Week 2 (The Cell)

Question 1

The Cell

Answer 1

 smallest unit that performs all vital physiological functions

 each cell maintains homeostasis at the cellular level

 basic unit of structure and function

 function and structure are closely related

Question 2

3 Main Components of the Cell

Answer 2

Cell Membrane: The outer boundary.

Cytoplasm: The internal fluid & organelles.

Nucleus: The control center (contains DNA).

Question 3

The Cell Membrane Functions

Answer 3

✅ Encloses cell contents.
✅ Regulates what enters & exits.
✅ Facilitates cell communication.
✅ Maintains cell shape.

Question 4

The Cell Membrane Constituents

Answer 4

✅ Lipid Bilayer (Phospholipids)
✅ Cholesterol
✅ Glycolipids
✅ Proteins

Question 5

PLASMA MEMBRANE

Answer 5

✅ Fluid Mosaic Model
Proteins float in fluid lipid bilayer

✅ Membrane Lipids
Phospholipids (75%) – Hydrophilic head, hydrophobic tail (forms bilayer).
Cholesterol (20%) – Stabilizes membrane & maintains flexibility.
Glycolipids (5%) – Cell recognition markers.

✅ Proteins
-integral / transmembrane proteins
-peripheral proteins

Question 6

Phospholipid

Answer 6

hydrophilic (“water-loving”) head
hydrophobic (“water-fearing”) tail

Question 7

Cholesterol

Answer 7

stabilises membrane
maintains fluidity

Question 8

Glycolipids

Answer 8

lipids with a carbohydrate attached
cell recognition

Question 9

Integral Proteins

Answer 9

 inserted into lipid bilayer

 have both hydrophilic & hydrophobic regions

 Function: enzymes, transport, receptors (relay messages)

Question 10

Peripheral Proteins

Answer 10

 Attached loosely to membrane

 Function: support, enzymes, movement, linkage

Question 11

Glycoproteins

Answer 11

 Protein with carbohydrate attached

 Function: specific biological marker (cell recognition)

Question 12

PLASMA MEMBRANE 2

Answer 12

 selectively permeable
-only allows some substances to enter cell
-restricts other substances
*nutrients in
*products and wastes out

 by passive or active transport

Question 13

Factors That Affect Membrane Transport

Answer 13

 membrane structure (phospholipid bilayer and proteins)

 size of molecules (smaller molecules traverse easily)

 ionic charge (charged molecules do not traverse easily)

 lipid solubility (lipids traverse easily)

 carrier molecules (number of embedded proteins with channels)

 pressure differences (greater pressures help push substances through)

Question 14

Passive Transport

Answer 14

No energy (ATP) required, moves from high to low concentration

 Simple Diffusion
 Facilitated Diffusion
 Osmosis
 Filtration
 Dialysis (artificial)

Question 15

Active Transport

Answer 15

Requires energy (ATP), moves from low to high concentration

 Protein pumps
 Exocytosis (“out of cell” – eject substances)
 Endocytosis (“within the cell”- ingest substances)
 Pinocytosis (uptake of liquids)
 Phagocytosis (uptake of solids)

Question 16

Primary Active Transport

Answer 16

Uses ATP directly (e.g., sodium-potassium pump).

Question 17

Secondary Active Transport

Answer 17

Uses energy from another gradient (e.g., sodium-glucose cotransport).

Question 18

Simple Diffusion

Answer 18

nonpolar and lipid soluble substances diffuse directly through lipid membrane eg. oxygen (O2), carbon dioxide (CO2), fat-soluble vitamins

Question 19

Facilitated Diffusion

Answer 19

transport proteins (carrier or channel proteins) assist water-soluble / lipid insoluble molecules across membrane eg. glucose, amino acids, water (H2O), ions

Question 20

Channel Proteins

Answer 20

water-filled channels eg. ions
Carrier Proteins: bind to molecule, change shape, transport it across membrane eg. glucose transporter

Question 21

Carrier Proteins

Answer 21

bind to molecule, change shape, transport it across membrane
eg. glucose transporter

Question 22

Osmosis: A SPECIAL CASE OF DIFFUSION

Answer 22

 net diffusion of H2O across a selectively permeable cell membrane from a region of low solute conc.→high
solute conc.

 movement of H2O down conc. gradient

 membrane must be freely permeable to H2O, selectively permeable to solutes

 aquaporins: specific channel proteins for H2O passage

Question 23

Filtration

Answer 23

 hydrostatic pressure pushes on water
 water crosses membrane
 solute follows water
 filtration initiates urine formation

Question 24

Primary Active Transport

Answer 24

 directly uses ATP to drive transport

 protein pumps

 ion pumps move ions [Sodium (Na+), Potassium (K+), Calcium (Ca2+)]

 exchange pump counter transports
2 ions at the same time

 eg. Na+-K+ pump, Ca2+ pump,
Hydrogen (H+) pump

Question 25

Sodium-Potassium Exchange Pump

Answer 25

 active transport, carrier mediated  movement of Na+ OUT, K+ IN 1 ATP moves 3 Na+ out and 2 K+ in

