AP Biology Unit 2 Test

Cells

The basic unit of structure and function in all living things

all cells are/contain:

bound by a plasma membrane

contain cytosol

contain chromosomes

contain ribosomes

Prokaryotes

domains bacteria and archea

DNA in nucleoid region

smaller

eukaryotes

Protists (unicellular), fungi, animals, and plants

DNA in nucleus

membrane-bound organelles

bigger

Organelles

membrane-enclosed structures within eukaryotic cells

endomembrane organelles

1. Nuclear envelope

2. Endoplasmic reticulum

3. Golgi complex

4. Lysosomes

5. Vesicles/vacuoles

6. Plasma membrane

energy organelles

1. Mitochondria

2. Chloroplasts

Compartmentalization

-allows for different metabolic reactions to occur in different locations

-increases surface area for reactions to occur

-prevents reactions interfering with each other

Unique Cell Components of Plants

1. chloroplasts

2. central vacuole

3. cell wall

4. plasmodesmata

Unique Cell Components in Animals

1. Lysosomes

2. Centrosomes

3. Flagella

Nucleus

-Contains chromosomes

-enclosed by nuclear envelope (double membrane)

-Nuclear pores (regulate entry/exit of materials)

-contains nucleolus

nucleolus/ribosome formation

- dense region of nucleus where rRNA is synthesized

-rRNA+proteins= ribosomes

-subunits exit nuclear pores-> assemble into ribosomes

Ribosomes

-translate messages found on mRNA into primary proteins

-RNA+proteins

-2 locations:

Cytosol (aka free ribosomes)

Rough ER or nuclear envelope (proteins can be secreted from cell, in transport vesicles)

Endoplasmic Reticulum (ER)

-synthesizes membranes

-compartmentalize the cell to separate rough ER proteins and free ribosome proteins

Rough ER

contains ribosomes for protein synthesis bound to ER membrane

Smooth ER

-Contains no ribosomes

-Synthesizes lipids, metabolizes carbohydrates, and detoxifies the cell

Golgi Complex

-Contains flattened membranous sacs called cisternae (not connected)

-seperate sacs from cytosol

-directionality:

Cis face- receives vesicles from ER

Trans face-sends vesicles back out into cytosol or plasma membrace for secretion

Golgi Complex Functions

- Receives transport vesicles with materials from the ER

- Modifies the materials

- Sorts the materials

- Adds molecular tags

- Packages materials into new transport vesicles that exit the membrane via exocytosis

Lysosomes

-membranous sac with hydrolytic enzymes

-hydrolyzes macromolecules in animal cells

-Autophagy

Autophagy

-lysosomes recycle their own cell's organic materials

-allows cell to renew itself

-break into (ex. CHO) and uses elsewhere

Peroxisomes

-similar to lysosomes

-membrance bound metabolic compartment

-catalyze reactions that produce H2O2

-enzymes in peroxisomes that break down the H2O2 to H2O

What are vacuoles?

Large vesicles that stem from the ER and Golgi.

Food vacuole

Forms via phagocytosis and is then digested by lysosomes.

Contractile vacuoles

Maintain water level in cell

Central vacuole

A vacuole found in plants that contains inorganic ions and water, important for turgor pressure (without it, plants shrink)

Protein Synthesis Steps

1. Transcription (Nucleus)- mRNA copied

2. Translation (ribosomes)- mRNA read->polypeptide chain

3. Modification (Golgi app)- packaged

4. Secretion (plasma membrane)- deliver out or in specific cell locations

Endosymbiont Theory

-similarities of mitochondria and chloroplasts have to prokaryotes- might have been enveloped a long time ago

evidence: x2 membrane, ribosomes, circular DNA, capable of independant function

mitochondria

-site of cellular respiration

-Contains: enzymes for cellular respiration and and produce ATP, mitochondrial DNA, Ribosomes

-# of mitochondria in cells correlates with metabolic activity

cells with high metabolic activity=more mitochondria (ex. muscles)

mitochondria membrane

-x2 membrane

-outer=smooth

-inner=folds called christae

- divides mitochondria into 2 internal compartments and increases surface area

intermembrane- space between inner and outer membrane

mitochondrial matrix

-enclosed by inner membrane

-location for Krebs Cycle (producing ATP)

