bio test 2 <3

prokaryotic cells

- without a nucleus

- dna not enclosed in a membrane (instead concentrated in nucleoid region)

- simple, smaller, no membrane-bound organelles

eukaryotic cells

- with a nucleus enclosed in nuclear membrane

- complex, larger, membrane-bound organelles

cytoplasm

the entire region between the nucleus and the membrane bounding the cell (plasma membrane)

- made up of semi-fluid medium where the organelles are suspended within, called cytosol

- (cytosol + organelles)

cell size

the requirement for a favorable ratio of membrane surface to cell volume sets up the upper limits on cell size

- as an object of a particular shape increases in size, its volume grows (cubed) proportionately more than its surface area (cubed)

plasma (cell) membrane

functions as a selective barrier that allows sufficient passage of oxygen, nutrients, and wastes to service the entire volume of the cell (semipermeable)

phospholipid bylayer

makes up plasma membrane

- embedded with proteins

animal cell picture

know + label

- plasma membrane

- cytoplasm

- nucleus + nucleolus

- endoplasmic reticulum

- mitochondria

- ribosomes

- golgi apparatus

plant cell picture

know + label

- cell wall

- plasma membrane

- nucleus + nucleolus

- central vacuole

- mitochondria

- chloroplasts

- endoplasmic reticulum

- golgi apparatus

nuclear envelope

pores in the envelope allow for exchange of macromolecules between the nucleus and the cytoplasm

- surrounds nucleus

chromatin

dna organized along proteins (uncoiled chromosome)

- in the nucleus

- condenses (into chromosomes) as the cell prepares to divide

chromosomes

thick, condensed chromatin

- each eukaryotic species has a specific number (humans: 46)

- eukaryotes have linear chromosomes

- prokaryotes have circular chromosomes

nucleolus

the nuclear site where the parts of ribosomes are produced

ribosomes

carry out protein synthesis in the cytosol (free ribosomes) or attached to the outside of the membranous endoplasmic reticulum (bound ribosomes)

- made up of nucleic acids

ribosome parts

two parts that come together when building proteins (are apart otherwise)

endoplasmic reticulum (er)

a network of membrane-enclosed compartments (cisternae)

- smooth + rough er

cisternae

flattened stacked membrane folds that make up the golgi apparatus

smooth er

lacks ribosomes

- synthesizes steroids, metabolizes carbohydrates, stores calcium in muscle cells, and detoxifies poisons in liver cells

rough er

contains bound ribosomes

- continuous with the nuclear envelope

- functions in producing cell membrane and manufacturing proteins for secretion

- membrane + secretory proteins can be transferred to other locations in the cell by the budding of transport vesicles from er

golgi appartus

consists of stacks of membranous sacs that synthesize various macromolecules + modify, store, sort, and export products from the er

- have two poles: cis (receiving) + trans (releasing)

cis face of golgi apparatus

receives secretory proteins from the er through transport vesicles

trans face of golgi apparatus

where secretory proteins are released after being chemically modified and sorted in golgi apparatus

lysosomes

membrane-enclosed sac of hydrolytic enzymes that hydrolyze (break down) proteins, polysaccharides, fats, and nucleic acids (food)

- lysosome and food in membrane fuse together to be digested

- hydrolytic enzymes + the membrane of the lysosome are made in the er and transferred to golgi for further processing

- if lysosomes break or leak into cytosol, the cell will be destroyed by autodigestion

metamorphosis

a form of programmed cell destruction by lysosomes to help development of many organisms

- ex: tadpoles, human embryo

storage diseases

rare inherited diseases of lysosomes

- ex: pompe's disease, tay-sachs disease

- a particular enzyme is missing in the lysosome which causes the accumulation of the undigested product inside the cell interfering with its function

vacuoles

an organelle which is a membrane-enclosed sac larger than a vesicle

- include food, contractile, and central vacuoles

food vacuole

formed by phagocytosis

- is the site of intracellular digestion in some protists and macrophages

contractile vacuole

pumps excess water from the cell (so cell doesn't burst)

