Gen Bio test 1 review

Describe the rapid response that occurs in leaves when the soil surrounding roots dries up and why this response is crucial for the survival of the plant.

Leaves have openings that allow gas exchange required for photosynthesis but inadvertently cause water loss. When roots since dry soil they send a signal to the leaves to close the openings so that the leaf cells will not become dehydrated (wilt). Although this halts photosynthesis, it is crucial to survival because leaf cells will die if they lose too much water. A plant can’t survive if too many of its leaves die since these organs provide the sugars necessary to feed the entire plant.

What is adhesion and Cohesion

Adhesion- Water molecules that adhere to the glass pull upward at the perimeter

Cohesion- Water molecules at the surface form hydrogen bonds with nearby water molecules and resist the upward pull of adhesion

Why do drops of water form this shape?

Drops of water are almost spherical because this is the shape that minimizes interaction with the air (surface area) and maximizes hydrogen bonding between the water molecules.

Why is it important that the liquid that forms our blood, interstitial and intracellular fluids is water rather than oil?

Carbohydrates, proteins, nucleic acids, and the building blocks of which they are composed are polar molecules that life depends upon. These molecules must be transported throughout the body. The formation of solutions is crucial because it separates molecules into individual units that can interact to carry out the metabolic reactions that life depends upon.

Match the building block to the macromolecule.

a. glucose b. nucleotide c. amino acid d. fatty acid

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Protein,Lipid, DNA, polysaccharide

c Protein d Lipid b DNA a polysaccharide

What is condensation synthesis

the process where you move water ( from a covalent bond) to make a monomer.

What is hydrolysis

when we add in water ( to covalent bonds) to break down the polymers into their individual monomers

Explain the relationship between polymers and monomers

Monomers are known as the building blocks for polymers, for example, glucose or fructose could be a monomer, and carbohydrates or any macromolecules would be the polymer. We eat polymers and digest them into monomers, they are then able to enter our body so our cells take up monomers and convert them back to polymers.

What happens to molecules in the intestinal lumen that can’t be hydrolyzed to monomers (for example, cellulose)?

Molecules that can not be digested into monomers can not cross cell membranes, so they can’t enter the body. The undigested matter will travel through the GI tract and be released with feces.

What is the importance of fats, what are the downsides

Fats store 6 times the amount of energy than other molecules such as glycogen. (which is why we have specialized cells that only store fats). The problem with fats is that since they’re non-polar they’re hard to move around the body, and this can lead to cardio vascular disease when that transport fails.

What are phospholipids

one end is polar and non-polar (hydrophilic and hydrophobic), this performs a barrier from aqueous solutions

Some people inherited a mutant form of the lactase gene that is beneficial because

it allows them to keep drinking milk and eating dairy into adulthood

Label each letter shown

A: DNA B: RNA C: Ribosome D: Protein E: Amino acids

What is the primary structure of a protein

the sequence of amino acids linked together to form a polypeptide chain.

What is the secondary structure of a protein

Results from regular and repeated bonds between the oxygen and hydrogen atoms in the backbone of the polypeptide chain. ( eithier a alpha belix or a beta pleated sheet.)

What is the tertiary structure of a protein

Describes the relationship between those side chains and are much more varied. Describes the interactions that made the protein form its shape ( alpha helix or beta pleated sheet) it describes the interactions between the subunits.

Sickle cell anemia demonstrates

the role a single amino acid can have on the tertiary and quaternary structure of proteins.

The formation of covalent bonds between nucleotides a. occurs by condensation synthesis b. forms nucleic acids like DNA and RNA c. is catalyzed by enzymes d. connects the phosphate group of one nucleotide to the sugar group of another nucleotide e. all of the above

E. All of the above

What is the difference between prokaryotic and eukaryotic cells

Both prokaryotes and eukaryotes are living things and thus share all the characteristics of life such as growth, response to stimuli, metabolism etc.. Prokaryotes are much smaller than eukaryotes and do not contain membrane bound compartments (organelles). Prokaryotes are almost always unicellular and have cell walls. Only some eukaryotes are unicellular (protists and some fungi) and only some have cell walls (fungi and plants). Another major difference is in the quantity, structure and organization of chromosomes. Prokaryotes have a single, circular chromosome of about a million bp and eukaryotes have many more (humans have 46) linear chromosomes (6 billion bp in humans) organized into condensed regions by histone proteins.

