Unit 2 Cell Structure and Function

Question 1

Eukaryotic Cells

Answer 1

Contain DNA within an nucleus and membrane-bound organelles → animals, plants, and fungi.

Question 2

Prokaryotic Cells

Answer 2

Do not enclose their DNA in the the nucleus and lack and membrane-bound organelles → bacteria and archaea.

Question 3

What are common cellular components found in both eukaryotes and prokaryotes?

Answer 3

Cytosol, ribosomes, and a plasma membrane.

Question 4

What is the the endosymbiotic theory?

Answer 4

States that some eukaryotic organelles (mitochondria and chloroplasts) were once prokaryotic cells that were engulfed by larger cells.

Question 5

Nucleus

Answer 5

Structure: double membrane (nucleus envelope) with pores.
Function: stores genetic information, makes RNA and ribosomes.

Question 6

Rough Endoplasmic Reticulum

Answer 6

Structure: membrane studded with ribosomes attached to the nuclear envelope.
Function: processes and packages proteins for transport.

Question 7

Smooth Endoplasmic Reticulum

Answer 7

Structure: folded, tub-like structure (cisternae)
Function: detoxification, calcium storage, makes lipids.

Question 8

Golgi Complex

Answer 8

Structure: membrane-bound structure composed on flattened sacs (cisternae).
Function: folding & chemical modification of proteins and transports proteins in vesicles.

Question 9

Ribosomes

Answer 9

Structure: composed of rRNA and proteins → large and small subunits.
Function: protein synthesis

Question 10

Mitochondria

Answer 10

Structure: double membrane → outer is smooth, inner is highly folded (cristae).
Function: site of oxidative phosphorylation & the Krebs Cycle and produces ATP.

Question 11

Chloroplast

Answer 11

Structure: double outer membrane (stacked thylakoids: grana & fluid: stroma).
Function: site of photosynthesis → thylakoids: light reactions & stroma: Calvin Cycle.

Question 12

Lysosome

Answer 12

Structure: membrane-enclosed sacs that contain hydrolytic enzymes.
Function: intracellular digestion (recycle cell’s organic material & programmed cell death: apoptosis).

Question 13

Vacuole

Answer 13

Structure: membrane-bound sac.
Function: storage & release of macromolecules/cellular waste products, central: water retention → turgor pressure, contractile: osmoregulation (protists).

Question 14

Surface Area-to-Volume Ratio

Answer 14

Smaller cells have a higher surface area-to-volume ratio → more efficient at exchanging materials with the environment.
Surface Area/Volume

Question 15

Structure of the Plasma Membrane

Answer 15

Composed of:
- Phospholipid Bilayer
- Membrane Proteins
- Glycolipids/Glycoproteins
- Cholesterol
Called the fluid mosaic model.

Question 16

Function of the Plasma Membrane

Answer 16

Separates the cell from its surroundings and maintains a stable internal environment.

Question 17

Selective Permeability

Answer 17

Allows some substances to cross more easily than others.

Question 18

Small Nonpolar Molecules

Answer 18

Move freely across the membrane.

Question 19

Larger Polar & Charged Molecules

Answer 19

Cannot directly pass through the hydrophobic core of the membrane → require transport mechanisms.

Question 20

Channel & Transport Proteins

Answer 20

Facilitate the movement of large polar molecules & ions across the membrane.

Question 21

Water Movement

Answer 21

Water molecules move across the membrane through specialized channels called aquaporins.

Question 22

Passive Transport

Answer 22

Movement of molecules across the cell membrane from high to low concentration → diffusion, facilitated diffusion, & osmosis.

Question 23

Diffusion

Answer 23

Passive transport of small, nonpolar molecules down the concentration gradient.
Ex. CO2, O2, N2, steroids

Question 24

Facilitated Diffusion

Answer 24

Uses transport proteins (channels/carriers) to move polar molecules across the cell membrane.
Ex. water, Na+, K+, Ca+

Question 25

Channel Proteins

Answer 25

Integral membrane proteins that form channels across the cell membrane (always passive transport). Ex. aquaporins, ion channels, gated channels

Question 26

Ion Channels

Answer 26

Allow specific ions to pass through the cell membrane → crucial for processes like muscle contraction. Ex. Sodium (Na+), Potassium (K+)

Question 27

Gated Channels

Answer 27

Open or close in response to specific signals. Ex. ligand-gated channels

Question 28

Carrier Proteins

Answer 28

Integral membrane proteins that bind to specific molecules and undergo a conformational change (either passive/active transport). Ex. GLUT4: passive transport of glucose & sodium-potassium pump: actively transports sodium ions out of the cell & potassium ions in.

Question 29

Active Transport

Answer 29

Energy-driven transport of molecules from low to high concentration → primary uses ATP, while secondary uses a sodium-potassium pump.

Question 30

Endocytosis

Answer 30

Cells take in molecules by engulfing them in a vesicle. Ex. Phagocytosis: cellular eating, pinocytosis: cellular drinking & receptor-mediated endocytosis.

Question 31

Exocytosis

Answer 31

Cells move molecules out of the cell by releasing them from a vesicle.

Question 32

Osmosis

Answer 32

Movement of water from an area of low solute concentration to an area of high solute cocentration.

Question 33

Tonicity

Answer 33

Ability of a solution to cause a cell to gain or lose water → depends on concentration of solutes that cannot cross the cell membrane.

Question 34

Hypertonic Solution

Answer 34

High solute concentration OUTSIDE the cell causing water to move OUT of the cell → cell shrinks.

Question 35

Hypotonic Solution

Answer 35

High solute concentration INSIDE the cell causing water to move INTO to the cell → cell expands.

Question 36

Isotonic Solution

Answer 36

EQUAL solute concentration resulting in no net movement of water in/out of cells.

Question 37

Animal Cell Environment

Answer 37

Isotonic Conditions

Question 38

Plant Cell Environment

Answer 38

Hypotonic Conditions → Turgor Pressure

Question 39

Turgor Pressure

Answer 39

Force of water against cell wall. Isotonic: flaccid Hypertonic: plasmolyzed Hypotonic: turgid (ideal)

Question 40

Water Potential

Answer 40

Predicts the direction of water flow → influenced by solute concentration & pressure.

Question 41

Water moves from _______ water potential to _______ water potential.

Answer 41

High to Low

Question 42

Water Potential Formula

Answer 42

Ψ = Ψs + Ψp

Question 43

Solute Potential Formula

Answer 43

Ψs = -iCRT i: ionization constant → # of dissociated ions in water C: molar concentration R: pressure constant (0.0831) T: temperature in Kelvin (C + 273)

Question 44

Pure water has a solute potential of ___.

Answer 44

0

Question 45

Higher solute concentration leads to _______ solute potential.

Answer 45

Lower, more negative

Question 46

The more solutes present, the _______ the water potential.

Answer 46

Lower

Question 47

Osmoregulation

Answer 47

Controlling the movement of water & ions across the cell membrane to maintain homeostasis.