Ap Bio Unit 2 review
The Na+/K+ ATPase pump requires ATP so it is _________________ transport and is vital to the function of nerve cells. it maintains an electrochemical gradient so that one side of the membrane is more positive, leaving the other side more negative
active
Peripheral protein
adhere to the membrane - found on surface of cytoplasmic or extracellular side
Exocytosis:
a process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.
Carrier proteins
a transport protein that changes shape and transports materials across the membrane. Use in active transport (sodium-potassium pump) and facilitated diffusion (glucose transporter)
Channel proteins
a transport protein that moves hydrophilic materials - a channel is opened and materials flow into or out of the cell. Passive transport. Inner part of channel is hydrophilic but the part of the channel protein that touches the phospholipid tails is hydrophobic.
Lysosomes
contain enzymes that break down faulty cell parts and invaders. often described as the recycling centers of the cell
Golgi complex
proteins come here to be modified and tagged to be sent to other parts of the cell, or to leave the cell
What two things do internal membrane (organelles) do for a cell?
provide surface area for reactions to happen (ex. high surface area of the Rough ER for greater number of ribosomes) and they create compartmentalized micro-environments for specialized functions (ex. lysosome)
What forms a ribosome?
rRNA and proteins
Large protein hormone and cell membrane
requires a protein channel to move across membrane because it is too large to move across the membrane
which cell part(s) are found in both eukaryote and prokaryote cells?
ribosomes, cell membrane,
Isotonic
same There is the same solute concentration on both sides of the membrane (same water potential, and osmolarity)
chloroplast
site of photosynthesis in autotrophs. Light energy is used to create glucose, converting radiant energy into chemical energy
Simple diffusion molecules that can pass
small non-polar, lipid hormones, oxygen, carbon dioxide
Active transport pump molecules that can pass?
specific example: Na/K pump in neurons
Cholesterol
steroid this is very important for maintaining the fluidity of the plasma membrane. Prevents membrane from becoming too rigid or too fluid.
Where does the Calvin Cycle (Carbon fixation) take place?
stroma
What is selective permeability?
the cell has properties that allow it to allow only some molecules to pass across the membrane, allowing it to help maintain homeostasis within the cell
Protists with cell walls do not have (or need) contractile vacuoles - why not?
the cell wall acts as a physical constraint against taking in too much water. the cell can only swell so much, before the cell wall pushes back and prevents any further swelling. it is kind of like trying to blow up a balloon inside a small cardboard box - you will not be able to blow it up to the point where it pops because the box will prevent the balloon from expanding too much
you are studying a cell and notice that protein A is in the wrong location. what organelles may not be functioning properly? (there are two possibilities)
the golgi complex or the Rough ER
Active transport
- active transport - energy IS used - proteins ARE used - does not use vesicles - low to high concentration (against gradient)
Diffusion
- passive transport - no energy use - does not use proteins - does not use vesicles - high to low concentration (with gradient)
Osmosis
- passive transport - no energy use - does not use proteins - does not use vesicles - high to low concentration (with gradient)
Facilitated diffusion
- passive transport - no energy use - proteins ARE used - does not use vesicles - high to low concentration (with gradient)
Exocytosis
- active transport - energy IS used - proteins are not used - vesicles ARE used
Endocytosis
- active transport - energy IS used - proteins are not used - vesicles ARE used
If you put a protist in the same three environments, which environment would you expect its contractile vacuole to be most active
A protist's contractile vacuole would be most active in the hypotonic environment. In low levels of solute (areas of high water potential) water will be constantly entering the cell through osmosis. The protist will combat this by squeezing water out via its contractile vacuole. in hypertonic solutions, the protist would have another problem - losing too much water to its environment
Phagocytosis
A type of endocytosis in which a cell engulfs large particles or whole cells
Pinocytosis
A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes.
What is the big difference between passive and active transport (as indicated by their names)?
Active transport requires the cell to use ATP to move molecules across the membrane, while passive transport does not require ATP, molecules move via diffusion
What is the sodium potassium pump? (Na+/K+)
An electrogenic pump in which ATP is used to keep Na+ and K+ in disequilibrium and maintain membrane potential. This allows for a neuron to generate an impulse.
How does the fluid mosaic nature of the cell membrane impact is ability to allow some small molecules to pass through freely?
As phospholipids are flowing around, small non-polar molecules are able to diffuse through the membrane more easily. A rigid cell membrane would be less permeable to these molecules
Oxygen and cell membrane
Can move freely across the membrane - it is both small and non-polar
Small lipid hormone (steroid) and cell membrane
Can move freely into/out of cell across membrane - being small, and a lipid, it can pass through the hydrophobic portion of the lipid bilayer
What is cytolysis?