Describe the structure and function of the bacterial cell wall. Explain a peptidoglycan and discuss the features that are crucial to its function.

The bacterial cell wall plays a structural role, preventing the liquid membrane from popping (bursting) as a result of water uptake. In a hypotonic environment (water entering the cell is keeping the cell turgid) the cell membrane pushes against the cell wall, and therefore the cell wall determines the shape of the cell. The structural integrity of the cell wall is the result of two components, proteins and carbohydrates that are linked together by covalent bonds forming a strong but porous material called peptidoglycan.

Refer to the images below to explain why the antibiotic, penicillin, is effective at getting rid of pathogenic bacteria with the type of cell wall structures shown on the left but are not effective against those with an outer membrane covering the peptidoglycan layer as shown on the right.

The grey block is meant to depict the cell wall. Penicillin can easily penetrate it and bind to and inhibit transpeptidase, the enzyme that connects the protein and carbohydrate subunits of the cell wall. The cell on the right has two cell membranes: A plasma membrane that contains the contents of the bacterium, and another membrane that is outside the cell wall. Penicillin can’t cross this outer membrane to access the transpeptidase, so it can’t interfere with cell wall construction.

What are Fimbriae and Pili, describe their role in pathogenicity

Fimbriae are extensions of the cell wall that allow bacteria to grab a hold of slippery mucous-secreting cell layers (like the vagina) that would otherwise wash them away. Capsules are sticky polysaccharide coats that, like fimbriae allow bacteria to adhere to a mucous lining (like the trachea) that would otherwise sweep them away. In addition to sticking to body surfaces, both of these structure allows the bacteria to stick to each other resulting in the growth of clumps (or colonies) of bacteria.

Cell A and Cell B have the same volume of cytosol. But Cell A has a plasma membrane that folds inward, greatly increasing the total surface area of the plasma membrane without increasing the volume of the cytosol. How might this trait have provided a selective advantage for bacteria?

Plasma membranes (specifically, membrane proteins) allow passage of nutrients from the pond water (the blue solution in the image above) into the cell thereby providing the bacteria with glucose to make ATP and the building blocks needed for the synthesis of macromolecules like DNA and proteins. Other plasma membrane proteins transfer waste from the cytosol to the pond water cell to prevent the buildup of deadly toxins. Increasing the surface area of the plasma membrane while maintaining the same volume of cytosol results in greater efficiency in both of these essential functions.

What is meant by an “opportunistic” infection? Provide examples.

An opportunistic infection occurs when commensalists encounter a new environment (opportunity) that favors increased growth. Most ear infections are opportunistic. The bacteria causing the infection are already present in our ears, but their growth is slowed because immune cells secrete an antimicrobial agent and other cells secrete wax to repel water. If the immune system is impaired (usually because of a cold virus) the normal processes that slow the growth of the commensalists are interrupted and the bacteria increase in number and interfere with hearing and/or cause pain.

What is the role of the nucelus

houses the DNA, where RNA is synthesized from DNA. This also contains the nuclear envelope which is made to allow the exchange of large molecules between the cytosol and the nucleus ( the pore is highly regulated so everything has to be allowed in or out).

Ribosomes are composed of two types of macromolecules – name them.

rRNA and proteins.

Provide an example of a protein synthesized by “free-floating” ribosomes and distinguish these from “attached” ribosomes.

Hemoglobin, & glycogen synthase are examples of cytosolic proteins. “Attached” ribosomes are docked on the rough endoplasmic reticulum because they synthesize proteins that are headed to either an organelle or to \n the plasma membrane for secretion. All membrane proteins must be synthesized by ribosomes attached to the RER as well.

Describe the process by which a secretory protein such as insulin is synthesized, beginning with the insulin mRNA traveling through a nuclear pore and ending with its exocytosis across the plasma membrane.

When the mRNA encoding the insulin protein reaches the cytoplasm ribosomes will bind to it and initiate protein synthesis. The first few amino acids incorporated will cause the ribosome to pause and it will not resume protein synthesis until it has been docked on the surface of the RER. As the insulin synthesis resumes it is threaded through the RER membrane and accumulates in the lumen of the RER. Vesicles containing a collection of newly synthesized proteins (including insulin) will bud off the RER and coalesce with the cis side of the Golgi. Insulin will travel from one compartment of the Golgi to the next and in the process it will be modified (a peptide bond is broken and a disulfide bond formed to connect the two fragments) When the insulin reaches the trans side of the Golgi it is tagged (attached to a glycosyl group) so that it can be sorted into vesicles headed for the plasma membrane. Exocytosis will release insulin into the extracellular fluid.

