Biology - Structures and Functions of Cells

Cell

- the basic structural, functional, and biological unit of known organisms
-the smallest unit of life or the "building blocks of life"

Cytology

- study of cells

surface area to volume ratio

- as a cell's size increases, its volume increases much more rapidly than its surface area
- when this happens, the cell must divide into smaller cells with favorable ratios
- the reason why cells are small

Robert Hooke(1665)

- named the basic structure of all living things as a cell and observed cork cells & cells walls under a microscope
- he named them "cells" as they reminded him of the cells or rooms in monasteries

Anton van Leeuwenheok

- discovered "bacteria" from looking at dental scrapings on his teeth using hi own microscope
- named bacteria "Animalcules" because they looked like little animals

light micoscope (LM)

- visible light is passed through the specimen, through glass lenses, and is bent through the lens allowing you to see a magnified image of a specimen

Bright-field microscope

- illumination light is transmitted through the sample and the contrast is generated by the absorption of light in dense areas of the specimen.
- light then gets transmitted through the specimen and appears against an illuminated background.
- best used by fixed stained specimens to improve contrast

dark-field microscope

- Light is directed at an angle toward the specimen
-A microscope that only shows light that was reflected off the sample due to a condenser lens.
- ideally used to illuminate unstained samples causing them to appear brightly lit against a dark background

phase-contrast microscope

- its components bring light waves out of phases and produces differences in image contrast and brightness when the light waves recombine.
- internal details and organelles of live, unstained organisms can be seen and called phase objects

differential-interference-contrast microscope

- splits polarized light into to beams that have slightly different paths through the sample.
- combining these two beams produces greater contrast, producing a pseudo 3D-effect

fluorescence microscope

- its stains absorb light at one wavelength, then emit it at another.
- It filters only the emitted light
- used to image specific features of small specimens such us the genetic material within a cell

confocal microscope

- designed to reject background from matter outside the focal plane and therefore allowing images of different sections of a specimen to be obtained.
- produces a point source of light and rejects out of focus light, providing 3D reconstructions of imaged samples

Electron Microscope(1950)

- rather than focusing light, focuses a beam of electrons through the specimen or onto its surface

scanning electron microscope (SEM)

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

transmission electron microscope

- focuses a beam of electrons through a specimen

Cell Fractionation

- takes cells apart and separates the major organelles from one another
- enable scientist to determine the functions of organelles

Ultracentrifuge

- fractionate cells into their component parts

Prokaryotes

- simplest organisms
- most of its genetic material lies in a single circular molecule of DNA that resides in the NUCLEOID, but the area is not segregated from the rest of the cell's interior

Eukaryotes

- complex organisms
- its DNA is contained in the NUCLEUS surrounded by a double-membrane structure called the Nuclear Envelope

Cytoplasm

- a common feature among all types of cells
- a semifluid matrix that fills the interior of the cell
- contains all of the sugars, amino acids, and proteins the cell uses to carry out its everyday activities.
-contains the organelles and cytosol

Organelle

- any discrete macromolecular structure the cytoplasm specialized for a particular function

Cytosol

- part of the cytoplasm that contains organic molecules and ions in solution to distinguish it from larger organelles suspended in its fluid

Plasma membrane

- a common feature among all types of cells
- encloses a cell and separates its contents from its surroundings
- it is a PHOSPHOLIPID BILAYER about 5 to 10 nm thick, with proteins embedded in it.

Ribosomes

- a common feature among all types of cells
- particles made of ribosomal RNA and protein
- carry out protein synthesis
- made up of different subunits

Svedberg unit(S)

- sedimentation coefficient
- not additive
- determines how fast a particle/organelles pellet out during centrifugation

