Cell Structure and Microscopy

A set of vocabulary flashcards covering cell structure, organelles, microscopy, prokaryotes, and viruses based on the lecture notes.

Magnification

How much bigger a sample appears to be under a microscope than it is in real life.

Resolution

The ability to distinguish between 2 separate points, where higher resolution increases image clarity and detail.

Cell surface membrane

A $7\,\text{nm}$ selectively permeable phospholipid bilayer that acts as a barrier between cytoplasm and external environment, controlling substance exchange and cell recognition.

Nucleus

A $7\,\mu\text{m}$ organelle surrounded by a double-membraned nuclear envelope continuous with the RER that controls cell activities and divides first during cell division.

Nuclear pores

Structures in the nuclear envelope that control substances entering (proteins to make ribosomes, ATP, hormones, nucleotides) and leaving (mRNA, ribosomes) the nucleus.

Nucleolus

A $2.5\,\mu\text{m}$ structure within the nucleus containing loops of DNA from several chromosomes that synthesises ribosomes.

Ribosomes

$25\,\text{nm}$ structures composed of 2 subunits that carry out protein synthesis, categorized as $80\text{S}$ in cytoplasm and $70\text{S}$ in chloroplasts, mitochondria, and prokaryotes.

Rough endoplasmic reticulum (RER)

A single-membraned extended system of fluid-filled sacs (cisternae) covered with ribosomes where proteins are synthesized, modified, and packaged into vesicles.

Golgi body

A single-membraned stack of flattened sacs (cisternae) that packages substances into vesicles, carries out glycosylation, phosphorylates proteins, folds/assembles proteins, and removes the 1st amino acid methionine.

Smooth endoplasmic reticulum (SER)

An organelle that synthesizes lipids and steroids such as cholesterol, estrogen, and testosterone.

Lysosomes

Spherical single-membraned sacs ($0.1-1\,\mu\text{m}$) containing hydrolytic enzymes for the breakdown/digestion of unwanted structures or whole cells.

Mitochondria

Organelles ($0.5-10\,\mu\text{m}$) that carry out aerobic respiration and synthesize ATP, featuring a outer membrane containing the transport protein porin.

ATP (adenosine triphosphate)

The energy-carrying molecule in all living cells that releases energy when broken down to ADP in a hydrolysis reaction.

Microtubules

Long, rigid, hollow tubes made of $\alpha$ and $\beta$ tubulin dimers arranged into 13 protofilaments in a ring to support and shape the cell.

Microtubule organizing centers (MTOCs)

Special locations in cells that control the assembly of microtubules from tubulin molecules.

Centrioles

Hollow cylinders about $500\,\text{nm}$ long located close together at right angles in animal cell centrosomes that produce spindle fibers and organize microtubules.

Chloroplasts

Plant organelles ($3-10\,\mu\text{m}$) that carry out photosynthesis, contain starch grains, circular DNA, and $70\text{S}$ ribosomes, and produce ATP.

Cell wall

A rigid, freely permeable structure made of cellulose that gives plant cells a definite shape and prevents them from bursting.

Plasmodesmata

Fine strands of cytoplasm passing through pores in plant cell walls that link neighboring cells for transport and signaling.

Symplastic pathway

The movement of water, sucrose, amino acids, and ions between neighboring plant cells via plasmodesmata without crossing membranes.

Tonoplast

A partially permeable membrane surrounding plant cell vacuoles that regulates exchange between the vacuole and cytoplasm.

Prokaryotes

Unicellular organisms ($1-5\,\mu\text{m}$) lacking nuclei or proper nuclear membranes, with cell walls made of murein, circular DNA, $70\text{S}$ ribosomes, and no ER.

Murein

A peptidoglycan composed of protein and polysaccharides that makes up the cell wall of prokaryotes.

Viruses

Noncellular/acellular structures made of a protein coat and nucleic acid core (DNA or RNA strand) that replicate strictly inside host cells.