Cell Structure and Functions Lecture Notes

Flashcards covering cell structures, functions, organelle details, and microscopy based on the provided biology lecture notes.

Resolving Power (Light Microscope)

The ability of a light microscope to distinguish two close objects as separate, which is $250\,nm$.

Magnification (Electron Microscope)

The degree to which an object is enlarged using an electron microscope, reaching up to $2,000,000X$.

Micrometry

The scientific process of measuring the size of objects viewed under a microscope.

Ocular Micrometre

A glass disc marked with $100$ equal divisions of arbitrary value, placed in the eye piece of a microscope.

Stage Micrometre

A glass slide containing an exact miniature scale used to calibrate the ocular micrometre.

Peptidoglycan

The chemical substance that makes up the cell walls of prokaryotes.

Chitin

The chemical substance that makes up the cell walls of fungi.

Middle Lamella

The layer present between the primary cell walls of adjacent cells, composed of magnesium and calcium salts of pectin.

Pectin

A polymer of approximately $200$ galacturonic acid molecules that serves as a major component of the middle lamella.

Secondary Cell Wall

A thick, rigid layer formed between the primary wall and plasma membrane in sclerenchyma cells, containing cellulose, hemicelluloses, lignin, inorganic salts, and waxes.

Lignin

A substance in the secondary cell wall that cements cellulose microfibrils together and provides rigidity.

Plasma Membrane Composition

Chemically consists of proteins ($60\text{-}80\%$), lipids ($20\text{-}40\%$), and a small quantity of carbohydrates.

Fluid Mosaic Model

A model proposing the membrane is a phospholipid bilayer ($7\,nm$ thick) with proteins scattered in an irregular pattern.

Cytosol

The less viscous, inner portion of the cytoplasm located towards the nucleus.

Cytogel

The more viscous, peripheral part of the cytoplasm located towards the plasma membrane.

Cyclosis

A circular streaming movement of the cytoplasm caused by microfilament activity, responsible for distributing cell contents.

Sarcoplasmic Reticulum

The name given to smooth endoplasmic reticulum specifically found in skeletal muscle cells.

80S Ribosomes

Large Ribosomes characteristic of eukaryotic cells, composed of $60S$ and $40S$ subunits.

70S Ribosomes

Smaller ribosomes found in prokaryotic cells, as well as in the mitochondria and chloroplasts of eukaryotic cells.

Polysome

A chain of several ribosomes attached to a single $mRNA$ molecule during protein synthesis.

Cisternae

The stack of flattened, membrane-bound sacs that make up the Golgi complex and endoplasmic reticulum.

Cis Face

The convex "forming face" of the Golgi complex where new cisternae are created by fusing vesicles.

Trans Face

The concave "maturing face" of the Golgi complex where cisternae break up into vesicles.

Phragmoplast

A structure formed during plant cell cytokinesis by the fusion of Golgi vesicles, eventually giving rise to the new cell wall.

Primary Lysosomes

Newly formed, spherical vesicles containing hydrolytic enzymes before they begin their digestive function.

Autophagy

A "self-eating" process where lysosomes digest a cell's own unwanted structures or organelles.

Autolysis

A programmed cell death process where lysosomes burst, releasing enzymes that disintegrate the entire cell; also known as "suicidal bags."

Tay-Sachs Disease

A lysosomal storage disease caused by a missing lipid-digesting enzyme, leading to brain impairment from lipid accumulation.

Peroxisomes

Microbodies containing oxidative enzymes like catalase and peroxidase, primarily involved in the detoxification of alcohol and the breakdown of $H_2O_2$.

Glyoxysomes

Plant-specific microbodies present in oil-seed seedlings that convert stored fatty acids into carbohydrates via the glyoxylate cycle.

Tonoplast

The specialized membrane that separates the central vacuole from the surrounding cytoplasm in plant cells.

Porins

Special proteins in the outer mitochondrial and chloroplast membranes that allow free passage of various molecules.

Cristae

The inward folds of the inner mitochondrial membrane that increase surface area for $ATP$ production.

Leucoplasts

Colourless plastids found in roots and seeds used for food storage, including amyloplasts, elaioplasts, and proteinoplasts.

Chromoplasts

Plastids that synthesize non-green pigments, found in flower petals and fruit walls to attract pollinators.

Granum

A stack of $25\text{-}50$ smaller thylakoids found within the chloroplast; plural is grana.

Centrioles

Non-membranous organelles composed of nine triplets of microtubules, involved in forming spindle fibres and basal bodies.

Microfilaments

Thin contractile fibres ($7\,nm$ diameter) made of actin, involved in cyclosis and muscle contraction.

Microtubules

Hollow cylinders ($25\,nm$ diameter) composed of tubulin protein, forming centrioles, cilia, flagella, and spindle fibres.

Intermediate Filaments

Fibres ($8\text{-}10\,nm$ diameter) composed of vimentin, providing mechanical support to the nuclear envelope and plasma membrane.

Axoneme

The internal bundle of eleven longitudinal microtubules in cilia and flagella, typically arranged in a "9+2" pattern.

Nucleoporin

A specialized transport protein that composes the nuclear pores and regulates exchange between the nucleus and cytoplasm.

Nucleolus

A non-membrane bound structure within the nucleoplasm responsible for the construction of ribosomes.

Kinetochores

A complex of proteins on opposite sides of the centromere that serves as the attachment site for microtubules during cell division.

Binary Fission

The simple method of cell division used by prokaryotic cells instead of mitosis or meiosis.