Unit 2: Cell Structure and Function

Question 1

What are the two types of cells?

Answer 1

Prokaryotic (D. Bacteria and D. Archaea) and eukaryotic (D. Eukarya).

Question 2

What are the traits of prokaryotes?

Answer 2

-No nucleus.
-DNA in a nucleoid.
-Cytosol.
-No organelles other than ribosomes.
-Small in size.
-Primitive.

Question 3

What are the traits of eukaryotes?

Answer 3

-Has a nucleus and nuclear envelope.
-Cytosol.
-Membrane-bound organelles with specialized structures and functions.
-Large in size.
-Complex.

Question 4

Why is it necessary for cells to maintain a large surface area to volume ratio?

Answer 4

Having a large surface area allows the chemical exchange rates between cells and their environment to increase.

Question 5

What are the traits of the nucleus?

Answer 5

-Control center of the cell.
-Contains DNA and mRNA.
-Surrounded by a double membrane that is continuous with the rough ER called the nuclear envelope.
-Contains chromatin, which makes up chromosomes.
-Contains the nucleolus, which forms ribosomal subunits.

Question 6

What are ribosomes used for? What are the two types of ribosomes, and what do they do?

Answer 6

Ribosomes are used for protein synthesis. Free ribosomes float in the cytosol and produce proteins that will be used by the cell. Bound ribosomes are attached to the ER, making proteins that will be transported outside of the cell.

Question 7

What are the traits and functions of the rough endoplasmic reticulum (ER)?

Answer 7

The rough ER has ribosomes on its surface. Its functions include:
-Packaging proteins for secretion.
-Sending transport vesicles to the Golgi apparatus.
-Making replacement membrane.

Question 8

What are the traits and functions of the smooth endoplasmic reticulum (ER)?

Answer 8

The smooth ER does not have ribosomes on its surface. Its functions include:
-Synthesizing lipids.
-Metabolizing carbs.
-Detoxifying the cell.

Question 9

What are the traits and functions of the Golgi apparatus?

Answer 9

-Composed of a series of flattened membrane sacs called cisternae.
-Synthesizes and packages materials for transport in small vesicles.
-Cis-face receives vesicles.
-Trans-face ships vesicles.

Question 10

What do lysosomes do?

Answer 10

Lysosomes are responsible for intracellular digestion and recycling of materials. They also conduct apoptosis, or programmed cell death.

Question 11

What do vacuoles do? What are the differences between plant and animal vacuoles?

Answer 11

Vacuoles store cell materials. Animal cells have multiple small vacuoles that store food or contract to prevent the overabsorption of water. Plant cells have one large vacuole that stores water and ions.

Question 12

What are the traits and functions of mitochondria?

Answer 12

The mitochondria is the powerhouse of the cell, or the site of cellular respiration.
-Has a double membrane (inner and outer).
-Contains folds called cristae, which increase surface area and contain enzymes to speed up ATP production.
-Contains a matrix, which is the fluid-filled inner compartment.

Question 13

What are the traits and functions of chloroplasts?

Answer 13

Chloroplasts serve as the site of photosynthesis. They are only found in plant cells.
-Has a double membrane (inner and outer).
-Contains discs called thylakoids. These discs are found stacked in the chloroplast, forming grana.
-Filled with stroma (fluid).
-Contains chlorophylls, or pigments, for capturing sunlight energy.

Question 14

What do peroxisomes do?

Answer 14

Peroxisomes break down fatty acids and detox alcohol from cells by producing hydrogen peroxide (H2O2).

Question 15

What are the functions of the cytoskeleton? What is it made up of?

Answer 15

The cytoskeleton supports the structure of the cell, provides motility, and regulates biochemical activities.
-Composed of three types of fibers: Microtubules (biggest), intermediate filaments, and microfilaments (smallest).
-Contains a centrosome, the center of microtubule development and organization. (These are called centrioles in animal cells.)
-Utilizes cilia (short, numerous hairs) and flagella (long, few “tails”) to propel cells and provide motility.

Question 16

What are the traits and functions of the cell wall? In which cells can it be found?

Answer 16

The cell wall can only be found in plant cells. It protects the cell and maintains its shape.
-Composed of cellulose.
-Contains plasmodesmata, which are channels between cells that allow the passage of molecules.

Question 17

What are the traits and functions of the extracellular matrix (ECM)? In which cells can it be found?

Answer 17

The ECM can only be found in animal cells as the outer plasma membrane.
-Contains glycoproteins (collagen).
-Strengthens tissues and transmits external signals to cells.

Question 18

What is the endosymbiotic theory? What evidence is there to prove this?

Answer 18

The endosymbiotic theory states that prokaryotic cells were engulfed by the ancestors of eukaryotic cells. (Prokaryotic-cannibalism.) Evidence between both includes:
-Similar double-membrane structure.
-Contains ribosomes and DNA.
-Reproduces independently within cells.

Question 19

What are the traits of the cell membrane? What is it composed of?

Answer 19

-Selective permeability; Allows some substances to cross more easily than others.
-Held together by weak interactions.
The cell membrane is composed of phospholipids but also contains embedded/surface proteins and carbohydrates.

Question 20

How is membrane fluidity affected by other lipids and changes in temperature?

Answer 20

-At low temperatures, kinks in the unsaturated tails of phospholipids prevent close-packing.
-Cholesterol limits fluidity at low temperatures and encourages it at high temperatures.

Question 21

What are the two types of membrane proteins? Where are they located.

Answer 21

Integral proteins are embedded in the membrane. Peripheral proteins are found on the surface of the membrane.

Question 22

What functions does the cell membrane have?

Answer 22

-Transport.
-Enzymic activity.
-Signal transduction.
-Cell-cell recognition.
-Intercellular-joining.
-Attachment to cytoskeleton and ECM.

Question 23

What is the function of carbohydrates in the cell membrane?

Answer 23

In the cell membrane, carbohydrates participate in cell-cell recognition and help develop organisms. (The two types of carbohydrates found in the cell membrane are glycolipids and glycoproteins.)

Question 24

How does the selective permeability of the cell membrane work?

Answer 24

The cell membrane allows small molecules to pass through easily. This process is usually faster with nonpolar molecules rather than polar ones. The hydrophobic core (phospholipid tails) prevents the passage of ions and large polar molecules.

Question 25

What is passive transport?

Answer 25

Passive transport is the diffusion of molecules down a concentration gradient (high to low concentration). This process does not require ATP.

Question 26

What is osmosis? How does osmosis occur?

Answer 26

Osmosis is the diffusion of water. It will occur from high to low water potential, low to high solute, or high to low pressure.

Question 27

What are the three types of external environments cells live in?

Answer 27

Isotonic environments have a concentration of solute that is equal to that in the cell. Hypotonic environments have a concentration of solute that is less than that in the cell. Hypertonic environments have a concentration of solute that is more than that in the cell.

Question 28

What is facilitated diffusion? How does it occur, and what proteins may it utilize?

Answer 28

Facilitated diffusion is diffusion using proteins to help hydrophilic substances cross the membrane. Proteins may either provide hydrophilic channels or loosely bind to and carry molecules across. For example, aquaporins are embedded channel proteins that only allow the passage of water, and glucose transport proteins are common carrier proteins.