Cell burst from water intake. Plant cells do not experience this.
For each cellular process below, explain the internal region that prokaryotes use since they do not have a specific organelle. Cellular respiration - Photosynthesis - DNA replication - Transcription - Translation -
Cellular respiration - occurs the cell membrane Photosynthesis - photosynthetic bacteria have thylakoid membranes DNA Replication - the nucleoid region (DNA in plasmid ring) Transcription- the nucleoid region (translation can begin before transcription is complete Translation - also on ribosomes
Why is compartmentalization of functions helpful to a cell? use the rooms in your own home as an analogy. Also include one specific organelle example
Compartmentalization keeps all the ingredients and enzymes necessary for specific reactions in a concentrated space so they do not diffuse away from one another. Like your kitchen, you need kitchen supplies and food ingredients in the same room in order to make a meal. Compartmentalization also separates competing reactions, or prevents damage to other components (enzymes located in lysosomes can not destroy other organelles). Similar to the mess left in the garage of a house - you want to keep the dirty tools, oil, outdoor items out of the other rooms of the house
If a loaf of bread is sliced up and the other one is not and are both dropped in water, which will become saturated first?
Cutting the loaf of bread into slices increases the surface area exposed to the water. The higher surface area to volume ratio of the sliced bread will cause it to become fully saturated sooner than the un-cut loaf
Addition of solute to a solution causes a:
Decrease in water potential
What happens across the inner membrane of the mitochondria? Why is the inner membrane so highly folded (what is the advantage)?
Electron transport chain enzymes located here (final step in cellular respiration) - more surface area can hold more enzymes, allowing for higher production of ATP molecules
What is the Endosymbiotic theory: describe what is believed to have happened to form the first Eukaryotic cell
Endo-sym-biot means inside-together-life. the theory states that the common ancestor of all eukaryotic cells was once a prokaryotic cell, that engulfed another prokaryote cell, these engulfed cells were not destroyed, but rather began living in and depending on the host cell. The endosymbionts that were able to perform aerobic cellular respiration became mitochondria, while those that could do photosynthesis were the ancestors of the chloroplast
Which of the following claims is scientifically accurate and consistent with an observation that a decrease in lysosome production within a cell leads to a decline in mitochondrial activity?
Fewer lysosomes will be available to break down macromolecules to provide the necessary nutrients for cellular respiration.
Function of centrioles
Form the spindle during cell division, only in animal cells
Describe a solution with high osmolarity.
High solute/low water
Where would the hydrophobic R groups go in a phospholipid bilayer?
Hydrophobic R groups would embed in the hydrophobic region between phospholipid layers, while the hydrophilic R groups would be sticking out, of the membrane expose to water
Describe how animal cells react in hypotonic, hypertonic and isotonic solutions.
Hypotonic - cell swells, cytolysis Hypertonic - cell shrinks, plasmolysis Isotonic - prefered, cell/solution at equilibrium
Describe how plant cells react in hypotonic, hypertonic and isotonic solutions.
Hypotonic - prefered environment, large,central vacuole filled with water, presses cytoplasm into plasma membrane and cell wall. Can maintain turgor pressure Hypertonic - cell looses water, plasma membrane can detach from cell wall (but the cell does not shrink) Isotonic - plant wilts, lose of turgor pressure
Why is it important for cells to have a large surface area to volume ratio?
In order to allow for adequate exchange of materials (nutrients, water, waste) to keep the cell alive
How does exocytosis work?
Large materials such as proteins leave the cell. A vesicle surrounds the material and transports it to the plasma membrane (after proteins leave the golgi bodies). The vesicle fuses with the plasma membrane and the materials are pushed out of the cell.
How does endocytosis work?
Large materials transported into the cell/press into the cell membrane/phospholipids pinch off and surround the material and transport it into the cell. Phagocytosis - cell eating - solid materials/Pinocytosis - materials dissolved in liquid first.
If the loaf were a living organism, why would it be better for that organism to be composed to many small pieces rather than one large piece?
Living organisms must be able to quickly take in substances from the environment (oxygen, water, nutrients) and get rid of waste (nitrogenous waste, carbon dioxide). The smaller the organism, the higher its surface area to volume ratio is, allowing it to preform transport into and out of the cell more quickly
Describe a solution with low osmolarity.
Low solute/high water
Predict what would happen if the lysosomes membrane broke open. Explain you prediction:
Lysosomes are full of enzymes designed to break down cell parts. if these enzymes were not contained (spilled out into the cell) they could destroy the cell and kill it
Describe the structure of the Rough ER
Membrane bound organelle formed of folded membranes in order to greatly increase surface area and allow for multiple ribosomes to bind to the Rough ER.