What are the functions of the smooth endoplasmic reticulum in all animal cells?

The SER synthesizes lipids, including phospholipids- which are constantly needed for the synthesis of new organelles and plasma membrane. In addition, some drugs and detoxified in the SER.

The membranes of lysosomes contain proton pumps. What do these transport proteins do and why is it crucial to the function of lysosomes?

Proton pumps move H+ from the cytosol into the lumen of the lysosome creating an acidic pH of 5. This is crucial because the enzymes (hydrolases) present in the lumen have an ideal pH of 5. This means that they are most active at this pH.

Lysosome contain hundreds of different hydrolytic enzymes including nucleases, proteases, lipases and amylases. How do these enzymes allow lysosomes to perform their job?

Lysosomes breakdown (digest and recycle) organelles which are composed of proteins, phospholipids, nucleotides & polysaccharides. The enzymes listed above break the covalent bonds between the monomers of these macromolecules so that the products can be released into the cytosol and use for making new macromolecules and organelles.

What is the role of the outer mitochondrial membrane?

The outer mitochondrial membrane keeps the H+ ions from leaving the compartment between the inner and outer membranes. It is simply a barrier.

The surface area of the inner mitochondrial membrane is approximately 3X greater than that of the outer mitochondrial membrane. How is this related to the function of the inner mitochondrial membrane?

The inner mitochondrial membranes contain the enzymes needed to synthesize ATP. So, the greater the surface area of the inner membrane the more efficient the ATP production.

Distinguish between the roles of peroxisomes and the SER in cell detoxification.

The SER metabolizes molecules that foreign to the body, like medicines, narcotics, antibiotics etc. Peroxisomes detoxify molecules that arise as a result of normal metabolic processes.

Why is it important that the detoxification reactions catalyzed by peroxisomes occur within the enclosed membrane of this organelle rather than in the cytosol?

The main reaction that occurs in peroxisomes is the addition of oxygen to molecules and although this detoxifies the molecule, it also creates a toxic product called hydrogen peroxide. It is crucial that the cytosol is not exposed to this H2O2. The peroxisomes therefore have the enzymes necessary to convert the H2O2 back into water and O2.

Describe the role that the cytoskeleton plays in each of the following cells: Nerve cells and cells lining the intestine

The cytoskeleton determines cell shape in all animal cells, but it is most apparent in these two cell types. Without a cytoskeleton these cells would be spherical. The long fibers (axons) of nerve cells and the extensions (microvilli) of intestinal cells are the result of cytoskeletal fibers.

Describe the role that the cytoskeleton plays in each of the following cells:Sperm cells and cells lining the trachea

Specialized structures called flagella and cilia have similarities to cytoskeletal fibers and can be classified as such. They are used to either move cells (as in flagella) or move fluids past cells (as in the lining of the) trachea.

Describe the role that the cytoskeleton plays in each of the following cells: White blood cells

The cytoskeleton is important for several functions of white blood cells (WBCs). It allows shape changes required for the cells to squeeze between tight junctions. It also allows WBCs to extend structures called “pseudopodia” (false feet) to contact and engulf nearby bacteria. And finally, WBCs are specialized in their ability to dissolve (disassemble) their cytoskeletal fibers and reform them in a direct way to push the cell forward. In this way, they can migrate through the body (not solely dependent of the vascular system to be pushed along).

Describe the role that the cytoskeleton plays in each of the following cells:Embryonic cells

The rapid reproduction of embryonic cells to form a new organism requires repeated rounds of cell division. Each round of division uses cytoskeletal components to arrange chromosomes and then move them to separate poles. This is followed by the pinching in and splitting of the cell into two cells – a process also facilitated by cytoskeletal components.

Name one difference and one similarity between plant and bacterial cell walls?

Plant cell walls are composed of cellulose, bacteria use peptidoglycan to build their walls. Both prevent the liquid cell membrane from bursting in a hypotonic environment.

The main role of the central vacuoles in plants is to “take up space”, meaning to enlarge the cell without diluting the cytosol. Therefore, most vacuoles simply contain water and dissolved ions (salt water). How does this benefit plants? Contrast this with the demands on animals: imagine if our cells contained big sacs of salt water. This asset in plants would be a major liability for animals. Explain.