- found in some fresh-water protozoa

central vacuole

has many functions: storage, waste disposal, cell elongation, and protection

- develops by the coalescence of smaller vacuoles derived from the er and golgi apparatus

- enclosed by a membrane called the tonoplast

- large and found in most mature plant cells

peroxisomes

membrane-bound organelles that contain specialized teams of enzymes for specific metabolic pathways

- all contain peroxide-producing oxidases

- produce hydrogen peroxide as a waste product (of metabolic processes)

- enzyme in the peroxisome converts the peroxide to water

mitochondria

organelles that are the sites of cellular respiration

- catabolic oxygen requiring process that uses energy extracted from organic macromolecules to produce atp

- has two membranes

- number of mitochondria depend on cell and correlates with its metabolic activity

cristae

infoldings of the inner membrane of a mitochondria that houses the electron transport chain and the enzyme catalyzing the synthesis of atp

matrix

space enclosed by the inner membrane that some of the metabolic reactions of respiration takes space

- extranuclear dna located here

plastids

a group of plant and algal membrane-bound organelles

- includes amyloplasts, chromoplasts, and chloroplasts

amyloplasts

colorless plastids that store starch

- found in roots and tubers

chromoplasts

plastids containing pigments other than chlorophyll

- responsible for the color of fruits, flowers, and autumn leaves

chloroplasts

chlorophyll-containing plastids which are sites of photosynthesis

- enclosed by two membranes surrounding the fluid inside called the stroma

- thylakoids embedded in stroma which stack to create grana

stroma

in plants, the solution that surrounds the thylakoids in a chloroplast

thylakoids

membranous sacs embedded in the stroma

grana

flattened stacks of thylakoids

cytoskeleton

a network of fibers throughout the cytoplasm that forms a dynamic framework for support and movement

- not an organelle

- three different fibers: microtubules, microfilaments, and intermediate fibers

cytoskeleton function

- gives mechanical support to the cell and helps maintain its shape

- enables the cell to change shape

- associated with mobility by interacting with specialized proteins called motor molecules (ex: organelle movement, muscle contraction, and locomotor organelles)

microtubules

straight, hollow fibers constructed from globular proteins called tubulin, which may be disassembled and recycled to build microtubules elsewhere in the cell

- in the cytoplasm of all eukaryotic cells

- thickest cytoskeleton fiber

centrosome

an area near the nucleus that surrounds the centrioles of most animal cells

microtubules function

- may radiate from the centrosome and form a framework for cellular support

- bundles near the plasma membrane reinforce shape

- guide the movement of organelles

- participate in chromosome separation during cell division

centrioles

pair of cylindrical structures in animal cells

- composed of nine sets of triplet microtubules arranged in a ring (9 + 0)

- area bout 150 nm in diameter and are arranged at right angles to each other

- replicate during cell division

- may organize microtubule assembly during cell division (not mandatory because plants don't have centrioles)

cilia and flagella

motile cellular appendages consisting of a 9 + 2 arrangement of microtubules

- anchored to the cell by a basal body

- cilia usually occur in large numbers on the surface of the cell

- flagella are the same diameter as cilia but are limited to one or two

cilia and flagella function

- the movement of flagellum usually drives the cell in the same direction as the axis of the flagellum

- the beating of the cilia moves the cell or the fluid around the cell perpendicular to the axis of the cell (prevents mucus from entering lungs; paralyzed by nicotine)

- movement of cilia + flagella occurs when arms consisting of the protein dynein move the microtubule doublets past each other

microfilaments (actin filaments)

solid rods built from the protein actin

- thinnest cytoskeleton fiber

microfilaments (actin filaments) function

- in muscle cells: interact with the protein myosin to cause contraction

- provide cellular support

- small actin-myosin aggregates exist in some parts of the cell and cause localized contractions