Describe the structure of golgi bodies
Membrane bound structure that is formed of flattened sacs (cisternae) that greatly increase surface area, contains enzymes that modify molecules
Function/structure of lysosomes?
Membrane sacs filled with hydrolytic enzymes - intracellular digestion - food vacuoles, watse, apoptosis (programmed cell death) Produced by the golgi bodies
Changing the shape or morphology of the mitochondrial inner membrane can change the efficiency of mitochondrial function. Which of the following outcomes will most likely result from a change in the shape of the mitochondrial inner membrane from a highly folded surface to a smooth, flat surface?
Mitochondria will become less efficient because the surface area of the inner mitochondrial membranes will decrease. Correct. The change to the inner mitochondrial membrane will result in a decrease in the membrane's surface area, which will reduce the efficiency of mitochondrial function because there will be less surface area for reactions to occur.
What are contractile vacuoles?
Organelle found in some single celled eukaryotes such as paramecium. Pumps out excess water because they live in a hypotonic environment (freshwater).
Membrane-bound organelles have been an important component in the evolution of complex, multicellular organisms. Which of the following best summarizes an advantage of eukaryotic cells having internal membranes?
Organelles isolate specific reactions, increasing metabolic efficiency.
What is the benefit of having membrane bound organelles?
Organelles provide compartmentalization of cellular processes. This prevents competing reactions from interfering and increases surface area allows for the organelle to be more efficient (ex. More ribosomes on Rough ER due to more surface area = more proteins produced)
Na+ ions and cell membrane
Requires a protein channel to move across membrane, while is is small, Na+ is a charged ion so it will not be able to cross the hydrophobic barrier of the membrane
Define each component of the plasma membrane: Phospholipid - Glycoprotein - Glycolipid -
Phospholipid - polar head, fatty acid, nonpolar tails. Polar heads exposed to extracellular environment or cytoplasm. Responsible for semi-permeable nature of plasma membrane. Glycoprotein- carbohydrate attached to a protein (blood type) Glycolipid- carbohydrate attached to a lipid
What kinds of cells have cell walls (three), and what type of carbohydrate material is each cell wall made of?
Plant cell walls: made of glucose Fungus cell walls: made of chitin Bacterial cell walls: made of peptidoglycan
Some functions of the cell wall:
Provide structural support for the cell - prevent the cell from taking in too much water via osmosis, providing pressure against the inflow of water, so that the cell does not burst in hypotonic environments
Why is the shape of a red blood cell important to its function?
RBCs are flattened, with an impression in the middle. This increases the surface area of the cell, allowing for more rapid absorption of oxygen into the cell, and release of oxygen as it move through the body tissues
Water and cell membrane
Requires a protein channel to move across membrane (aquaporin) because water is polar (though some water will still seep in through the lipid bilayer)
Glucose and cell membrane
Requires a protein channel to move across membrane - it is too large to cross the membrane
You are told that an unidentified cell contains a single, circular DNA molecule but no nucleus. Which of the following would you also expect the cell to possess?
Ribosomes
Ribosomes:
Ribosomes are the location of protein synthesis (translation) RNA is read and the code used to form a polypeptide chain
What happens to proteins formed in the rough ER vs. in the cytoplasm?
Rough ER-site specific proteins leave the cell or embedded in cell membrane Cytoplasm - proteins remain the cell
Surface area to volume ratio of: cube 3cm x 3cm
SA = 3*3 = 9cm2 6 sides = 9*6 = 54 cm2 Volume = 3*3*3 = 27 cm3 SA to V ratio 54/27 = 2
Surface area to volume ratio of: sphere 3cm diameter
SA = 4 (3.14)(1.5*1.5) = 28.3 cm Volume = 4/3 (3.14)(3*3*3) = 14.1 cm3 SA to V ratio = 28.3/14.1 = 2.007
Rought ER
Studded with ribosomes, proteins are made here that are then transported to other parts of the cell. Rough ER also plays a role in intracellular transport
What is tonicity?
The ability of extracellular fluid to make water move into or out of a cell.
You have not watered your plant in a few days. it is droopy and floppy. What has happened on a cellular level (be specific to a particular organelle)? What will happen if you water it?
