Author Notes

hey there ! thank you for visiting my unit 2 cram sheet on cell structure and function ! majority of the info are derived from ap daily videos, teacher lectures, and the campbell biology in focus ap editon (3rd edition) textbook :)

• like this cram sheet? check out my other cram sheets via my profile ;D

• external links to other resources will also be linked to help you better understand this topic !!!!

• this is probably the only cram sheet that’ll have some textbook info lol

╭ Other Resources :

:: cararra ﹒﹒ 20 min ap bio review video based from the campbell biology 11th edition textbook!

:: sticky science﹒﹒short, bite-sized review videos in the form of reels from a previous ap bio student who got a 5 on the AP exam!

:: the APsolute recAP﹒﹒15 min review video based on all the topics of unit 2!

:: khan academy ﹒﹒the entire unit 2 course from khan academy!!

:: fiveable ﹒﹒ reviews unit 2 with articles and quizzes for you to practice your knowledge on!

﹙✦﹚﹒﹒note that abbreviations are used throughout!

﹙2.10 + 2.11 - Compartmentalization﹚

✦﹒prokaryotes are a single-celled organism that has no nucleus

• has one chromosone, with naked DNA that is not associated with protein

• reproduces asexually

✦﹒eukoryotes are organisms that have a nucleus

• can be single or multicelled

• multiple chromosones

• has additional internal membrane-organelles that compartmentalize the cells

  • cellular compartments allow for various processes and reactions to occur, increasing efficiency within the cell

  • internal membranes generally minimize competing interactions and increase surface areas at reaction sites

  • loss of/changes to intracellular compartments hinder cell function

✦﹒endosymbiotic theory (endosymbiosis) is a theory where the mitochondria and chloroplasts are prokaryotes that were engulfed by eukaryotes

• oragnelles were prokaryotes that were engulfed by endocytosis

  • overtime, engulfed cell lost some of its independent functionality, becoming the mitochondria/chloroplast

• evidence —

  • mitochondria and chloroplasts are the same shape and size as prokaryotes

  • organelles have their own DNA, double membranes, and ribosomes

• proves how eukaryotes and prokaryotes are similar in structure

╭ Other Resources :

:: amoeba sisters ﹒﹒ breakdown on endosymbiotic theory !!

﹙✦﹚﹒have a good understanding of endosymbiotic theory and its evidences ! it’ll likely come up in mcqs and frqs

﹙2.1-2.2 + 2.10 - Parts of the Cell﹚

✦﹒ribosomes synthesize protein according to the mRNA sequence within the cell

• made of ribosomal RNA (rRNA) and proteins

• has a large and small subunit

• either free (majority) or bound ribosomes

  • free ribosomes produce proteins

  • bound ribosomes are used to exporting

✦﹒the endoplasmic reticulum (ER) is a network of membrane tubes

• rough ER synthesizes with proteins that are generally secreted by the cell

  • has ribosomes attached to membrane

  • compartmentalizes the cell

    • packages newly synthesized proteins made by attached ribosomes for possible export from the cell

    • as proteins are produced by rough ER, polypeptide chains travel across ER membrane and into cisternal space

• smooth ER functions in diverse metabolic processes, varies in cell type

  • has no attached ribosomes

  • processes include synthesis of lipids, metabolism of carbs, detoxification of drugs and poisons, and storage of calcium ions

✦﹒the golgi apparatus is the warehouse of receiving, sorting, manufacturing, and shipping proteins

• involved in the correct folding and chemical modification of newly synthesized proteins and packaging for protein trafficking

✦﹒the mitochondria is the powerhouse of the cell (had to say it)

• functions in production of ATP energy that is used for cell work

• has a double membrane

  • outer membrane is smooth

  • inner membrane is highly convoluted, forming folds called cristae

    • cristae help increase the surface area to enhance the productivity of cellular respiration, allows more ATP to be made

    • electron transport and ATP synthesis occur there

✦﹒the lysosome is the trashcan of the eukaryotic cell

• a membrane-enclosed sac of hydrolytic enzymes that are used to digest (hydrolize) macromolecules or damaged cell parts

• works best in a acidic environment

  • breaking open/leaking will result in malfunctioning of enzymes

✦﹒vacuoles are membrane-bound sacs that are found in eukaryotic cells

• perform a variety of functions—

  • contractile vacuoles pumps excess water out of the cell to maintain concentration of ions + molecules and water balance

  • releases waste from a cell

  • stores water

• central vacuoles play a major role in plant cell growth

  • a major difference between animal and plant cells

  • can take up 80% of volume, typically the largest compartment of cell

✦﹒chloroplasts are the site of photosynthesis

• found in photosynthetic eukaryotic cells

• has a double outer membrane

• captures energy from the sun and producing sugar for the organism

• contains thylakoids that are highly folded to increase the efficiency of light dependent reactions

  • like the cristae in mitochondria, the high foldings help maximize surface area

﹙✦﹚﹒i know its a lot, but just keep focus on the process of protein synthesis with what each compartment does + remember the impact of cristae and thylakoids via surface area AND lysomes’ + vacuoles’ role briefly…

﹙2.3 - Cell Size﹚

✦﹒cells are small because they have a high surface area-to-volume ratio (SA:V)

• a high SA:V makes a more efficient exchange of materials with the environment

• limitations can restrict cell size and shape

• to calculate the SA:V—

  • SA = 4πr²

  • V = 4/3πr³

  • SA/V = SA:V

  • a high value = high SA:V = smaller cell

╭ Other Resources :

:: science sauce ﹒﹒ surface area to volume ratio explained !!!!

