheral proteins

Molecules that temporarily attach to the membrane surface, acting as communicators and structural supports.

Adhesion proteins

Proteins on the cell surface that allow cells to stick to each other and their environment to form tissues.

Diffusion

The net movement of molecules from high concentration to low concentration until equilibrium is reached.

Osmosis

The net movement of solvent molecules (water) from a region of high solvent concentration to low solvent concentration through a semipermeable membrane.

Osmotic pressure

The pressure created by water moving across a semipermeable membrane due to osmosis.

Isotonic

A state where the fluids inside and outside a cell have equal solute concentrations, resulting in no net water movement.

Hypotonic

An external solution with a lower solute concentration than the cytoplasm, causing water to move into the cell.

Hypertonic

An external solution with a higher solute concentration than the cytoplasm, causing water to move out of the cell.

Active transport

The movement of molecules from low to high concentration, requiring energy input ($ATP$) and carrier proteins.

Endocytosis

The process by which the cell membrane surrounds and engulfs large particles to bring them into the cell.

Phagocytosis

A type of endocytosis involving the engulfing of solid particles; also known as 'cell eating'.

Pinocytosis

A type of endocytosis involving the engulfing of fluid; also known as 'cell drinking'.

Exocytosis

A process where vesicles fuse with the cell membrane to release their contents, such as waste or proteins, out of the cell.

Autotrophs

Producers that synthesize their own organic molecules from inorganic sources like $CO_2$ and $H_2O$.

Heterotrophs

Consumers that cannot make their own food and must obtain nutrients by consuming other organisms.

Calvin Cycle

The light-independent stage of photosynthesis where carbon dioxide is fixed into organic molecules using energy from $ATP$ and $NADPH$.

RuBisCO

The enzyme responsible for fixing carbon dioxide into an organic molecule during the Calvin cycle.

CAM photosynthesis

An adaptation to hot/dry environments where plants open stomata at night to absorb $CO_2$, storing it to use during the day while stomata remain closed.

Cellular respiration

The process of breaking down glucose to transfer stored chemical energy into $ATP$.

Glycolysis

The first stage of respiration occurring in the cytosol where glucose is split into two pyruvate molecules, producing a net gain of $2$ $ATP$.

Electron Transport Chain

A series of protein complexes that creates a proton gradient to power the production of $32$ $ATP$ through chemiosmosis.

Adenosine Triphosphate (ATP)

The primary energy currency of all living cells used to power cellular processes.

NADH

A high-energy coenzyme that shuttles electrons and hydrogen ions to the electron transport chain.

Alcohol Fermentation

Anaerobic respiration in plants and microorganisms producing ethanol, $CO_2$, and $2$ $ATP$.

Lactic Acid Fermentation

Anaerobic respiration in animals producing lactic acid and $2$ $ATP$, used during strenuous exercise.

Enzymes

Protein molecules that act as biological catalysts, increasing the rate of reactions by lowering activation energy.

Activation energy

The minimum amount of energy required to start a chemical reaction.

Active Site

The specific region on the surface of an enzyme where the substrate binds.

Induced Fit Model

A model where the binding of a substrate induces the enzyme to alter its shape slightly for a tighter, more efficient fit.

Anabolic Reaction

A metabolic process that uses energy to build complex molecules from simpler ones.

Catabolic Reaction

A metabolic process that breaks down complex molecules into simpler ones to release energy.

Denaturation

The process where a protein loses its 3D shape and function due to extreme temperature or pH, preventing substrate binding.

Saturation point

The point at which all available enzymes are busy catalyzing reactions, and increasing substrate concentration no longer increases the reaction rate.

Coenzymes

Non-protein organic cofactors, such as vitamins, $ATP$, $NADH$, and $NADPH$, that assist enzyme function.

Competitive Inhibition

When an inhibitor molecule with a similar shape to the substrate binds to the active site, physically blocking the substrate.

Non-competitive Inhibition

When an inhibitor binds to an allosteric site away from the active site, changing the enzyme's shape and altering active site function.

Feedback Inhibition

A regulatory process where the final product of a pathway inhibits an enzyme involved earlier in that pathway to prevent overproduction.