2.1: Structures and Functions of Eukaryotic Cells

eukaryotic cell

DNA contained in membrane bound nucleus

purpose of phospholipid bilayer

seperate cells contents from surroundings

interior of eukaryotic cell

filled with jelly-like cytoplasm

organelle

smaller part of a cell with specific function, work together so the cell can perform all life functions

nucleus

where genetic info is stores and replicated

how are chromosomes formed

DNA molecules combine with histone proteins to form a chromosome

how many chromosomes in humans

46, 23 pairs

nucleoplasm

thick fluid that fills the nucleus

nucleolus

denser region, contains RNA, proteins, chromatin

nuclear envelope

double membrane with 2 phospholipid bilayers

nuclear pores

groups of proteins that form opening in the nuclear envelope to allow water and ions to flow

ribosomes

small particles that consist of rRNA and proteins

function of ribosomes

translate mRNA into chains of amino acids (make proteins)

endoplasmic reticulum

complex of membrane bound tubules and sacs that are connected to nuclear enveloper

rough er

er surface studded with ribosomes, devoted to synthesis of proteins

purpose of rough er

assemble proteins that are part of membranes or intended for export from cell, freely suspended ribosomes make proteins that function in cytosol

smooth er

regions or the er that have no bound ribosomes

purpose of smooth er

synthesize lipids and lipid containing molecules, detoxifies drugs and alcohol in liver, produces testosterone and estrogen in testes and ovaries

vesicle

membrane bound sacs used to transport and store substances in the cell

vesicle formation

form by pinching off from cell and organelle membranes

how do vesicles release contents

fuse with cell and organelle membranes to release contents

vesicles in animal cells

many small vesicles

vacuole

storage of water, ions, sugars, amino acids, macromolecules, central vesicle in plants

function of vacuole

contains enzymes to break down macromolecules, controls turgor pressure

cisternae

layers of membranous tubules

function of golgi body

collect and package materials (lipids and proteins) to be removed from the cell, make and secrete carbohydrates

structure of golgi body

dynamic, joins with vesicles at cis face, pinches off/produces vesicles at trans face

cis face

takes in vesicles (er)

trans face

where contents are released

parts of the endomembrane system

nuclear envelope, er, golgi body, vesicles

purpose of endomembrane system

transportation and product precession, organelles connected by transport vesicles or directly

lysosomes

membranous sacs filled with enzymes that catalyze hydrolysis reactions

purpose of lysosomes

act as garbage disposal or digester of old cell parts and bacterial foreign particles

peroxisomes

membrane bound sac, dense crystal core, made in smooth er

purpose of peroxisomes

contain oxidative enzymes that break down excess fatty acids and hydrogen peroxide, liver cells: synthesis of cholesterol and bile acids

mitochondria purpose

power plants, make energy available to cells

cristae

folds of inner membrane in mitochondria

matrix

fluid filled space in inner membrane, contain some of their own DNA and encodes own proteins

how to mitochondria perform cellular respiration

contains enzymes that help convert glucose to ATP through cellular respiration

mitochondria structure

smooth outer membrane, folded inner membrane

cellular respiration

C6H12O6→O6+6O2→6O2+6H2O+38 ATP

chloroplasts

absorb light energy, double membrane

chlorophyll

pigment

autotrophs

obtain energy from the sun to make glucose by photosynthesis, contain some of their own DNA

stroma

thick liquid in inner membrane

cell wall

rigid, semi permeable protective layer in plant, fungi, bacteria, algae, archaea

consumption of cell wall

combination of polysaccharides, glycoproteins

function of cell wall

barrier against viruses and water loss, maintains turgor pressure, mechanical strength and support

turgor pressure

force exerted against cell wall as contents of cell push cell membrane against cell wall

cytoskeleton

cell skeleton, internal network of protein fibres that extend through cytoplasm

function of cytoskeleton

structure, anchor membrane and organelles in place, transport vesicles and other organelles along fibres

pseudopods

appendages that enable the cell to propel itself through the fluid surrounding it

centriole

nine bundles of microtubules

microtubules

hollow tubes that give organelles their shape, arranged in a ring

centrosome

two centrioles at right angles, close to nucleus, formation of miotic spindle fibres, creates/organizes microtubules for cytoskeleton

cilia

short appendages that develop on outside of eukaryotic cells, paramecium

cilia and flagella structure

internal shaft made of microtubules, covered with continuation of cell membrane

flagella

one or two long appendages, tail-like, whip-like movement, sperm, euglenoids

cytoplasm functions

suspends organelles, maintains shape, cell movement, material exchange, H2O needed for reactions

fluid mosaic model

cell membrane, phospholipid bilayer, mixture of molecules (phospholipids, cholesterol, proteins, carbohydrates)

phospholipid bilayer

held together by weak intermolecular bonds, allow molecules in membrane to more, contains [roteins and macromolecules

structure of phospholipid bilayer

hydrophilic (polar head) faces aqueous environment, hydrophobic (non-polar) tails face in

bilayer is too fluid

permits too many molecules

bilayer is not fluid enough

prevents too many molecules

bilayer at room temp

vegetable oil viscosity

bilayer at high temp

too fluid, not a barrier

bilayer at low temp

solidifies to a gel-like state

double bonds in tails

form kinks, less tightly pack, higher fluidity

fatty acid tail length

longer, more intermolecular attractions, held together tightly, lower fluidity

average tail length

16 or 18 carbon atoms

cholesterol in cell membrane

maintains fluidity

cholesterol at high temp

increases intermolecular forces in membrane, lowers fluidity

cholesterol at low temp

breaks intermolecular forces, raises fluidity

proteins in cell membrane

stabilize by linking with cytoskeleton of cell

integral proteins

embedded in membrane

transmembrane proteins

on both sides of bilayer

peripheral proteins

loosely attached to outer regions of membrane or to integral proteins

purpose of proteins in cell membrane

transport, reaction catalysis, cell recognition, signal reception and transduction

protein cell recognition

carbohydrate chains protrude from glycoproteins on outer later of cell membrane, enables cells to recognize each other

protein signal reception and transduction

receptor proteins in membrane bind to signal molecules and change shape, initiates cellular response

carbohydrate structure in cell membrane

attached to proteins or phospholipids and protrude outside the cell

carbohydrate function in cell membrane

allows other cells to recognize cell as belonging to the body instead of the intruder

glycolipid

membrane lipid bound to a carbohydrate

glycoprotein

membrane protein bound to a carbohydrate