Ap Biology - Unit 2

high SA:V ratio

allows for specialization

in order to get enough nutrients, be able to reduce waste, get resources, acquire or dissipate thermal energy, etc

higher efficient exchange of materials with the environment

endosymbiotic theory

led to the evolution of complex eukaryotic cells with compartmentalization

a free-living aerobic prokaryotic cell was engulfed by an anaerobic cell through endocytosis

electron microscope

allowed for scientists to figure out the exact functions of cells

prokaryotes

only in domains bacteria and archaea

circular DNA in nucleoid region, no nucleus

cell wall- made of peptidoglycans

filled with semi-fluid cytosol

no membrane bound organelles

eukaryotes

more complex, ordered into smaller structures called organelles

DNA in nucleus bounded by a membranous nuclear envelope

cytoplasm between plasma membrane and nucleus

plasma membrane

complex outer envelope

composed of phospholipid bilayer

regulates movement in/out of cell.

flexible due to weak bonds holding it together, has higher fluidity when phospholipids have double bond (bend in tail) or when it has cholesterol in it

amphipathic

a molecule containing both hydrophilic and hydrophobic parts

semipermeable membrane

only small hydrophobic molecules can pass through unaided

anything large/hydrophilic must pass through active/passive transport

water can’t move through easily due to its polarity

fluid mosaic model

describes the fluid and flexibility of the membrane, and also the components its made from.

peripheral proteins

are loosely associated with the lipid bilayer

located on inner/outer surface (the hydrophilic head part of the plasma membrane)

is polar and hydrophilic

integral proteins

firmly bound into the plasma membrane

some extend all the way through the membrane

amphipathic to allow anchoring

hydrophilic with charged and polar side groups, but also hydrophobic with nonpolar side groups that penetrate the hydrophobic interior of the bilayer

6 major protein functions

transport

cell to cell recognition

enzymatic activity

signal transduction

intercellular joining

attachment to ECM and cytoskeleton for anchoring

adhesion proteins

membrane proteins form junctions between adjacent cells

helps cells interact with each other and with the extracellular matrix

receptor proteins

serve as docking sites for arrivals at the cell

ex: horomones

transport proteins

form pumps that use ATP to actively transport solutes across the membrane (active transport)

hydrophilic channel that certain molecules/ions can use as a tunnel

specific for the substance it moves

carrier proteins

bind to molecules and change shape to shuttle molecules across the membrane

channel proteins

selectively allow the passage of ions/molecules

hydrophilic tunnel

cell surface marker

exposed on cellular surface 

play a role in cell recognition/adhesion

ex: glycoproteins, glycolipids, proteins

carbohydrate side chains

attached to surface of some proteins

found only on outer surface

cholesterol

a type of steroid that maintains fluidity in the plasma membrane by increasing the space between phospholipids due to bend

can also prevent plasma membrane from becoming too fluid in hot conditions

randomly distributed and wedged between phospholipids in the cell membrane of eukaryotic cells

nucleus

largest organelle of cell

directs what goes on in cell

responsible for cell’s ability to reproduce

home of hereditary information (DNA)

DNA organized into large structures called chromosomes

nucleolus

is the most visible structure of nucleus, which is where rRNA is made and ribosomes are assembled

nuclear envelope

a highly regulated membrane barrier that separates the nucleus from the cytoplasm in eukaryotic cells

ribosomes

sites of protein synthesis

manufacture all proteins required/secreted (discharged) by the cell

bind messenger RNA (mRNA) and transfer RNA (tRNA) to synthesize proteins

round structures consisting of 2 subunits: the large subunit and the small subunit. composed of RNA and proteins

can either be free floating or attached to the endoplasmic reticulum (ER)

endoplasmic reticulum

continuous channel that extends into many regions of the cytoplasm

lipid proteins synthesis/transport

rough endoplasmic reticulum

attached to nucleus

studded with ribosomes, which makes it appear ‘rough’

proteins generated here are trafficked to/across plasma membrane, or used to build Golgi bodies, lysosomes, or the ER.

smooth endoplasmic reticulum

lacks ribosomes

makes: lipids, hormones, steroids

breaks down toxic chemicals (detoxify)

golgi complex

Once the ribosomes on the rough ER have completed synthesizing proteins, the Golgi bodies modify, process, and sort the products (proteins, lipids, etc)

packaging/distribution centers for materials destined to be sent out of cell

package final products into vesicles, which carry products to plasma membrane

involved in production of lysosomes

mitochondria

responsible for converting the energy from organic molecules (glucose) into useful energy for the cell

energy molecule in the cell is adenosine triphosphate (ATP). ATP production.

unique oblong shape and characteristic double membrane consisting of an inner portion and an outer portion

mitochondria structure

inner membrane forms folds called cristae

separates innermost area (called the matrix) from the intermembrane space

outer membrane separates the intermembrane space from the cytoplasm

production of ATP done on the cristae

lysosomes

tiny sacs that carry digestive enzymes

break down old/worn out organelles/debris/large ingested particles

cells clean-up crew

keep cytoplasm clear of unnecessary flotsam

sometimes contain hydrolytic enzymes that function only at an acidic pH, which is enclosed inside the lumen of the lysosome

centrioles

small, paired, cylindrical structured often found within microtubule organizing centers (MTOCs)

