Unit 1 - Cell Structure

Question 1

What 3 basic characteristics are common to all types of cells?

Answer 1

1. Cell/plasma membrane: all cells are surrounded by a membrane where all materials enter or exit through
2. Cytoplasm: portion of the cell within the membrane that includes the fluid and all organelles except the nucleus
3. Control center: coded info in the form of DNA stores the instructions for cell functions/reproduction, DNA may be either floating in the cytoplasm or in a nucleus

Question 2

What are the main differences between Prokaryotic and Eukaryotic cells?
- Prokaryotic:
1. No nucleus, membrane-bound organelles
2. Generally smaller, less complex than eukaryotes
3. Have a cell wall, cell membrane, and ribosomes
- Eukaryotic”
1. Generally larger, more complex
2. True nucleus and membrane-bound organelles

Answer 2

• Prokaryotic:
  1. No nucleus, membrane-bound organelles
  2. Generally smaller, less complex than eukaryotes
  3. Have a cell wall, cell membrane, and ribosomes
• Eukaryotic”
  1. Generally larger, more complex
  2. True nucleus and membrane-bound organelles

Question 3

What are the functions of the cell/plasma membrane?

Answer 3

• Separates the internal chemical reactions of the cell from the external environment
• Separates animal cells
• Regulates the passage of materials into/out of the cell by only allowing certain molecules to enter/leave
• Made mainly of lipids and proteins

Question 4

Describe the nucleus of the cell

Answer 4

• Filled with nucleoplasm which is a jellylike liquid similar to cytoplasm
  ~ Nucleoplasm holds the contents of the nucleus
• Nucleus contains nearly all the cell’s DNA, which codes instructions for the genetic makeup of future cells and for making proteins and other important molecules for cell functions
• Nucleus is surrounded by a nuclear membrane, a double membrane with pores that allow movement of materials into/out of the nucleus
• Nucleus: site where DNA -> RNA
• RNA carries protein-building instructions to ribosomes, travels to cytoplasm through pores in nuclear membrane

Question 5

What is the function of the nucleolus?

Answer 5

• Manufactures the subunits that make up ribosomes
• 2 subunits: large and small
  ~ These subunits pass through pores of the nucleus to the cytoplasm where they combine to form ribosomes

Question 6

Describe ribosomes

Answer 6

• May be found free-floating in cytoplasm or attached to the rough E.R
• Most numerous organelles
• Composed of protein and RNA, are not membrane bound organelles
• Site of protein synthesis

Question 7

What is the endoplasmic reticulum?

Answer 7

• Internal membrane system that accounts for most of the membrane in a cell
• Functions as an intracellular highway, providing a path for molecules to move from one part of the cell to another

Question 8

What is the specific function of the rough E.R?

Answer 8

• Is covered with attached ribosomes and is involved in the making of proteins
• Newly made proteins exit the ribosome and are inserted into spaces of the E.R where they’re modified and shaped into proteins

Question 9

What is the specific function of the smooth E.R?

Answer 9

• Has no ribosomes
• Makes lipids that will be used in membranes

Question 10

What is the function of the Golgi apparatus?

Answer 10

• Proteins from the rough E.R are transported here
• Appears as a stack of loosely connected membranes
• Modifies, sorts, packages proteins which will either be stored in the cell or secreted outside of it
• Completes protein modifications before they are shipped away to their destination

Question 11

Describe vesicles

Answer 11

• Small, spherical sacs surrounded by a single membrane
• Classified by their contents
  ~ Types include transport vesicles, peroxisomes, lysosomes

Question 12

Name the steps of protein synthesis and transport

Answer 12

1. Proteins are assembled by ribosomes on the rough E.R
2. Vesicles transport these proteins to the Golgi
3. The Golgi completes modifications on the proteins
4. Functional proteins are packaged in vesicles and leave the Golgi
5. Vesicles fuse with the cell membrane to release the new proteins outside the cell
6. Vesicles containing enzymes remain in the cell as lysosomes

Question 13

What are the functions of lysosomes?

Answer 13

• Bud from Golgi, are filled with digestive enzymes
• These enzymes break down large molecules of carbs, lipids, and proteins into smaller molecules
  ~The enzymes recycle the cell’s own organic materials, breaking them down into their building blocks and returning them to the cytoplasm to be re-used
• Responsible for destroying old organelles
• Help destroy any debris that may build up in the cell
• Surrounded by a thick membrane as the cell would be destroyed if the enzymes were released

Question 14

What is a vacuole?

Answer 14

• Storage area, may store water, salts, proteins, carbs
• Central vacuole, contractile, and food vacuole

Question 15

What is the mitochondria?

