Bio 1700 Exam 2 Chapters 5-7

What is the cell theory?

1. All organisms are made up of cells
2. The cell is the fundamental unit of life
3. Cells come from preexisting cells

What are cells defined by?

a plasma membrane

What is the purpose of a plasma membrane?

* separate external and internal environments
* maintain homeostasis
* compartmentalize

What are plasma membranes made of?

phospholipid bilayers

What is the structure of a phospholipid?

* amphipathic


* heads = hydrophilic
* tails = hydrophobic

What does amphipathic mean?

hydrophilic and hydrophobic in the same molecule

What is the fluid mosaic model?

* moving model that plasma membrane follows
* fluid: van der Waals forces (interactions between fatty acid tails) are easily broken and reformed
* mosaic: many other components found in the membrane

What is FRAP?

* fluorescent recovery after photobleaching
* evidence that cell membranes are fluid

Using FRAP, what would happen if the membrane wasn’t fluid?

Results if membrane is fluid?

* Not fluid - continually low fluorescence (things aren’t moving around)
* Fluid - things will move around and non bleached and bleached will mix together, so you will gradually return to fluorescence

What affects the cell membrane’s fluidity?

* length
* presence/absence of a double bond
* temperature
* cholesterol

How could you decrease the cell membrane’s fluidity?

* longer fatty acid tails
* increase saturated fatty acids
* lower temperature
* add cholesterol at a high temperature to counteract

How could you increase the cell membrane’s fluidity?

* shorter fatty acid tails
* increase unsaturated fatty acids
* raise the temperature
* add cholesterol at a low temperature to counteract

What is the purpose of cholesterol?

* prevent dramatic swings in permeability
* buffer

What does selectively permeable mean? Why is it important?

* allows some things to pass through while other things can’t
* control what comes in and out

What can get through the phospholipid bilayer?

* small and non polar things
* hydrophobic and small
* polar (hydrophilic) and small

What can’t get through the phospholipid bilayer?

big molecules or anything ionic/charged

What is passive transport? What are the 3 types?

* move high → low concentration (with gradient)
* no energy needed
* simple diffusion
* facilitated diffusion
* osmosis

What is active transport? What are the 3 types?

* move low → high concentration (against gradient)
* energy needed
* primary active transport
* secondary active transport
* endocytosis/exocytosis

What is simple diffusion?

* natural movement of solutes through the plasma membrane
* solutes move with the concentration gradient (high → low)
* no energy needed
* no net movement once concentration ins equal on both sides of the membrane

What is facilitated diffusion?

* transmembrane proteins provide a passage for molecules to travel through the plasma membrane
* solutes move with concentration gradient
* Channel protein = provides the right size/charge opening
* Carrier protein = binds to the solute and changes shape

What are integral membrane proteins?

any protein that has a part in the cell and a part outside the cell

* middle portions are hydrophobic
* ends are hydrophilic

What are peripheral membrane proteins?

temporarily associated with either the internal or the external side of the membrane (all hydrophilic just on one side)

What is osmosis?

* solvent (water) diffusion
* simple or facilitated (aquaporin = protein that helps speed up diffusion of water)
* movement of water until concentration is equal on both sides

What is a hypotonic environment?

* solutes are low on the outside of the cell
* water moves into the cell
* swells

What is an isotonic environment?

* same concentration as the inside
* no net movement of water

What is a hypertonic environment?

* lots of solute on the outside
* water moves out of the cell
* shriveled

What is primary active transport?

* using energy **directly** to move a substance either in/out of cells
* **against** concentration gradient
* energy and transport protein needed (pumps)
* symporter
* antiporter

What is a symporter?

transport protein that moves two substances in the **same** direction

What is an antiporter?

transport protein that moves two substances in **different** directions

What is secondary active transport?

* builds from primary active transport
* potential energy of an electrochemical gradient(difference in charge) drives movement against the concentration gradient
* 3 steps

What are the 3 steps of secondary active transport?

