Chapter 2 - Review Flashcards

Question

Which of the following is a function of the cytoskeleton? * transports materials outside the cell * provides energy for the cell * aids in cell movement * stores materials for the cell

Answer 1

aids in cell movement

Answer 2

the phosphate group and the glycerol head

Answer 3

a type of endocytosis that takes in large particles

Answer 4

It is fast because O₂ is a small non-polar molecule.

Answer 5

Facilitated transport is faster if there are enough transporters.

Answer 6

Water diffuses to an area where the solute concentration is higher.

Answer 7

False Mitochondria **have** their own DNA.

Answer 8

False **Only** plants and **some algae** have plastids.

Answer 9

False The purpose of the cuticle is to **protect the outer surface of leaves and prevent water loss**.

Answer 10

False A cell with a double membrane filled with membrane-bound organelles is a **eukaryotic** cell.

Answer 11

False Membranes contain **sterols** that help to maintain their fluidity.

Answer 12

False Integral membrane proteins are **embedded into** the phospholipid layer.

Answer 13

False The evolution of more **internal** membranes allowed for more complex processes to develop within cells.

Answer 14

False Voltage-gated channel **are closed** during the rest phase.

Answer 15

Is the following statement true or false? If it is false, correct it. **No** binding by surface receptors takes place in bulk-phase endocytosis.

Answer 16

Most materials that are ingested by endocytosis **change** in form once they enter the cell.

Answer 17

moves the cell and its components

Answer 18

produces energy for the cell

Answer 19

digests and recycles cellular materials

Answer 20

makes lipids and breaks down fats and carbohydrates

Answer 21

synthesizes and modifies proteins

Answer 22

inactivates toxins

Answer 23

transports and stores cellular materials

Answer 24

stores and ships proteins and lipids

Answer 25

responsible for regulating the substances moving in and out of the cell

Answer 26

is composed of 18% protein and 82% lipids

Answer 27

span the entire membrane bilayer and have regions that are exposed to the aqueous environment

Answer 28

are generally found on the cytosol side of the membrane and some of the membrane and some are part of the cytoskeleton

Answer 29

A cell that is surrounded by a wall or other secretions is not isolated; it can interact through cell junctions with other cells and with its surroundings. Cells can send and receive ions, molecules, and signals through some junctions. Other junctions help cells recognize and stick to each other and the extracellular matrix.

Answer 30

First, the nucleus keeps the DNA isolated from the metabolic reactions of the cell, away from where it might be damaged. Second, the nucleus has a system of transporters and pumps that regulate the passage of various molecules across the nuclear membrane, allowing certain molecules to access DNA and control the production of RNA and proteins.

Answer 31

Golgi bodies contain enzymes that modify (attach phosphate groups or sugars, or cleave polypeptide chains) polypeptide chains and lipids that have been delivered from the endoplasmic reticulum. They create membrane proteins, enzymes and other proteins for secretion, which are then packaged and exported in vesicles.

Answer 32

The stroma is the semi-fluid interior of a plastid, surrounded by two outer membranes. The stroma contains enzymes and the plastid’s DNA. A third highly folded membrane inside the stroma forms a single compartment.

Answer 33

The endoplasmic reticulum is a membrane-bound organelle that folds into flattened sacs and tubes. The rough ER has ribosomes attached to its outer surface, while the smooth ER does not. The rough ER is involved in the production and folding of proteins. The smooth ER does not participate in protein production and instead produces most of the cell’s membrane lipids. As well, smooth ER participates in the breakdown of carbohydrates, fatty acids, and some drugs and poisons.

Answer 34

Chloroplasts produce sugars through photosynthesis that allow the tomato to grow and mature. As the tomato ripens, green chloroplasts are converted into red chromoplasts: the chloroplasts lose their chlorophyll and orange and red carotenoids become visible, resulting in a red tomato.

Answer 35

The following organelles have a membrane: nucleus, endoplasmic reticulum, Golgi body, vesicles, mitochondrion, plastids, lysosome, peroxisome, and vacuole.

Answer 36

The endoplasmic reticulum and Golgi body are the most likely organelles to pinch off vesicles that contain proteins.

Answer 37

The organelle is a chloroplast. Chloroplasts are found in photosynthetic eukaryotes. The dark areas in the centre are made from membrane.

Answer 38

The pack of microtubules in a sperm make up its tail, which is a type of flagellum. It whips back and forth to help the sperm cell “swim.”

Answer 39

The extracellular matrix in fungi is made of chitin. Animal bone is mostly made of collagen, a fibrous protein, and hardened by mineral deposits.

