Unit 2 cell structure, function, and transport mechanisms

cell

basic unit of life
example of emergent properties

emergent property

characteristic an entity fails when it is part of a larger system

prokaryotic cells

eubacteria and archaea
evolved before the evolution of the nuclear membrane and nucleus
smaller than eukaryotic cells
always unicellular

eukaryotic cells

evolved after the evolution of the nucleus
all organism other than eubacteria and archaea
membrane bound nucleus and other membrane bound organelles
sometimes unicellular sometimes multicellular

endosymbiotic hypothesis

hypothesizes that prokaryotes began to live in a symbiotic relationship with smaller prokaryotes living inside larger prokaryotes

smaller cells gain protection
larger cells gain energy production or better mobility
overtime DNA segments were "swapped" to create a more permanent existence

how did endosymbiotic hypothesis provide survival advantages

genetic annealing

the smaller prokaryotes eventually become the membrane bound organelles in the larger prokaryotes

mitochondria and chloroplast

evidence for genetic annealing

single chromosome like bacteria
ribosomes similar to those found in bacteria
independently reproduce within larger eukaryotic cells - binary fission
double phospholipid bilayer

characteristics of mitochondria and chloroplasts

binary fission

process where an organism duplicates its genetic material and then divides into two parts with each new organism receiving one copy of DNA

importance of the surface area to volume ratio

- as cells grow surface areas to volume ratio decreases
- as cells get larger it gets harder for cells to transport in and out of the required materials
- larger cells are unable to transport enough nutrients and enough waste materials out of the cell to survive
cells want a higher surface area to volume ratio

adaptations for increasing surface area to volume ratio

surface area to volume ratio can be used to explain shape of many celll/cellular surfaces

folds inside to mitochondria
flat pancake-like structures in chloroplasts
folding in the lining of our stomachs
long, thin cells have a higher surface area to volume ratio than shorter, thicker cells
surface area to volume ratio determines rate of heat exchange between an organism and its environment
higher surface area = higher amount of heat exchange

examples for increasing surface area to volume ratio

prokaryotes are unicellular
singular circle chromosome
ribosomes
cytoplasm
non membrane bound organelles
most have a cell wall
protects underlying cell membrane
helps prevent prokaryotes from bursting in an aquatic environment

prokaryotic cell structure

peptidoglycan

protein and complex carb that eubacteria cell wall is composed of

pili

hair like appendages that can be involved in the process of conjugation, movement, or attachment to surfaces

eukaryotic cell structure

plants animals fungi algae Protozoa
larger and more complex than prokaryotic cells
membrane bound nucleus and membrane bound organelles

cell membrane

mainly double phospholipid bilayer
proteins are embedded into phospholipid bilayer

integral proteins

run completely through through the membrane

channel proteins

form channels in which terrain substances can pass

carrier proteins

substances can bind to these membrane proteins, speed up substances diffusion
facilitated proteins

peripheral proteins

located on one side of the membrane
do not extend through the bilayer
act as receptors for cell signals and as structural components of the cytoskeleton

cholesterol

lipid molecule that functions to keep the membrane from being too fluid
helps secure embedded proteins
helps keep plant cell membranes from freezing in cold

carry out transport

main job of membrane

selective permeability

typically small non polar molecules can enter the cell easily
larger non polar molecules can either not enter or have to be brought in through protein channel
water molecules can diffuse even though they are polar because they are very small

nucleus

controls activities of the cells because it contains the DNA which acts as instruction for building cells proteins and determining its traits

nuclear envelope

surrounds nucelus
composed of double phospholipid bilayer
encloses DNA
contains nucleolus

nucleolus

Found inside the nucleus and produces ribosomes
contains pores made of proteins where materials enter and exit the nucleus
mRNA exits nucleus and goes to ribosomes

cytoplasm

fluid filled space contains organelles makes up volume of cell

organelles

structures specialized to carry specific functions within the cell
distribution of cell differs from cell type to cell type

ribosomes

cell particles made out of RNA and proteins
ribosomes are not usually considered organelles because they are not enclosed within the cell membrane
site of protein synthesis

free ribosomes

float in cytoplasm of the cell
found in all cell types
make functions that stay and function within the cell

attached/bound ribosomes

ribosomes attached to rough ER
found in eukaryotes only
make protein that leave the cell

endoplasmic reticulum

composed of a network of small tubes called cisternae

smooth endoplasmic reticulum

structure helps with synthesis of lipids. phospholipids, and steroids
helps with carbohydrate breakdown
detoxifies blood

rough ER

protein synthesis, modification, transport
ribosomes bound to organelle
protein folding
functions to compartmentalize the cell

Golgi apparatus

flattened membranous sacs calls cisternae
small membrane enclosed vesicles - filled with cytoplasm
when vesicles with proteins from the rough ER fuse with Golgi membrane, proteins are released into lumen