- ex: contracting ring of microfilaments pinches an animal cell in two during cell division, elongation and contraction of pseudopodia during amoeboid movement, involved in cytoplasmic streaming in plant cells

pseudopodia

a cellular extension of amoeboid cells used in moving and feeding (extensions of the cytoplasm)

- microtubes break down and reform

cytoplasmic streaming

flowing of the entire cytoplasm around the space between the vacuole and plasma membrane in a plant cell

- warmth causes faster movement

microvilli

microscopic folds

intermediate fibers

constructed from keratin subunits

- more permanent than microtubules or microfilaments

intermediate fibers function

- framework for the cytoskeleton

- reinforce cell shape

- fix organelle position (ex: around nucleus)

- compose the nuclear lamina, lining the nuclear envelope's interior

cell wall

the cells of plants, prokaryotes, fungi, and some protists are reinforced by cell walls external to the plasma membrane

- plant cells: composed of cellulose fibers embedded in other polysaccharides and protein

- shared between cells

extracellular matrix (emc)

meshwork of macromolecules outside the plasma membrane of animal cells, which functions to provide support and anchorage (adhesion) for the cell

- also helps control the activity of the genes in the nucleus

intercellular junctions

neighboring cells often adhere and interact through special patches of direct physical contact

- plants: plasmodestmata

- animal: tight junctions, desmosomes, and gap junctions + adherence junctions

plasmodesmata

cytoplasmic channels that pass through adjoining cell walls

- allow things to pass through

adherence junctions

connect cells + keep them together

- organs lined by adhelium

gap junctions

allows chemical communication through cells

plasma membrane

the boundary that separates the living cell from its non-living surroundings

- about 7-8 nm thick

- selectively permeable

- too small to be seen under light microscope so early models were deduced from indirect evidence

selectively permeable

allows some substances to cross more easily than others

plasma membrane: indirect evidence

1) evidence: lipid and lipid soluble materials enter cells more rapidly than substances that are insoluble in lipids

- deduction: membranes are made of lipids

2) evidence: phospholipid content of membranes isolated from red blood cells is just enough to cover the cells with two layers

- deduction: cell membranes are actually phospholipid bilayers, two molecules thick

3) evidence: membranes isolated from red blood cells contain proteins as well as lipids

- deduction: there is protein in biological membranes

j.f danielli and h. davson (1935)

proposed a model of cell membrane structure

- cell membrane is made up of a phospholipid bilayer sandwiched between two layers of globular protein; the polar heads of the phospholipids are oriented towards the protein layers forming a hydrophilic zone, while the non-polar tails are oriented in between the polar heads forming a hydrophobic zone

s.j singer and j.l nicolson (1972)

proposed the fluid mosaic model

- the membrane is a mosaic of dispersed individual proteins floating laterally in a fluid bilayer of phospholipids

- proteins with diverse functions are either embedded in the lipid bilayer (integral proteins) or attached to the surface (peripheral proteins)

- membranes have specific inside and out faces arising from differences in the lipid composition of the two bilayers and the directional orientation of proteins and any attached carbohydrates

- carbohydrates linked to the proteins (glycoproteins) and lipids (glycolipids) are important for cell-cell recognition (the ability of a cell to determine if other cells it encounters are alike or different from itself)

- the plasma membrane regulates the passage of nutrients, waste molecules, respiratory gases, and inorganic ions that the cell requires

- hydrophobic substances pass through membranes rapidly because of their solubility in the lipid layer

- small polar molecules, such as h20 and co2 can also pass through

- large polar molecules and ions require specific transport proteins, which provide channels

membrane protein functions

- transport proteins

- enzymes

- receptor cites

- intercellular junctions

- cell-cell recognition

- attachment to the cytoskeleton and emc

modes of transport of molecules across membranes

- passive transport (diffusion, osmosis, facilitated diffusion)

- active transport (exocytosis, endocytosis)

passive transport

the diffusion of molecules across a biological membrane

- does not require the cell to expend energy

- a spontaneous process which is a function of a concentration gradient when a substance is more concentrated on one side of the membrane (high to low)