Answer 40

The four functions of membrane proteins are as follows: facilitating the transport of molecules that cannot freely diffuse across the membrane; enzymatic activity like those associated with cellular respiration and photosynthesis; triggering signals of specific molecules, like hormones, by binding of the molecule to the protein and triggering a cascade of events within the cell; and attachment and recognition of cytoskeleton elements, as well as components involved in cell-cell recognition and bonding to the extracellular matrix. Sorry that one was long and hard.

Answer 41

Integral Membrane Proteins

Answer 42

Peripheral Membrane Proteins

Answer 43

Non-Polar End

Answer 44

Phospholipid Molecule

Answer 45

Cholesterol (Sterol)

Answer 46

The relatively slow movement of proteins within a plasma membrane is mainly due to their large, ungainly size. The lipid molecules are small and so it is easier for them to spin and flex and trade places with others of their size.

Answer 47

Metabolic processes require some molecules to enter or exit the cell at a faster rate than they are able to diffuse across the membrane. For example, large polar or charged molecules do not readily undergo simple diffusion. These molecules may require facilitated diffusion. Examples include: water, amino acids, sugar, and ions.

Answer 48

When particles diffuse in a space, they move randomly in all directions. In a concentration gradient, the net movement of particles occurs from a region of higher concentration to a region of lower concentration, causing the particles to become evenly distributed in space. In the case of diffusing through the plasma membrane, the particles vibrate and randomly move through the lipid bilayer down the concentration gradient between the cytosol and extracellular fluid created and maintained by the plasma membrane.

Answer 49

Cells receive ions and small molecules such as sugars and amino acids through passive transport (simple diffusion and facilitated diffusion) or active transport (primary and secondary). They can ingest larger molecules such as proteins by endocytosis (pinocytosis, phagocytosis, and receptor-mediated endocytosis).

Answer 50

Particles can be pumped out of the cell by active transport or secreted from the cell by exocytosis.

Answer 51

Sample Answer: Vesicles may form by pinching off from the endoplasmic reticulum. When they pinch off, they carry materials inside them for transport to another location. By fusing with a lysosome, they might receive digestive enzymes to process some cell waste. By fusing with the cell membrane, they would transport a protein to the outside of the cell by exocytosis.

Answer 52

Both of these membranes are made of lipid bilayers and both are selective gatekeepers, letting in certain molecules and keeping out others. However, the nuclear membrane is doubled, with its outer layer being connected to the endoplasmic reticulum. Some students may say that the key difference is location, while others might say the doubling over of the lipid bilayer membrane for the nuclear envelope is the key difference

Answer 53

Rough endoplasmic reticulum is where proteins are synthesized, and pancreatic cells synthesize a great deal of enzymes for export.

Answer 54

Amyloplasts are unpigmented plastids that store starch.

Answer 55

Amyloplasts are abundant in cells of tubers because they store starch energy in those locations. When packed with starch, they are dense and may function as gravity-sensing organelles.

Answer 56

The ribosome makes the protein and injects it into the rough ER, where it will complete its tertiary folding. The ER will pinch off into a vesicle that will move to fuse with the Golgi apparatus for the finishing touches to be put on the protein. Then it will travel in a vesicle pinched off from the Golgi apparatus to the plasma membrane where it fuses for the exocytosis of the protein.

Answer 57

Cytoskeleton - muscle contrations Mitochondria - production of energy

Answer 58

Golgi Body - packaging of cell products and wastes for export Plasma Membrane - fusion of secretory vesicles (exocytosis)

Answer 59

Ribosomes - production of hair keratin proteins

Answer 60

Rough ER - production of proteins Centrioles - organize cytoskeleton elements for cell division

Answer 61

Nucleus - stores DNA Cytoskeleton - involved in seperation of duplicated chromosomes, cell divisions, and gamete mobility (flagellum of sperm cells)

Answer 62

Rough ER - production of digestive enzymes Golgi Body - modifications to enzymes Secretory Vesicles - export

Answer 63

The lipids that make up the plasma membrane’s bilayers are extremely mobile. They spin, vibrate, and change places millions of times per second. The membrane is also fluid in the sense that it can flex, bend, form, and reform. It is even able to open up and then close again. It is called a mosaic because it has many parts imbedded in the lipid—a variety of proteins and carbohydrates that have various functions and that act as recognition sites.

Answer 64

Peripheral membrane proteins are perched on the surface of the membrane, and do not insert into the core of the membrane. Integral membrane proteins contain hydrophobic regions that allow them to be inserted into, and pass through, the core of the bilayer membrane of a cell.

