AP Biology: Unit 2: The Cell
Which organelles does: Autolysis
lysosomes
What are the large central vacuole roles?
The vacuoles main functions are storage, waste disposal, regulation of cell turgor, and increases cell size during growth.
Where does the energy for active transport come from?
Adenosine triphosphate(ATP) gives energy for active transport, when ATP is hydrolyzed energy is released forming ADP.
What is the purpose of carrier proteins in the membrane?
Carrier proteins transport specific molecules across the membrane by active transport or facilitated diffusion
Which organelles does: Photosynthesis
Chloroplast
Which organelles does: Respiration
Cytoplasm and mitochondria
The role of: aquaporins
Due to the tertiary structure a pore is created enabling molecules to pass through the membrane, these channel proteins speed up the passage of water molecules.
Is endocytosis active or passive transport?
Endocytosis is active transport, where the cell engulfs necessary material into the cell.
what is the purpose of exocytosis?
Exocytosis actively transports necessary large molecules such as proteins across the membrane through fusion of a secretory vesicle and the plasma membrane.
how does it occur and what cellular components are involved?
Exocytosis is an active transport process, where fusion occurs between secretory vesicles and the plasma membrane. The vesicles from the Golgi originally transport the molecule to the plasma membrane where it then fuses with the plasma membrane, the molecules then go into the extracellular space.
Can diffuse through the plasma membrane on their own:
Gases like CO2 and O2, and hydrophobic molecules such as benzene.
What are the consequences of this to the cell's exchange rates with the environment?
If the SA:V ratio decreases because of the volume increasing the cell will grow, meaning there will be less membrane to surround the cell, making it easier for molecules from the environment to enter the cell, meaning the cell won't get all of it's necessary materials.
Must be transported across the membrane by carrier proteins:
Large polar molecules are unable to cross the membrane without carrier proteins.
The two photomicrographs below show several types of animal cells. Identify the features indicated by the letter A-C:
Nucleus Plasma membrane Golgi apparatus
Describe: Phagocytosis
Phagocytosis (cell eating), the cell engulfs solid material to form large phagosomes or vacuoles.
What is the difference between phagocytosis and pinocytosis?
Phagocytosis binds to the receptor which causes the cell to engulf the molecule or other cell, and is restricted to specialized cells. Pinocytosis brings fluids and dissolved molecules into the cell, a major difference is pinocytosis nonspecific to what they bring into the cell.
What happens to the SA:V ratio of a spherical cell as its volume increases?
The SA:V ratio decreases because the volume is increasing at a greater rate than the surface area.
Which organelles does:Cell division
nucleus, centrioles
The role of: Cell surface antigens
they distinguish between foreign cells and the body's own cells
Which organelles does: Endocytosis
vacuoles (plasma membrane - engulfing)
Intermediate filaments
50 different kinds, and they have six molecular classes based on amino acid sequences. Tough, ropelike protein assemblages that are 8-12nm in diameter. They anchor the cell structures, and radiate from nuclear envelope that help maintain position of organelles
What is diffusion?
A passive process which randomly transports particles from regions of high concentration to regions of low concentration, diffusion doesn't use an input of energy.
Why is ATP required for membrane pump systems to operate?
ATP is required for the membrane pump system because some molecules and ions cannot diffuse directly into the plasma membrane. ATP gives energy so the ion can cross the membrane.
Describe what all components of the cytoskeleton have in common:
All components of the cytoskeleton are made up of polymers of protein.
Microfilaments
Assembled from actin monomers that attach from the plus end and detach from the minus end Usually in bundles, and each filament is 7nm in diameter Can move the entire cell or parts of the cell, and determines/stabilizes cell shape.
Compare the structure and function of bacterial cell walls with those of bacterial cytoskeletons.
Both the bacterial cell wall and cytoskeleton help support the cells shape, but the bacteria cell wall is a single giant molecule made up of peptidoglycan, these are linked at regular intervals to peptides. The cytoskeleton is made up of polymers which help with cell division. Unlike the bacterial cell wall, the cytoskeleton forms helical structures, that are the length of the bacterial cell.
Describe two functions of cell walls:
Cell wall gives support, structure, and protection. The cell wall gives protection to the cell preventing over expansion of the cell. The support the cell wall gives allows for the cell to maintain its shape while internal pressure (turgor) continues.
Compare the process of facilitated diffusion through a channel and by a carrier protein. Which might be faster, and why?
