A Tour of the Cell

Flashcards on cell biology, covering cell theory, cell functions, prokaryotic and eukaryotic cells, microscopy, cell size, cell structure, organelles, and the endomembrane system.

Cell Theory

Cells are the smallest fundamental units of life; All living organisms are composed of cells; All cells come from preexisting cells by cell division.

Cell Functions

Nutrient Acquisition and Dispersal; Waste Detoxification and Disposal; Energy Production; Structural Support; Building, Maintenance, Repair; Reproduction; Maintain homeostasis, Protection; Information Acquisition, Retrieval and Storage.

Prokaryotes

No nucleus, simple cell structure.

Eukaryotes

More complex cells, DNA enclosed within membrane-bound nucleus, internal membranes form organelles, can be single or multicellular.

Magnification

Ratio of an object’s image size to its real size.

Resolution

The measure of the clarity of the image, or the minimum distance between two distinguishable points.

Contrast

The difference in brightness between the light and dark areas of the image.

Scanning Electron Microscope (SEM)

Focuses a beam of electrons onto the surface of a specimen, producing images that look three-dimensional.

Transmission Electron Microscope (TEM)

Focuses a beam of electrons through a specimen, mainly used to study the internal structure of cells.

Surface Area to Volume Ratio

Critical to cell size; as cell size increases, surface area increases proportional to the square of the linear dimension, while volume increases proportional to the cube of the linear dimension.

Basic Features of All Cells

Plasma membrane, semifluid substance called cytosol, chromosomes, ribosomes.

Prokaryotic Cells

No nucleus, DNA in an unbound region called the nucleoid, no membrane-bound organelles.

Eukaryotic Cells

Membrane-enclosed nucleus contains DNA, other membrane-enclosed compartments or organelles in cytoplasm.

Bacteria

Small cells, 1-10 μm in diameter, abundant in environment and our bodies, some species cause disease.

Archaea

Small cells, 1-10 μm in diameter, less common, often found in extreme environments.

Typical Bacterial Cell Components

Cytoplasm, nucleoid region, ribosomes, cell wall, glycocalyx, appendages.

Plasma Membrane

The plasma membrane is a selective barrier that allows passage of oxygen, nutrients, and waste, and is a double layer of phospholipids.

Cytosol

Region of a eukaryotic cell that is outside the cell organelles but inside the plasma membrane.

Cytoplasm

Everything inside the plasma membrane - cytosol, endomembrane system, semiautonomous organelles.

Nuclear Envelope

Double membrane enclosing the nucleus; perforated by pores; continuous with ER.

Nucleolus

Located within the nucleus, site of ribosomal RNA (rRNA) synthesis.

Ribosomes

Complexes that make proteins; free in cytosol or bound to rough ER or nuclear envelope.

Endoplasmic Reticulum (ER)

Network of membranous sacs and tubes; active in membrane synthesis and other synthetic and metabolic processes; has rough (ribosome-studded) and smooth regions.

Golgi Apparatus

Organelle active in synthesis, modification, sorting, and secretion of cell products.

Lysosome

Digestive organelle where macromolecules are hydrolyzed.

Mitochondrion

Organelle where cellular respiration occurs and most ATP is generated.

Peroxisome

Organelle with various specialized metabolic functions; produces hydrogen peroxide as a by-product and then converts it to water.

Plasma Membrane

Membrane enclosing the cell.

Centrosome

Region where the cell’s microtubules are initiated; contains a pair of centrioles.

Cytoskeleton

Reinforces cell’s shape; functions in cell movement; components are made of protein (microfilaments, intermediate filaments, microtubules).

Chromatin

Material consisting of DNA and proteins; visible in a dividing cell as individual condensed chromosomes.

Flagellum

Motility structure present in some animal cells, composed of a cluster of microtubules within an extension of the plasma membrane.

Cell Wall

Outer layer that maintains cell’s shape and protects cell from mechanical damage; made of cellulose, other polysaccharides, and protein.

Central Vacuole

Prominent organelle in older plant cells; functions include storage, breakdown of waste products, and hydrolysis of macromolecules; enlargement of the vacuole is a major mechanism of plant growth.

Chloroplast

Photosynthetic organelle; converts energy of sunlight to chemical energy stored in sugar molecules.

Plasmodesmata

Cytoplasmic channels through cell walls that connect the cytoplasms of adjacent cells.

Smooth ER Functions

Synthesizes lipids, metabolizes carbohydrates, detoxifies drugs and poisons, stores calcium ions.

Rough ER Functions

Has bound ribosomes, which secrete glycoproteins; distributes transport vesicles; is a membrane factory for the cell.

Ribosomes Functions

Carries out protein synthesis in the cytosol (free ribosomes) and on the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes).

Golgi Apparatus Functions

Modifies products of the ER, manufactures certain macromolecules, sorts and packages materials into transport vesicles.

Lysosome

A membranous sac of hydrolytic enzymes that can digest macromolecules.

Autophagy

Uses enzymes to recycle the cell’s own organelles and macromolecules.

Mitochondria

The sites of cellular respiration, a metabolic process that uses oxygen to generate ATP.

Chloroplast

Contains the green pigment chlorophyll, as well as enzymes and other molecules that function in photosynthesis.

Peroxisomes

Are specialized metabolic compartments bounded by a single membrane, produce hydrogen peroxide and then convert it to water.

Cytoskeleton

A network of fibers extending throughout the cytoplasm; organizes the cell’s structures and activities.

Microtubules

Hollow rods constructed from globular protein dimers called tubulin; shape and support the cell, guide movement of organelles, and separate chromosomes during cell division.

Microfilaments

Thin solid rods, built from molecules of globular actin subunits; bear tension, resisting pulling forces within the cell.

Intermediate Filaments

Fibers with diameters in a middle range; reinforce cell shape and fix organelles in place.

Cell Wall

An extracellular structure that distinguishes plant cells from animal cells; protects the plant cell, maintains its shape, and prevents excessive uptake of water.

Extracellular Matrix (ECM)

Made up of glycoproteins such as collagen, proteoglycans, and fibronectin.

Plasmodesmata

Channels that perforate plant cell walls, through which water and small solutes can pass from cell to cell.

Main Types of Cell Junctions in Animal Cells

Tight junctions, desmosomes, gap junctions.

Vacuoles

Large vesicles derived from the endoplasmic reticulum and Golgi apparatus.