cellular structure, organization and function

organelle

a structure within a cell that has a specific function and is separated from the rest of the cell by a membrane

eukaryotic cells

unicellular or multicellular organism has membrane-bound organelles

amoebas, fungi, animals, plants

examples of eukaryotic cells

prokaryotic cells

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a unicellular organism that lacks membrane-bound organelles

bacteria

example of prokaryotic cell

the presence of membrane-bound organelles in eukaryotes allows eukaryotic cells to compartmentalize activities in different parts of the cell

reason why eukaryotic cells are more efficient

plant cells and fungi

eukaryotic cells with cell walls

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1. ribosomes
2. endoplasmic reticulum (smooth and rough)
3. golgi apparatus
4. lysosomes
5. peroxisomes
6. mitochondria
7. chloroplasts

eukaryotic organelles

nucleus

contains the DNA genome and nucleolus and is separated from the rest of the cell by the nuclear envelope

nuclear envelope

double membrane that has a large number of pores for communication of material between the interior and exterior of the nucleus

nucleolus

dense structure that contains ribosomal RNA and is the site of ribosome assembly

ribosome

large complex structures involved in protein production (translation) and are found freely in the cytoplasm or bound to the outer membrane of the endoplasmic reticulum

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endoplasmic reticulum

an extensive network of membrane-enclosed spaces in the cytoplasm involved in protein synthesis, lipid synthesis, and the detoxification of drugs and poisons

rough ER

the region of the ER that contains ribosomes and is involved in protein synthesis

smooth ER

the region of the ER that does not have ribosomes and is involved in lipid synthesis and the detoxification of drugs and poisons

golgi apparatus

a stack of membrane-enclosed sacs located between the ER and the plasma membrane

cis golgi

closest golgi stacks to the ER that take newly synthesized proteins from the ER and fuse them to repackage them for \n delivery to other destinations in the cell

trans golgi

closest golgi stacks to the plasma membrane that sort protein packages into vesicles and send them to their final destination

lysosomes

contain hydrolytic enzymes that are involved in intracellular digestion of proteins, carbohydrates, and nucleic acids, also aid in renewing a cell’s own components by breaking old components down and then releasing molecular building blocks into the cytosol for reuse

break down bacteria or damaged cells

function of a lysosome in a white blood cell

provide food for the cell

function of a lysosome in a protist

peroxisome

contain oxidative enzymes that catalyze reactions in which hydrogen peroxide is produced and degraded, breaks fats down into smaller molecules that can then be used for fuel, detoxifies compounds (such as alcohol) in the liver

peroxides

molecules produced in the peroxisomes that would be hazardous to the cell if present in the cytoplasm due to being highly reactive and capable of covalently altering macromolecules (such as DNA)

mitochondria

the source of most energy in the cell, site of aerobic respiration in eukaryotic cells \n \n -area bounded by the inner membrane is the \n matrix: site of electron transport, Krebs cycle, and \n ATP production \n -semiautonomous: contain their own \n circular DNA & ribosomes

outer and inner phospholipid bilayer membrane

binds the mitochondria

outer mitochondrial membrane

has many pores that allow molecules to pass through based on their size

inner mitochondrial membrane

has convolutions called cristae and a high protein count

mitochondrial matrix

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area bound by the inner membrane that is the site of electron transport, Krebs cycle, and ATP production

contain their own circular DNA & ribosomes

unique features of mitochondria

cellulose cell wall

provides structure and strength to plants

chloroplasts

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similar to mitochondria in the way it contains their own \n DNA & ribosomes, and is semi-autonomous, have \n chlorophyll, site of photosynthesis, and 2 membranes (inner \n and outer) \n

thylakoid

membrane sacs derived from the inner membrane and form stacks called grana

thylakoid membranes

contain the chlorophyll of the cell

stroma

the fluid inside the chloroplast surrounding the grana

vacuoles

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membrane-enclosed sacs within the cell used for storage of waste products and helping the plant maintain stiffness/structure

large: can make up 90% of the cell

vacuoles in plants

the pressure of lipid and solutes in the vacuoles

characteristic of vacuoles that helps the plant maintain stiffness/structure

cytoskeleton

a massive network of 3 fibers within the cytoplasm

1. actin
2. myosin
3. intermediate filaments

3 fibers of the cytoskeleton

actin

most abundant protein in the cell cytoplasm that regulates complex movements such as phagocytosis and pseudopod extension and is responsible for pinching off a cell in cytokinesis

microfilament

another name for actin

rapidly changing lengths of actin filaments

method by which the cell uses actin to regulate complex movements

plasma membrane

site that actin is highly concentrated in

ameboid-like motion

motion of actin

1. globular monomer (G-actin)
2. long filament (F-actin)

two forms that actin exists as in the cytoplasm

myosin

motor proteins that enable actin and other filaments to pull along one another in a shearing or contractile motion and is involved in muscle contraction and cytokinesis

