exam 2 Flashcards
What feature of phospholipids accounts for the fluidity of cell membranes?
Individual phospholipids are not covalently bonded together in the membrane.
What is the direct result of the inside of the phospholipid membrane being non-polar?
Ions cannot easily pass through the membrane.
Molecules that interact well with water molecules are called?
Hydrophilic
Which microscope is used to view organelles such as the endoplasmic reticulum?
Transmission electron microscope
How is DNA stored in a prokaryotic cell compared to a eukaryotic cell?
DNA in a eukaryotic cell is found in a membrane-bound nucleus.
Which types of cells contain ribosomes?
Both prokaryotic cells and eukaryotic cells
Why does compartmentalization of eukaryotic cells allow for greater complexity?
The compartments allow for the partial separation of metabolic reactions.
Cells were originally discovered by the use of?
A compound light microscope
What limits the maximum size of cells?
Surface to volume ratio
Which organelles are found in plant cells only?
Chloroplasts
What is an example of cellular homeostasis?
Maintenance of constant internal pH
Which organelle is associated with ribosomes?
Rough endoplasmic reticulum
Which organelle is more predominant in plant cells versus animal cells?
Central vacuole
Where is most of the DNA stored in a cell?
Nucleus
Where are ribosomes assembled?
Nucleolus
What are the folds in the inner mitochondrial membrane called?
Cristae
Where do protons from electron transport accumulate in the mitochondrion?
Intermembrane space
What are the pores in plant leaves that allow for gas exchange known as?
Stomata
How can plant cells communicate?
Plasmodesmata
What adheres one plant cell to another?
Desmosomes
Which type of animal cell junction is found in the lining of the epithelial layers of the small intestine?
Tight junctions
Which type of animal cell junction is predominant in heart muscle cells?
Gap junctions
Which concept explains why mitochondria, nuclei, and chloroplasts have double membranes?
Endosymbiosis
Which type of cell uses an electrochemical gradient to power its flagella?
Prokaryotic
What feature of phospholipid bilayers allows transport vesicle to take protein from the endoplasmic reticulum to the Golgi?
fluidity
Fluidity is essential for the movement of vesicles as it allows for membrane fusion and transport processes.
What would you conclude if treatment of the outside of a cell membrane with an enzyme that removes carbohydrates inhibits the function of some surface proteins?
Carbohydrates are important for external protein function
Carbohydrates often play roles in cell recognition and signaling on the cell surface.
The proton gradient in mitochondria powers what enzyme?
ATP synthase
ATP synthase uses the energy from the proton gradient to synthesize ATP from ADP and inorganic phosphate.
Which experiment would show whether an electrochemical gradient is necessary for ATP generation in the mitochondria?
add molecules called ionophores that allow free passage of ions across membrane
Ionophores disrupt the electrochemical gradient, which can help assess its role in ATP synthesis.
Which feature of phospholipids is the most critical to their ability to form bilayers in cell membranes?
they are amphipathic
Amphipathic molecules have both hydrophilic and hydrophobic parts, essential for bilayer formation.
Which plasma membrane component can be either found on its surface or embedded in the membrane structure?
protein
Proteins can be integral (embedded) or peripheral (attached to the surface) in the membrane.
In which way would eukaryotic cell organelle membranes differ from plasma membranes?
The proportions of proteins, lipids, and carbohydrates will vary
Different organelles have unique functions, leading to variations in membrane composition.
Which characteristic of a phospholipid increases the fluidity of the membrane?
unsaturated fatty acid tail
Unsaturated fatty acids create kinks that prevent tight packing, enhancing membrane fluidity.
How would an organism maintain membrane fluidity in an environment where temperatures fluctuate?
Greater proportion of unsaturated phospholipids in membranes
Unsaturated phospholipids help prevent membranes from becoming too rigid at low temperatures.
According to the fluid mosaic model of the plasma cell membrane, what is the location of carbohydrates in the cell membranes?
Carbohydrates are in contact with the aqueous fluid outside the cell
This positioning allows carbohydrates to participate in cell signaling and recognition.
What do double bonds in phospholipid fatty acid tails contribute to?
the fluidity of membranes
Double bonds prevent fatty acids from packing closely, enhancing membrane fluidity.
Identify the principal force driving movement in diffusion.
concentration gradient
Diffusion occurs when substances move from areas of high concentration to low concentration.
Which of the following is an example of passive transport across a membrane?
the movement of water from a nephron into the collecting duct of the kidney
This movement is driven by osmotic gradients without the use of energy.