Question 26

Secondary Active Transport

Answer 26

 movement of more than 1 substance at a time  Symport: 2 substances moved in same direction  Antiport: 2 substances moved in opposite directions  eg. cotransport of sugars, amino acids, ions

Question 27

Vesicular Transport

Answer 27

 fluid and large particles transported across cell membranes in vesicles (sacs)  materials move into or out of cell in vesicles Endocytosis (“within the cell”- ingest substances)  Receptor-Mediated  Phagocytosis  Pinocytosis Exocytosis (“out of cell” – eject substances)

Question 28

PHAGOCYTOSIS

Answer 28

cell eating: engulf large or solid material eg. white blood cells (wbcs) engulf bacteria

Question 29

PINOCYTOSIS

Answer 29

cell drinking: fluid with dissolved molecules eg. intestinal cells

Question 30

2 Major Components of the Cell

Answer 30

Nucleus (Control Center) Cytoplasm (The Cell’s Interior)

Question 31

Nucleus (Control Center)

Answer 31

 Largest organelle  Function: Controls cellular activity & contains genetic material (DNA)  Most cells have only one nucleus  3 Main structures of the nucleus: +Nuclear Envelope – A double membrane surrounding the nucleus, continuous with rough endoplasmic reticulum (RER). +Perinuclear Space – Space between the two layers of the nuclear envelope. +Nuclear Pores – Communication passages controlling the entry and exit of molecules.  DNA (Deoxyribonucleic Acid): +The Blueprint of Life +Contains all the instructions for building and running the organism. +Found in different forms: ++Chromatin – Loosely coiled DNA (when the cell is not dividing). ++Chromosomes – Tightly coiled DNA (during cell division).  Other Nuclear Components +Nucleoplasm – Fluid containing ions, enzymes, nucleotides, and RNA. +Nucleoli – Sites of ribosomal RNA (rRNA) production and ribosome assembly.

Question 32

Cytoplasm (The Cell’s Interior)

Answer 32

Located between the plasma membrane and the nucleus. It contains 3 elements: +Cytosol (Intracellular Fluid) Contains dissolved materials such as nutrients, ions, proteins, and waste products (e.g., water, salts). +Organelles ("Little Organs") Specialized structures performing specific functions within the cell. +Inclusions (Stored Substances) Chemical substances that vary depending on cell type, e.g.: -Glycogen (liver cells) -Lipid droplets (fat cells) -Melanin (skin & hair cells)

Question 33

2 Types of Organelles

Answer 33

Membranous Organelles Nonmembranous Organelles

Question 34

Mitochondria

Answer 34

The "Powerhouse" of the cell -Converts chemical energy from food into ATP (energy currency). -Regulates intracellular Ca²⁺ concentration.

Question 35

Smooth ER (SER)

Answer 35

No ribosomes attached -Synthesizes lipids (e.g., phospholipids, cholesterol). -Detoxifies drugs. -Stores and releases Ca²⁺ (important for muscle contraction).

Question 36

Rough ER (RER)

Answer 36

Surface covered with ribosomes. -Synthesizes proteins and glycoproteins. -Folds polypeptide chains. -Packages proteins into transport vesicles for shipment to the Golgi Apparatus

Question 37

Golgi Apparatus

Answer 37

The "Post Office" of the Cell -Modifies and packages proteins & lipids from the ER. -Produces vesicles for transport.

Question 38

Lysosomes

Answer 38

The Cell’s Recycling System Contain powerful digestive enzymes that: -Break down large molecules. -Attack and digest bacteria. -Recycle damaged organelles.

Question 39

Peroxisomes

Answer 39

The Cell’s Detox Center Contain enzymes that: -Neutralize toxins. -Break down fatty acids. -Produce hydrogen peroxide (H₂O₂) as a byproduct.

Question 40

Cytoskeleton

Answer 40

The Cell’s Structural Framework -Provides shape and strength. Composed of: +Microfilaments (smallest, involved in movement). +Intermediate filaments (reinforce cell shape). +Microtubules (largest, involved in transport & cell division).

Question 41

Microvilli

Answer 41

Tiny Projections for Absorption +Increase surface area. +Found in intestinal and kidney cells.

Question 42

Centrioles & Centrosome

Answer 42

Essential for Cell Division Centrioles – Organize spindle fibers for mitosis. Centrosome – The region surrounding centrioles.

Question 43

Cilia

Answer 43

The Cell’s Moving Extensions -Small, hair-like structures that move fluids across the cell surface. -Found in respiratory tract cells.

Question 44

Ribosomes

Answer 44

The Cell’s Protein Factories They build polypeptides for protein synthesis. Two Types: *Free Ribosomes – Floating in cytoplasm, make proteins for the cell. *Bound Ribosomes – Attached to the RER, make proteins for export.

Question 45

Endomembrane System

Answer 45

A system of organelles that work together to produce, store, and transport biological molecules.