Biology - Chapter 6: A Tour of the Cell

Light microscope (LM)

A microscope where visible light is passed through a specimen and then through glass lenses

Magnification

The ratio of an object’s image size to its real size

Resolution

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

Contrast

The visible differences in brightness between parts of the sample

Electron Microscopes (EMs)

An electron microscope is a microscope that uses a beam of electrons as a source of illumination, there is currently two basic types to study subcellular structures

Scanning electron microscopes (SEMs)

An EM that focuses a beam of electrons onto the surface of a specimen, providing images that look 3-D

Transmission electron microscopes (TEMs)

An EM that focus a beam of electrons through a specimen, used mainly to study the internal structure of cells in 2-D

Cryo-electron microscopy (cryo-EM)

An EM that allows preservation of specimens at very low temperatures, allowing visualization of structures in their cellular environment, with no need for preservatives or other alteration

Cell fractionation

A method that takes cells apart and separates the major organelles from one another via Centrifuges

Prokaryote Cell

Cells that has no nucleus but a nucleoid instead (susceptible to viruses), no membrane-bound organelles but has specialized regions that acts like organelles.

Cytosol

The Semifluid substance in the cytoplasm

Nucleoid

The DNA in an unbound region in a Prokaryote Cell.

Cytoplasm

The region between the plasma membrane and nucleus

Eukaryotic cells

Cells that has DNA in a nucleus that is bounded by a double membrane and membrane-bound organelles.

Plasma Membrane

Is the selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell

Nucleus

An organelle that contains most of the cell’s genes plus RNA and is usually the most conspicuous organelle

Nuclear Envelope

A double membrane that encloses the nucleus, separating it from the cytoplasm

Nuclear Lamina

Lining the envelope, is composed of proteins and maintains the shape of the nucleus

Chromosomes

A discrete units that DNA is organized into.

Chromatin

A DNA molecule associated with proteins that each chromosome contains one.

Nucleolus

located within the nucleus, is the site of ribosomal RNA (rRNA) synthesis (rRNA is a special type of RNA that builds ribosomes)

Ribosomes

complexes made of ribosomal RNA and protein, builds proteins in the cytosol (free ribosomes), on the outside of the endoplasmic reticulum, or the nuclear envelope

Endomembrane System

A group of membranes and organelles in eukaryotic cells that works together to modify, package, and transport lipids and proteins, includes the Nuclear envelope, Endoplasmic reticulum, Golgi apparatus, Lysosomes, Vacuoles, and Plasma membrane

Vesicles

A self-contained structure consisting of fluid or gas surrounded and enclosed by an outer membrane, naturally forms during the processes of secretion, uptake, and the transport of materials within the plasma membrane

Endoplasmic Reticulum (ER)

The transportation system of the eukaryotic cell, and has many other important functions such as protein folding, contains 2 relatively distinct regions.

Rough ER

An organelle whose surface is studded with ribosomes and is used as a membrane factory (transport vesicles) for the cell with bound ribosomes that secrete glycoproteins

Smooth ER

An organelle that lacks ribosomes and is used to Synthesizes fats and lipids, Detoxifies drugs and poisons, and Stores calcium ions

Glycoproteins

Sugar protein complexes where proteins are covalently bonded to carbohydrates, acting as signaling molecules with membrane-bound ones functioning as the surface receptors

Transport Vesicles

A secretory proteins surrounded by membranes (imagine sack made of a membrane skin)

Golgi Apparatus

This organelle consists of flattened membranous sacs called cisternae (storage centers), and it modifies products of the ER (in order to packets it somewhere else), manufactures certain macromolecules (some lipids are “finished” in this organelle), and sorts and packages materials into transport vesicles

Lysosome

A membranous sac of hydrolytic enzymes that can digest macromolecules using hydrolytic enzymes

Phagocytosis

A membrane forms around the “food” and separates from the main cell’s plasma membrane to create a food vacuole, forming something alike to an organelle

Vacuoles

Another type of membrane bound organelle, are large vesicles derived from the ER and Golgi apparatus

Contractile vacuoles

Found in many freshwater protists, pump excess water out of cells so they don’t pop

Central vacuoles

A very large vacuoles found in many mature plant cells, contain a solution called sap

Mitochondria

The sites of cellular respiration, the metabolic process that uses oxygen (and sugar) to generate ATP

Chloroplasts

Found in plants and certain algae, are the sites of photosynthesis

Endosymbiont Theory

Suggests that an early ancestor of eukaryotes engulfed an oxygen-using non photosynthetic prokaryotic cell, and photosynthetic prokaryotic cell for plants

Cristae

The membrane highly folded into this for a greater surface area to volume ratio

Mitochondrial Matrix

The equivalent to a cytosol of the cell for the mitochondria

Thylakoids

A flattened sacs inside a chloroplast, bounded by pigmented membranes on which the light reactions of photosynthesis take place and stacked to form granum (like pancakes)

Stroma

An internal gel-like fluid, a very sugary substance inside the chloroplast

Peroxisomes

Specialized metabolic compartments bounded by a single membrane and contain enzymes that remove hydrogen atoms from various substances and transfer them to oxygen in the form of hydrogen peroxides

Cytoskeleton

A network of fibers extending throughout the cytoplasm, made of protein

Motor Proteins

A protein that moves along the cytoskeletal filaments via a force-dependent mechanism that is driven by the hydrolysis of ATP molecules

Microtubules

A hollow rods about 25 nm in diameter made of alpha and beta tubulin and is used for shaping the cell, guiding movement of organelles, and separating chromosomes during cell division

Centrosome

A non-membranous, nucleus-associated organelle responsible for producing microtubules in animal cells

Centrioles

A nine triplets of microtubules arranged in a ring (forming a star/flower shape structure) that is found as pairs in centrosomes.

Basal Body

An organelle that anchors the cilium or flagellum with the triplet formation

Dynein

A motor protein that drives the bending movements of a cilium or flagellum, are found in between the microtubules, where a large group “walks” to make the flagella/cilia move.

Microfilaments

A solid rods about 7 nm in diameter, built as a twisted double chain of actin protein subunits, that forms a cortex just inside the plasma membrane to help support the cell’s shape, perform cellular motility with a protein called myosin, allow it to crawl with a pseudopodia, and conduct cytoplasmic streaming.

Cortex

A thin actin network bound to the plasma membrane that is present in most animal cells

Myosin

A motor protein that moves along actin filaments for cellular motility

Pseudopodia

A temporary protrusion of the surface of an amoeboid cell for movement and feeding

Cytoplasmic Streaming

Is a circular flow of cytoplasm within cells, driven by actin-protein interactions in plant cells

Intermediate filaments

A filament that ranges 8 to 12 nanometers in diameter (ranges because of different proteins composition), and acts as a more permanent cytoskeleton fixtures than the other two classes, supporting cell shape and fix organelles in place in certain organisms

Cell Wall

An extracellular structure (substance) that distinguishes plant cells from animal cells

Extracellular Matrix (ECM)

In place of the cell wall, animal cells has this that’s made up of glycoproteins (sugar proteins attached together) such as collagen, proteoglycans, and fibronectin

Integrins

The principal receptors used by animal cells to bind to the extracellular matrix, which Helps integrate alike cells into groups, like skin with skin, or stomach with stomach

Plasmodesmata

Channels made of protein that connect plant cells where water and small solutes (and sometimes proteins and RNA) can pass from cell to cell through them