Biology - Structures and Functions of Cells

Cell

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