Unit 2 - Biochemistry and Cells

Question 1

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

Answer 1

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.

Question 2

What is the term for passive movement across a semipermeable membrane that occurs in the direction of the concentration gradient?

Answer 2

Diffusion

Question 3

What is the process called in which a cell engulfs matter and forms a vacuole around it?

Answer 3

Endocytosis

Question 4

Following endocytosis, where are the receptors located on the resulting vacuole?

Answer 4

On the inside of the vacuole

Question 5

What organelle is involved in the synthesis and packaging of proteins both for storage and secretion from the cell?

Answer 5

The endoplasmic reticulum

Question 6

What is the main difference between rough and smooth ER?

Answer 6

Rough ER contains bound ribosomes

Question 7

What theory asserts that mitochondria and chloroplasts were once independent prokaryotic cells?

Answer 7

Endosymbiotic Theory

Question 8

What type of cell stores its genetic material via chromosomes in a distinct nucleus?

Answer 8

A eukaryotic cell

Question 9

True or False: Eukaryotes are exclusively multi-cellular organisms with membrane bound organelles?

Answer 9

False - there are many single celled eukaryotes

Question 10

What is the process in which a vesicle within a cell secretes its contents outside of the cell?

Answer 10

Exocytosis

Question 11

What type of passive transport uses specific integral proteins within the cell membrane?

Answer 11

Facilitated diffusion

Question 12

What integral protein is involved in the facilitated diffusion of water?

Answer 12

An aquaporin

Question 13

What organelle involved in motility protrudes from a cell and has a lash-like appearance?

Answer 13

A flagellum

Question 14

True or False: both eukaryotes and prokaryotes may have flagella

Answer 14

True - both types of cells my have this organelle

Question 15

Who were the scientists who developed the fluid mosaic model of the cell?

Answer 15

SJ Singer and GL Nicolson

Question 16

What is the term for an organism’s complete set of genetic code?

Answer 16

Genome

Question 17

What is the difference between active transport and passive transport?

Answer 17

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.

Question 18

How does adhesion differ from cohesion in plants?

Answer 18

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.

Question 19

How do the amphipathic properties of lipids allow for the creation of the double bilayer cell membrane?

Answer 19

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.

Question 20

What type of transport are all aquaporins used for and explain their functions.

Answer 20

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.

Question 21

What are the key aspects of binary fission and what organism(s) primarily use it?

Answer 21

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.

Question 22

Describe the two main phases of the cell cycle.

Answer 22

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.

Question 23

What is the purpose of the cell wall and is it used by all cells?

Answer 23

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.

Question 24

What is the function of centrioles in mitosis/meiosis and is it found in all cells?

Answer 24

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.

Question 25

Where is the centromere located and how is it involved during mitosis/meiosis?

Answer 25

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.

Question 26

What is the centrosome?

Answer 26

Centrosomes (2) are synthesized during prophase and move to opposite sides of the cell. In animal cells, they contain centrioles.

Question 27

What type of macromolecule is cholesterol and what is its role in the fluid mosaic membrane?

Answer 27

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),

Question 28

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)

Answer 28

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.

Question 29

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)

Answer 29

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)

Question 30

Describe the relationship of temperature and tonicity to water potential. (Water Potential WS)

Answer 30

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.

Question 31

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)

Answer 31

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).

Question 32

For the Nitrogen cycle, explain nitrogen fixation, denitrification, and assimilation of nitrogen. Explain the role of decomposers in this process as well as how humans can impact this important cycle. (Nitrogen Cycle Game; Essential Knowledge: 4.A.6)

Answer 32

Nitrogen fixation is when nitrogen fixing bacteria (usually in soil, water, legumes) can convert atmospheric nigtrogen to ammonia, which becomes ammonium in water. Ammonium or nitrate ions can be used by plants, be asorbed via the root xylem, which is assimilation. Denitrification is the reduction of nitrates back into gas and is the last part of the nitrogen cycle. Decomposers are significant because they initiate ammonification, where the organic nitrogen of decaying organisms is turned back into ammonium. 3 ways humans can impact the nitrogen cycle is use of nitrogen-containing fertilizers in agriculture, dumping sewage and organic matter into water-bodies (environmental damage), and emmissions of large quanitities of NOx gases to the atmosphere (power plants, cars, etc.).

Question 33

Which types of cells are chloroplasts found in? What part of photosynthesis takes place in the chloroplasts (where exactly)?

Answer 33

Plant cells The Light Reactions, within the thylakoid membrane

Question 34

What are chromosomes composed of and where are they located?

Answer 34

Proteins and DNA; in the nucleus

Question 35

What is chromatin? When does chromatin condense to form chromosomes?

