UNIT 2: Cell & Cell Transport

Question 1

What is the function of a cell wall?

Answer 1

Support and Protection

Question 2

What is the composition of a cell wall?

Answer 2

Contains polysaccharides

Question 3

What is the plasma membrane composed of?

Answer 3

Phospholipid bilayer with embedded proteins

Question 4

What is the function of the plasma membrane?

Answer 4

Separates internal environment of the cell from its surroundings and regulates what leaves and enters to maintain homeostasis

Question 5

Describe the positioning of the phospholipids in the plasma membrane.

Answer 5

Hydrophilic polar heads face the outside and inside of the cell where water is found.
Hydrophobic non polar tails face each other.

Question 6

What is the purpose of the cholesterol in the plasma membrane?

Answer 6

Regulate fluidity, stiffen, and strengthen the membrane.

Question 7

Describe integral proteins.

Answer 7

Integral proteins span the membrane, can protrude from one or both sides. They are embedded in the membrane but can move laterally, changing their position in the membrane.

Question 8

What are peripheral proteins?

Answer 8

Peripheral proteins are associated with only one side of the plasma membrane. Ones located on the inside of the membrane are often held by cytoskeletal filaments.

Question 9

What are the carbohydrate chains on the plasma membrane?

Answer 9

Glycolipids and glycoproteins. They play an important role in cellular identification.

Question 10

What is the nucleus composed of?

Answer 10

Nuclear envelope, nucleoplasm, chromatin, and nucleoli.

Question 11

What is the function of the nucleus?

Answer 11

Storage of genetic information; synthesis of DNA & RNA. ‘Head office’ of the cell.

Question 12

What is the composition of the nucleoli?

Answer 12

Concentrated area of chromatin, RNA, and proteins.

Question 13

What is the function of the nucleoli?

Answer 13

Responsible for producing rRNA (ribosomal RNA) and where rRNA joins with proteins to form the subunits of ribosomes.

Question 14

What is the function of ribosomes?

Answer 14

Responsible for protein synthesis using mRNA (messenger RNA).

Question 15

What are ribosomes composed of?

Answer 15

“Large” and “small” subunits, each a complex of unique rRNA and protein molecules.

Question 16

Differentiate the composition of rough and smooth endoplasmic reticulum.

Answer 16

Both are networks of folded membranes but the rough ER is studded with ribosomes while smooth is not.

Question 17

What is the function of both ERs?

Answer 17

Rough ER folds, modifies, and transports proteins.
Smooth ER has various functions such as lipid synthesis in some cells, produces testosterone in the testes, detoxifies drugs in the liver, and stores calcium ions in muscle cells. Also forms vesicles in which products are transported to the Golgi body.

Question 18

What is the Golgi body composed of?

Answer 18

Stacks of small membranous sacs.

Question 19

What is the function of the Golgi body?

Answer 19

Processing, packaging, and distribution of proteins and lipids. Modifies lipids and proteins before they are repackaged in secretory vesicles.

Question 20

What is the function of lysosomes?

Answer 20

Intracellular digestion. Fuses with an incoming vesicle and the lysosomal enzymes digests its contents into simpler subunits that then enter the cytoplasm.

Question 21

What are lysosomes composed of?

Answer 21

Membranous vesicles produced by the Golgi apparatus containing digestive enzymes.

Question 22

What are vacuoles and vesicles?

Answer 22

Membranous sacs of various sizes which serves as a storage of substances.

Question 23

What are peroxisomes?

Answer 23

Are similar to lysosomes, however, the enzymes are synthesized by cytoplasmic ribosomes & transported into a peroxisome by carrier proteins.

Question 24

What is the mitochondria?

Answer 24

Power plants of the cell. They are composed of an inner membrane (cristae) which are bounded by an outer membrane. They are responsible for cellular respiration.

Question 25

Describe the composition of chloroplasts and their function.

Answer 25

Membranous grana bounded by two membranes responsible for carrying out photosynthesis.

Question 26

What is chromatin?

Answer 26

Chromatin consists of DNA and associated proteins. It undergoes coiling when the cell is ready to divide and becomes highly condensed structures called chromosomes.

Question 27

What is the nucleoplasm?

Answer 27

Semifluid medium where chromosomes are immersed.

Question 28

What is the nuclear envelope?

Answer 28

A double membrane that separates the nucleus from the cytoplasm which is continuous with the endoplasmic reticulum.

Question 29

What are nuclear pores?

Answer 29

They are located on the nuclear envelope and permits bidirectional transport of proteins and ribosomal subunits.

Question 30

What is the cytoplasm?

Answer 30

Semifluid medium composed of water, salt, and dissolves organic molecules.

Question 31

What are the four functions of proteins in the plasma membrane?

Answer 31

1. Transport material across the membrane 2. Receive molecules, such as hormones 3. Cell recognition (glycoproteins that help the body recognize pathogens) 4. Enzymes (carry out metabolic reactions directly)

Question 32

Describe the permeability of the plasma membrane.

Answer 32

Selectively (differentially) permeable, meaning certain substances can move across the membrane while others cannot.

Question 33

Which molecules pass through the membrane? Which do not?

Answer 33

Small, uncharged molecules pass through the membrane following their concentration gradient. Charged molecules do not pass through the nonpolar interior and macromolecules cannot pass through because of their size.

Question 34

What is a concentration gradient?

Answer 34

Gradual change in chemical concentrations between two areas of differing concentrations.

Question 35

Describe passive transport and the two types.

Answer 35

Passive transport does not use chemical energy. Diffusion is the movement of molecules from higher to lower concentration until equilibrium is achieved. Gases and other small lipid soluble molecules (alcohols) move by diffusion. Facilitated transport moves molecules from higher to lower concentration even though they are not lipid soluble.

Question 36

Describe active transport.

Answer 36

Requires chemical energy in the form of ATP and a carrier protein called ‘pumps’ and moves molecules across the membrane against the concentration gradient.

Question 37

What is exocytosis?

Answer 37

Fusion of the vesicle with the plasma membrane for secretion.

Question 38

What is endocytosis?

Answer 38

Endocytosis occurs when cells take in substances by vesicle formation and forms an intracellular vesicle.

Question 39

What are the three types of endocytosis?

Answer 39

1. Phagocytosis - occurs when the material taken in is a large particle (ex: food particle or another cell). 2. Pinocytosis - occurs when vesicles form around a liquid or a small particle. 3. Receptor-mediated endocytosis - form of pinocytosis that uses a receptor protein shaped so that a specific molecule (ex: vitamin, peptide hormone, lipoprotein) can bind to it. The proteins are found in the ‘coated pit’ of the plasma membrane.

Question 40

What is osmosis?

Answer 40

The diffusion of water across a selectively permeable membrane due to concentration differences. Net flow of molecules from an area of low concentration solute to high concentration solute.

Question 41

What is osmotic pressure?

Answer 41

Osmotic pressure is the pressure that builds up in a system due to osmosis. The greater the possible osmotic pressure, the more likely it is that water will diffuse in that direction.

Question 42

What is a hypotonic solution? How does it affect cells?

Answer 42

Hypotonic solutions have less solute. It causes animal cells to swell and possibly burst. It increases turgor pressure in plant cells which maintain a plant’s erect position and do not burst because they have a cell wall.

Question 43

What is a hypertonic solution? How does it affect cells?

Answer 43

Hypertonic solutions have more solute. They cause cells to lose water. Animal cells undergo crenation (shrivel up) while plant cells undergo plasmolysis (shrinking of cytoplasm causing the membrane to separate from the cell wall).