Cells: The Fundamental Units of Life

Flashcards covering vocabulary related to cell structure, types, organelles, and functions based on the lecture notes.

Cell

The smallest unit that can carry out all activities associated with life.

Cell Theory

A scientific theory proposed in the 1850s stating that all living organisms are made up of cells, the cell is the basic unit of structure and organization, and cells arise from pre-existing cells.

Plasma membrane

A selective barrier that encloses cells and controls the entry and exit of substances.

Cytoplasm

Consists of organelles and cytosol (the fluid component) within a cell.

Organelles

Internal cellular structures that are specialized to carry out certain cellular activities, usually membrane-bound.

Prokaryotic Cells

Small cells (Bacteria and Archaea) that are approximately 1/10 the size of eukaryotes and lack membrane-enclosed internal organelles.

Nucleoid

The region in a prokaryotic cell where the DNA is located, not enclosed by a membrane.

Cell wall (prokaryotic)

A tough, fibrous protective layer outside the plasma membrane in most prokaryotes, composed of peptidoglycan, which gives the cell its shape.

Peptidoglycan

A component of prokaryotic cell walls, consisting of long chains of amino sugars connected by peptide bridges.

Gram-positive bacteria

Bacteria that absorb and retain crystal violet stain due to a thick peptidoglycan layer in their cell wall.

Gram-negative bacteria

Bacteria that do not absorb and retain crystal violet stain due to a thin peptidoglycan layer and an outer membrane.

Capsule

A polysaccharide layer that surrounds the cell wall of some prokaryotes, helping cells adhere and protecting them from immune cells.

Fimbriae

Numerous hairlike projections on prokaryotic cells, usually used for adherence to surfaces.

Pilus

Longer, less numerous projections than fimbriae, involved in adherence and, as the F pilus/sex pilus, in DNA transfer.

Flagellum 

Motility structures in prokaryotes that project outward from the cell and spin like a propeller.

Bacterial Flagellum

A motility structure with three parts: basal body (motor), hook, and filament, which spins to allow movement (chemotaxis).

Ribosome (prokaryotes)

Complexes of RNA and protein in prokaryotes, smaller than eukaryotic ribosomes, that are the site of protein synthesis.

Inclusion/Storage Granule

An area within a prokaryotic cell where nutrients like glycogen, lipids, or phosphate are stored.

Eukaryotic Cell

Cells that are larger than prokaryotic cells and are divided into compartments by multiple membrane-enclosed organelles.

Compartmentalization

The division of eukaryotic cells into compartments, localizing substrates to increase reaction efficiency and allowing multiple reactions simultaneously.

Nucleus

A membrane-bound organelle in eukaryotic cells that contains most of the cell's DNA (chromatin, packaged into chromosomes) and is the site of DNA and RNA synthesis.

Chromatin

DNA complexed with protein within the nucleus of eukaryotic cells.

Chromosome

A tightly packaged structure of chromatin found in the nucleus.

Nuclear envelope

The double membrane surrounding the nucleus, consisting of an inner membrane (with binding sites for chromosomes and nuclear lamina) and an outer membrane (continuous with the ER).

Nuclear lamina

A meshwork of protein filaments that lines the inner nuclear membrane and provides structural support.

Nuclear pores

Large protein complexes within the nuclear envelope that control the entry and exit of molecules to/from the nucleus.

Nuclear Localization Signal

A specific sequence required for large macromolecules to enter the nucleus through nuclear pores.

Importins

Proteins that bind to cargo containing a Nuclear Localization Signal (NLS) to facilitate nuclear import.

Nucleolus

A compact, non-membrane-enclosed structure within the nucleus that is the site of ribosomal RNA synthesis and assembly of ribosomes.

Ribosome

Particles composed of proteins and rRNA found in eukaryotic cells, which are the site of protein synthesis and may be free in the cytoplasm or attached to the ER.

Endoplasmic Reticulum

A network of interconnected membranes surrounding the nucleus and extending into the cytoplasm, involved in protein and lipid synthesis.

Lumen

The space or cavity between the membranes of the endoplasmic reticulum.

Smooth Endoplasmic Reticulum

The tubular portion of the ER that appears smooth, involved in the synthesis of lipids, carbohydrates, and steroid hormones, and detoxification.

Rough Endoplasmic Reticulum

The portion of the ER studded with ribosomes, involved in the assembly and modification of proteins (e.g., disulfide bonds, glycosylation).

Molecular chaperones

Proteins that aid in the proper folding of other proteins, particularly in the ER.

Golgi Apparatus

An organelle consisting of flattened membrane-bound sacs called cisternae, involved in further modification, sorting, and packaging of proteins and lipids.

