Chapter 6- A Tour of the Cell

why are cells so small

cell surface to volume ratio

why is cell surface to volume ratio important

plasma membrane surrounding cell must provide sufficient surface area for exchange of oxygen, nutrients, and wastes relative to the volume of the cell

nucleus structure

surrounded by nuclear envelope, double membrane with pores, most DNA located in the nucleus

nucleus function

double membrane with pores regulates movement of materials between nucleus and cytoplasm

nucleolus structure

dense structure inside nucleus

nucleolus function

synthesizes rRNA & combines it with proteins to make ribosomal subunits

ribosome structure

composed of protein and RNA

ribosome function

making protein

two different types of ribosomes

free and bound

free ribosomes

produce proteins to be used within the cytosol

bound ribosomes

attached to ER or near nucleus, make proteins that will be included with membranes, packed into organelles, or exported from the cell

what does the endomembrane system consist of

nuclear envelope, ER, golgi apparatus, lysosomes, vesicles, vacuoles, plasma membrane

what is the endomembrane system

The endomembrane system is a network of membranes that function to modify, transport, and package proteins and lipids in the cell

endoplasmic reticulum location

continuous within the nuclear envelope

smooth ER function

multifunctional, has enzymes involved in phospholipid/steroid synthesis, carbohydrate metabolism, and drug detoxification. works on storage and release of calcium ions during muscle contractions

smooth ER structure

no ribosomes on outside surface

rough ER structure

ribosomes on outside surface

rough ER function

manufactures proteins intended for secretion, manufactures membranes

Golgi apparatus function

shipping and receiving

Golgi apparatus structure

stack of flattened sacs

lysosomes function

in animal cells only, digests food and takes apart damaged parts of cell

what is phagocytosis

when lysosomes digest food and pass products into the cytosol

what is autophagy

when damaged organelles fuse to lysosome, enzymes dismantle the membrane bound material, organic monomers are returned to cytosol for reuse

lysosome structure

membrane- enclosed sacs containing hydrolytic enzymes that digest macromolecules

different functions of vacuoles

food, contractile vacuole (pump excess water out of freshwater protists), storage vacuole (in only plants), large central vacuole (in only plants)

storage vacuoles function

store organic compounds/inorganic ions for the cell, may contain dangerous metabolic by products, poisonous or unpalatable compounds for protection from predators

large central vacuole function

encloses a solution called cell sap, a plant increases in size as a vacuole absorbs water and expands, can fill 80 percent or more of a cell

endosymbiont theory

mitochndeia and chloroplasts originated as prokaryotic cells engulfed by an ancestral eukaryotic cell

evidence of endosymbiont theory- both organelles____

surrounded by double membrane, grow and reproduce independently within the cel, contain some DNA and ribosomes, synthesize some of their own proteins

mitochondria structure

double membrane- narrow inner membrane space exists between the two layers, smooth outer membrane, inner membrane folded for cristae, respiratory enzymes embedded in membrane

mitochondria function

chemical energy conversion, provides ATP for the cellc, folding in membrane increases surface area for enzymatic reaction

mitochondrial matrix

inside inner membrane, contains respiratory enzymes, mitochondrial DNA, and ribosomes

chloroplast structure

two membranes separated by thin inner membrane space, thylakoids, storm, amylopasts, chromoplasts

thylakoids

inside inner membrane, flattened sacs, the stacks of sacs called grana, photosynthetic enzymes embedded

stroma

fluid surrounding thylakoids, contain chloroplast DNA, ribosomes, and enzymes

amyloplasts

store starch

chromoplasts

contain pigments for fruits and flowers

cytoskeleton structure

network of protein fibers

cytoskeleton function

give mechanical support, cell movement

3 types of protein fibers

microtubules, microfilaments, intermediate filaments

what proteins produce cellular movements

motor proteins

microtubules

hollow rods, provide supporting framework for the cell, separate chromosomes during cell division

motor proteins

powered by ATP hydrolysis, transports organelles, responsible for muscle contraction, responsible for cell division

cilia and flagella

universal structure, may be used to move through aqueous media, stationary cells use to move fluid past the cell

cell wall of plants

protects the cell from damage and maintains shape, some cells add a secondary cell wall between the plasma membrane and primary wall for more protection and support (wood)

extracellular matrix

attached to outside of animal cells, mechanical signaling pathway between firbronectins/integrins of ECM and microfilaments of cytoplasm

plant junction

plasmodesmata- channel in plant cell wall that connects plasma membrane of bordering cells, small solutes, water, some proteins, and RNA can move cell to cell

3 animal cell junctions

tight, desmosomes, gap

tight junctions

hold adjacent cell membranes tightly together

desmosomes

anchoring junctions hold cells in strong sheets

gap junctions

communicating junctions for exchange of ions and small molecules between cells