- types: (simple) diffusion, osmosis, and facilitated diffusion

(simple) diffusion

a passive process that is the net movement of a substance down a concentration gradient (from higher concentration to lower concentration)

- continues until dynamic equilibrium is reached (the molecules continue to move but there is no net directional movement)

- spontaneous process (-G)

- a substance diffuses down its own concentration gradient and is not affected by the gradients of other substances

osmosis

the diffusion of water across a selectively permeable membrane

- water diffuses down its concentration gradient (water will diffuse from the hypotonic solution to the hypertonic solution)

- direction of osmosis is determined by the difference in total solute concentration, regardless of the type of diversity of solutes in the solution

tonicity

ability of a surrounding solution to cause a cell to gain or lose water

hypertonic solution

a solution with a greater solute concentration than the inside of the cell (high solute-low water)

- water will leave cell and shrivel

- animal: will crenate

- plants, prokaryotes, fungi, and some protists (with cell walls): will plasmolyze (cell wall will shrivel inside cell wall)

- saltwater

hypotonic solution

a solution with a lower solute concentration compared to that of inside a cell (low solute-high water)

- water will enter cell and swell

- animal: become lysed (cell destruction)

- plants, prokaryotes, fungi, and some protists (with cell walls): will become turgid (dynamic equilibrium)

- freshwater, distilled water, lakes, saline

- some protists have contractile vacuoles to pump, suck, and push excess water out of cell to sustain life

isotonic solution

a solution with an equal solute concentration compared to that inside a cell (equal amounts of water in/out cell)

- no water is gained or lossed (water still moves but equally)

- animal: osmoregulation (normal)

- plants, prokaryotes, fungi, and some protists (with cell walls): will become flaccid (limp because there isn't gained water to support cell)

facilitated diffusion

diffusion of solutes across a membrane with the help of transport proteins

- diffuses polar substances that need help to pass through

- transport proteins are specific for the solutes they transport and can be saturated with solute

- can be inhibited by molecules that resemble the solute

active transport

energy requiring process during which a transport protein pumps a molecule across a membrane against its concentration gradient (low to high)

- requires the cell to expend energy (+G)

- transport proteins involved in active transport harness energy from atp to pump molecules against their concentration gradients (ex: sodium-potassium)

- bulk transport: exocytosis and endocytosis

sodium-potassium pump

3 sodium leave, 2 potassium enter

exocytosis

process of exporting macromolecules from a cell by fusion vesicles with the plasma membrane

- out of cell

- vesicle pushes on cell membrane

endocytosis

process of importing macromolecules into a cell by forming vesicles derived from the plasma membrane

- into cell

- three types: phagocytosis (solids), pinocytosis (liquids), and receptor-mediated endocytosis (specific substances)

phagocytosis

endocytosis of solid particles ("cellular eating")

- cell engulfs particle with pseudopodia and pinches off a food vacuole (changes shape and closes around food)

- lysosomes in vacuole break down food

pinocytosis

endocytosis of fluid droplets ("cellular drinking")

- droplets are taken into small vesicles

receptor-mediated endocytosis

the process of importing specific macromolecules into the cell by the inward budding of vesicles formed from coated pits

- occurs in response to the binding of specific ligands to receptors on the cell surface

cellular respiration

an atp-producing catabolic process (breaking down), which results in the partial degradation of sugars with the help of oxygen

- organic to inorganic process that releases energy (exergonic)

- C6H12O6 + 6 O2 --> 6 CO2 + 6 H2O + energy (atp + heat)

- burns glucose --> releasing energy to extract water

- has three metabolic stages: glycolysis, krebs cycle, electron transport chain (etc) + oxidative phosphorylation

glycolysis

a six-carbon glucose is split into two three-carbon sugars called pyruvate

- in the cytosol

- each reaction (10) is catalyzed by a specific enzyme dissolved in the cytosol

- occurs without the need for oxygen (used by all cells)