The central vacuole of the plant cells is designed to fill with water and push against cell walls, holding the plant upright. when dehydrated, the vacuoles shrink, and are no longer pushing against cell walls, so they sag, leading to drooping plants. When the plant is watered, vacuoles will fill again, push against the walls, and the plant will stand upright again
The hot potato is now a mouse, and the GIANT hot potato is now an elephant. Which organism must have a higher metabolic rate (burn more energy) to maintain its body heat? Explain why
The elephant has a low SA to V ratio, so it holds onto heat, meaning it needs to spend less energy heating itself. The mouse, being small has a high SA to V ratio and looses heat to the environment at a higher rate - so it must to burn more energy per unit mass in order to maintain its body temp - the mouse has a higher metabolic rate than the elephant
Predict what would happen if a mutation caused one of the hydrophobic R groups to be switched with a hydrophilic R group
The hydrophobic R groups are anchoring the protein the phospholipid membrane, as it is the water-free between the membrane layers. If those R groups were hydrophilic, the protein would fall out of the membrane and could no longer perform its function
What property of the phospholipid bilayer prevents the movement of small polar molecules across the membrane
The hydrophobic portion of the bilayer prevents polar (hydrophilic) molecules from being able to come across the membrane
A plant cell changes the osmolarity of its central vacuole, lowering its water potential. This will cause the vacuole to __________ water
gain
Why are plasma membranes important?
The keep the internal environment of the cell separate from the external environment.
Picture a hot potato. Now picture a GIANT HOT POTATO! Which potato will cool off faster? Why? Explain in terms of SA/V ratio
The large potato would take a lot longer to cool off, as it has a smaller surface area to volume ratio. The best way to cool a hot potato is to open it up and cut it into pieces, increasing the surface area exposed to cool air
The bigger the surface area to volume ratio is...
The more efficient a cell will be when performing chemical reactions
Describe how the phospholipids of a plasma membrane regulate the movement of large or polar molecules across the membrane. Explain how osmosis will affect animal cells when the cells are placed into an environment with a low water potential (high solute concentration) compared to the intracellular water potential.
The phosopholipids are what make the cell membrane semi-permeable. Their polar, hydrophilic polar heads are on the outside and their hydrophobic, nonpolar tails are on the inside of the cell. Since the tails are on the inside, only certain materials can enter and exit. Large polar molecules need to enter through transport proteins since they are unable to enter through the membrane as they could disturb the tails. When cells are placed in a low water potential, the animal cells will shrink since the water will exit out of the cells and into the environment. Water flows from an area of high water potential to low water potential, and since the intracellular water potential was higher than the environment it was placed in, makes this situation hypertonic and making the water exit out of the animals cells which can lead to dehydration and may be fatal. The response indicates that osmosis will cause an overall movement of water out of the cells and that the cells will shrink.
What is the role of an aquaporin protein
They allow water molecules to move freely across the membrane into or out of the cell
What is osmolarity?
Total concentration of all solutes in the solution
How does a vacuole increase the rate that plant cells can exchange materials with their environment?
Vacuoles store food and nutrients, as well as wastes witch can quickly diffuse into or out of the cytoplasm either to the environment, or do the vacuole
Calculate the water potential of 0.3 molar glucose solution in an open beaker at 25 degrees celsius. Show your work
Water potential = pressure potential + solute potential Solute potential = iCRT = -1(0.3)(0.0832)(25+273) = -7.4 In an open beaker the pressure potential is 0 So water potential = solute potential = -7.4
What is plasmolysis?
When the cell shrivels due to water lose Plant cells do not shrivel due to their cell wall (plasma membrane disengages from the cell wall)
Predict the results of doubling the number of thylakoids on glucose production in the chloroplast. Explain;
With twice the number of thylakoids, there would be double the surface area to conduct light dependent reactions. This would likely lead to an increase in glucose production (if the enzymes in the Calvin Cycle can keep up) Additional glucose would allow the plant to row faster (more cell wall material and more energy) provided that other requirements for growth are met (sufficient nitrogen and phosphorus available)
Which of the following factors would be most likely to increase membrane fluidity? a. a greater proportion of unsaturated phospholipids b. a greater proportion of saturated phospholipids c. a relatively high protein content in the membrane d. a greater proportion of relatively large glycolipids
a. a greater proportion of unsaturated phospholipids
Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly? a. oxygen b. an amino acid c. Cl- ion d. starch
a. oxygen
Endocytosis and exocytosis are examples of ___________ transport
active
Which of these beakers has the lowest solute potential? a. 1 molar solution of glucose b. 0.5 molar solution of glucose c. 1 molar solution of NaCl d. 0.5 molar solution of NaCl
c. 1 molar solution of NaCI The formula for solute potential = -iCRT, so the larger molarity is a more negative (lower) number. Also, NaCl disassociates into Na+ and Cl- so the ionization constant (i) of NaCl is 2, while glucose does not disassociate so its ionization constant is 1
Small, hydrophilic across cell membrane
can cross but slowly - water/carbon dioxide
Hydrophobic across cell membrane
can typically cross lipid bilayer
Large, hydrophilic across cell membrane
cannot cross, repelled by the fatty acid tails. Must use protein or vesicle to enter the cell
Macrophage cell
do lots of endocytosis to move bacteria across the membrane
Plasma B cell:
do lots of exocytosis to move antibodies across the membrane
Palisade Plant cell
do lots of exocytosis to move glucose (sending to other cells in the plant) across the membrane
Neuron
do lots of exocytosis to move neurotransmitters across the membrane
do you think cells kill other cells on purpose? they do! when?