Seedlings, benefit from rapid growth upward to compete with other plants for greater sun exposure and rapid downward growth to maximize water and mineral absorption. The process of cell reproduction is very costly energy-wise because cells must replicate their DNA and produce sufficient organelles before they can split into two. Instead, plants evolved to increase in size. But if they did this simply by taking up water and ions, the volume of their cytosol would increase and this would decrease the chance of collisions between molecules or cellular structures (like ribosomes and mRNA) thereby decreasing the efficiency of cellular reactions. Instead, it is the central vacuole that takes up the solution and causes the cell to expand.

Why do plants need chloroplasts?

The roots of plants take up minerals & water and the leaves take up CO2. But plants do not take up organic molecules such as amino acids or nucleotides for cell synthesis. They must make their own organic molecules. This requires organelles called chloroplasts which are capable of absorbing energy from the sun and using it to make ATP which is then used to convert CO2 into sugars and other organic molecules needed for biosynthesis.

Recall the function of mitochondria. What do chloroplasts and mitochondria have in common (refer to the proton gradient). How do they differ (function)?

Both use a proton gradient to synthesize ATP. They differ in HOW they establish the proton gradient. Chloroplasts use the sun’s energy to move protons against their gradient from the stroma to the thylakoid space. Mitochondria use the energy from the bonds of glucose to move protons from the cytosol and mitochondrial matrix into the intermembrane space.

The evolution of specialized cells is driven by natural selection. What selective advantage drove red blood cells to jettison their organelles?

They deliver O2 to cells so that ATP can be made. Death comes very quickly without this service. RBCs are propelled through the body by the force of the heart muscle. Small, light cells require less force. The O2 the RBCs deliver is transferred by diffusion, so the closer the RBCs can get to their delivery target the faster the delivery. This explains the narrow vessels called capillaries through which the RBCs must travel. Organelles are heavy and take up space, so they are discarded. The trade off is that without the cellular machinery to sustain life, the RBCs don’t live long.

What is Plasmodium, describe the specialized feature(s) crucial to the function of the cell and to the survival of the organism.

(protist that transmits malaria) Has specialized organelles to penetrate (and infect) RBCs

Sperm cell, describe the specialized feature(s) crucial to the function of the cell and to the survival of the organism.

as a long flagellum to propel itself through the fallopian tubes to reach an egg for fertilization. Has very few organelles, (to lighten it’s load) a highly condensed nucleus and many mitochondria to produce the ATP needed to propel the flagellum.

Egg cell, describe the specialized feature(s) crucial to the function of the cell and to the survival of the organism.

Mammalian egg cells are large and carry everything needed to undergo repeated rounds of cell division to create a multicellular embryo.

Muscle cell, describe the specialized feature(s) crucial to the function of the cell and to the survival of the organism.

Skeletal muscle cells have highly organized bundles of contractile fibers and specialized SER (called the sarcoplasmic reticulum) surrounding them along with nerve cells innervating the fibers.

Adipose cell, describe the specialized feature(s) crucial to the function of the cell and to the survival of the organism.

These cells are made up of one large sphere of liquid fat surrounded by a very small amount of cytosol with a nucleus and small numbers/quantity of all other organelles. They have a very low maintenance level since all they do is take up and release fat.

Human skin, describe the specialized feature(s) crucial to the function of the cell and to the survival of the organism.

deep within the dermis cells are rapidly reproducing, enlarging being pushed toward the outermost layer. As they progress toward the surface they produce and secrete a tough extracellular material called keratin. Eventually the cell dies leaving it’s outer crust of tough keratin to protect the surface against abrasion.

If a blood cell with an osmolarity of .3M is placed in a .1M NaCl solution it will

swell

Name the functions of the letters shown

A. Collagen, fibrous protein that strengthens the extracellular matrix.

B. Glycolipid, identification tags indicating cell type (used by the immune system to differentiate self from non-self)

C. Integral membrane protein, transport of solutes across the membrane, receptors, and enzymes D. Peripheral membrane proteins, often enzymes that are part of a series of reactions. These proteins are mobile and can travel from one region of the plasma membrane to another.