- has two phases: energy-investment and energy-yielding

- produces two net atp and two nadhs (1 nadh = 3 atps)

energy-investment phase

phase of glycolysis that uses two atps to phosphorylate the intermediates of glycolysis

energy-yielding phase

second phase of glycolysis that uses four atps and two nadhs (nad+), a coenzyme

- energy conserved in the high energy electrons of nadh (oxidizing agent/electron acceptor) can be used to make atp by oxidative phosphorylation

- nadh: nicotinamide adenine dinucleotide

oxidation of pyruvate to acetyl CoA

junction between glycolysis and the krebs cycle

- occurs in the mitochondrial matrix

- each pyruvate molecule (3c) is changed into acetyl CoA (2c) with the release of one molecule of co2 and the making of one molecule of nadh

krebs cycle (citric acid cycle, tca cycle)

completes glucose oxidation by breaking down a pyruvate derivative (acetyl CoA) into carbon dioxide

- occurs in the mitochondrial matrix

- for each molecule of acetyl CoA that enter the krebs cycle, two molecules of co2 are released

- each cycle produces one atp, three nadhs, and one fadh2

electron transport chain (etc)

the exergonic transfer of electrons down the etc to oxygen is coupled to atp synthesis

- occurs on the inner mitochondrial membrane

- the etc yields between two-three atps per nadh and two atps for fadh2

- oxygen: final acceptor (binds to hydrogen ions ofter accepting to make h2o)

- hydrogen ion (proton): accumulate in inner mitochondrial space to flow and move motor to create atp

aerobic

existing in the presence of oxygen

anaerobic

existing in the absense of oxygen

fermentation

the anaerobic catabolism of organic nutrients

- can generate atp by substrate-level phosphorylation as long as there is sufficient supply of nad+ (oxidizing agent for glycolysis)

facultative anaerobe

can do both aerobic and anaerobic respiration (with and without oxygen)

- yeasts, many bacteria and mammalian muscle cells

substrate-level phosphorylation

atp production by direct enzymatic transfer of phosphate from an intermediate substrate in catabolism to adp (adp + p --> atp)

- without some mechanism to recycle nad+ from nadh, glycolysis would soon deplete the cell's pool of nad+ and shut itself down for lack of of oxidizing agent

- fermentation recycles nad+ from nadh (this process consists of anaerobic glycolysis plus subsequent reactions that regenerate nad+)

- two most common types: alcohol fermentation (cheese, yogurt) and lactic acid fermentation (muscle cells when oxygen is scarce)

lactic acid fermentation

the chemical breakdown of carbohydrates that produces lactic acid as the main end product (yeast, brewing, winemaking, baking)

- muscle cells when oxygen gets scarce: lactate accumulates but is gradually carried to the liver where it is converted back to pyruvate when oxygen becomes available

alcohol fermentation

glycolysis followed by the reduction of pyruvate to ethyl alcohol, regenerating nad+ and releasing carbon dioxide

strict (obligate) aerobe

organism that requires oxygen for growth and as the final electron acceptor for aerobic respiration

strict (obligate) anaerobe

microorganisms that only grow in the absence of oxygen and are poisoned by it

photosynthesis

transforms solar light energy trapped by chloroplasts into chemical bond energy stored in sugar and other organic molecules

- synthesizes energy-rich organic molecules from the energy-poor molecules: co2 and h2o

- uses co2 as a carbon source and light energy as the energy source

- directly or indirectly supplies energy to most living organisms

autotrophic nutrition

nutritional mode of synthesizing organic molecules from inorganic raw materials

- plants require co2, h2o, and minerals as nutrients

- producers

- energy source can be light (photoautrophic) or from the oxidation of organic substances (chemoautotrophic)

- photoautotrophs: plans, algae, some prokaryotes (cyanobacteria, blue-green bacteria)

- chemoautotrophs: some bacteria (purple-sulfur bacteria)