CH4: Cell Structure

Anton van Leeuwenhook

Father of Microbiology. discovered cells with microscope

Surface Area : Volume ratio

Surface area must be larger than volume so material can pass through the cell membrane

Matthias Scheliden and Theodor Schwann

hypothesized cells have a life of their own (cell theory)

cell theory

all living things are made of cells, cells are the basic unit of life, cells arise from pre-existing cells, hereditary info is passed from cell, all cells have basic chemical composition, energy flow occurs within cells

3 main parts of a cell

cell membrane, nucleus, cytoplasm

cytosol

mix of water, ions, protons, and sugar. organelles are suspended in this substance

defining characteristic of eukaryotes

nucleus

cytoplasm

collective of cytosol, organelles, and all other cellular components

eukaryotes have this structure, but prokaryotes do not.

nucleus

ribosomes

smaller and simpler in prokaryotes, synthesize proteins

plasmids

freely floating DNA in prokaryotes

nucleoids

cluster of DNA, nucleus-like structure

cell membrane

regulates what passes through the cell

cell wall

rigid, provides protection, encloses cell membrane

capsule

provides protection, sticky layer of proteins, helps bacteria stick to surfaces

pili

protein filaments, helps movement and sticking to surfaces, used for conjugation/reproduction

flagella

long slender cellular projections, used for motion like a propeller

functions of the nucleus

store DNA

chromatin

tightly packed DNA with specific proteins bound together

nucleoplasm

fluid inside nucleus, chromatin suspended here

nucleolus

dense region of protein and nucleic acids; ribosomes made here

Nuclear envelope

membrane that surrounds nucleus, made of lipid bilayer

components of nucleus

DNA, chromatin, nucleoplasm, nucleolus, nuclear envelope

endomembrane system

modifies, transports, and packages proteins and lipids in the cell

organelles in the endomembrane system

vesicles, endoplasmic reticulum, golgi body

vesicles

sacs formed by budding; cell taxi

endoplasmic reticulum (ER)

made from nuclear envelope. ribosomes give it a rough appearance. cell taxi

golgi body

"finishing touches" on proteins and lipids from ER. makes membrane proteins/lipids, protein for secretion, enzymes

organelles

cell organ system

exocytosis

moving something inside the cell to the outside

mitochondria

breaks the sugar bonds to make ATP

chloroplasts

specific type of plastid; photosynthesis

plastid

organelle in plants and algae that help with photosynthesis, storage, and pigmentation

cytoskeleton

interconnected protein filaments that reinforce, organize, and move cell structures

microtubules

hollow cylinders; movement and shape

microfilaments

support plasma membrane and movement

intermediate filaments

stable framework; structure and strength

motor proteins

activated by ATP, move materials throughout cell

cilia

short hair-like structures projecting from cell

pseudopods

temporary stretched lobe, moves and grabs prey

cell junctions

structures that connect a cell to other cells and the environment

tight junctions

animal cells. fasten cell membranes of adjacent cells together, keep bodily fluid contained

adhering junctions

animal cells. make up cardiac muscles and skin

Gap junctions

animal cells. closable channels between cells; let substances flow quickly between cells

plasmodesmata

plant cells. open channels between cytoplasm of two cells, similar to gap junction in animal cells.