Answer 35

Genetic material composed of proteins and DNA that’s not visibly condensed in the nucleus; during interphase

Question 36

What are cilia and in what cells are they found?

Answer 36

Organelles that extend from the cell and are involved in movement and sensation; in eukaryotic cells

Question 37

During what stage of cell division does the cleavage furrow form? What is cleavage in cell division?

Answer 37

Cytokinesis The cell membrane is pinching in two to form the new daughter cells.

Question 38

What occurs in a concentration gradient?

Answer 38

Particles are moving from areas of higher concentration to areas of lower concentration.

Question 39

What is cohesion? Name a common example where this occurs.

Answer 39

Attraction of the same molecules. Water sticks together, and this property helps water to be transported up plant stems and tree trunks.

Question 40

What occurs during cytokinesis?

Answer 40

The cytoplasm of the dividing cell is split into two with a cleavage furrow down the middle of the cell. The cleavage furrow then pinches the cell into two new daughter cells.

Question 41

What is the cytoplasm, what does it contain, and where is it located?

Answer 41

All cellular contents within the cell membrane; contains any organelles; made up of water, protein, and salts

Question 42

What are the main roles of the cytoskeleton? List the three kinds of filaments that are a part of this structure.

Answer 42

Structural support (maintains cell shape), arrangement of organelles, and intracellular transport Actin filaments (microfilaments), intermediate filaments, microtubules

Question 43

How is the cytosol different from the cytoplasm?

Answer 43

The cytosol only consists of the fluid part of the cytoplasm (cytoplasm not including any organelles).

Question 44

What organelles are found in plant or animal cells, but not the other? Why is this significant? (Plant and Animal Cell Diagrams)

Answer 44

Animal ONLY: centrosomes, lysosomes Plant ONLY: chloroplasts, large central vacuole, plastids, cell wall The structures differ due to the different demands of plants and animals. Plant cells require a cell wall and large central vacuole for rigidity and cell support in order to maintain their general shape. Chloroplasts are available in order for the plant cell to synthesize their own food (autotrophs). However, animal cells are more fluid because of a need for rapid cell division/growth and other body functions (e.g. blood cells). Also, animals must consume other organisms in order to live (heterotrophs), so they have no need for chloroplasts.

Question 45

Explain the importance of water potential and cohesion/adhesion in the process of transpiration in plants. (Transpiration Lab)

Answer 45

Differences between water potential of the roots and soil/leaves and external air will affect the overall rate of transpiration. Greater differences in water potential will lead to more rapid exchange of water and nutrients that may need to be regulated (e.g. stomata can close to prevent water loss). Cohesion must be exhibited between water cells in order for groups of water molecules to be transported up the xylem, and adhesion allows the water molecules to stick to the cell walls.

Question 46

How does the looser nature of chromatin facilitate gene transcription? (DNA Histone Model)

Answer 46

Since DNA is not as tightly coiled around histone proteins as in condensed chromosome, there are segments of DNA that are exposed. These nucleosomes (histone/DNA complexes) can wind up or unwind to close off or open up DNA for transcription, respectively. Open segments of DNA are then available for transcription factors to bind and for RNA polymerase to transcribe into RNA for protein synthesis.

Question 47

What are glycolipids and their main function?

Answer 47

Glycolipids are sugars attached to lipids and are located on the cell surface and serve as a cell signal for recognition.

Question 48

What are glycoproteins and their main function?

Answer 48

Glycoproteins are sugars attached to proteins and are located on the cell surface to function for cell to cell recognition.

Question 49

What does the Golgi Apparatus do in the cell?

Answer 49

The golgi apparatus recives, sorts, modifies, and exports protein products from the ER to outside the cell.

Question 50

What happens to the stomata when guard cells are flaccid or rigid?

Answer 50

When the guard cells are flaccid, the stomata are closed. When the guard cells are turgid, the stomata are open.

Question 51

If a cell is hypertonic compared to its surroundings, will water flow out, in, or stay neutral?

Answer 51

When a cell is hypertonic, water will flow in.

Question 52

If a cell is hypotonic compared to its surroundings, will water flow out, in, or stay neutral?

Answer 52

When a cell is hypotonic, water will flow out.

Question 53

What are the three stages in interphase and the events in each?

Answer 53

Interphase is made of the G1 phase (cell growth), S phase (DNA replication), and G2 phase (growth and preparation for cell division).

Question 54

If a cell is isotonic compared to its surroundings, will water flow out, in, or stay neutral?

Answer 54

When a cell is isotonic, the outside is also isotonic, and water will have not net flow in either direction.

