Notes – The Cell - Section 4-2
Nucleus
Microfilament
Golgi
Lysosome
Centriole
DNA (chromatin)
Nucleolus
Smooth ER
Nuclear envelope
Rough ER
Nuclear Pore
Microtubule
Cell Membrane
3 Main Parts of an Animal Cell
1. Cell Membrane
2. Cytoplasm
3. Organelles
Mitochondria
(and cristae)
Ribosome (on ER)
Cytoplasm
Ribosome (in cytoplasm)
Cell Membrane
-also called plasma membrane
-outer boundary of animal cell
-gives shape and flexibility to the organism
-is selectively permeable: only lets certain things through the membrane
(also called ‘semi-permeable’)
-made of 2 layers of phospholipids and proteins (lipid bi-layer!)
2 kinds of proteins in cell membrane
1. peripheral proteins – proteins located on both the inside & outside of the membrane
2. integral proteins – proteins embedded inside the lipid bi-layer)
-functions of the proteins in the lipid bilayer
1. create channels or holes for things to pass through
2. carry some molecules across and into or out of cell
3. outside ones have carbs attached to hold the cell together
4. provide attachment sites for hormones and viruses
-represented by the fluid mosaic model – because it is always moving, and the proteins form an ever
changing mosaic ( pattern) of particles
Cytoplasm
-cytoplasm: jelly like material inside the cell membrane containing water & salts- surrounds organelles
-cytoplasmic streaming: the constant motion of the cytoplasm moving organelles around
-most visible in plant & protozoa cells
Organelles ( means “little organs”)
Organelle: parts of the cell that perform specific functions to keep the cell alive
1. Ribosomes “Protein Factory” of the cell
-small round structures where proteins are made
-smallest & most numerous organelle (we need lots of protein!)
-made of RNA and protein
-have no membrane (in prokaryotes)
-found in 2 places:
1. floating free in the cytoplasm – proteins made here are used in the cell
2. attached to ER – proteins made here are used outside of the cell
2. Endoplasmic Reticulum “ Highway” of the cell
-a system of folded membranes, sacs, and tunnels through which proteins move
-act like a “intracellular” highway- path for the proteins to move on
- 2 types of ER
1. Rough ER
-has ribosomes attached
-makes proteins that are exported outside the cell
2. Smooth ER
-has no ribosomes attached so its smooth
-makes steroids in glands, controls calcium in muscles, and helps
liver break down toxins
3. Golgi – “ Factory “ of the cell
-The part of the cell that processes, packages, and secretes proteins – like a factory
-made of stacks of fluid sacs
-operates like a production line-
Protein made in ribosome-----passes to inside of ER to smooth area------protein gets enclosed
in a membranous pouch called a vesicle------ pinches off from smooth ER-----travels from 1 Golgi sac to another changing as it goes----last golgi sac moves it to the cell
membrane where it dumps its contents outside the cell
4. Mitochondria – “Powerhouse” of the cell
-oval organelles with 2 membranes
1. smooth outer membrane that separates it from the cell
2. folded inner one (called cristae) that maximizes surface area available to make ATP
-ATP : the energy of the cell that drives all cell reactions
-respiration centers of the cell
-respiration: process that releases chemical energy from food & creates ATP
-lung respiration brings in oxygen so the cell can turn food into ATP
-lots of mitochondria in cells that need a lot of energy like liver & muscles
-has its own DNA- scientists think it was a mutualistic relationship between 2 organisms initially
5. Lysosomes – “Clean up Crews” of the cell
-small round organelles containing digestive enzymes to break down materials
-found in animal, fungus, and protozoa – (plants have vacuoles)
-plays role in early development- “chisels” away extra tissue til proper structures form
6. Nucleus - “Control Center” of the cell
-site where nucleic acids are made
-DNA (instructions to make proteins)
- RNA (stores & transmits info to make proteins)
-surrounded by a double membrane called the nuclear envelope that has many pores
-contains nucleoplasm: the dense protein rich substance in the nucleus
-contains DNA in either of 2 forms:
Chromatin: uncoiled DNA in a cell that is not actively dividing
Chromosome: coiled DNA in a cell that is in the process of dividing
-has the nucleolus: small dark round area in the nucleus where ribosomes are partially made
7. Microtubules & Microfilaments (Cytoskeleton)
-help support cell and give it shape (like our bony skeleton does)
-microtubules
-long slender tubes made of protein
-spindle fibers: special microtubules that move chromosomes during cell division
-microfilaments
-thin protein strands
-found just under cell membrane- play role in cytoplasmic streaming & move organelles
and play a role in muscle contraction
- are a polymer made of many linked protein molecules called actin
8. Centrosomes & Centrioles
- Centrosomes: small dark bodies near the nucleus that contain centrioles
-Centrioles: Barrel shaped structures containing triplets of microtubules right angles to each
other with spindle attached
-only seen during active cell division
- in animal cells, but not plants
Cilia & Flagella
-2 kinds of structures that extend out from the surface of the cell
cilia: many short hairlike extensions on cells
-many line the surface of organs to move fluids & mucus
Flagella: 1 or 2 whip like extensions that extend out to help the cell move
-both have a similar structure – a “9 + 2” structure – 9 pairs of microtubules arranged around a
central pair
Parts of the Plant Cell
Nucleus (circle)
Nuclear Envelope
Microfilament
Nuclear Pore
Ribosome
(in cytoplasm)
Golgi
Leukoplast
Chloroplast
Vacuole
Microtubule
Mitochondria
Rough ER
Smooth ER
Chromoplast
Cell Wall
Cell Membrane
Thylakoids-in chloroplast
Has all the same organelles as animal cell and 3 ADDITIONS
1. Cell Wall
-rigid outer covering of the plant cell that supports and protects it
2 types of cell wall
1. Primary Cell Wall
-forms while plant is still growing
-made of cellulose
2. Secondary Cell Wall
-forms after plant is done growing
-made of cellulose and lignin
-lignin: substance that makes the wood of plants-hardens it
-middle lamella: a “glue” that is found between plant cells that holds them together
-made of pectin: sticky stuff that makes jelly a gel
2. Vacuoles
-largest organelle in plant cells – 90% of the volume
-similar to lysosomes-stores enzymes and waste
-may keep toxins from the plant cell
3. Plastids
-similar to mitochondria- have 2 membranes and own DNA
-capture sunlight and convert it to energy
3 types
1. Chloroplast
-contains chlorophyll: green pigment in plants
-has thylakoids: system of flattened sacs where PHOTOSYNTHESIS occurs
2. Chromoplasts
-stores other color pigments
-carotene = orange pigment
-anthocyanin= red pigment
-xanthophyll = yellow pigment
3. Leukoplasts
-stores food as STARCH (which is white)
Tissue Systems of Plants
1. Dermal Tissue System
-forms the outer layer of the plant (like the skin)
2. Ground Tissue System
-makes up the roots and stems (they are in the ground)
3. Vascular Tissue System
-this is the water transport system of the plant (carried in vessels)
-Xylem: transfers water and minerals from root to leaves
-Phloem: transfers dissolved sugars (food) in the plant
4 Organs of the Plant
1. Roots
2. Stems
3. Leaves
4. Flowers