AP Biology Unit 2 Review

Cells are

the simplest collection of matter that can be alive

Light microscopy (LM)

Light passes through a specimen, then refracted by glass lenses. Image is magnified.

Can see living things, but not good magnification compared to electron microscopy.

Electron microscopy (EM)

Electron beam is focused through a specimen

Good magnification

Scanning electron microscope (SEM)

electron beam is focused through a gold-coated specimen. Excited electron patterns are translated to a screen with a 3D image.

Transmission electron microscopy (TEM)

electron beam is focused through a specimen stained with metal atoms (so fewer electrons are transmitted). Transmitted electron pattern is displayed on-screen.

Disadvantage of electron microscopy

preparation methods kill specimen cells

Resolution is _____________ related to the wavelength of light/electron beams

inversely

Magnification

ratio of an object’s image size to its real size

Resolution

a measure of clarity of an image

Contrast

the difference in brightness between light and dark areas of an image

Cell fractionation

when broken up cells in a tube are spun in a centrifuge, forcing the largest components to settle at the bottom (forms a pellet).

Left over liquid is spun again, faster and for longer, until several pellets of organelles and other organic matter are made

Types of cells

Eukaryotic and Prokaryotic

Both eukaryotic and prokaryotic cells have

a plasma membrane, cytosol, ribosomes, and chromosomes

DNA’s location in eukaryotic cells

stored in the nucleus, which is bound by a double membrane

DNA’s location in prokaryotic cells

concentrated in a region not membrane-enclosed, called the nucleoid

cytoplasm

the interior of either cell type (Eu cells: only the region betw. the nucleus and cell membrane)

Cytosol

a semifluid, jellylike substance in which subcellular components are suspended

plasma membrane

the semipermeable boundary of every cell that functions as a selective barrier

Cells need a ___________________ for the exchange of materials with its environment and to meet metabolic requirements

high surface area to volume ratio

High vs low SA-to-V ratio

High: good; cell is efficient and gets enough of what it needs

Low: bad; not enough nutrients to take care of the cell

Organelle

membrane-enclosed structures w/in eukaryotic cells that divide the cell into compartments that provide local environments for specific metabolic functions

(allows incompatible process to go on simultaneously in the same cell)

most biological membranes are made of

a double layer (bilayer) of phospholipids and other lipids (with proteins embedded or attached)

Flagellum

motility structure in some animal cells, composed of a cluster of microtubules w/in an extension of the plasma membrane

Centrosome

region where the cell’s microtubules are initiated; contains a pair of centrioles

Cytoskeleton

reinforces cell shape; functions in cell movement; components are made of proteins (3 components)

Parts of the cytoskeleton

microfilaments, intermediate filaments, and microtubules

Microvilli

projections that increase cell surface area

peroxisome

organelle with various specialized metabolic functions; produces hydrogen peroxide as a by-product and then converts it to water

Mitochondrion

organelle where cellular respiration occurs and most ATP is generated

lysosome

digestive organelle where macromolecules are hydrolyzed

phagocytosis

the formation and fusion (with a lysosome containing hydrolytic enzymes) of a food vacuole that engulfs smaller organisms and molecules for digestion

autophagy

when lysosomes recycle cellular organic material, like damaged organelles, by surrounding it in in a double membrane vesicle and fusing with the outer layer to release hydrolytic enzymes

A lysosome’s hydrolytic enzymes are made by ______ and then transferred to the ________

the rough ER

Golgi apparatus for further processing

Golgi apparatus

organelle active in synthesis, modification, sorting, and secretion of cell products. Also made of cisternae, separating the internal space from the cytosol.

Products of the ER are further modified, stored, and sent other places as it travels from one side to the other of the Golgi

Golgi stack directionality

(Golgi function) receiving end (near ER) = cis face. ER vesicles add themselves and the contents of its lumen by fusing with the cis face.

shipping end = trans face. Vesicles pinch off and travel elsewhere from here.

marcomolecule synthesis

(Golgi function) some macromolecules are made in the Golgi, like secretory polysaccharides

Identification tagging

(Golgi function) before vesicles leave the trans face, the Golgi sets targets for them and adds identification tags (like phosphate groups)

vesicles may have external membrane molecules to recognize “docking sites” on specific organelles or membranes

Golgi apparatus path of ER products

1. vesicles move ER → Golgi

2. vesicles fuse with the cis face of the Golgi cisternae

3. cisternal maturation: cisternae move in a cis → trans direction, carrying contents with it

