Unit 2: Cell Structure and Function

AP BIO

What is a cell?

a cell is a life’s basic unit of structure and function.

• as cells increase in volume, the sa/v ratio decreases so the exchange in materials becomes less efficient.

• as organisms increase in size, their ratio decreases and affects its properties like heat exchange with surroundings.

• small organisms lose heat at higher rates than larger organisms bc of efficient exchange in heat

what type of microscopes are used to see cells?

• light microscopes study stained or living cells bc they can magnify the size of it to 1000

• electron microscopes study detailed structure of the cell that cant be seen by light microscope

What is a prokaryotic cell?

• it is smaller and simpler

• examples are bacteria and Archaean

• the cell is filled with cytoplasm

• the genetic material is one continuous circular DNA molecule that's free-floating in the nucleoid

• most have a cell wall made of peptidoglycans that surround the plasma membrane

• some have small ribosomes

• some have one or more flagella for motility and a thick capsule for protection

• THEY DO NOT HAVE MEMBRANE BOUND ORGANELLES.

What is a eukaryotic cell?

• more complex

• examples are fungi, protists, plants, animals

• they have organelles

What is the plasma membrane?

• the outer envelope of the cell made of phospholipids and proteins

• regulates movement of substances into and out —> semipermeable

• peripheral proteins are on the inner or outer surface of the membrane

• integral proteins are bound to the membrane and are amphipathic

• a transmembrane protein is a integral protein that extends all the way through the membrane

• fluid mosaic model is the arrangement of the membrane

• adhesion proteins form Junctions between adjacent cells. receptor proteins like hormones are docking sites. transport proteins form pumps that use ATP to actively transport solutes across the membrane. channel proteins selectively allow ions or molecules.

• glycoproteins cell surface markers and lipids like glycolipids are for cell recognition and adhesion

• carbohydrate side chains are on the outer of the membrane

What is the nucleus?

• largest organelle of the cell

• hereditary info DNA stored as chromosomes

• nucleolus is where rRNA is made and ribosomes are assembled

• it has a double membrane called the nuclear envelope with pores

what are ribosomes?

• ribosomes are made of rRNA and proteins

• can be bound or free

• sites of protein synthesis as it manufacture proteins needed/secreted by the cell

• two subunits, large and small,

What is the ER

• continuous channel that extends into regions of the cytoplasm and provides mechanical support and transportation

• smooth ER lacks ribosomes and makes lipids, hormones, steroids and breaks down toxic chemicals

what is the golgi complex?

• membrane bound structure made on flattened sacs

• after ribosomes on the RER made proteins, the golgi modifies, processes, and sorts them

• they package and distribute the materials to be sent out through vesicles

what is the mitochondria?

• converts energy from organic molecules into useful energy like ATP

  • the site of oxidative phophorylation (cristae)

  • site of krebs cycle (matrix)

• inner mitochondrial membrane forms folds called the cristae separating the innermost part, the matrix, from the intermembrane space

• outer membrane separates inner membrane space from cytoplasm

what are lysosomes?

• membrane bound sacs

• have sacs that carry digestive enzymes that breaks down old organelles, debris, large ingested particles

• made when vesicles with specific enzymes from the trans golgi fuse with vesicles made during endocytosis

• programmed cell death called apoptosis

what are vacuoles?

• membrane bound sac

• fluid filled sacs storing water, food, wastes, salts, or pigments

• the central is for water retention and turgor pressure

• contractile is for omsoregulation in protists

what are peroxisomes?

• organelles that detoxify substances

• produces hydrogen peroxide as byproduct

• has enzymes break down hydrogen peroxide into oxygen and water

what is the cytoskeleton?

• network of fibers called microtubules and microfilaments

• microtubules are made of protein tubulin and help for cellular division and movement

• microfilaments help with movement. has rod-like structure made of protein acting. breaking and synthesis of actin monomers allows filament to grow and shrink

what are cilia and flagella?

• locomotive properties in single celled organisms

  • beating motion of structures allows it to move

what is the difference between a plant cell and a animal cell?

• plant cells have cell wall made of cellulose that's rigid and for cell support

• plants have chloroplasts containing chlorophyll making them green

• cytoplasm in the plant cell is taken up by a large central vacuole

• plant cells do not have centrioles

how are molecules able to move across membrane?

• semipermeability and size and charge of particles

• small substances pass without resistance

• facilitated transport allows hydrophilic substance to pass

• aquaport are water specific channels

• glucose and ions Na+ and K+ also transported through proteins

  • membranes can be polarized as ions move across them

what is passive transport?

• this is simple and facilitated diffusion. its called passive bc no outside energy is needed to move

• goes from high concentration to low which is down the concentration gradient

• small non-polar molecules that are hydrophobic can do simple diffusion where they just pass through

  • co2, o2, n2, steroids, small h20

• when the diffusion needs help its facilitated

  • na+, water, k+, ca+

what is osmosis?

• in osmosis, the membrane is not permeable to solute like diffusion

• the cell wall is imp. for osmotic changes bc when the cell membrane shrinks away from the wall called plasmolysis, it loses water while it can expand if its tight against the wall

• tonicity describes the osmotic gradients

  • isotonic means the cell and environment solute [] is the same

  • if something is hypertonic to another, it has more solutes

  • if something is hypotonic to another, it has less solutes

• water potential measures potential energy of water to move from high potential to low

• pressure potential + solute potential = water potential

  • pressure is only positive while solute ranges from 0 to negative numbers

what are the water potential formulas?

solute potential = -iCRT where i is ionization constant, C is molar concentration, R is pressure constant, and T is temperature in Kelvin (*C + 273)

• adding solute lowers the water potential bc its less likely to leave the solution and instead flow more into it bc there's less water.

• the more solute molecules, the more negative solute potential

what is active transport?

• goes from low to high concentration, against the [] gradient

• Ex. sodium potassium pump that ushers out 3 sodium ions and brings in 2 potassium ions across the membrane. the pump depends on ATP to get ions across

• primary active transport is when ATP is directly used to transport something

• secondary active transport is when something is actively transported using the energy from the movement of another substance flowing DOWN its [] gradient

what is endocytosis?

• when particles too large to enter cell —> cell uses portion of membrane to engulf the substance. it forms a pocket, pinches in, and forms a vacuole/vesicle

• pinocytosis is when cell injests liquid

• phagocytosis is when cell takes solids

• receptor mediated endocytosis is when cell surface receptors work with the pits that are lined with protein called clathrin. when a particle/ligand binds to the receptor, the Logan is brought into the cell by invagination or folding of the membrane. a vesicle then forms around the incoming ligand and brings it in

what is bulk flow?

• one way movement of fluids brought by pressure

• for example, blood moves through a blood vessel and the movement of fluids in xylem and phloem of plants

what is dialysis?

• diffusion of solutes across selectively permeable membrane

• for example, kidney dialysis filters blood using machines and [] gradients

what is exocytosis?

• cell ejects waste products or secretion products like hormones

• it fuses with the vesicle of the membrane and then expels it's content into extracellular space

• reverse endocytosis

• rough er to synthesize —> golgi to package —> membrane