Lesson Topic 1.3: Structural and Functional Organization of Cells

Question 1

Cell Structure

Answer 1

Plasma membrane

Cytoplasm: cytosol + organelles

Nucleus

Question 2

Cell Membrane Function

Answer 2

Barrier between inside and outside of cell

Controls entry of materials: transport

Receives chemical and mechanical signals

Transmits signals between intra- and extra- cellular spaces

Question 3

Body Fluid Pools

Answer 3

Intracellular (ICF)
Within cells: 2/3 of total

Extracellular (ECF):
Between cells = Interstitial
In blood vessels = Plasma
In lymphatic vessels = Lymphatic

Question 4

Solvent:

Answer 4

the liquid doing the dissolving
Usually water

Question 5

Solute:

Answer 5

the dissolved material (particles or gas)

Question 6

Concentration

Answer 6

Amount of solute in a given amount of solvent
Concentration gradient

Question 7

Passive Transport
Requirements for simple diffusion

Answer 7

Concentration gradient of solute present
Solute can diffuse across a membrane if membrane is present

Question 8

Passive transport
Pathways of simple diffusion:

Answer 8

Pass across lipid bilayer if lipid-soluble (O2, CO2, N2, fatty acids, steroids, fat-soluble vitamins), or if polar molecules (H2O, urea)
Pass through ion channels (which may be gated: gates open and close) if ions such as K+, Ca2+, Cl–

Question 9

Facilitated Diffusion

Answer 9

Requires a carrier in membrane but not ATP

Solute goes down concentration gradient

Maximum transport speed depends on number of carriers
insulin increases number of carriers for glucose in
plasma membrane

Question 10

Osmosis

Answer 10

Diffusion of water across selectively permeable membrane:
Permeable to solvent
Impermeable to solute

Question 11

Types of solutions surrounding human RBCs

Answer 11

Isotonic: solution outside RBC has same concentration of solute as RBC: 0.9% NaCl

Hypotonic: solution outside of RBC has lower concentration: 0% NaCl  hemolysis

Hypertonic: solution outside of RBC has higher concentration: 4% NaCl  crenation

Question 12

Active Transport

Answer 12

Requires a carrier (called a pump)

Requires energy (ATP)

Can transport up a concentration gradient

Critical for moving important ions

Major active transport in most cells is sodium-potassium (Na+/K+) pump

Question 13

Transport in Vesicles

Answer 13

Requires energy (ATP)

Involves small membrane sac

Endocytosis: importing materials into cell
-Phagocytosis: ingestion of particles such as bacteria into white blood cells (WBCs)

-Pinocytosis: ingestion of fluid

Exocytosis: exporting materials

Question 14

Cell Organelles: Table 3.2 Pg. 86

Answer 14

Cytoskeleton
Flagella, cilia & centrioles
Endoplasmic reticulum
Golgi apparatus
Mitochondrion
Nucleus, nucleolus, nuclear envelope
Vesicles, e.g. lysosome

Question 15

Cytoplasm

Answer 15

Cell contents
Includes organelles and cytosol
Excludes nucleus

Question 16

Cytoskeleton

Answer 16

Maintains shape of cell

Positions organelles

Changes cell shape

Includes: microfilaments, intermediate filaments, microtubules

Question 17

Centrosome

Answer 17

Structure:
Two centrioles arranged perpendicular to each other

-Composed of microtubules: 9 clusters of 3 (triplets)
-Pericentriolar material
Composed of tubulin that grows the mitotic spindle

Function: moves chromosomes to ends of cell during cell division

Question 18

Cilia and Flagella

Answer 18

Specialized for motion

Flagellum: single tail like structure on sperm
-Propels sperm forward in reproductive tract

Cilia: in groups
-Found in respiratory system: move mucus

Question 19

Ribosomes

Answer 19

Made within the nucleus (in nucleolus)

Sites of protein synthesis (on E.R. or freely within cytoplasm)

Consist of ribosomal RNA (rRNA) + proteins

Contain large and small sub-units

Can be attached to endoplasmic reticulum or free in cytosol

Question 20

Endoplasmic Reticulum (E.R.)

Answer 20

Structure: network of folded membranes

Functions: synthesis, intracellular transport

Types of E.R.
-Rough E.R.: studded with ribosomes (sites of protein synthesis)
-Smooth E.R. lacks ribosomes. Functions:
lipid synthesis

release of glucose in liver cells into bloodstream

drug detoxification (especially in liver cells)

storage and release of Ca2+ in muscle cells (where smooth E.R. is known as sarcoplasmic reticulum or SR)

Question 21

Golgi Complex

Answer 21

Structure:
Flattened membranes (cisterns) with bulging edges (like stacks of pita bread)

Functions:
Modify proteins  glycoproteins and lipoproteins that:
-Become parts of plasma membranes
-Are stored in lysosomes, or
-Are exported by exocytosis

Question 22

Small Bodies

Answer 22

Lysosomes: contain digestive enzymes
-Help in final processes of digestion within cells
-Carry out autophagy (destruction of worn out parts of cell) and death of old cells (autolysis)
-Tay-Sachs: hereditary disorder; one missing lysosomal enzyme leads to nerve destruction

-Peroxisomes: detoxify; abundant in liver
-Proteasomes: digest excess or faulty proteins
Faulty proteins accumulate in brain cells in
persons with Parkinson or Alzheimer disease.

Question 23

Mitochondria

Answer 23

Structure:
-Sausage-shaped with many folded membranes (cristae) and liquid matrix containing enzymes
-Have some DNA, ribosomes (can make proteins)

Function:
-Nutrient energy is released and trapped in ATP; so known as “power houses of cell”
-Chemical reactions require oxygen

Abundant in muscle, liver, and kidney cells
-These cells require much ATP

Question 24

Nucleus

Answer 24

Round or oval structure surrounded by nuclear envelope with nuclear pores

Contains nucleolus: makes ribosomes that pass into cytoplasm through nuclear pores

Store genetic material (DNA) in genes arranged in 46 chromosomes (the human genome containing 30,000 genes!)

DNA contains information for directing protein synthesis:
-In this cell
-In new cells (formed by cell reproduction)

Question 25

Cell Size and Shape

Answer 25

The body of an average human adult is composed of nearly 100 trillion cells. Cells vary considerably in size

The sizes of cells are measured in units called micrometers.

The largest cell, a single oocyte, has a diameter of about 140 μm and is barely visible to the unaided eye.