Cell Structure and Microscopy Vocabulary

Vocabulary flashcards covering microscope techniques, cell structures, organelles, prokaryotic and eukaryotic distinctions, and viruses from CIE A Level Biology notes.

Magnification

How many times bigger the image of an observed specimen is in comparison to the actual real-life size of the specimen.

Resolution

The ability to distinguish between two separate points; if two points cannot be resolved, they are observed as a single point.

Eyepiece Graticule

A scale-less disc placed in the microscope eyepiece with 100 divisions, which must be calibrated against a stage micrometer to measure specimens.

Stage Micrometer

A microscope slide with an accurate scale in micrometres (typically in $10\,\mu\text{m}$ divisions) used to calibrate an eyepiece graticule.

Cell Surface Membrane

A partially permeable membrane surrounding all cells, formed from a phospholipid bilayer about $10\,\text{nm}$ thick, that controls material exchange between the internal and external cell environment.

Cell Wall

A freely permeable structural layer formed outside the cell membrane, composed of cellulose in plants and peptidoglycan in most bacterial cells.

Plasmodesmata

Narrow threads of cytoplasm surrounded by cell membrane that pass through plant cell walls to connect adjacent plant cells.

Nucleus

A large organelle in eukaryotic cells enclosed by a porous double membrane (nuclear envelope) that contains chromatin (DNA and histone proteins).

Nucleolus

A darkly stained region within the nucleus that serves as the site of ribosome production.

Nuclear Pores

Channels in the nuclear envelope allowing mRNA and ribosomes to exit the nucleus, and allowing enzymes and signaling molecules to enter.

Mitochondria

Double-membrane-bound eukaryotic organelles that serve as the site of aerobic respiration and ATP synthesis, containing cristae, matrix, circular DNA, and ribosomes.

Cristae

Folds of the inner mitochondrial membrane containing embedded protein complexes vital for the later stages of aerobic respiration.

Matrix

The internal fluid region of a mitochondrion formed by the cristae, containing enzymes for aerobic respiration, mitochondrial DNA, and ribosomes.

Chloroplast

A double-membrane-bound plant organelle containing chlorophyll, grana, thylakoids, and stroma, serving as the site of photosynthesis.

Thylakoids

Membrane-bound compartments within chloroplasts containing chlorophyll, which stack together to form grana.

Grana

Stacks of thylakoids inside chloroplasts connected to one another by thin, flat thylakoid membranes called lamellae.

Stroma

The fluid matrix within chloroplasts surrounding the grana, where the light-independent stage (Calvin Cycle) of photosynthesis takes place.

Ribosome

A cellular structure composed of rRNA and proteins that serves as the site of translation; exists as $80\text{S}$ in eukaryotic cytoplasm and $70\text{S}$ in prokaryotes, mitochondria, and chloroplasts.

Rough Endoplasmic Reticulum (RER)

A network of continuous membrane folds studded with ribosomes and continuous with the nuclear envelope, responsible for processing proteins made by ribosomes.

Smooth Endoplasmic Reticulum (SER)

A network of membrane folds lacking ribosomes that is involved in the production, processing, and storage of lipids, carbohydrates, and steroids.

Golgi Apparatus

Flattened sacs of membrane that modify proteins and package them into vesicles or lysosomes.

Lysosome

A specialized vesicle containing hydrolytic enzymes used to break down waste materials, worn-out organelles, and pathogens, as well as function in apoptosis.

Tonoplast

The selectively permeable membrane surrounding the large permanent vacuole in plant cells.

Centriole

Hollow fibers made of microtubules; two centrioles positioned at right angles form a centrosome that organizes spindle fibers during cell division.

Microtubules

Cytoskeletal cylinders about $25\,\text{nm}$ in diameter formed from 13 protofilaments of $\alpha$ and $\beta$ tubulin dimers, providing cell support and internal transport.

Microvilli

Cell membrane projections that increase the surface area of a cell for absorption.

Cilia

Hair-like projections made from microtubules that move substances across the cell surface.

Flagella

Long microtubule structures similar to cilia that contract to provide locomotion for cells such as sperm cells.

Adenosine Triphosphate (ATP)

A nucleotide produced during respiration that acts as the universal energy currency to transfer energy across all cellular processes.

Prokaryote

An organism lacking a membrane-bound nucleus and membrane-bound organelles, possessing circular DNA and $70\text{S}$ ribosomes.

Capsid

The protective protein coat surrounding the nucleic acid genome of a virus.

Virus

A non-cellular, parasitic infectious particle between $20\,\text{nm}$ and $300\,\text{nm}$ in diameter, consisting of nucleic acid inside a protein capsid, replicating only inside host cells.