- 5S RNA, 23S RNA, 16S RNA
- 50S large subunit + 30S small subunit

Subunit of prokaryote

- 5S RNA, 5.8S, 28S RNA, 18S RNA
- 60S large subunit + 40S small subunit

Subunit of eukaryote

Prokaryotic Cells

- cells without a nucleus or other membrane-bound organelles
- -pro(before) + -karyon(nucleus)
- consists of bacteria and archaea

nucleoid/nuclear region

- part of a prokaryote
- contains the DNA

plasmid

- part of a prokaryote
- the extrachromosomal source of DNA that can replicate independently

plasma/cell membrane

- part of a prokaryote
- made up of phospholipids and proteins, semi-permeable

ribosomes

- part of a prokaryote
-site of protein synthesis

Cell wall

- part of a prokaryote
- made of peptidoglycan, structural support

Peptidoglycan

- A protein-carbohydrate compound that makes the cell walls of the prokaryotic cell

Gram Staining method

- can use cell wall composition to classify bacteria into either Gram + (purple) or Gram - (pink)

Flagellum

- part of a prokaryote
- for locomotion

Pilus

- part of a prokaryote
- for conjugal(reproduction) exchange & locomotion

Capsule

- part of a prokaryote
- extra layer made of glycolipids for protection

Endospore

- part of a prokaryote
- dormant, tough, non-reproductive structure for protection against severe environment stresses

Eukaryotic Cells

- cells that have a nucleus and other membrane-bound organelles
- -eu(true) + -karyon(nucleus)
-consists of plants, animals, fungi, and protists

Nucleus

- part of a eukaryote
- contains most of the cell's genes and is usually the most conspicuous organelle
- the DNA and proteins inside it form a genetic material called CHROMATIN

Nuclear membrane

- part of a eukaryote's nucleus
- a double membrane each consists a lipid bilayer
- its pores regulate the entry and exit of molecules from the nucleus

nuclear lamina

- part of a eukaryote's nucleus
- maintains the shape of the nucleus
- composed of protein

nucleolus

- part of a eukaryote's nucleus
- located within the nucleus
- is the site of ribosomal RNA(rRNA) synthesis

Endomembrane System

- part of a eukaryote
- has 6 components
- its components are either continuous or connected via transfer by vesicles
- modifies, packages, and transports lipids and proteins

Nuclear envelope

- component of the endomembrane system
- encloses the nucleus, separating it from the cytoplasm

Endoplasmic Reticulum(ER)

- component of the endomembrane system
- accounts for more than half of the total membrane in many eukaryotic cells
- continuous with the nuclear envelope
- has 2 distinct regions: smooth ER & rough ER

Smooth ER

- component of the endomembrane system
- lacks ribosomes
- synthesizes lipids
- metabolizes carbohydrates
- detoxifies poison
- stores calcium

Rough ER

- component of the endomembrane system
- has bound ribosomes which secrete GLYCOPROTEINS(protein covalently bonded to carbohydrates)
- distributes transport vesicles, proteins surrounded by membranes
- a membrane factory for the cell

Golgi Apparatus

- component of the endomembrane system
- consists of flattened membranous sacs call CISTERNAE
- modifies products of the ER
- manufactures certain macromolecules
- sorts and packages materials intro transport vesicles

Cisternae

- what the Golgi apparatus consists of
- has two types:
cis face" receiving" and transface "shipping"

Lysosome

- component of the endomembrane system
- membranous sac of hydrolytic enzymes that can digest macromolecules
- its enzymes can hydrolyze proteins, fats, polysaccharides and nucleic acids

Phagocytosis

- a process in which some types of cell can engulf another cell forming a food vacuole
- the food vacuole created fuses with LYSOSOME and digests the molecules

Autophagy

- a process in which lysosomes uses enzymes to recycle the cell's own organelles and macrimolecules

Vacuole

- component of the endomembrane system
- a eukaryotic cell may have one or several
- help in the storage and disposal of various substances
- has 3 kinds

Food vacuole

- temporarily stores food
- formed by phagocytosis

contractile vacuole

- found in many freshwater protists
- pump excess water out of cells

central vacuole

- found in many mature plant cells
- hold organic compounds and water

plasma membrane

- part of a endomembrane system
- a double layer of lipids that separates the cell interior from the outside environment

endosymbiotic theory

- a theory that eukaryotic cells formed from symbiosis among several different prokaryotic organisms

Mitochondria

- nearly in all eukaryotic cells
- have a smooth outer membrane and an inner membrane folded in CRISTAE

mitchondrial matrix

- catalyzes some metabolic steps in cellular respiration
- a compartment created by the inner membrane along with the intermembrane space