Answer 15

• Powerhouse of the cell
• Aids in cellular respiration = process of converting glucose molecules into usable energy
• Have an inner and outer membrane, folds on inner membrane are called cristae
• Cristae increases surface area for respiration
• Have their own DNA, replication

Question 16

Describe the cytoskeleton

Answer 16

• Internal framework/support system of the cell to give it organization and shape
• Network of protein tubes and fibres that help the cell maintain its shape
• Involved in cell movement
• 2 types of fibres found here are microfilaments, microtubules

Question 17

Describe microfilaments

Answer 17

• Solid, threadlike protein structures
• Form extensive frameworks inside the cell to support it
• Help to bear mechanical stress
• Help cells move
• Assemble and disassemble rapidly, are involved in muscle contraction

Question 18

Describe microtubules

Answer 18

• Maintain cell shape
• Needed for the separation of chromosomes during cell division
• Help with the formation of cilia and flagella

Question 19

What are the functions of centrioles?

Answer 19

• Two short cylinders at right angle to one another
• Organize microtubules in cell division to form framework for separating chromosomes

Question 20

What organelles are never found in plant cells?

Answer 20

• Centrioles
• Lysosomes
• Flagella (except for sperm)

Question 21

What organelles are never found in animal cells?

Answer 21

• Central vacuole
• Cell wall
• Chloroplasts (plastids)

Question 22

What is a cell wall?

Answer 22

• Supporting structure of plant/fungi cells, lies outside the cell membrane
• Main function is protection
• Composed mostly of cellulose (tough carbohydrate fibre)

Question 23

What is a central vacuole?

Answer 23

• Very large fluid-filled vacuole found in mature plant cells
• When filled with water, it creates turgor pressure to give strength and support to the cell
• Can also store organic compounds

Question 24

Describe the cell membrane

Answer 24

• It regulates what enters/leaves the cell
• Provides protection and support to the cell
• Consists of a phospholipid bilayer in which proteins are embedded, this bilayer gives the membrane a flexible structure that forms a strong barrier between the inside/outside of the cell
• Phospholipids are structural components

Question 25

What are the different types of proteins within the phospholipid bilayer?

Answer 25

1. Transport proteins: Form channels and pumps to help move materials across the membrane
2. Receptor proteins: Recognize and bind to substances at the cell’s surface, forming a method of communication between the cell and its external environment
3. Enzymes: Assist the chemical reactions inside the cell
   - Carbs serve as identification markers so cells can identify each other

Question 26

What is Homeostasis?

Answer 26

• Process by which cells maintain a stable internal environment even when the external one is constantly changing
• Requires the self-regulation of materials going into/out of the cell
• Cell requires constant input of matter/energy and constant output of waste

Question 27

What is the Concentration Gradient?

Answer 27

• The difference in the concentration of molecules across a distance, molecules will almost always move from an area of higher concentration to lower concentration

Question 28

What is passive transport?

Answer 28

• The movement of substances across the cell membrane without the use of energy
• Types: diffusion, osmosis, facilitated diffusion

Question 29

What is diffusion?

Answer 29

• The spreading out of molecules from a region of higher concentration to lower concentration
  -Depends on size and type of molecule
• Small, non-polar molecules dissolve directly through the phospholipid bilayer while polar molecules go through protein channels/transport proteins

Question 30

What is osmosis?

Answer 30

• Movement of water across a membrane from a region of higher concentration to a region of lower concentration
• Passive transport of water, no energy needed

Question 31

What is an isotonic solution?

Answer 31

• When the concentrations of solutes outside/inside the cell are equal, as well as the water concentrations
• Water flows back and forth across the membrane at the same rate in both directions
• In an animal and plant cell: water diffuses in/out at equal rates

Question 32

What is a hypertonic solution?

Answer 32

• When the concentration of solute molecules is higher outside of the cell than inside the cell
• Water diffuses out into equilibrium is reached (risk of plasmolysis
  ~ Plasmolysis: too much water moves out and cell collapses
• In an animal cell: plasmolysis occurs
• In a plant cell: more water leaves the cell than enters

Question 33

What is a hypotonic solution?

Answer 33

• Concentration of solute molecules outside the cell is lower than the concentration of solutes inside the cell
• Water diffuses into the cell until equilibrium is reached (cytolysis may occur)
• In an animal cell: more water enters the cell than leaves
  -In a plant cell: more water enters than leaves, cytolysis is unlikely due to turgor pressure

Question 34

What is facilitated diffusion?

Answer 34

• Type of passive transport used for molecules that don’t readily diffuse through membranes
• May be polar or too large to fit through membrane pores
• Carrier proteins/ transport proteins help these molecules pass through the membrane more easily

Question 35

What is active transport?

Answer 35

• When materials must move against the concentration gradient, possibly from an area of low to high concentration
• Energy is needed

Question 36

What is endocytosis?

Answer 36

• Process of taking material into the cell by means of folds/pockets of the cell membrane
• Pocket that results breaks loose from the cell membrane and forms a vesicle within the cytoplasm
• Large molecules and clumps of food are taken up this way

Question 37

Describe the two types of endocytosis

Answer 37

1. Phagocytosis = the engulfing of large food particles
2. Pinocytosis = “cellular drinking”

Question 38

What is exocytosis?

Answer 38

• The release of large materials from the cell
• A vesicle fuses with the cell membrane, forcing the contents out of the cell