Bio Unit 2

Eukaryotic Cell Structure

• membrane made out of phospholipid bilayer

• plants have cell wall made out of cellulose

• fungi have a cell wall made of chitin

• water based cytoplasm

• Have a nucleus 

Prokaryotic cell structure

• lipid bilayer cell membrane and cell wall made of peptidoglycan

• water based cytoplasm

Nucleus

has a 2 layer membrane, protects DNA from enzymes in cytoplasm, pores in the membrane allow movement of mRNA

Eukaryotic DNA

is linear, double stranded, has paired chromosomes

stored in nucleus

multiple chromosomes

DNA is wrapped around histone proteins

Prokaryotic DNA

• nucleoid region

• 1 circular, double stranded chromosome

• can have plasmids (extra chromosomal pieces of DNA called plasmids) which can be shared

eukaryotic protein production: ribosomes

60s subunit/40s subunit

big and small ribosomal subunits 80s

made up of proteins and rRNA

can be free floating in cytoplasm or attached to endoplasmic reticulum

prokaryotic protein production: ribosomes

50s subunits, 30s subunit

big and small ribosomal subunits, 70s 

subunits made of protein and rRNA

ribosomes are free floating in cytoplasm

where is protein packing and sorting done?

in eukaryotic cells, it is done in Golgi apparatus, rough ER, and the vesicle

in prokaryotic cells, it is done in the cytoplasm

smooth ER

• detoxification of alcohol, medicine, drugs

• phospholipid synthesis

• calcium storage

lysosome

breaks down/digests food, cell waste, recycles organelles in animal cells

vacuole

maintains cell turgidity, stores water ions nutrients and waste

perioxisome

a type of vesicle that is filled with enzymes that oxidize and break down fatty and amino acids, producing hydrogen peroxide in the cell

produces cholesterol for cell membrane

found in plant and animal cells

nucleolus

site of rRNA production, created ribosomal subunits

eukaryotic motility

flagella (single), cilia, pseoduopodia (extended cytoplasm)

prokaryotic motility

flagella (single or multi)

invagination theory

explains that the plasma membrane of ancestral eukaryotic cells folded inward to form internal compartments and organelles like the nucleus and endoplasmic reticulum 

endosymbiotic theory

explains that the mitochondria and chloroplasts in eukaryotic cells were once free living prokaryotic cells that were engulfed by larger host cells and formed a permanent symbiotic relationship

functions of the endomembrane system

synthesis of proteins

transport of proteins to membranes, some organelles or out of cell

metabolism and movement of lipids

detoxification of poisons

nuclear envelope

pores in the envelope allow mRNA to leave the nucleus

ribosomes

MRNA fed through ribosomes to make proteins

rough ER

continuous with nuclear envelope

proteins folded and modified with sugar tags

proteins can be used in membranes inside the cell or packaged in vesicles and sent to the Golgi for further labeling

chaperonin proteins

assistant with protein folding and protein trafficking 

cell stress response

assist with protein degradation 

cytoskeleton

anchros organelles

aids in cell motility

can be dismantled and reassembled

road that vesicles travel on

microtubules

hollow rods made of proteins called tubulin

can grow in length and be disassembled

support the shape of cell, serves as tracks for motor proteins or secretory vessels, separate chromosomes during cell division

motor proteins

cell motility requires the interactions between motor proteins and cytoskeleton

with plasma membrane, entire cell

bend cilia and flagella

muscle cell contraction

endocytosis

cell junction

allow for adhesion, communication, and maintaining tissue structure

plasmodesmata

perforations in cell walls of plants which allow cytosol to pass through

joins intervals environments of adjacent cells

allows water and small solutes to pass freely from cell to cell

some proteins and even RNA can move along cytoskeleton to pass through as well

gap junction

also called communicating junctions

provide cytoplasmic channels from one cell to an adjacent cell

allow ions, sugars, amino acids, and small molecules to pass 

necessary for cell communication in animal cells

tight junctions

animal cells

plasma membranes of neighboring cells are very tightly pressed against each other

bound together by specific type of proteins

form continuous seals around cells

prevent leakage of extracellular fluid

desmosome

anchoring junction

functions like rivets

fasten cells together in sheets

anchored by intermediate filaments made of keratin

attach muscle cells to each other

muscle tears can mean rupture of desmosomes

what do cell membranes do?

they protect the inside of the cell from the external environment

they are selectively permeable, so they control movement in and out of the cell

serves a role in cell communication, maintaining cell shape and cell to cell adhesion

without cholesterol (cold)

• rigid, not as fluid/flexible

• may break

without cholesterol (hot)

too fluid/flexible

wont hold shape

channel proteins

selective

allow polar, hydrophilic, and large compounds to avoid the hydrophobic core of the plasma membrane, which could slow or block their entry into the cell

open or gated

carrier protein

selective

change shape in response to binding of their target molecule, moving the molecule to the opposite side of the membrane

allows polar, hydrophilic and charged compounds to avoid the hydrophobic core of the plasma membrane

turgid cell

water enters the cell by osmosis, vacuole swells and pushes against the cell wall

flaccid cell

water lost from cell, vacuole shrinks, cell loses shape

receptor mediated endocytosis

receptor proteins on the cell surface are used to capture a specific target molecule

when the receptor binds to its specific target molecule, endocytosis is triggered, and the receptors and their attached molecules are taken into the cell in a vesicle

allows the cell to lake up large amounts of molecules

phagocytosis

large particles, such as cells or cellular debris, are transported into the cell

food vacuole will fuse with the lysosome and break contents down into usable components (sugars, amino acids) 

pinocytosis

cell takes in small amounts of extracellular fluid

cell samples surrounding fluid to get whatever nutrients and other molecules

held in small vesicles