Cis face

The entry surface of the Golgi apparatus, which receives vesicles from the ER.

Trans face

The exit surface of the Golgi apparatus, which sorts and transports molecules to other organelles or the plasma membrane.

Endomembrane System

A network of organelles including the ER, Golgi apparatus, lysosomes, vacuoles, and the plasma membrane, all involved in vesicular transport.

Coated pits

Regions of a membrane where receptors bind specific cargo and cluster, initiating the formation of coated vesicles for transport.

Coated vesicles

Vesicles formed from coated pits, which are enveloped by a protein coat that helps shape the membrane and capture specific cargo molecules.

Adaptins

Proteins that secure the coat to the vesicle membrane and help select cargo molecules for vesicular transport.

Dynamin

A GTP-binding protein that assembles around the neck of a budding vesicle and pinches it off from the membrane.

Rab proteins

Proteins on vesicles that interact with tethering proteins on organelle membranes, facilitating vesicle docking.

Tethering proteins

Proteins on organelle membranes that interact with Rab proteins on vesicles, promoting vesicle docking.

Snares

Proteins involved in the specific recognition and fusion of vesicles with target membranes during vesicular transport.

Lysosomes

Small membrane sacs containing hydrolytic enzymes (acid hydrolases), found only in animal cells, which digest food and break down malfunctioning cell structures.

Acid hydrolases

Hydrolytic enzymes found within lysosomes that function optimally in acidic conditions to digest cellular waste and foreign materials.

Primary lysosomes

Lysosomes that are formed by budding directly from the Golgi apparatus.

Secondary lysosomes

Lysosomes formed by the fusion of a primary lysosome with an endosome or phagosome containing material to be digested.

Autophagy

A cellular process by which damaged organelles or cellular components are enclosed by a double membrane and subsequently fused with a lysosome for degradation.

Vacuole

A large membrane-bound sac found in plants, fungi, and protozoa, involved in digesting nutrients, storing salts/pigments/wastes, and creating turgor pressure.

Turgor pressure

Pressure created by water accumulating in the central vacuole of plant cells, pushing on the cell wall to provide structural strength.

Peroxisome

A membranous sac, formed by budding from the smooth ER, involved in the oxidation of fatty acids, synthesis of some phospholipids, and detoxification.

Hydrogen peroxide 

A toxic byproduct of oxidation reactions in peroxisomes, which is broken down by catalase.

Catalase

An enzyme present in peroxisomes that breaks down hydrogen peroxide into water and oxygen, neutralizing its toxicity.

Mitochondria

Double-membrane organelles in eukaryotic cells that are the primary site of oxidative phosphorylation and ATP generation.

Chloroplasts

Disc-shaped, double-membrane organelles found in plant and algal cells, which are the site of photosynthesis.

Inner Membrane

The inner of the two mitochondrial membranes, which is folded into cristae to increase surface area and contains protein complexes of the electron transport chain.

Outer Membrane

The smooth outer membrane of the mitochondria, which allows most small molecules to pass freely.

Cristae

The folds of the inner mitochondrial membrane that increase its surface area, where the electron transport chain resides.

Intermembrane space 

The fluid-filled space located between the outer and inner membranes of the mitochondria.

Matrix

The innermost compartment of the mitochondria, enclosed by the inner membrane, containing mitochondrial DNA and enzymes.

Chlorophyll

A green pigment found in chloroplasts that is responsible for trapping light energy for photosynthesis.

Stroma

The fluid-filled space within the inner membrane of a chloroplast, containing enzymes for carbohydrate production from CO2 and H2O.

Thylakoids

Flattened, disc-like sacs within the chloroplast, where the light-dependent reactions of photosynthesis occur and chlorophyll is located.

Granum

A stack of thylakoids within a chloroplast (plural: grana).

Cytoskeleton

A dense network of protein fibers (microfilaments, intermediate filaments, microtubules) that gives cells mechanical strength, shape, and the ability to move, also functioning in cell division and transport.

Cilia

Hairlike structures extending from the cell surface that beat in a whiplike fashion, involved in locomotion, food collection, and movement of substances.

Flagellum (eukaryotic)

A longer, less numerous motility structure in eukaryotic cells, similar in structure to cilia.

9 + 2 microtubule array

The core internal structure of eukaryotic cilia and flagella, consisting of nine fused pairs of microtubules in a circle and two unfused microtubules in the center.

Basal body

A structure with a 9x3 microtubule organization that anchors eukaryotic cilia and flagella in the cell.

Dynein

A motor protein responsible for the movement of cilia and flagella by causing microtubules to slide against each other.

Cell wall

A protective and structural layer surrounding the cells of fungi, algae, and plants, composed of polysaccharides (e.g., cellulose in plants, chitin in fungi).