4. Vesicles form and leave the trans face of the Golgi, taking specific things to organelles or the plasma membrane

5. some proteins go to less-mature cisternae, where they function

6. vesicles also take certain proteins back to the ER where they function

The Golgi apparatus is the _________ of the cell

warehouse for receiving, sorting, shipping, and even some manufacturing

ribosomes

complexes that make proteins; free in cytosol or bound to rough ER or nuclear envelope (can switch betw. roles)

free ribosomes

suspended in the cytosol. make proteins that are loose and function in the cytoplasm (not organelles)

bound ribosomes

attached to the outside of the ER or nuclear envelope. makes proteins that are inserted into membranes or secretion

plasma membrane

membrane enclosing the cell

Nucleus

contains most of the genes in eukaryotic cells

3 parts: nuclear envelope, nucleolus, chromatin

nuclear envelope

double membrane (each with a lipid bilayer) enclosing the nucleus; perforated by pores; continuous with ER

At the lip of each nuclear envelope pore, the inner and outer membranes are

continuous.

pore complex

an intricate protein structure that lines each pore of the nuclear envelope.

Helps with regulating the entry/exit of proteins, RNAs, and macromolecules

nuclear lamina

(except at the pores) lining of protein filaments on the nuclear side of the envelope that helps maintain the shape of the nucleus through mechanical support

chromosomes

discrete units/structures that carry the genetic information of a cell. Contains one long DNA molecule

chromatin

material consisting of DNA and proteins; visible in a dividing cell as individual condensed chromosomes

(euchromatin) loose = expressed

(heterochromatin) bundled = not actively expressed

Nucleolus

nonmembranous structure involved in production of ribosomes (can be multiple)

ribosome synthesis

ribosomal RNA in made in the nucleolus from DNA + imported cytoplasm proteins = large and small subunits of ribosomes

subunits exit thru nuclear pores into the cytoplasm where they assemble into a ribosome

Endoplasmic Reticulum (ER)

a network of membranous sacs and tubes (cisternae); active in membranes synthesis and other synthetic and metabolic processes

ER lumen/cavity/cisternal space

the internal compartment of the ER separated from the cytosol by the ER membrane

also continuous with the space betw. the nuclear envelope membranes

Rough ER

region of the ER studded with ribosomes

secretory protein synthesis

(rough ER function) polypeptide chains from a bound ribosome are threaded into the ER lumen through a protein complex pore

Carbs are attached in the lumen by ER membrane enzymes, then separated from cytosol proteins by the ER membrane.

Secretory proteins leave the transitional ER in a transport vesicle to go to the Golgi apparatus

membrane synthesis

(rough ER function) adds membrane proteins and phospholipids to its own membrane. Also transfers portions in the form of vesicles to other parts of the endomembrane system.

secretory proteins are mostly

glycoproteins (proteins w/ carbs covalently bonded to them)

Smooth ER

region of the ER with no ribosomes

lipid synthesis

(smooth ER function) enzymes help create oils, steroids, and new membrane phospholipids

detoxification

(smooth ER function) detoxifying drugs and poisons by adding a hydroxyl group, making the molecules polar/hydrophilic (water soluble)

Cell wall (plant cells)

out layer that maintains cell’s shape and protects cell from mechanical damage; made of cellulose, other polysaccharides, and protein

Plasmodesmata (plant cells)

cytoplasmic channels through cell walls that connect the cytoplasms of adjacent cells

chloroplast (plant cells)

photosynthetic organelle; converts energy of sunlight to chemical energy stored in sugar molecules

central vacuole (plant cells)

prominent organelle in older plant cells; functions include storage, breakdown of waste products, and hydrolysis of macromolecules; enlargement is a major mechanism of plant growth

vacuole

large vesicles from the ER and the Golgi apparatus that are used for selective transport (compartmentalization)

Food vacuoles

(formed by phagocytosis) used to digest molecules or organisms

contractile vacuoles

pumps excess water out of a cell

endomembrane system

includes the nuclear envelope, the ER, the golgi apparatus, lysosomes, vesicles, vacuoles, and the plasma membrane

carries out protein synthesis, protein transport, metabolism/lipid movement, and detoxification

vesicle

sacs made of membrane

compartmentalization

the creation of microenvironments in each organelle (different from outside them) so individual process can occur at the same time in a cell

Endomembrane system relationships

1. The nuclear envelope is connected through the rough ER, which is also continuous with the smooth ER

2. Membranes and proteins produced by the ER flow in the form of transport vesicles to the Golgi

3. The Golgi pinches off transport vesicles and other vesicles that give rise to lysosomes, other times of specialized vesicles, and vacuoles

4. the lysosome is available for fusion with other vesicles for digestion

5. a transport vesicle carries proteins to the plasma membrane for secretion

6. the plasma membrane expands by fusion of vesicles; proteins are secreted from the cell