jjf MCAT BIO ch1

Coarse adjustment knob

part of a compound light microscope that roughly focuses the image

Fine adjustment knob

part of a compound light microscope that sharply focuses the image

Small, nonpolar (hydrophobic) molecules generally _____________.

pass through the cell membrane freely (diffuse)

Nuclear pores

pores on the nuclear membrane which allow selective two-way exchange of materials between the nucleus and the cytoplasm.

Cell adhesion molecules (CAMs)

proteins that contribute to cell recognition and adhesion and are particularly important during development

Free ribosomes

ribosomes found in the cytoplasm

Bound ribosomes

ribosomes that line the outer membrane of the endoplasmic reticulum

Centrifugation of a eukaryotic cell

sediments high-density ribosomes at the bottom of the test-tube, while low-density mitochondria and lysosomes remain at the top.

Plasmids

small rings of DNA consisting of just a few genes separate from chromosomes

Histones

structural proteins that form chromosomes

Selective permeability

the cell membrane allows some compounds/molecules to pass through freely, where others are prohibited or regulated.

Resolution

the differentiation of two closely situated objects.

Cytosol

the fluid component of the cytoplasm that consists of an aqueous solution containing free proteins, nutrients, and other solutes.

Phospholipid bilayer

the hydrophilic regions are found on the exterior surfaces of the membrane, whereas the hydrophobic regions are found on the interior of the membrane. The bilayer structure allows the cell membrane to regulate the passage of material and molecules in and out of the cell and exhibits selective permeability.

Magnification

the increase in apparent size of an object

Microscopy

the most basic tool used by scientists to study cells

Ribosomes

the sites of protein production, synthesized by the nucleolus. Ribosomes consist of two subunits, one large and one small, each composed of rRNA and proteins.

Prokaryotes

unicellular organisms with a simple cell structure. Prokaryotes have a cell membrane, but have no membrane bound organelles. Include bacteria and cyanobacteria

Compound Light Microscope

used in the observation on non-living species and uses a series of lenses to magnify objects

Centrifugation

used to separate cells or mixtures of cells without destroying them in the process.

Electron Microscope

uses a beam of electrons to allow a thousand-fold higher magnification than is possible with light microscopy. Tissues must be fixed and sectioned and sometimes stained with solutions of heavy metals, making examination living specimens impossible

Secretory vesicles

vesicles produced by the golgi apparatus that release their contents to the cell's exterior by the process of exocytosis

Cell membrane

(aka plasma membrane) encloses the cell and regulates passage of materials in both directions

Cell Theory

-All living things are composed of cells -The cell is the basic functional unit of life -Cells arise only from pre-existing cells -Cells carry genetic information in the form of DNA. This genetic material is passed from parent cell to daughter cell

Fluid mosaic model

A cell membrane has a mixed composition (mosaic) of lipids and proteins, the interactions and motions of which impart fluidity to it.

Rough ER (RER)

ER with ribosomes lining its outer surface; involved in protein synthesis.

Smooth ER

ER without ribosomes lining its surface; is involved in lipid synthesis and the detoxification of drugs and poisons.

Vesicles and vacuoles

Membrane-bound sacs involved in the transport and storage of materials that are ingested, secreted, processed, or digested by the cell. Vacuoles are larger than vesicles and are more likely to be found in plant cells.

Are viruses eukaryotic or prokaryotic cells?

Neither, viruses occupy a unique category and are not considered cells because they are not capable of living independently.

Bacteria have ____________________.

a cell wall, a cell membrane, cytoplasm, ribosomes, and sometimes flagella

Nucleolus

a dense structure in the nucleus where ribosomal RNA (rRNA) synthesis occurs.

Nuclear membrane

a double membrane that maintains a nuclear environment distinct from that of the cytoplasm

hemotoxylin

a dye used in light microscopy that reveals the distribution of DNA and RNA within a cell due to its affinity for negatively charged molecules

Endoplasmic Reticulum (ER)

a network of membrane-enclosed spaces connected at points with the nuclear membrane. Generally involved in the transport of materials throughout the cell, especially those materials destined to be secreted from the cell.

Autolysis

a process where a cell in an injured or dying tissue "commits suicide" by rupturing the lysosome membrane and releasing its hydrolytic enzymes, which digest cellular contents.

Phase Contrast Microscope

a special type of light microscope that permits the study of living cells, without killing the specimen.

Autoradiography

a technique using radioactive molecules to trace and identify cell structures and biochemical activity.

Eukaryotes

all multicellular organisms and all nonbacteria unicellular organisms are composed of eukaryotic cells. A typical eukaryotic cell is bounded by a cell membrane and contains cytoplasm

Nucleoid region

an area of a prokaryotic cell which contains a concentrated circular molecule of DNA and possibly smaller rings of DNA called plasmids

Receptors

complex proteins or glycoproteins generally embedded in the membrane with sites that bind to specific molecules in the cells environment and may carry the molecule into the cell via pinocytosis

Golgi Apparatus

consists of stacks of flat membranous sacs that modify, store, and route products of the smooth endoplasmic reticulum.

Nucleus

controls the activities of the cell, including cell division. surrounded by a nuclear membrane, or envelope

Diaphragm

controls the amount of light passing through a specimen in a compound light microscope

charged large molecules such as proteins and complex carbs generally_______________.

do not freely pass through the cell membrane

Cytoskeleton

found in the cytosol, composed of microtubules, microfilaments, intermediate fibers, and other accessory proteins. Cytockeleton gives the cell its shape and anchors the organelles.

Phospholipids

have both a hydrophilic (polar) phosphoric acid and a hydrophobic (nonpolar) fatty acid region.

Microbodies

membrane-bound organelles specialized as containers for metabolic reactions

Lysosomes

membrane-bound vesicles that contain hydrolytic enzymes involved in intracellular digestion. These enzymes are maximally effective at a pH of 5 and, therefore, need to be enclosed within the lysosome-- an acidic environment distinct from the neutral pH of the cytosol.

Transport proteins

membrane-spanning proteins that allow certain ions and polar molecules to pass through the lipid bilayer.