Most active during cellular division

When cell is ready to divide, centrioles produce microtubules, which pull the replicated chromosomes apart and move them to opposite ends of the cell

common in animal cells but not in plants

centrisomes

pair of centrioles

vacuoles

latin for “empty cavity”

large vesicles, fluid-filled sacs that store water/food/wastes/salts/pigments for later use/removal

larger in plant cells (plant cells have a central vacuole) to take up cytoplasm space to increase intracellular transport speed

peroxisomes

uses peroxide to break down molecules

breakdown of long fatty acids through beta-oxidation

cytoskeleton

network of fibers that maintain cell shape (microfilaments and microtubules)

microtubules

made up of protein tubulin

participate in cellular division/movement

integral part of centrioles/cilia/flagella

microfilaments

important for movement

composed of protein actin

actin monomers joined together and broken apart as needed to allow microfilaments to grow and shrink

assist during cytokinesis/muscle contraction/formation of pseudopodia extension during cell movement

cilia

allow motion in cells

in respiratory tract, cilia sweep constantly back and forth to keep out pathogens/dust

flagella

allow for motion in cells

every sperm cell has flagellum, enabling it to swim through the female reproductive organs to fertilize the waiting ovum

extracellular matrix

also known as ECM

molecules secreted by cell, mostly glycoproteins or other carb/containing molecules, especially collagen

provides structure/biochemical support

plasmodesmata

connections between plant cells that allow communication amongst them

cell wall

rigid layer of cellulose (polysaccharide) in plant cell walls, chitin in fungi cell walls, and peptidoglycan in bacterial cell walls

outside of plasma membrane

provides support for cell and prevents lysis

comprised of complex carbohydrates

chloroplasts

contain chlorophyll, making them green

involved in photosynthesis

part of plastid family, has double membrane

central vacuole

takes up most of cytoplasm and crowds out other organelles

contains cell sap in mature plants

full vacuole means plant is not dehydrated

facilitated transport

substances must pass through a specific channel protein instead of directly through the membrane due to its hydrophilic/charge/etc. 

depends on a number of proteins that act as tunnels through the membrane

ex: aquaporins are water specific-channels

diffusion

a substance will move down its concentration gradient

simple diffusion

if the diffusion molecule is hydrophobic, the nonpolar molecule can drift through the membrane unaided

facilitated diffusion

diffusion of a substance requires the help of a channel protein

passive transport

when the substance is moving down its concentration gradient

no energy required

dynamic equilibrium

as many molecules cross the membrane in one direction as the other

osmosis

process where water is diffused

water always moves from areas where it is more concentrated to where it is less concentrate

water moves to dilute solid particles

tonicity

describes osmotic gradients

isotonic

the solute concentration is the same inside as outside

no net water movement

plant cells become flaccid in an isotonic environment, normal for animal cells

hypertonic

solution has more total dissolved solutes than the cell

cell loses water

plant cells experience lethal plasmolysis in a hypertonic environment. In animal cells it is called crenatation

hypotonic

solution has less total dissolved solutes than the cell

cell gains water

plant cell in a hypotonic solution swells until the wall opposes uptake, becoming turgid/firm (which is optimal); while an animal cell in a hypotonic solution will lyse/burst since their membrane are not as strong

water potential

Ψ

is the measure of potential energy in water and describes the eagerness of water to flow from an area of high water potential to an area of low water potential

affected by pressure potential Ψ_p and solute potential Ψ_s

active transport

allows a substance to move against its concentration gradient by using energy to help it along

Performed by specific proteins along membrane

ion pumps

membrane potential = voltage difference across a membrane

voltage created by difference in the distribution of positive/negative ions across a membrane

2 combined forces (electrochemical gradient) drive diffusion of ions across a membrane

electrogenic pump is a protein that generates voltage across a membrane

ex: sodium-potassium pump, which pushes out 3 Na⁺ and brings in two K⁺ and depends on ATP

cotransport

occurs when active transport of a solute indirectly drives transport of other solutes

symport

a process by which two different molecules are transported across a cell membrane in the same direction

antiport

a process that moves two or more different molecules in opposite directions across a cell membrane

endocytosis

when the particles that want to enter a cell are too large to be transported by a channel protein, the cell uses a portion of the membrane to engulf that substance

Membrane forms a pocket, pinches in, and eventually forms a vacuole/vesicle

pinocytosis

the endocytosis of liquids

phagocytosis

the endocytosis of solids

receptor mediated endocytosis

cell surface receptors work with endocytic pits that are lined with a protein called clathrin

when a ligand binds to one of these receptors, it is brought into the cell by the folding in of the cell membrane

vesicle forms around incoming ligand and carries it to cell’s interior

exocytosis

large particles transported out of cell ex. waste, specific secretion products (like hormones)

fusion of a vesicle with plasma membrane

reverse endocytosis

bulk flow

one-way movement of fluids brought about by pressure

ex. movement of blood through a blood vessel

dialysis

diffusion of solutes across a selectively permeable membrane

cell junctions

result of cells in close contact with each other

allow neighboring cells to form strong communication connections/nutrient flow

fastens cells to each other

provide contact between neighboring cells or cell and extracellular matrix

3 types

desmosomes

hold adjacent animal cells tightly together

pair of discs associated with the plasma membrane of adjacent cells + intermediate filaments within cells that are also attached to discs

gap junctions

protein complexes that form channels in membranes and allow communication between cytoplasm of adjacent animal cells for the transfer of small molecules/ions

tight junctions

tight connections between membranes of adjacent animal cells

so tight that there is no space in between cells

seal off body cavities

prevent leaks

go all around cells rather than random spots like desmosomes