1. Primary active transport: energy is used to move a proton against its gradient
2. An electrochemical gradient is created such that the proton would naturally flow back across the membrane through simple diffusion
3. A co-transporter moves a different molecule against its concentration gradient

What is endocytosis and exostosis?

* vesicle transport (passage into a vesicle and spits onto other side)
* don’t cross the membrane
* endocytosis = into the cell
* exocytosis = out of the cell

What are characteristics of prokaryotes?

* no nucleus
* small phili
* plasmid (circular DNA)
* smaller

What are characteristics of eukaryotes?

* has nucleus
* many organelles (made of phospholipid bilayer)
* bigger

What are typical features of an animal cell?

* nucleus
* mitochondria
* plasma membrane
* cytoskeleton
* endoplasmic reticulum
* lysosomes
* Golgi apparatus
* organelles

Which features of a cell are organelles?

* nuclear membrane
* endoplasmic reticulum (smooth and rough)
* mitochondrion
* lysosome
* golgi body

What are typical features of a plant cell?

* cell wall (rigid, structure)
* vacuoles (maintain turgor pressure, store water)
* chloroplasts (harness energy of sunlight)

What is the endomembrane system?

* all organelles except mitochondria and chloroplasts
* make, modify, sort, and potentially secrete proteins
* take in extracellular molecule and digest them
* functionally connected - lots of communication

What is the nucleus? Why do you need pores in the nuclear envelope?

stores DNA

* mRNA needs a way to get out

What happens in the nucleus?

transcription

Does transcription require proteins?

yes

Where does translation take place?

outside nucleus

What is the nuclear envelope/membrane made of?

2 layers of phospholipid bilayers

* to travel through, have to pass 4 layers in total

What is the lumen?

inside space of an organelle

What is the Endoplasmic Reticulum (ER)? What is the function?

* organelle in the endomembrane system
* smooth ER- lipid synthesis
* cholesterol
* phospholipids
* rough ER - protein synthesis
* rough because ribosomes are attached

What is the structure of the endoplasmic reticulum?

interconnected flattened sacs

What happens with protein synthesis with the endoplasmic reticulum and without it?

(protein synthesis occurs on rough ER or free ribosomes in the cytosol)

* with rough ER
* secreted by exocytosis or stays in membrane or in endomembrane group
* In cytoplasm/without rough ER
* stays in cytosol or other organelles outside endomembrane system

How are proteins sorted?

* signal sequences
* amino terminal signal sequences
* hydrophobic signal anchor sequence
* internal signal sequences

What is the difference between an amino terminal signal sequence and the internal signal sequence?

The amino terminal sig. seq. is located at the very beginning of a protein

While the internal sig. seq. is near the beginning but not the very start

Where would a protein with no signal sequence go?

cytosol

Where would a protein with an amino terminal signal sequence go?

* mitochondria
* Rough ER/endomembrane system
* RER lumen
* GA
* Lys
* Plasma membrane
* Chloroplasts

Where would a protein go if it has an amino terminal signal sequence + a hydrophobic signal anchor sequence?

It would become an integral membrane protein

Where would a protein go if it has an internal signal sequence?

nucleus

What is the first part of a protein to get inside?

the amino terminal sequence

If there is a problem with protein sorting, how do you know which step is interrupted?

look at where there is a build up of proteins

What is the Golgi apparatus?

* sorts proteins to final destination
* carbohydrate synthesis
* modifies proteins and lipids

How does the Golgi apparatus modify proteins and lipids?

* attaches carbohydrates to proteins and lipids
* carbohydrate forms a protective coating on cell surface
* glycocalyx
* recognition and binding of other molecules
* blood types

What are lysosomes?

* bud off from the Golgi apparatus
* digest macromolecules
* work in acidic environments
* primary active transport pump in H+ ions to create the pH
* (There are lysosomal diseases)

What is the mitochondria?

* have a double membrane, consisting of an inner and outer membrane and an aqueous compartment in between
* not part of the endomembrane system
* contain their own DNA (circular)
* plant and animal cells
* Cellular respiration
* use O2 to synthesize ATP
* release CO2 as waste

What are chloroplasts?