Channel proteins are composed of integral membrane proteins which form channels across the membrane, these channels move ions across the membrane because of its structure. Carrier proteins are proteins that are bonded to substances and when the carrier protein changes its shape the substance is released. The channel protein would be quicker because it requires less steps to transporting substances.
What is the purpose of channel proteins in the membrane?
Channel proteins transport water soluble molecules across the hydrophobic interior of the membrane.
Identify two structures in the diagram that are not found in animal cells:
Chloroplast and the starch granule are both not found in animal cells. Chloroplasts are specialized plastids that are the site of photosynthesis, which occurs in leaves. The starch granule is where carbohydrates stored in amyloplast, these plastids are specialized for storage.
Explain how compartmentalization within the cell is achieved and how it contributes to functional efficiency
Compartmentalization within the cell contributes to functional efficiency because the reaction rate is controlled by the rate in which substrates are entering and exiting the cell, making certain material available for reactions.
How is cotransport used to move glucose into the intestinal epithelial cells?
Cotransport is used to move glucose molecules by using specific transport protein that couples the return of Na+ down its concentration gradient to the transport of glucose into the intestinal epithelial cells.
Explain what is meant by cotransport
Cotransport means coupled transport, specific transport proteins couple with other molecules so they can transport down its concentration gradient.
Distinguish between the cytoplasmic ribosomes and the ribosome found in chloroplasts and mitochondria:
Cytoplasmic ribosomes are small and are free in cytoplasm, and contain 80s subunits. Ribosomes found in chloroplasts and mitochondria contain 70s subunits.
Why is energy required for active transport?
Energy is required for active transport because it's moving substances against their concentration gradients, this requires a lot of work, which means it needs a great input of energy.
Describe two ways in which eukaryotic cells can efficiently obtain the raw materials they need for materials they need for metabolism, even as they become larger:
Eukaryotic cells contain organelles, cellular compartments, that concentrate materials into specific regions of the cell. The plasma membrane surrounds the cell and regulates the movement of substances coming in and out of the cell.
Which organelles does:Secretion
Golgi and plasma membrane
Identify two examples of intracellular membranes and describe their functions:
Golgi apparatus is a secretory vesicle that modifies and moves substances around the cell and specific part of the cell. The rough endoplasmic reticulum translates genetic information into proteins.
What are the functions of the cell wall in plants?
In plants the cell wall supports the cell, and limits the cell's volume, by protecting the cell and also preventing excessive H2O.
Describe two examples of the purpose of exocytosis in cells:
In the transportation of neurotransmitters exocytosis is key because the transmitters are transported into the synapse to transmit nervous signals. In bacteria and fungi, exocytosis secretes digestive enzymes which break down molecules so nutrients can be absorbed.
Microtubules
Made up of dimers of the protein tubulin. Each dimer has one -tubulin and one-tubulin. There are 13 chains of tubulin dimers; Long, hollow, and unbranched cylinders that are 25nm in diameter. They form rigid internal skeleton for some cells, and act as framework which help motor proteins move structures.
Explain how the plasma membrane can from a vesicle
Materials that are engulfed by folding the material by the plasma membrane, this vesicle begins to form when the plasma membrane punches inwards. Then the vesicle is made and then carries the molecules into the cell to their specific location to then be digested and delivered to the vacuole by lysosomes.
Would a small molecule such as an amino acid enter a cell by receptor endocytosis?
No, a small molecule wouldn't enter a cell by a receptor endocytosis because endocytosis is the process of a macromolecule being brought into the cell. It has a certain mechanism for bringing specific large molecules, so the small molecule may not be recognized by the receptors.
In general terms describe the energy requirements of passive and active transport:
Passive transport doesn't require an input of energy to transport molecules through the membrane, while active transport requires energy, usually ATP, to transport molecules against their concentration gradient.
What are the differences between peripheral and integral membrane proteins?
Peripheral membrane proteins lack exposed hydrophobic groups and are not embedded within the bilayer. The polar regions interacted with parts of the integral membrane proteins or with polar molecules. Unlike peripheral membrane proteins, integral membrane proteins are partially embedded within the bilayer. They are composed of both hydrophilic and hydrophobic regions and interact noncovalently.
What is the difference between primary active transport and secondary active transport?
Primary active transport directly uses ATP energy to transport molecules across the membrane, while secondary active transport stores energy in a concentration gradient, the molecules being transported is coupled to another molecule, so ATP is not directly used.