during controlled cell death - apoptosis
Glucose diffuses slowly through phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most likely functioning in the intestinal cells?
facilitated diffusion
Hypertonic
higher describes the side of the membrane with a higher solute concentration Higher osmolarity Lower water potential
Why would a cell want to lower the water potential of its vacuole?
if the cell needs to take more water into itself from the soil, it can do so by lowering its water potential. The greater the contrast between the soil and the cell, the faster water will enter. Maybe the soil is more dry than usual, or the plant is located in a more hypertonic environment
Smooth ER
in charge of detoxification and formation of new phospholipids
How would the cell lower is water potential
increasing the solute potential (amount of solute) inside the vacuole of the plant cell would increase the osmolarity/decrease the water potential of the cell. It could do this by pumping Na+ ions or glucose molecules into the vacuole
The Na+/K+ ATPase proteins maintain a membrane potential so that the _______________ has a more negative charge compared to the _________________ of the cell
inside, outside
Facilitated diffusion molecules that can pass
large and/or polar - glucose, proteins, water, ions
Mitochondria
location of cellular respiration, forming ATP that powers cellular processes
Hypotonic
low describes the side of the membrane with a lower solute concentration lower osmolarity higher water potential
List three pieces of evidence that supports the Endosymbiotic theory
mitochondria and chloroplasts contain their own rings of DNA (plasmids) they divide independently of the cell, they contain ribosomes which have similar structures to prokaryotes, they have a double membrane (suggesting the other memrbane was part of the host membrane as it engulfed the smaller prokaryote) and they are about the same size as prokaryotes
Would movement through an aquaporin protein be an example of what type of transport? (passive or active?)
passive transport - facilitated diffusion
Endocytosis:
process by which a cell takes material into the cell by infolding of the cell membrane
Major differences between Prokaryote and Eukaryote cells:
prokaryotic cells ('before nucleus') include eubacteria and archeabacteria. they don't have a nucleus or any other membrane bound organelles (though they do have ribosomes). Prokaryotic cells rely on infolding of their outer membranes to perform tasks such as photosynthesis and aerobic cellular respiration. Their DNA is circular, and includes small rings called Plasmids which can be transferred from one prokaryotic cell to another. Prokaryotic cells are small. They sometimes have peptidoglycan cell walls for protection and osmoregulation
Integral protein
protein embedded throughout the lipid bilayer. Areas exposed to the extracellular environment and cytoplasm are hydrophilic while areas touching the nonpolar tails are hydrophobic
Preidct the symptoms of a person whose mitochondria have 50% less folding (less surface area) in their inner membrane. Explain your prediction
the inner membrane holds enzymes involved in the Electron Transport Chain. The more membrane, the more surface area there is for ATP Synthase, which generates ATP. With less membrane, there would be fewer ATP Synthase, so less ATP production. This person would be tired all of the time, having very little energy and not able to do physical activities - muscles require a large amount of ATP. They may also have trouble thinking or concentrating, nerve cells also use a lot of ATP
What does this suggest about the history of life (parts found in eukaryotic and prokaryotic cells)
the last universal common ancestor to all life likely had ribosomes and a cell membrane, which it then passed down to all of its descendants, eventually evolving into all domains of life
How would these now-organelles have lived on their own (what did they do to acquire energy for themselves)?
the mitochondria could do aerobic respiration, embedding the Electron Transport Chain on infoldings of its membrane - as many prokaryotes do today. the chloroplast could do photosynthesis to make its own glucose, but then must also have done some form of respiration to make ATP
Where does the light dependent reaction take place?
thylakoid membranes
What is the function of ribosomes?
to synthesize proteins (following instructions from mRNA)
What are aquaporins?
transport proteins (channel proteins) that move water
Vacuole
used for storage of water and other dissolved compounds needed by the cell. Large central vacuole in plants also used for support to hold up the cell wall
Osmosis is the diffusion of
water across the membrane