* have a double membrane
* not part of the endomembrane system
* contain their own DNA
* plant only!
* photosynthesis
* used chlorophyll to capture energy from sunlight
* synthesize carbohydrate from CO2

What is energy?

The capacity to do work

* harness energy → do work
* fuel molecules → cellular work

What are the classifications of organisms?

* phototroph or chemotroph
* autotroph or heterotroph

What is a phototroph?

organism that gets energy from sunlight

What is a chemotroph?

an organism that gets energy from chemical compounds

What is an autotroph?

an organism that gets carbon from CO2

What is a heterotroph?

an organism that gets carbon from organic compounds

What is an example of a photoautotroph?

* vascular plants

What is an example of a photoheterotroph?

Heliobacteria

What is an example of a chemoautotroph?

deep sea things (hydrogen bacteria)

What is an example of chemoheterotrophs?

all non phototrophic eukaryotes (humans)

What is metabolism?

entire set of chemical reactions that maintain life

* molecule → molecule
* make/use energy
* linked to form pathways

What are the two main types of metabolism?

* Catabolism
* Anabolism

What is catabolism?

* chemical reactions that breakdown molecules
* Big → small
* release energy

What is anabolism?

* Chemical reactions that build larger molecules
* small → big
* Require energy

What are the two main types of energy?

* kinetic = energy of motion
* potential = stored energy

What are examples of kinetic energy?

* sunlight
* electrivity
* heat

What are examples of potential energy?

* chemical energy

How does energy relate to biology/chemistry?

* covalent bonds have potential energy
* polymers have energy > monomers

What is ATP?

* chemical energy available for use in cells
* universal - all living things
* adenosine
* monophosphate
* diphosphate
* triphosphate

What is the First Law of Thermodynamics?

* conservation of energy
* energy is not created or destroyed
* total energy before = total energy after

What is the Second Law of Thermodynamics?

* entropy
* energy transformations result in an increase in disorder

What is entropy?

degree of disorder

What is Gibbs free energy?

energy available to do work

What is the difference between -G and +G

* -G = energy released
* +G = energy is required

What is an endergonic reaction?

* products have more energy in the bonds than the reactants did (low energy → high energy)


* Input of energy, positive G
* need 3rd party for that energy, non-spontaneous

What is an exergonic reaction?

* Reactants have more energy than the products
* -G
* give energy off yourself, spontaneous

Consider the hydrolysis of ATP (ATP → ADP)

Is there more energy in products or reactants?

Exergonic or endergonic?

Spontaneous or non spontaneous?

Change in G?

* reactants have more energy
* exergonic
* spontaneous
* -G

What is energetic coupling?

* spontaneous reactions (-G) can provide the energy to drive non spontaneous reactions (+G)
* Net of the two reactions must be negative
* ex. Does hydrolysis of ATP (-7.3) provide enough energy to phosphorylate glucose (+3.3) = yes

What is an enzyme?

(usually a protein)

catalyst that speeds up the reaction rate by a factor of 1 million

* not consumed
* form a complex with reactants (substrate) and products
* highly specific

What is activation energy?

initial energy input needed for a reaction

How do enzymes relate to activation energy?

* enzymes reduce activation energy
* accelerate the reaction by reducing activation energy
* Change of G is the same with or without an enzyme

What is the active site?

facilitates catalytic reaction

* protein folding brings specific amino acids close to each other to form the active site
* (where substrates bond for a reaction)

How could you increase the rate of reaction?

* add more enzymes
* ad more substrates
* increase temperature
* smaller space

What are things that alter Enzyme Activity?

* activators
* inhibitors

What is an irreversible inhibitor of enzymes?

* bind covalently at the active site
* permanently inactivate

What is a reversible inhibitor?

* form weak bonds with enzymes
* transient association

What are two types of reversible inhibitors?

* competitive
* allosteric

What is a competitive inhibitor?

* substrate and inhibitor compete for the same site
* binds to active site