Answer 65

Temperature might affect the efficiency of cell membranes. When temperature is low, the fatty acids pack more tightly together and the membrane becomes less permeable. The presence of sterols keeps the membrane more fluid and increases its efficiency. The degree to which the fatty acids in the membranes are unsaturated also increases fluidity and efficiency.

Answer 66

The plasma membrane is non-polar on the inside, so ionic particles, which are charged, are not attracted to the nonpolar inner layer of the membrane and don’t pass through. Instead they remain attracted to the highly polar water molecules on either side.

Answer 67

Adenosine triphosphate (ATP) is used to obtain energy for active transport. About 25% of the total energy use of a cell is devoted to active transport.

Answer 68

The cell has evolved transport proteins that span the plasma membrane. In facilitated diffusion, molecules that would only slowly diffuse through the membrane can be transported by these proteins at a faster rate based on the concentration gradient. In active transport, molecules can be transported against the concentration gradient when energy is supplied to the transport proteins.

Answer 69

In symport transport pumps, the solute moves through the membrane channel in the same direction as the driving ion. In antiport transport pumps, the driving ion moves through the membrane channel in one direction, and this provides energy for the active transport of another molecule in the opposite direction.

Answer 70

Voltage-gated ion channels open and close depending on voltage, or a difference in electric potential across the membrane caused by unequal concentrations of positive and negative ions on each side. During resting potential voltage-gated channels are closed. As the voltage increases to a threshold, the electronic environment around the voltage–gated channel causes a conformational change in the channel. This conformational change causes the channel to open and allows certain ions to diffuse through it.

Answer 71

Proteins are synthesized in the rough endoplasmic reticulum, and completed in the Golgi body. They look similar, except the endoplasmic reticulum may have ribosomes on it and is joined to the nuclear envelope.

Answer 72

Both control what goes in and out (of the nucleus, or of the cell). The nuclear membrane does not perform endocytosis and exocytosis, but does have transport “pores.” The nuclear envelope is a double layer, consisting of two lipid bilayers that are folded together, while the plasma membrane consists of a single lipid bilayer.

Answer 73

Exocytosis gets rid of waste and exports cell products such as enzymes, while endocytosis ingests nutrients. Endocytosis can be receptor-mediated, which is more specific. Endocytosis makes the membrane smaller as it pinches off a vesicle, while exocytosis makes it bigger as a vesicle joins the membrane.

Answer 74

Lysosomes contain digestive enzymes and help to chop up the building blocks the cell needs, while vacuoles generally only store particles. Lysosomes are usually smaller than vacuoles. Vacuoles in plant cells can expand to help cells hold their shape.

Answer 75

During receptor-mediated endocytosis the molecules to be ingested are captured by recognition proteins, known as receptors, on the outside of the cell. After enough of the particles are attached, the cell folds inward into a clathrin-coated pit, pinches off into a vesicle, and joins with a lysosome to deliver its cargo of nutrients or building blocks to the cell. This molecular recognition does not occur in regular bulk-phase endocytosis.

Answer 76

The many mitochondria in muscle cells give them plenty of energy to move. Fungus cells only need enough energy for stationary life activities. So, muscle cells are expected to have more mitochondria.

Answer 77

The ribosomes do not have a membrane and do not need one for their function of assembling polypeptide chains (for proteins). However, they do need to be bathed in a soup that contains the building blocks for their protein. Having no membrane ensures that the ribosome has unimpeded access to these building blocks. Once the polypeptide chain is assembled, however, the ribosome injects it into the endoplasmic reticulum where it can complete its tertiary folding. Then, membrane-bound organelles like the endoplasmic reticulum and pinched-off vesicles help to transport the protein where it needs to go.

Answer 78

The vesicles function in a cyclical manner. There are vesicles that go from the ER to the Golgi bodies and there are also vesicles that go from the Golgi bodies to the ER.

Answer 79

Smooth ER is responsible for detoxification of toxic substances such as drugs and alcohol. The liver is responsible for most of your body’s detoxification processes. Liver cells respond to the constant influx of alcohol and other drugs by synthesizing more smooth ER to try and cope with the increased presence of these toxic substances.

Answer 80

When a freshwater fish is accidentally placed in a saltwater tank, the concentrated salt solution will be hypertonic to the cytosol of the fish gill cells. Therefore, water will flow out of the cells into the surrounding solution by osmosis, and the cells will shrink.

Answer 81

Since pure water contains no solutes, giving it intravenously would make the blood hypotonic. As a result, the red blood cells would swell and burst releasing their hemoglobin into the watery plasma.

Answer 82

Salt water is a hypertonic solution—having a higher concentration of dissolved particles than the plant cells. Water would flow out of the plant cells into the environment by osmosis causing the plant to shrivel and die.