Question 55

Where does a ligand bind?

Answer 55

Ligands bind to a receptor on a cell, and can function in receptor-mediated endocytosis or cell signal reception.

Question 56

What does the lysosome do in the cell?

Answer 56

The lysosome is a sac of hydrolytic enzymes that digests macromolecules, such as those engufled by phagocytosis.

Question 57

What is the cell membrane composed of?

Answer 57

The cell membrane is made of phospholipids which have a hydrophilic head and hyrdrophoboic tail. In an aqueous solution, they form a phospholipid bilayer, with the hydrophilic heads on the outside and hydrophobic tails on the inside.

Question 58

What types of ions/molecules pass freely through the membrane and which cannot? (Use small polar ions, large polar molecules, small polar molecules, and small nonpolar molecules.)

Answer 58

Small polar ions cannot pass the membrane. Large polar molecules are mostly nonpermeable, but a few molecules can cross with difficulty. Small polar molecules are mostly nonpermeable because they are polar but a few colecules can cross due to their small size. Small nonpolar molecules are permeable and can cross cell membranes.

Question 59

Which phases do cells spend most of their time in?

Answer 59

Cells spend most to least time in interphase, prophase, metaphase, anaphase, and telophase, respectively.

Question 60

What are the three checkoints for the cell cycle and how do they regulate cell growth?

Answer 60

The G1 checkpoint is passed if there is enough energy, raw materials, and room for the cell. The G2 checkpoint is passed if the DNA has been completely replicated and checked for errors. It also requires a high concentration of MPF. The M checkpoint is passed if all chromosomes are attached to spindles from both spindle poles.

Question 61

How do cyclin and kinase help form the G2 checkpoint?

Answer 61

In a cell, cyclin depend kinases (Cdks) are more or less always present at a constant concentration. The concentration of cyclins changes over time. As the cell prepares for mitosis in interphase, the concentrations of cylins grows. The cyclins attach to Cdks and create Maturation promoting factor (MPF). When the concentration of MPF is high, the cell passes the G2 checkpoint and progresses to mitosis.

Question 62

What surrounds the genetic material in eukaryotic cells?

Answer 62

The Nuclear Membrane

Question 63

What is Osmosis?

Answer 63

The movement of water molecules through a selectively permeable membrane.

Question 64

What intermembrane transport does not require energy?

Answer 64

Passive Transport

Question 65

The process of engulfing a particle by a cell a forming a vacuole is called?

Answer 65

Phagocytosis

Question 66

What is the phloem?

Answer 66

A plant tissue that moves food from photosynthetic tissue like leaves to other plant parts.

Question 67

What model does the plasma membrane currently follow?

Answer 67

The fluid mosaic model, which is the concept that the plasma membrane is composed of a bilayer of phospholipids interspersed with proteins and cholesterol.

Question 68

A phospholipid is amphipathic. What does this mean?

Answer 68

This means that it has both a hydrophobic and hydrophillic region.

Question 69

What is plasmolysis?

Answer 69

The shrinking of protoplasm away from the cell wall due to water loss from osmosis.

Question 70

What makes a cell prokaryotic?

Answer 70

A prokaryotic cell has no nuclei or other internal membranes.

Question 71

Do free or bound ribosomes synthesize proteins for use within the cell?

Answer 71

Free ribosomes produce proteins for inside the cell.

Question 72

How is the rough ER different from the smooth ER?

Answer 72

The rough ER is studded with ribosomes, and these ribosomes synthesize proteins for export outside the cell.

Question 73

Where are sister chromatids found?

Answer 73

On a replicated chromosome.

Question 74

Sister chromatids are \_\_\_\_\_\_\_.

Answer 74

Identical copies of a single chromosome. The centromere holds them together.

Question 75

What are the 3 main functions of the Smooth ER?

Answer 75

-Assits in sythesis of steroid hormones and other lipids-Stores Calcium ions in mussle cells-Detoxifies drugs and posions from the body

Question 76

Where can your somatic cells be found?

Answer 76

All cells in the body are somatic cells except for sex cells like egg and sperm.

Question 77

What are stomata? What is its importance to plants?

Answer 77

Stomata are opening found on plants that allow CO2 into the plant and let out excess oxygen and water. It is made up of guard cells and a stoma.

Question 78

Why must cells remain small?

Answer 78

As a cell increases in size the surface area increases more slowly than the volume. This limits the amount of material that can enter and leave the cell, limiting growth.

Question 79

What is transpiration and how is it regulated?

Answer 79

The evaporation of water from leaves through stomates. Plants control the water let out using guard cells that absorb and lose water causing the stoma to open and close.