Cristae

- present a large surface area for enzymes that synthesize ATP
- folds the inner membrane of mitochondria

Chloroplasts

- part of a eukaryote
- a member of a family of organelles called PLASTIDS
- contain the green pigment chlorophyll, as well as enzymes and other molecules that function in photosynthesis
- found in leaves and other green organs and in algae

Thyakoids

- structure of chloroplasts
- membranous sacs stacked to form a GRANUM

Stroma

- structure of chloroplasts
- the internal fluid

mitochondria & chloroplasts

- not part of the endomembrane system
- a member of a family of organelles
- the site of cellular respiration, a metabolic process that generates ATP
- have a double membrane
-have proteins made by free ribosomes
- contain their own DNA

Peroxisomes

- part of a eukaryote
- specialized metabolic compartments bounded by a single membrane
- produce hydrogen peroxide and convert it to water
- uses oxygen to break down different types of molecules

Cytoskeleton

- a network of fibers extending throughout the cytoplasm
- organizes the cell's structures and activities, anchoring many organelles
- helps support the cell and maintain its shape
- interacts with MOTOR PROTEINS to produce motility
- provides "monorails" that vesicles can travel along in the cell
- may help regulate biochemical activities

Microtubules

- a type of fiber that makes up the cytoskeleton
- the thickest of the three components of the cytoskeleton
- function for intracellular trasnport

Microfilaments

- type of fiber that make up the cytoskeleton
-also called actin filaments
- the thinnest components

Intermediate filaments

- type of fiber that make up the cytoskeleton
- fibers with diameter in a middle range

Centrosome

- where microtubules grow
- a "microtubule-organizing center"

centrioles

- in animal cells, the centrosome has a pair of ________, each with nine triplets of microtubules arranged in a ring

Cilia and Flagella

- their beating is controlled by microtubules
- locomotor appendages of some cells
- compared to each other, they differ in beating patterns

muscle contraction

- is microfilaments that function in cellular motility that contain the protein MYOSIN in addition to ACTIN
- in muscle cells, thousands of actin filaments are arranged parallel to one another
- thicker filaments composed of myosin interdigitate(interlock) with the thinner actin fibers

Ctyoplasmic Streaming

- a circular flow of cytoplasm within cells
- speeds distribution of materials within the cell
- driven by actin-myosin interactions in plant cells

Amoeboid movement (pseudopodia)

- localized contraction brought about by actin and myosin
- Pseudopodia (cellular extensions)
extend and contract through the
reversible assembly and contraction
of actin subunits into microfilaments
- Actin flexibility allows the structural
change in the pseudopods of
Amoeba, allowing it to move.

Cell Wall

- an extracellular structure that distinguishes plant cells from animals cells
- plant cell walls are made of cellulose fibers embedded in other polysaccharides and protein
- prokaryotes, fungi, and some protists also have them

(1) Primary cell wall
(2) Middle lamella
(3) Secondary cell wall

- the three layers of Plant cell walls
- (1) relatively thin and flexible
- (2) thin layer between primary walls of adjacent cells
- (3) in some cells; added between the plasma membrane and the primary cell wall

extracellular matrix (ECM)

- its functions: support, adhesion, movement & regulation
- what animal cells are covered by instead of cell walls

collagen, proteoglycans and fibronectin

The ECM is made up of glycoproteins such as _______, _____________, and ______________.

integrins

ECM proteins bind to receptor proteins in the plasma membrane called _________

intercellular junctions

- facilitate the adherance, interaction communication through direct physical contact of neighboring cells in tissues, organs or organ systems

Plasmodesmata

- a type of intercellular junction
- channels between adjacent plant cells
- through this, water and small solutes(and sometimes proteins and RNA) can pass from cell to cell

Tight junctions

- a type of intercellular junction
- membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid

Desmosomes (anchoring junctions)

- a type of intercellular junction
- fasten cells together into strong sheets

Gap junctions (communicating junctions)

- a type of intercellular junction
- provide cytoplasmic channels between adjacent cells