Lecture 6

Question 1

All cells (prokaryotic or eukaryotic) have …

Answer 1

1. Surrounded by a selective barrier: plasma membrane
2. Filled with cytoplasm
3. Have a cytoskeleton
4. Have ribosomes (they are not organelles)
5. Contain chromosome(s): DNA + protein

Question 2

Cytoplasm

Answer 2

everything inside the cell, except for the nucleus.
Does not include the plasma membrane.
The cytoplasm is where the chemical reactions of a cell take place.

Question 3

Cytosol

Answer 3

fluid part of the cytoplasm

Question 4

PROKARYOTIC organisms

characteristics

Answer 4

No organelles: ex DNA not in a nucleus
Genomic DNA: (1) circular chromosome
All are unicellular (single-celled), but some can stick together to form colonies

Question 5

EUKARYOTIC organisms

Answer 5

Organelles, including a nucleus, are present
Genomic DNA: multiple linear chromosomes
Some are unicellular, others are multicellular

Question 6

2 types of cell membranes

Answer 6

Separation between internal & external environments must exist: Allows the internal environment to be different from the external environment.

1) The cell membrane that forms the boundary between the inside & outside of the cell is called a plasma membrane.
2) The cell membranes that are part of organelles are simply called cell membranes

Question 7

Where are the cell membranes for prokaryotes and eukaryotes

Answer 7

Prokaryotes: only the plasma membrane.
Eukaryotes: plasma membrane & as part of organelles

Question 8

Fluid Mosaic Model

Answer 8

Liquid at body temp.: like olive oil
Mostly phospholipid
Also contains sterol (lipid) & some carbs

Proteins, lipids can move within the membrane

Question 9

Microvilli

Answer 9

Microvilli: cell extensions that contain cytoskeleton, fluid, and enzymes for digestion.
Covered by plasma membrane

Function: Increase the surface area of the cell exposed to the lumen to enhance absorption and secretion

Question 10

Functions of plasma membrane

Answer 10

2-5 require proteins

1. Keeps each cell intact: boundary
2. Cell-to-cell contact: needed to form tissues
3. Cell-to-cell recognition: one cell recognizes another based on proteins present on the cell surface (ex immune response)
4. Cell signaling (communication): one cell releases chemicals that bind to receptors in the plasma membrane of another cell. Ex receptors for hormones, neurotransmitters
5. Movement of molecules into/out of cell
   Selectively permeable

Question 11

Plasma membrane

Answer 11

boundary between inside & outside of ALL cells

Question 12

Selectively permeable: how the membrane “decides”

Answer 12

Chemical properties determine what enters directly:
Small molecules pass through.
Membrane mostly lipid, so lipid-soluble molecules can pass.

Transporters are specialized proteins: channels or carriers are present for certain but not all molecules.

Bulk transport mechanisms: endocytosis, exocytosis

Everything else is excluded

Question 13

Exchange with the environment

Answer 13

Into cell
Nutrients: sugars, aa, fa, O2, ions, vitamins…
Some hormones

Out of cell
Metabolic wastes like CO2
Hormones, enzymes, neurotransmitters, ions…

Molecules are continually moving into & out of organelles as well

Question 14

Functions of The cytoskeleton in eukaryotes

Answer 14

1. Mechanical support & maintains cell shape
2. Cell motility
   Move entire cell (ex wbc) or parts of a cell ex organelles on “train tracks”, plasma membrane during phagocytosis)
3. Anchor organelles & enzymes
4. Cell division

Question 15

Cell extensions

Answer 15

Eukaryotic flagella, cilia, & microvilli are extensions of the plasma membrane (covered by the plasma membrane).
Contain proteins of the cytoskeleton & other proteins (ex transport proteins, enzymes).

Microvilli: folds of plasma membrane that serve to increase surface area of cell: for absorption or secretion.

Movement:
Cilia & Flagella contain complex set of proteins that cause the cilia & flagella to move

Cilia: move molecules over surface, ex in respiratory tract, or move entire cell, ex paramecium

Flagella: move entire cell, less numerous than cilia.

Question 16

Cell wall in

Answer 16

All fungi (most multicellular, some unicellular) 
All plants (multicellular)
Some protists (some unicellular, others multicellular)
Most bacteria (unicellular)

In multicellular or colonial organisms (whether they have a cell wall or not):
Intercellular junctions
Extracellular matrix (molecules that provide support & influence gene expression) & fluid

Question 17

Cell walls functions

Answer 17

1. Protects the cell
2. Maintains its shape
3. Prevents excessive uptake of water

Question 18

Between animal cells

Answer 18

Intercellular junctions:
Adhere
Communicate

Cell adhesion molecules-some act like Velcro, while others form a more permanent bond

Question 19

Between plant cells

Answer 19

Plasmodesmata are tiny channels that lie between the cell walls of plant cells. They allow molecules, nutrients, and water to move between cells – known as intercellular communication

Question 20

Extracellular matrix

Answer 20

Extracellular matrix (ECM)=
Fluids +
Nutrients (Proteins, minerals…) +
Signaling molecules

Provide support, nutrients, & can affect gene expression