﹙✦﹚﹒woohoo first bit of math in ap bio! understand the importance of why the SA:V value must be big and why cells are small

﹙2.4-2.5 - Plasma Membrane﹚

✦﹒cell membranes provide a boundary between the interior of the cell and the outside environment

• this is thanks to phospholipids, which form a bilayer in the environment

  • is amphipathic, with a polar head and nonpolar tails

• embedded proteins on the membrane are either hydrophilic or hydrophobic

  • peripheral proteins are loosely bound to the surface of the membrane

    • hydrophilic with charged and polar side groups

  • intergral proteins can be either hydrophobic/philic

    • hydrophobic protein has nonpolar side groups that penetrate the hydrophobic interior of bilayer

  • these proteins have a variety of functions like transport, cell-cell recognition, enzymatic activity, signal transduction, etc.

✦﹒the fluid mosaic model illustrates the the framework of the cell membrane

• structure is not static and is held together mostly by hydrophobic interactions

• a mosaic of protein molecules in a fluid bilayer of phospholipids

• consists of lipids, proteins, cholesterol, and carbs

  • cholesterol is a hydrophobic steroid that regulates bilayer fluidity under certain conditions

    • high temp →less fluid membrane

    • low temp → helps retain fluidity

fluid mosaic model with labeled areas of the membrane proteins’ functions

✦﹒the cell membranes are selectively permeable

• small nonpolar molecules (N₂, O₂, CO₂) can pass freely

• hydrophilic substances (large polar molecules + ions) cannot pass the membrane freely

  • to pass the membrane, they go thru transport proteins

    • channel proteins are a hydrophilic tunnel that allows specific molecules to pass through

    • carrier proteins change shape to move a target molecule from one side of the membrane to the other

• small molecules like H₂O can pass the membrane, but at a relatively small amount

  • large amounts of H₂O pass thru channel proteins called aquaporins

• plants, fungi, and prokaryotes have cell walls which have permeability as well

  • permeable via the plasmodesmata which are small holes between the plant cells

  • composed of complex carbohydrates

    • plants → cellulose, fungi →chitin, prokaryotes →peptidoglycan

﹙✦﹚﹒understanding the fluid mosaic model is useful, as well as the cell membrane’s permeability

﹙2.6-2.7 + 2.9 - Membrane Transport﹚

✦﹒passive transport is the movement of molecules from a high to low concentration, without the use of energy

• diffusion is a type of passive transport in which small nonpolar molecules (O₂ , N₂ , CO₂) pass freely

• facilitated diffusion is also a type of passive transport that involves transport proteins

  • typically for transferring hydrophilic molecules

  visual of the passive transport types

✦﹒active transport is the movement of molecules from a low to high concentration (against the concentration) using energy (ATP)

• uses carrier proteins called pumps

• cotransport is a secondary active transport that uses energy from a electrochemical gradient to transport two different ions across the membrane through a protein
  visual of cotransport

╭ Other Resources :

:: amoeba sisters ﹒﹒ can you tell i like amoeba sisters? talks about the types of passive and active transport

:: crash course ﹒﹒ very in depth on membranes and transport + includes some detail about osmosis and other processes ! (maybe stop at 6:37)

﹙✦﹚﹒this is like something you have to entirely understand.. I recommend having a understanding of the sodium na pump thing too

﹙2.8 - Tonicity and Osmoregulation﹚

✦﹒osmosis is the diffusion of water across a selectively permeable membrane

• water likes to go to an area of high solute concentration (low→high)

• solutes like to go to an area of low solute concentration (high→low), goes along their own gradient

• tonicity is the measurement of the relative concentrations of solute between two solutions (inside and outside of cell)—

  • hypotonic is more solute, less solvent

    • too much of this can cause the cell to burst/be lysed

  • isotonic is equal concentrations

  • hypERtonic is less solute, more solvent

    • cell is shriveled, likely would die

  visual of tonicity with red blood cells

✦﹒water potential measures the tendency of water to move by osmosis

• in this case, water moves from high water potential→low water potential

• the more negative the water potential, the more likely water would move into the area

✦﹒osmoregulation is the regulation of and organism’s internal solute composition and water potential and water balance

• increase in amount of solute in water will cause..

  • inc in solute potential

  • dec in water potential

• decrease in pressure potential → decrease in water potential

✦﹒there are equations for calculating potentials…

• in an open system, the pressure potential is zero, so water potential is equal to the solute potential →ψ = ψ_p + ψ_s

  • ψ_p = pressure potential, ψ_s = solute potential

• ψ_s = -iCRT

  • i = ionization constant, c = molar concentration, r = pressure constant, t = temp in kelvin (temp in Celsius + 273 = temp in Kelvin)

╭ Other Resources :

:: amoeba sisters ﹒﹒ discusses osmosis and water potential !

:: bozeman science ﹒﹒ also discusses osmosis and water potential !

﹙✦﹚﹒osmosis and water potential is something that’ll DEFINITELY come up in the exam (according to my teach), if you can maybe actually watch the ap daily videos for 2.8 (specifically video 3)