-Contains: enzymes for cellular respiration and and produce ATP, mitochondrial DNA, Ribosomes

Chloroplast

-Organelles in Photosynthetic organisms

-site of photosynthesis

-contains green pigment chlorophyll

Thylakoids and stroma

-inside x2 membrane

-thylakoid- membranous sacs that organize into stacks called grana

light dependent reactions occur

Stroma- fluid around thylakoids

-location for Calvin Cycle (glucose)

- contains chloroplast DNA, ribosomes, enzymes

Cytoskeleton

-network of fibers through cytoplasm

-gives structure and support

-anchors organelles

-allows for movements of vesicles and organelles within cell/whole cell

3 types of fibers in cytoskeleton

1. Microtubules

2. Microfilaments

3. Intermediate filaments

Microtubules

-hollow, rod-like structures made of protein tubulin

-grow from centrosome

-assist in microtubule assembly

-serve as structural support for movement of orgtanelles

-seperate chromosomes during cell division

-cell motility

microfilaments

-thin, solid rods made of protein actin

-maintain cell shape (bear tension)

-Assist in muscle contraction and cell motility

-actin works with myosin to cause contraction

-division of animal cells (contractile ring of cleavage furrow)

Intermediate filaments

-fibrous proteins made up of subunits

-permanent structural elements of cells

-maintain cell shape

-anchor nucleus and organelles

-form nuclear lamina (lines nuclear envelope)

Cellular Metabolism depends on...

Size

-cellular waste must leave

-dissipates thermal energy

-Nutrients/chemicals must enter

cell size dictates...

function

Cells need a _______ surface area-to-volume ratio to optimize the exchange of material through the plasma membrane

high

Cells tend to be...

Small.

Small cells have high SA:V Ratio

Optimizes exchange of materials

larger cells have a _______ SA:V ratio

Lower

-lose efficiency in exchanging materials

-more storage

-cellular demand for resources increases

-rate of heat exchange decreases

Phospholipid structures

Hydrophilic head: Phosphate and Glycerol

Hydrophilic tail: Unsaturated/Saturated fatty acids

plasma membrane

-separates internal cell environment

-composed mostly of phospholipids

Amphipathic

-hydrophobic head and hydrophilic tails

-forms a bilayer

Selective Permeability

- regulate which substances enter and exit

Easy passage through membranes:

-Small, nonpolar, hydrophobic molecules

-ex. hydrocarbons, gases (CO2, O2, N2)

Difficult or assisted passage through membranes:

-Hydrophilic, polar, large molecules- and ions

-ex. sugars, water, amino acids, Na+, K+

Phospholipid Orientation

- Hydrophilic heads- toward aqueous environments

-Hydrophobic tails- face inward, away from ater

Fluid Mosaic Model- Fluid

-membrane held together by weak hydrophobic interactions- can move and shift

- temperature affects fluidity

- unsaturated tails maintain fluidity at low temps

-kinked tails prevent tight packing

fluid mosaic model: Mosaic

-Membrane comprised of many macromolecules

Membrane proteins

-Integral and Peripheral

Integral proteins

-embedded into bilayer

-aka transmembrane proteins

-amphipathic- the hydrophobic part is attached to the membrane, but the inside is hydrophilic to allow for facilitated transport

Peripheral Proteins

- not embedded into lipid bilayer

-loosely bonded to surface

Membrane Carbohydrates

-important for cell to cell recognition

- glycolipids- carbohydrates bonded to lipids

-glycoproteins- carbs bonded to proteins

Plant cell membrane structure

- have a cell wall that covers plasma membrane

-protects cell and regulates water intake

-cell wall composed of cellulose

Plasmodesmata

-Hole like structures in the cell wall filled with cytosol that connect adjacent cells

-transfer materials and messages

Types of transport across membranes

passive and active

Passive Transport

-transport of a molecule that does not require energy from the cell because a molecule is moving with its concentration or electrochemical gradient

-involved in the import of materials and export of waste

Examples of passive transport

-Diffusion

-Osmosis

-Facilitated diffusion

Diffusion

-spontaneous process resulting from the constant motion of molecules

- substances move from a high to low concentration

-move down the concentration gradient

-molecules diffuse directly across the membrane

-different rates of diffusion for different molecules

Osmosis

-diffusion of H2O down its concentration gradient across a selectively permeable membrane