How does facilitated diffusion differ from simple diffusion?
Simple diffusion is the direct diffusion of a molecule across the membrane without assistance from other molecules/ channels. Facilitated diffusion requires assistance from either a channel or protein, so larger or charged molecules can pass through the membrane.
Can Diffuse through the membrane via channel proteins:
Small polar molecules and Ions diffuse through the membrane by aquaporins or ion channels.
A membrane sequence protein has the following amino acid sequence. Considering the R groups on the ami
The FIWLIWLV region of the amino acid sequence would be embedded within the membrane because the R groups are nonpolar and have hydrophobic side chains meaning that the hydrophobic region of the membrane will not repel the R groups of the amino acid, so the sequence can be embedded within the membrane.
The role of: G protein
The G-proteins binds to a receptor protein to signal a reaction involving the G-proteins, the main function of G-proteins is the signaling of pathways.
Explain why antibiotics targeting the bacterial cell wall will not affect the people taking them:
The bacteria cell wall will not affect the people taking them because they antibiotics only target the bacterial cell wall, within only plants, fungi, and bacteria. Animals don't contain cell walls, so the antibiotics will not target something that is not there.
The role of: Glut1 protein
The carrier proteins facilitates in the transport of glucose across the membrane of mammalian cells, this transportation into the cell is at a high rate to supply the cell with the necessary energy to work.
In considering the origin of the cells, why do biologist focus on the organ of the cell membrane?
The cell membrane is key to the origin of cells because it encloses the cell, giving it a stable internal environment. This allows metabolic reactions to occur within the cell
What are some functions of the cell nucleus? What are the advantages of confining these functions within the nucleus, separated from the cytoplasm?
The cell nucleus is the location of DNA, the site where DNA is replicated, DNA is transcribed into RNA, and contains the nucleolus where ribosomes are being made. The nucleus has two membranes which creates a barrier between DNA transcription and DNA translation. Separating the nucleus from the cytoplasm allows the nucleus to regulate the information coming in from the nuclear pores.
Describe the location and general composition of the bacterial cell wall:
The cell wall is located outside the plasma membrane, and serves as an anchorage point for the flagella. Peptidoglycan, lipopolysaccharide and lipoprotein compose the cell wall giving the cell it's functions of giving cell shape and preventing rupture.
Name one structure or organelle present in generalize animal cells but absent from plant cells and describe its function:
The centrioles are organelles made up of microtubules. The are structures within centrosomes associated with nuclear division.
Explain the importance of the cytoskeleton being a dynamic structure:
The cytoskeleton being a dynamic structure allows the cytoskeleton to change the cells shape, move materials, and move the cell, throughout all of this it hydrolyzes ATP at each step.
What is osmosis?
The diffusion of water down its concentration gradient across the membrane. Water molecules are able to directly pass through the membrane making the transportation simple diffusion.
What evolutionary advantages does a eukaryotic cell have compared with a prokaryotic cell?
The eukaryotic cell contains organelles, membrane enclosed compartments. Organelles are where metabolic functions occur. The division of labor provides regulation and efficiency to the cell, which helps it evolve complex organisms
Explain how fimbriae differ structurally and functionally from flagella:
The fimbriae structurally differs from the flagella because it is shorter, straighter and thinner. This makes the fimbriae ideal for attachment, unlike the flagella which it's main function is movement.
What is the evolutionary advantage of bacteria that have flagella over bacteria that do not?
The flagella is an appendage that helps some cells swim, that gives the bacteria an evolutionary advantage because it allows the cell to swim toward their food. The complex motor protein within the flagella acts as a propeller, moving the cell. Bacteria without the flagella are slower with getting food, giving them a disadvantage in their environment.
Describe the function of flagella in bacteria:
The flagella is anchored in the plasma membrane and is used for locomotion within the bacteria.
What happens to the glucose that is transported into the intestinal epithelial cells?
The glucose is then diffused out of the epithelial cell and is transported away in the blood.
What would happen to the height of the water in the capillary tube if the sucrose concentration was increased?
The height of the water would increase if the capillary tube increased in sucrose concentration because there would be less free water in the capillary tube than in the water.
What structure takes up the majority of space in the plant cell?
The large central vacuole, which is filled with an aqueous solution of ions takes up the majority of space in a plant cell.