Water moves via osmosis across plasma cell membranes in which direction?
from an area with a high concentration of water to one of lower concentration
Osmosis is the movement of water toward higher solute concentrations.
What problem is faced by organisms that live in fresh water?
Without compensating mechanisms, their bodies tend to take in too much water
Freshwater organisms must regulate water intake to avoid cellular swelling.
Which of the following questions can be asked about organisms that live in fresh water?
Will their bodies take in too much water?
This question addresses the challenge of osmoregulation in freshwater environments.
Which of the following explains why active movement of molecules across membranes must function continuously?
Diffusion is constantly moving solutes in opposite directions
Active transport helps maintain concentration gradients against passive diffusion.
How does the sodium-potassium pump make the interior of the cell negatively charged?
by expelling more cations than it takes in
This pump typically moves 3 sodium ions out and 2 potassium ions in, creating a net negative charge.
What is the difference between primary and secondary active transport?
Primary active transport is directly dependent on ATP, while secondary active transport is indirectly dependent on ATP
Primary transport uses energy directly from ATP, while secondary transport uses the energy from the gradients created by primary transport.
What happens to the membrane of a vesicle after exocytosis?
It fuses with and becomes part of the plasma membrane
This process allows the release of substances outside the cell while integrating vesicle components into the membrane.
In what important way does receptor-mediated endocytosis differ from phagocytosis?
It brings in only a specifically targeted substance
Receptor-mediated endocytosis is selective, while phagocytosis engulfs larger particles indiscriminately.
What does ∆G < 0 imply about ATP hydrolysis under standard biochemical conditions?
The hydrolysis reaction is spontaneous
This indicates that the reaction occurs without the need for an external energy source.
Where in the cell does glycolysis occur?
cytosol
The ____ law of thermodynamics states that energy can be neither created nor destroyed.
first
__________ is the exergonic breakdown of substrates.
catabolism
__________ is the endergonic synthesis of molecules.
anabolism
__________ includes all chemical reactions occurring within a cell.
metabolism
What is the name of the molecule that glucose is converted into for energy use in cells?
adenosine triphosphate
What is the primary molecule used to store energy released during cellular respiration?
ATP
Which of the following is a catabolic process?
digestion of sucrose
What food molecule is most directly related to the use of sun energy?
glucose
What reaction will release the largest amount of energy to help power another reaction?
ATP to ADP
Which of the following best describes energy?
the ability to do work
What is the ultimate source of energy on this planet?
the sun
Which of the following molecules is likely to have the most potential energy?
sucrose
Which of the following is the best way to judge the relative activation energies between two given chemical reactions?
Compare their reaction rates.
Which term in the Gibbs free energy equation denotes enthalpy?
ΔH
Which chemical reaction is more likely to occur?
exergonic
Which comparison between endergonic and exergonic reactions is false?
All endergonic and exergonic reactions require energy to overcome an activation barrier.
What counteracts entropy?
input of energy
Which of the following is the best example of the first law of thermodynamics?
a power plant burning coal and producing electricity
What is the difference between the first and second laws of thermodynamics?
The first law involves conserving energy while the second law involves the inability to recapture energy.
What effect does inputting energy into a living system have?
fuels catabolic rxns
Why is ATP considered the energy currency of the cell?
It can transport energy to locations within the cell.
What is ATP made from?
ADP + phosphate
What part of ATP is broken to release energy for use in chemical reactions?
the bond between the second and third phosphates
What does an allosteric inhibitor do?
binds to an enzyme away from the active site and changes the conformation of the active site, decreasing its affinity for the substrate
What happens if an enzyme is not functioning in a chemical reaction in a living organism that needs it?
The reaction proceeds, but much more slowly.
Which of the following is not true about enzymes?
They increase the ΔG of reactions.
Which analogy best describes the induced-fit model of enzyme-substrate binding?
2 people hugging
How does enzyme feedback inhibition benefit a cell?
Feedback inhibition benefits the cell by blocking the production of the products by changing the configuration of enzymes. This will prevent the cells from becoming toxic.
What is the function of enzymes?
to lower the activation energy of a reaction
If the nonprotein component of an enzyme is firmly attached to the protein, the complex is called a(n) __________.
holoenzyme
what can enzymes be?
enzymes are catalysts, proteins, highly specific for substrate.
Enzymes catalyze a reaction by __________.
decreasing the amount of activation energy needed to drive the reaction.