-aka diffusion of H2O from areas of low solute concentration to high solute concentration

Facilitated Diffusion

- diffusion via transport proteins

-increases rate of diffusion for small ions, water, carbs

-2 categories: channel and carrier- specific for substances it can facilitate movement for

Channel Proteins

-provide a channel for molecules and ions to pass

-channel is hydrophilic

-many channels are gated- only allow when there is a stimulus

Aquaporins

specific channel protein for water

Carrier Proteins

undergo conformational changes for substances to pass

Active transport

transport of a molecule that requires energy because it moves the solute against its concentration gradient

Types of active transport

-pumps

-cotransport

-exocytosis

-endocytosis

Adenosine triphosphate

-energy source used by cells

-ATP can transfer the terminal phosphate group to the transport protein, which changes its shape (and function) to better move a substance

Pumps

-maintain membrane potential

Membrane potential

-unequal concentrations of ions across the membrane results in an electrical charge (electrochemical gradient)

-cytoplasm relatively negative compared to extracellular fluid

-energy stored in electrochemical gradients

Electrogenic pumps

-proteins that generate voltage across membranes, which can be used later as an energy source for cellular processes

Sodium Potassium Pump

-animal cells regulate concentrations of Na+ and K+

-3 Na+ pumped out of cell

-2 K+ get pumped into cell

-results in a +1 net charge to the extracellular fluid

Proton pump

-integral membrane protein that builds up a proton gradient across the membrane

-used by plants, fungi, and bacteria

-pumps H+ out of cell

Favorable vs. Unfavorable movement

- favorable: downhill diffusion

- unfavorable: uphill transport

Cotransport

-the coupling of a favorable movement of one substance with an unfavorable movement of another substance

-uses energy stored in electrochemical gradients (generated by pumps) to move against gradient

-plants use for sugars and amino acids (ex. sucrose and H+)

Exo and endocytosis

transport of large molecules

Exocytosis

-secretion of molecules via vesicles that fuse to plasma membrane

-vesicles can fuse to the membrane by forming a bilayer

-once fused-> release to extracellular fluid

endocytosis

-uptake of molecules from vesicles fused from the plasma membrane

-phagocytosis, pinocytosis, receptor mediated

Phagocytosis

-a cell engulfs particles to be later digested by lysosomes

- cell surrounds particle with pseuopodia

- particle packaged into food vacuole- fuses to lysosome

Pinocytosis

-nonspecific uptake of extracellular fluid containing dissolved molecules

-cell takes in dissolved molecules in protein coated vesicle

-protein coat helps mediate transport of molecules

receptor-mediated endocytosis

-Specific uptake of molecules via solute binding to receptors on the plasma membrane

-allows cell to take up large quantities of specific substance

-when solutes bind to receptors->cluster in coated vesicles to be taken into cell

Tonicity

-the ability of an extracellular solution to cause a cell to gain or lose water

-depends on concentration of solutes that cannot pass through cell membrane

3 types of solutions cells can be in:

Isotonic- happy cell

Hypertonic- raisin

Hypotonic- fat hippo

Osmoregulation

-cells must be able to regulate their solute concentrations and maintain water balance

-(animal cells react differently than cells with cell walls)

Isotonic Solutions

-have no net movement of H2O

-concentration of solutes equal inside and outside of cell

-water diffuses into and out of cell at same rate

Hypertonic solutions

-loses water to its surroundings

-concentration of solutes is higher outside of cell

-water moves to extracellular fluid

-cells shrivel and die

Plasmolysis

vacuole shrinks and plasma membrane pulls away from cell wall

Hypotonic solutions

-gain water from surroundings

-concentration of solutes lower outside the cell

-cell will gain water-> cells swell and lyse (burst)

-plant cells work OPTIMALLY (maintain turgor pressure)

Water potential

-a physical property that predicts the direction water will flow

-includes the effects of solute concentration and physical pressure

Water will flow from areas of:

- high water potential to low water potential

-low solute to areas of high solute concentration

-high pressure to areas of low pressure

Unit for water potential

megapascals (MPa) or bars

water potential formula

solute potential formula

Ionization constant

-if no ions are formed the constant is one (basically all covalent bonds)

-ionic bonds= 2