myosin has small arm-like extensions that can attach to actin filaments and pull them “hand-over-hand”

mechanism by which myosin pulls actin

microtubules

cellular conveyor belts used to rapidly transport vesicles, organelles, and even chromosomes across the cell that rapidly shrink and grow out of a region near the center of the cell (centrosome)

tubulin

protein that makes up microtubules

tubulin dimers

fall off the ends of microtubules as GTP is hydrolyzed

microtubule-associated proteins (MAPs)

attach to tubulin on one end and to the vesicles, organelles, or granules on the other end and then rapidly shuttle the cargo down the length of the microtubule

kinesins

motor molecules that shuttle cargo toward the outer perimeter of the cell

dyneins

pull toward the microtubule-organizing center (centrosome)

cilia and flagella

composed of long, stabilized microtubules \n arranged in a 9+2 structure

9 pairs of microtubules surrounding 2 central microtubules for added stability

9+2 structure of cilia and flagella

basal bodies

anchor cilia and flagella into the cell membrane by arrangements of microtubule triplets

centrioles

the same as basal bodies, but are only found in animal cells

microtubule-organizing centers (MTOC)

anchor microtubules growing into the mitotic spindle

intermediate filaments

thin fibers that wind together into long coils found beneath the nuclear membrane and gives stability to the membrane

1. keratins
2. laminins
3. vimentin

proteins that make up intermediate fibers

keratins

proteins found in skin, hair, nails

laminins

proteins that make up nuclear lamina

myosin>intermediate filaments>actin

sizes of actin, myosin, and intermediate filaments in order

cellular membrane

fluid mosaic of lipids and amphipathic proteins that is embedded in the phospholipid bilayer

a very thin film of lipids that exist at the surface of the cell

cellular membrane structure

~5nm thick

cell membrane thickness

1. lipids (about 50% on average of the mass of a cell membrane)
2. membrane bound or transmembrane proteins (the remaining mass)

cell membrane composition

noncovalent interactions (hydrophobic)

holds the plasma membrane together

the unsaturated hydrocarbon tails of phospholipids

keep membranes fluid at lower temperatures

cholesterol

helps membranes resist changes in fluidity caused by temperature changes

the fluidity of a membrane affects both its permeability and the ability of membrane proteins to move to where their function is needed

reason why membranes must be fluid to work properly t

membrane proteins

function in transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, and attachment to the cytoskeleton and extracellular matrix.

short chains of sugars linked to proteins (in glycoproteins) and lipids (in glycolipids) on the exterior side of the plasma membrane

\n interact with surface molecules of other cells.

the ER

site of synthesis of membrane proteins and lipids

ER and Golgi apparatus

site of modification of membrane proteins and lipids

selective permeability of the plasma membrane.

controls the exchange of molecules and ions with the cell’s surroundings

passive transport

diffusion of a substance across a membrane with no energy investment

diffusion

the spontaneous movement of a substance down its concentration gradient

facilitated diffusion

a transport protein speeds the movement of water or a solute across a membrane down its concentration gradient

ion channels

facilitate the diffusion of ions across a membrane

carrier proteins

can undergo changes in shape that translocate bound solutes across the membrane

osmosis

process by which water tends to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one

hypertonic

the solution outside has a higher solute concentration than \n the cytosol

water diffuses out through the permeable membrane of a cell

result of a hypertonic solution

hypotonic

the solution outside has a lower solute concentration than the cytosol

water enters the cell

result of a hypotonic solution

isotonic

concentrations both inside and outside of the cell are equal

no net osmosis occurs

result of a isotonic solution

active transport

uses energy to move solutes against their gradients

energy such as ATP

does the work of active transport

1. concentration (chemical) gradient
2. electrical gradient (voltage)

two kinds of gradients ions can have

electrochemical gradient

the combination of the chemical and electrical gradients that determines the net direction of ionic diffusion

cotransport of two solutes

occurs when a membrane protein enables the “downhill” diffusion of one solute to drive the “uphill” transport of the other

bulk transport across the plasma membrane

occurs by exocytosis and endocytosis

exocytosis

process used to incorporate proteins into the cell membrane or discharge molecules outside the cell by transport vesicles migrating to the plasma membrane, fusing with it, and releasing their contents

vesicle

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a bubble-like structure formed by the phospholipid bilayer of the cell membrane surrounding waste proteins, frequently used in the cell for transportation of molecules across the cell membrane.

endocytosis

molecules enter cells within vesicles that pinch inward from the plasma membrane

1. phagocytosis
2. pinocytosis
3. receptor-mediated endocytosis.

three types of endocytosis

phagocytosis

process where the cell engulfs a molecule in order to move it to the interior of the cell

pinocytosis

process where a cell engulfs dissolved ions and other solutes in the liquid medium surrounding the cell.