Glycosylation

Golgi modifies proteins by attaching sugars to them
addition of sugars helps determine function or protein
serve as place where polysaccharides for plant cell wall are synthesized
may act as protein stooge but eventually ships out proteins in vesicles

lysosomes

membrane bound organelles that contain hydrolases
help maintain and internal acidic pH in the cell
without lysosomes internal pH would be neutral and loss of function of digestive enzymes
help carry out intracellular digestion
play a role in destruction of old cells

apoptosis

programmed cell death

phagocytosis

Cell eating
pocket forms in cell membrane, encloses material from outside the cell
pocket becomes a small vesicle containing molecule called phagosome

phagosome

fuses with primary lysosomes to form a secondary lysosome in which hydrolysis occurs
secondary lysosome moves undigested particle to cell membrane, fuses, and releases back into the environment

plant vacuole function

storage - toxic waste and by products made by plants
can't take up large part of the cell which is a central vacuole
reproduces pigment for flowers/seed - can be in vacuoles to help with pollination

catabolism

in some plants there are vacuoles that contain enzymes that hydrolyze seed proteins into monomers

contractile vacuole

found in freshwater artists to help pump out water

vesicles

a structure within or outside a cell consisting of liquid or cytoplasm enclosed by the lipid bilayer

endomembrane system

group of membranes and organelles in eukaryotic cells that work together to modify, package, and transport lipids and proteins
bound ribosomes synthesize protein in rough ER packaged into secretory vesicles
vesicles transport protein to the Golgi apparatus to be modified
then sent to cell membrane via vesicle

mitochondria

perform the process of aerobic cellular respiration
cells can have one or many mitochondria
has its own DNA< ribosomes, and enzymes can produce via binary fission

double phospholipid membrane

outer phospholipid bilayer is smooth with large pools, most substances can pass through
inner membrane separates biochemical processes from surrounding cytosol
inner membrane folding into cristae

evolutionary significance

believed to be descendants of aerobic bacteria

plastids

present in plants and algae can divide on their own

chloroplasts

type of plastic
site of photosynthesis
have their own DNA, ribosomes and enzymes
reproduced independently
inside composed of stacks of sack like structures called thylakoids
increase surface area needed for good light dependent stage

stroma

watery space between membrane and thylakoids

cytoskeleton

interior of the cell has a meshwork of protein filaments
support shape and protection cell
keeps inner organelles organized
make up structures like flagella and cilia which aid in cell mobility
anchors cell in place by interacting with extracellular structures
composed of various protein fibers

microfilaments

usually in bundles
help cell parts move and determine cell shape
made of proteins

cell wall

provide structural boundary
most prokaryotes, fungal, and plant cells have cell wall

cell wall of plants

composed of complex carb called cellulose
support and protection
protects cells that are exposed to hypersonic conditions from bursting

cell wall of fungi

composed of complex carb called chitin
same function as plants

bacterial cell wall

mostly complex carbs

passive transport

does not require metabolic energy
powered by energy from environment
diffusion, osmosis, facilitated diffusion

diffusion

materials flow from high concentration to low concentration until equilibrium is reached
majority of movement within the cell because it saves energy

osmosis

type of diffusion specific to water
water moves from areas of high water concentration to areas of low water concentration

hypotonic to hypertonic

what way does water always flow

hypotonic

low solute concentration, high water concentration

hypertonic

high solute concentration, low water concentration

osmolarity

solute concentration

when a membrane is impermeable to a solute that is present in different concentrations on each side of the membrane

when does osmosis usually happen?

osmoregulation

the process of regulating the solute and water concentrations of the cell or body

solute

a substance that is dissolved in a solution

solution

a liquid that is the homogenous mixture of two or more substances

solvent

dissolves other substances

turgid

refers to condition where there is lots of water in a cell that has a cell wall so cells are rigid and stiff

flaccid

refers to condition where the is not enough water in a cell with a cell wall do the cell is limp and wilted

plasmolysis

when the cell membrane shrivels away from the cell wall when plant is placed into hypertonic solution
this is why salty environments kill plants

tonicity

the ability of an extracellular solution to move water into or out of a cell
related to osmolarity

isotonic environment

relative concentrations of solute and water are equal on both sides of the membrane

water potential

measure of water's potential to move
water moves from areas of high water potential to low potential
pressure potential + solute potential

open container

when does the pressure potential equal 0

transpiration

the release of water as vapor from plant leaves

facilitated diffusion

what type of diffusion is passive transport

passive transport

requires the help of channel or carrier proteins

ion channel and aquaporins

2 types of channel proteins

ion channels

gated
in some cases the stimulus is the binding of a chemical signal or ligand

gated channel

opens when a stimulus causes a change in the 3D shape of a channel

ligand gated channel

An ion channel that is stimulated to open by the binding of a small molecule such as a neurotransmitter.

voltage gated channels

stimulated by change in electrical charge

aquaporins

water crosses membrane much faster through aquaporins

carrier proteins

involves actual bonding of substances to transport protein
sugars and amino acids
glucose transporter

active transport

primary active transport directly uses a source of chemical energy (ATP) to move molecules against the gradient

secondary active transport

uses an electrochemical gradient generated by active transport as energy source to move molecules across gradient

sodium potassium pump

pumps NA out of the cell and K inside of the cell against gradients
breaksdown ATP and ADP to free phosphate ion used to release energy to bring two K ions into cell and export 3 NA ions out

proton pump

push hydrogen form from areas of low concentration to high concentration

bulk transport

movement of molecules that are too big to transport

exocytosis

process of moving large materials out of the cell
secretion
typically involves vesicles from golgi

endocytosis

process of moving large materials into cell

phagocytosis

transports large solid materials into cell
engulfing of particles then the surrounding of particles via as vesicle
ex. white blood cells taking in bacterial cell

pinocytosis

cell drinking