What is the main difference between the cell walls of Gram-negative and Gram-positive bacteria?
The main difference is that Gram-negative has an outer membrane over the thin layer of peptidoglycan, but Gram-positive has a thick layer of peptidoglycan beyond the plasma membrane
Explain how the presence of a cytoskeleton could aid in directing movement of material within the cell:
The microtubules, a key part of the cytoskeleton, aid in the movement of material within the cell and moving the actual cell.
What is active transport?
The movement of molecules from low concentration to high concentration regions across a cellular membrane by transport proteins, the input of energy is needed to move the molecules because it's against their concentration gradient.
What is the purpose of endocytosis?
The purpose of endocytosis is to actively transport molecules across the plasma membrane into the cell.
What is the difference in ribosome between prokaryotic and eukaryotic cells?
The ribosomes in prokaryotic cells are 70s subunits, while the eukaryotic cells contain 80s subunits.
Explain how ribosomes, endoplasmic reticulum, transport vesicles, and the Golgi interact to enable cellular secretion
The ribosomes, which are on the surface of the endoplasmic reticulum, translate the mRNA into polypeptide chains, then are threaded through the endoplasmic reticulum into cisternal space, in this space the polypeptide folds into its 3-dimensional structure. The proteins leaving the ER are wrapped in transport vesicles which bud off the ER. The Golgi receives these vesicles and modifies, processes, and packages the proteins. After the protein is modified the protein is secreted from the Golgi.
Compare the structural and functional differences between the rough and smooth endoplasmic reticulum
The rough and smooth endoplasmic reticulum are interconnected membranes branching throughout the cytoplasm. However, the rough endoplasmic reticulum has ribosomes attached to the outer surface of the membrane, making it appear "rough" on electron micrographs. The ribosomes on the rough endoplasmic reticulum synthesizes proteins, so the endoplasmic reticulum can modify the proteins. The lack of ribosomes on the smooth endoplasmic reticulum causes a more tubular structure and causes less protein synthesis than the rough er.
What is the surface area-to-volume ratio of a giraffe's nerve cell? [For simplicity, assume that it is tubular (a cylinder), with a length of 3m and a diameter of 5μm?
The surface area of a giraffe's nerve cell would be 47163μm and the volume would be 58904μm, the ratio would then be 1.2:1
What properties of a substance determine whether, and how fast, it will diffuse across the membrane
The three main factors that determine how fast a substance will diffuse is the diameter of the molecule, the temperature, the concentration gradient. The smaller the molecule is the faster it will diffuse through the membrane, the higher temperature the faster diffusion will occur because the heat gives more energy for movement. The greater the concentration gradient is then the faster substances diffuse because substances diffuse from high concentration to low concentration.
Why did water move in this direction?
There is less free water meaning that there is a low concentration of water so the water molecules would diffuse from high to low concentration of free water.
Describe three features distinguishing prokaryotic cells from eukaryotic cells:
There is no nucleus No membrane bound organelles There is a cell wall which is complex and has a multi-layered structure
Describe two consequences of the extracellular accumulation of sodium ions:
There would be an increase in sodium ion concentration, if this occurred then there would be an excess amount of glucose to enter the cell meaning there would be less glucose going into the bloodstream.
What do the three types of diffusion described above all have in common?
They all randomly diffuse molecules across the membrane, so the molecules can go from high to low concentrations.
What might this suggest about the origins of these organelles
This may suggest that endosymbiosis may have occurred giving the origins of certain subunits in these organelles.
Describe: Receptor mediated endocytosis
When certain metabolites, hormones, or viral particles trigger when bound to specific receptor proteins, and then are engulfed by the plasma membrane.
If a cell has a cube shape that is 500μm on a side, what is its surface area-to-volume ratio? If the surface area-to volume ratio should be more than 0.1μm-1for optimal cell function, would dividing this cell into 1 million individual cells (also cubes) meet this standard?
Yes, they would meet the standard because the surface area is 1500000 and the volume is 125000000 making the ratio .12x10-1: 1, making it more than 0.1μm-1. Dividing the cell into 1 million would meet the standard because 150/125= 1.2:1 ratio.
Which organelles does: Protein synthesis
free ribosomes, nucleus, Rough ER
Which organelles does:Transport
plasma membrane and vacuoles
describe: pinocytosis
when non-specific liquid enter the cell to form pinocytic vesicles, this process is used to absorb extracellular fluid