E. Cholesterol, increases stability of liquid membrane (decreases permeability)

F. Cytoskeleton, anchors organelles, facilitates transport of vesicles, gives the cell its shape.

what is simple diffusion

the movement of molecules right across the phospholipid bilayer

What is facilitated Diffusion

The movement of molecules with the assistance of transport proteins

What is active transport

Refers to the movement of solute molecules against their gradient.

why can humans digest starch but not cellulose

humans have enzymes that can hydrolyze the alpha glycosidic linkages of starch but not the beta glycosidic linkages of cellulose

Polysaccharides, lipids, and proteins are similar in that they

are synthesized from monomers by dehydration reactions

Which of the following observations made with freeze-fracture electron microscopy provides evidence for the fluid-mosaic model of membrane structure

The inner surfaces of the membrane contained pits and mounds

Which of the following events takes place in the ETC

The extraction of energy from high-energy electrons remaining from gylcolysis and the krebs cycle

_____ is composed of DNA and protein

Chromatin

Choose the statement that correctly characterizes bound ribosomes

Bound ribosomes generally synthesize membrane proteins and secretory proteins

what function is most important for the glycoproteins of animal cell membranes

a cells ability to distinguish one type of neighboring cell from another

What role do liver cells play at this point?

At this point in the graph, the blood glucose level is rapidly going down because all body cells are taking up glucose and storing it as glycogen. However, the liver plays a major role here because it is huge, it’s cell membranes have more glucose transport proteins, and will continue to take up glucose even if G-6-P accumulates in the cells

Would you predict magnesium to have a higher or lower electronegativity as compared to S(16)

the 1st shell holds two electrons, the 2nd and 3rd each hold 8. So Mg, with 12 electrons has 2 in its outer shell. S has 6 in its outer shell and is therefore much more likely to attract electrons than Mg, which is more likely to give its 2 valence electrons away

What makes this molecule so useful for researchers and physicians?

it is measurable. The Carbon isotope will decay, but it otherwise behaves identically to any other glucose molecule. So it can be followed throughout A person‘s body

What type of polysaccharide takes up the least amount of space in a cell?

Amylose (in a plant cell). Note that cellulose is denser but it is outside the cell.

What happens to hydrocarbon chains when they are mixed with water? Why?

They are excluded (pushed out of the way) because they interfere with interactions between water molecules.

What happens to food we eat

carbohydrates are hydrolyzed in the mouth and small intestine. Glucose crosses the epithelial lining of the small intestine by facilitated diffusion through specific membrane transport proteins. Glucose travels through the body and is taken up by cells and used to make ATP or stored as glycogen (condensation synthesis) Proteins are hydrolyzed to amino acids in the stomach and small intestine and cross into the blood via facilitated diffusion. Cells take up what they need for protein synthesis and leave the rest for the liver to deaminate (ammonia > urea) and convert to glucose or fat. Fatty acids have a more complex route to cells because of their non-polarity. They end up in adipose (fat) cells. Nucleic acids are hydrolyzed into nucleotides and broken down into ribose, base and phosphate groups.

Name one advantage and one disadvantage animals have in storing carbohydrates as highly branched glycogen rather than the unbranched plant form, amylose.

The highly branched glycogen is more accessible to the enzymes that hydrolyze to bonds to liberate glucose. That means a cell can convert its stored glycogen quickly and consequently make ATP quickly. The disadvantage is that in an aqueous cell glycogen is fully hydrated by water molecules, it so it is very heavy. It also takes up a lot of space because it is branched rather than compact like amylose

How does penicillin kill Gram-positive bacteria?

Penicillin penetrates the peptidoglycan layer and binds to the active site of the enzyme needed to attach the peptide units to the carbohydrate units of the cell wall

A) What organelle is this?

B) Name the orange structure

C)Name this Fluid filled center

D) Provide a specific example of a protein that this could be

E) Where are all of these proteins headed?

A) RER B) Ribosome C) Lumen D) Glucose permease, Insulin Receptor, or ATP-synthetase

E) The golgi

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What type of cells in your body would be expected to have more smooth endoplasmic reticulum than rough endoplasmic reticulum?

Endocrine cells that make lipid hormones in the ovaries and the testes.

name the labeled parts and describe their functions

a. Collagen plays a structural role in the extra- cellular matrix (between cells) b. Cell adhesion molecule attaches cell membrane proteins to the collagen matrix to keep cells in place c. Integral membrane protein. Could be an enzyme, a transport protein or a receptor d. Cytoskeletal fiber, gives the cell its shape e. Glycolipid, identification tag for the cell.