Unit 2 - Biochemistry and Cells Flashcards
What happens to the surface area to volume ratio as a cell grows in size?
Why is this important in terms of omsosis and diffusion
As cells get bigger the surface area to volume ratio decreases.
Diffusion happens at a constant rate so the smaller cell can get nutrients to the center faster.
What is the term for passive movement across a semipermeable membrane that occurs in the direction of the concentration gradient?
Diffusion
What is the process called in which a cell engulfs matter and forms a vacuole around it?
Endocytosis
Following endocytosis, where are the receptors located on the resulting vacuole?
On the inside of the vacuole
What organelle is involved in the synthesis and packaging of proteins both for storage and secretion from the cell?
The endoplasmic reticulum
What is the main difference between rough and smooth ER?
Rough ER contains bound ribosomes
What theory asserts that mitochondria and chloroplasts were once independent prokaryotic cells?
Endosymbiotic Theory
What type of cell stores its genetic material via chromosomes in a distinct nucleus?
A eukaryotic cell
True or False: Eukaryotes are exclusively multi-cellular organisms with membrane bound organelles?
False - there are many single celled eukaryotes
What is the process in which a vesicle within a cell secretes its contents outside of the cell?
Exocytosis
What type of passive transport uses specific integral proteins within the cell membrane?
Facilitated diffusion
What integral protein is involved in the facilitated diffusion of water?
An aquaporin
What organelle involved in motility protrudes from a cell and has a lash-like appearance?
A flagellum
True or False: both eukaryotes and prokaryotes may have flagella
True - both types of cells my have this organelle
Who were the scientists who developed the fluid mosaic model of the cell?
SJ Singer and GL Nicolson
What is the term for an organism’s complete set of genetic code?
Genome
What is the difference between active transport and passive transport?
Active transport requires energy (ATP) while passive transport doesn’t. Active transport moves molecules (refer to sodium-potassium pump) against the concentration gradient from (low to high) while passive transport moves molecules with the concentration gradient (high to low), usually through diffusion.
How does adhesion differ from cohesion in plants?
In water transport in plants, adhesion is when water molecules stick to other materials (ie. when water sticks to a straw) while cohesion is when water molecules stick together via hydrogen bonds.
How do the amphipathic properties of lipids allow for the creation of the double bilayer cell membrane?
Since lipids are amphipathic, they each have a polar, hydrophillic heads and 2 nonpolar, hydrophobic tails. The amphipathic nature of lipids cuases them to spontaneously form bilayers in aqueous environments where lipids are clustered together with their tails facing each other in the interior and heads exposed to water. This amphipathic property is also responsible for the cell membrane’s closed structure, which allows lipids to avoid exposure of their hydrophobic hydrocarbon tails to water.
What type of transport are all aquaporins used for and explain their functions.
Aquaporins (aka water channels) are a form of passive transport. They facilitate rapid, highly selective water molecules transport in and out of the cell via diffusion, while preventing the passage of ions and other solutes. They are integral membrane pore proteins that span the cell membrane.
What are the key aspects of binary fission and what organism(s) primarily use it?
Prokaryotes and other single-celled eukaryotes (ie. bacteria) primarily use binary fission for propagation. Binary fission does not result in genetic variation and is a type of asexual reproduction.
Describe the two main phases of the cell cycle.
The two main phases of the cell cycle are interphase and cell division. Cells spend most of their time in interphase which is composed of 4 phases: G1, S, G2, and G0. During it, the cell copies its DNA in preparation for mitosis. Cell division is the 2nd phase of the cell cycle and includes mitosis and cytokinesis. Mitosis, which is when a eukaryotic cell undergoes nuclear division resulting in 2 identical daughter cells, consists of 5 steps: prophase, metaphase, anaphase, and telophase. During cytokinesis, the 2 newly formed nuclei are separated into 2 different cells and the cytoplasm is divided. In animal cell cytokinesis, a cleavage furrow forms instead of the cell plate in plant cells and the cell is pinched into two new cells.
What is the purpose of the cell wall and is it used by all cells?
The cell wall is only present in plant cells. It is made of cellulose, which is what makes plants so tough and rigid in structure. Cell walls are semi-permeable due to plasmodesmata, which connects the cytoplasm of adjacent plant cells. It also provides protection.
What is the function of centrioles in mitosis/meiosis and is it found in all cells?
Centrioles are the small, cylindrical bodies that compose centrosomes (a pair of centrioles=centrosome). They are microtubule organizing centers located outside the nuclear envelope and give rise to microtubules that make the spindle fibers used during cell division. Only animal cells have centrioles.
Where is the centromere located and how is it involved during mitosis/meiosis?
The centromere is located in the middle of the chromosome. During prophase, kinetochore fibers attach to each chromosome at its centromere and pull them to the center of the cell during metaphase to make the metaphase plate. During anaphase, the centromeres of the chromatids split.
What is the centrosome?
Centrosomes (2) are synthesized during prophase and move to opposite sides of the cell. In animal cells, they contain centrioles.
What type of macromolecule is cholesterol and what is its role in the fluid mosaic membrane?
Cholesterol is a type of lipid (more specifically, a steroid). It has multiple functions, such as being responsible for fluidity in the cell membrane’s phospholipid bilayer (more cholesterol=more rigid, less cholesterol=more fluid),
Real life application: Michael added extra fertilizer in order to increase the amount of corn crop output; however, after the next few months, the young corn plants had all wilted and began to die. What caused the corn plants to wilt and eventually die (hint: think about environment type around corn roots) and what could have been done to remedy the problem? (Osmosis is Serious Business: Part I)
The extra fertilizer created a hypertonic environment around the corn roots and in order to make the environment more isotonic, water diffused through osmosis from the corn cells into the soil since there was a higher concentration of solute outside of the cell. This would result in cell plasmolysis. To remedy this issue, more water would have to be added to the corn in order the dilute the fertilizer concentration and create a hypotonic environment where water diffuses into the plant cell.
Explain factors that can affect diffusion rate across membranes such as membrane thickness, surface area and concentration gradients. (Osmosis Lab; Essential Knowledge: 2.B.2)
No matter what circumstance, diffusion rate is constant. Only the Percentage of volume diffused changes proportionally with a cell’s surface area. In diffusion, the solvent, such as water, will always move from areas of high solute concentration to areas of low solute concentration. (examples of osmosis: plant root hairs, small intestine, small cell size)
Describe the relationship of temperature and tonicity to water potential. (Water Potential WS)
Temperature shares an inverse relationship with water potential. As temperature decreases, water potential increases. Addition of pressure increases water potential while addition of solutes decreases it. If water in the cell is higher in volume than that of its surroundings, the cell has high water potential and its environment would be hypertonic in relation to the cell.
What are the two key molecules that control and coordinate cell division and what are their roles? What would happen if they were to malfunction? (Cell Cycle Game; Essential Knowledge: 4.A.4)
These two key molecules are CDK and Cyclin. They are both “supervisors” of the cell cycle. They stop the cell cycle if the cell is damaged and either repair damage before letting the cell proceed OR destroy the cell. If CDK and cyclin were to malfunction, the cells may become cancer cells with altered chromosomes, which would lead to the growth of a tumor (clump of mutated cells).
