Cell Part Functions (bio - unit 2)

cell (plasma) membrane

• Protects cell

• Controls exchange (enter/exit) of materials with the environment

• Surrounds the cytoplasm (cytosol--jelly-like fluid--and organelles)

• Composed of phospholipid bilayer and proteins 

• Fluid Mosaic Model

• Category: Support/Movement/Communication

nucleus

• Stores DNA (cell’s “blueprint”)

  • Separates DNA from cellular activity in the cytoplasm, minimizing interference/damage

• Site of transcription in protein synthesis (copying of DNA into mRNA to be sent to ribosomes)

• Surrounded by nuclear envelope

  • Double membrane with pores

  • Connects to the endoplasmic reticulum

  • DNA is wrapped around proteins called histones and then supercoiled to form chromosomes

  • Copied in the nucleus before a cell divides (DNA replication)

• Category: Genetic Control

nucleolus

• Synthesizes rRNA (ribosomal RNA) and assembles ribosomal (small and large) subunits (2)

• Located inside of nucleus; nonmembranous

• Cells can have more than 1 nucleolus

• Category: Manufacturing/Distribution/Breakdown

endoplasmic reticulum: smooth ER and rough ER

• Produces lipids and transmembrane proteins

• Packages proteins/lipids into vesicles to send to the Golgi apparatus

• Smooth variety stores enzymes, many of which are used for lipid production

• Rough variety has ribosomes (site of protein synthesis) attached

• Flattened sacs & tubules

• (1st one):

  • (1) Synthesizes oils, phospholipids, steroids, sex hormones

  • (2) Contains enzymes for detoxification (high # in liver cells)

  • (3) Stores calcium for muscle contractions

• (2nd one):

  • (1) Site of secretory protein synthesis (proteins will leave the cell) such as enzymes for digestion 

  • (2) Site of protein quality checks/recycling if incorrect

• Vesicles bud off __ to carry products to the Golgi apparatus

• Category: Manufacturing/Distribution/Breakdown

ribosome

• Site of protein synthesis according to genetic instructions

• More protein synthesis = more ribosomes present

  • Example:  high # in pancreatic cell making digestive enzymes)

  • Free (in cytosol)—site of synthesis for proteins used inside of cells (ex. for catalyzing breakdown of glucose)

  • Bound (attached to rough ER)—site of protein synthesis for those exiting the cell (ex. insulin for blood sugar regulation)

• Category: Manufacturing/Distribution/Breakdown

lysosome

• not often found in plant cells

• Breaks down worn out proteins or organelles at the end of their usefulness

• Contains digestive enzymes

• May:

  • Fuse with food vacuoles to break down nutrients

  • Digest engulfed bacteria

  • Dismantle old organelles

• Category: Manufacturing/Distribution/Breakdown

golgi aparatus

• Processing station for products of the ER; accepts ER vesicles, modifies contents, packages and ships/secretes in new vesicles

• Flattened stacks—not connected (like a pile of pita bread)

• Ex. of modification—tagging with a functional group to indicate its destination (ex. going to the plasma membrane for export vs. a lysosome for being digested)

• Category: Manufacturing/Distribution/Breakdown

mitochondrian

• Site of generating the cell’s energy in the form of ATP; has its own independent genome (DNA)

• Contains unique proteins embedded in inner membrane folds (cristae) enabling cellular respiration

• C₆H₁₂O₆ + O₂ → CO₂ + H₂O + ATP (cellular energy)

• 4 parts: outer membrane, intermembrane space, inner membrane (has cristae, or folds, that increase surface area for reactions of cellular respiration), mitochondrial matrix (containing DNA and ribosomes)

• Category: Energy Processing

vacuole (central vacuole for plants)

• Stores water, nutrients and waste products

• Provides turgor pressure necessary for the shape of a plant cell and cells to stack on top of one another

• Category: Manufacturing/Distribution/Breakdown

• Category for plants: Support/Movement/Communication

cell wall

• Outer covering that protects and provides skeletal support for a plant cell

• Cellulose fibers embedded in polysaccharides and proteins

• Category: Support/Movement/Communication

chloroplast

• Site of photosynthesis

• Contains chlorophyll molecules and its own genome (DNA)

• CO₂ + H₂O + sunlight→ C₆H₁₂O₆ + O₂

• Outer membrane, intermembrane space, inner membrane

• Compartment inside inner membrane contains stroma with DNA, ribosomes, and stacks of thylakoids, or grana (contains chlorophyll for trapping solar energy)

• Category: Energy Processing

plasmodesmata

• Channels connecting adjacent plant cells for sharing materials

• Water, nutrients and chemical messages are exchanged

• Category: Support/Movement/Communication

peroxisome

• Metabolic compartment

• Enzymes break down fatty acids for cellular energy

• Detoxify harmful chemicals by first producing H₂O₂ and then converting it to water and oxygen

• Category: Manufacturing/Distribution/Breakdown

cytoskeleton

• Network of fibers inside of the cell providing structural support

• Microtubules (compose cilia and flagella and an animal organelle for division, centrosomes; also act as “roads” for organelles in eukaryotic cells)

• Intermediate and microfilaments (reinforce cell shape)

• Microfilaments (involved in movement)

• Category: Support/Movement/Communication

centrosome

• Aids in cell division using microtubules to attach to and pull apart chromatids

• Found in animal cells

• Duplicate just before the division of a nucleus in the process of cell division

• Category: Support/Movement/Communication

(note) endomembrane system

* endo = “within”

*group of membranes and organelles in eukaryotic cells that works together to modify, package, and transport lipids and proteins

* nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and plasma membrane

(note) endosymbiont theory

*mitochondria and chloroplasts were formerly small prokaryotes that took up residence in larger cells

*the prokaryotic endosymbiont could use oxygen to release energy from organic molecules; safer from the environment inside of the larger cell