A2.2 Cell Structure

A set of vocabulary flashcards to review key concepts related to cell structure and microscopy for biology.

Cells

The basic structural units of all living organisms.

Cell theory

States that living organisms are composed of cells and that cells can only arise from pre-existing cells.

Eukaryote

Cells that contain a nucleus and membrane-bound organelles.

Prokaryote

Cells without a true nucleus and without membrane-bound organelles.

Homeostasis

The maintenance of a stable internal environment within a cell or organism.

Quantitative observation

Measurements collected using instruments.

Qualitative observation

Descriptive information observed without numerical measurement.

Eyepiece graticule

A transparent ruler used to measure specimens in a microscope eyepiece.

Magnification

The process of enlarging the appearance of an object under a microscope. M = actual size / image size

Resolution

The ability to distinguish between two close objects.

Cryogenic electron microscopy

A method that uses flash-freezing techniques to preserve samples for high-resolution imaging.

Freeze-fracture electron microscopy

A technique used to study membrane structures by freezing and fracturing the specimen.

Fluorescence microscopy

A microscopy technique that uses fluorescent dyes to label and visualize biomolecules.

Immunofluorescence microscopy

A method that uses antibodies labeled with fluorescent dyes to detect specific proteins in cells. Sample is then viewed under the microscope.

Cell differentiation

The process by which unspecialized cells develop into specialized cells with distinct functions.

Genome

The complete set of genetic information in an organism.

Proteome

The entire set of proteins expressed by a cell or organism at a given time.

Multicellularity

The state of being composed of multiple cells that can specialize for different functions.

Cell division

The process by which a parent cell divides into two or more daughter cells.

Organelles

Discrete structures within a cell that carry out specific functions.

Microtubules

Thick, hollow fibers that are part of the cytoskeleton and assist in cell shape and transport.

Multicellular organisms

Organisms composed of more than one cell, allowing for cellular specialization.

Atypical cell structure

Structures in cells that vary from the norm; often seen in specialized or unique cell types. Cells that lack a nucleus: red blood cell and phloem sieve tube elements. Cells that have multiple nuclei: aseptate fungi hyphae, skeletal muscle cell and red blood cell.

Staining

A technique used to enhance contrast in microscopic images by coloring cell structures.

Cell wall

Mechanically strong fibrous layer deposited by a cell outside its plasma membrane. Found in most plants and algae, and fungi, but not present in most animal cells. It is made of cellulose in plant cells. It is peptidoglycan in bacteria and chitin in fungi.

Centrioles

Cylindrical array of microtubules (9 triplets) usually found in pairs at the centre of a centrosome in animal cells. Also found at the base of cilia and flagella, where they are called basal bodies.

Cytoplasm

Contents of a cell that are contained within its plasma membrane (except the nucleus in eukaryotic cells).

Flagellum and cillia

Long, whip-like structure. Contain a ring of 9 double microtubules plus 2 central ones (9+2 structure). Can be used for locomotion.

Ribosomes

Large complex composed of ribosomal RNAs and ribosomal proteins. Translates messenger RNA into protein. They can be free in cytoplasm or bound to the endoplasmic reticulum. In eukaryotes, it is 80S. In prokaryotes & organelles such as mitochondria & chloroplasts, it is 70S.

Golgi apparatus

A collection of membrane-bound flattened sacs called cisternae. Contains enzymes that modify proteins and lipids made in the endoplasmic reticulum and sorts them for transport to other sites, such as packaging proteins into secretory vesicles for secretion, or into lysosomes.

Lysosomes

Membrane-enclosed organelle that breaks down worn-out organelles and other waste materials, as well as molecules taken up by endocytosis; contains digestive/hydrolytic enzymes that are typically most active at the acidic pH found inside these organelles. Formed from Golgi vesicles.

Nucleus

The membrane bound structure that contains the DNA bounded by the nuclear membrane. DNA is associated with histone proteins to form of chromatin. Site of DNA replication and transcription. Contains nucleoplasm and the nucleolus.

Plasma membrane

The protein-containing lipid bilayer that surrounds a living cell.

Smooth endoplasmic reticulum

Small membrane-enclosed organelle that contains enzymes that degrade lipids and destroy toxins.

Nuclear pores

Channels through which selected large molecules move between the nucleus and the cytoplasm.

Nucleolus

Large structure within the nucleus where ribosomal RNA is transcribed and ribosomal subunits are made.

Chloroplast

Specialized organelle in algae and plants that contains chlorophyll and serves as the site in which photosynthesis takes place. Contains the stroma, the large interior space that contains the enzymes needed to incorporate carbon dioxide into glucose during the carbon-fixation stage of photosynthesis. Also contains the thylakoids, which contains chlorophyll and is the site of light-dependent reactions of photosynthesis. May contain starch grains.

Nuclear membrane

Double membrane surrounding the nucleus. Consists of outer and inner membranes, perforated by nuclear pores. Controls the passage of substances into and out of the nucleus.

Rough endoplasmic reticulum

Consists of flattened sacs called cisternae and associated with ribosomes. Secreted and membrane-bound proteins are synthesised by the ribosomes, enter into the RER and are packaged into vesicles for transport to the Golgi apparatus.

Vesicle and vacuole

Small, membrane-enclosed, spherical sac in the cytoplasm of a eukaryotic cell. Transports material within the cell. Vacuole stores dissolved substances and water.