2. Structure And Functions Of Cells

Question 1

Cellular housekeeping

Answer 1

The viability of normal activity of cells depend on a variety of fundamental housekeeping functions that all differentiated cells must perform

Protection
Movement
Absorption
Communication
Catabolism
Energy generation
Excretion

Question 2

Plasma membrane

Answer 2

Protection and nutrient absorption, made up of lipid bilayer (hydrophilic outside and LipoPhillic inside)

Provides a barrier to passive diffusion of large and charged molecules

Question 3

Passive Transportation

Answer 3

Movement of substance from an area of high concentration to an area of low concentration (with concentration gradient)

Can include channel or carrier protein

Diffusion
Osmosis
Facilitated diffusion

Question 4

Passive diffusion

Answer 4

Down concentration gradient, depends on size, electric charge and lipid solubility

Question 5

Osmosis

Answer 5

Passive transport of water down concentration gradient

Question 6

Facilitated diffusion

Answer 6

Movement of molecules across the cell membrane via special transport proteins within the cellular membrane

Ex glucose transporter

Question 7

Active Transport

Answer 7

Movementment of a substance from an area of low concentration to an area of high concentration - against concentration gradient - requires energy

ONLY carrier molecules used - binds and makes conformational change (Na-, K+, ATP pump)

Endocytosis - pinocytosis, phagocytosis
Exocytosis

Question 8

Endocytosis

Answer 8

Process of bringing a substance into a cell

Pinocytosis - cell drinking (engulfing liquid)
Phagocytosis - cell eating (engulfing solids such as bacteria)

Question 9

Exocytosis

Answer 9

Release of materials from inside to the outside of the cell

Question 10

Cytoskeletal proteins

Answer 10

Structure that provides mechanical support and helps cells maintain their shape, polarity and internal organization

Microtubule
Intermediate filaments
Actin mictofilaments

Question 11

Microtubule

Answer 11

(25nm) transportation and cell division, thickest and most diversified, forms flagella, cilia and pulls cells apart during mitosis

Question 12

Intermediate filaments

Answer 12

(10nm) nuclear lamen and structure of nucleus, bears mechanical stress

Question 13

Actin microfilaments

Answer 13

(5-9 nm) thinnest, muscle contraction, plays a role in exocytosis, most abundant fragment in the cell and gives it its shape

Question 14

Occluding junctions (tight junctions)

Answer 14

Prevents diffusion of molecules between cells (paracellular)

Ex: bladder - we do not want to leak urine, kidney

Question 15

Anchoring Junctions (desmosomes)

Answer 15

Mechanically attach cells and their intracellular skeletons to other cells or the extracellular matrix - distribute mechanical stress

Ex: skin, intestine

Question 16

Communicating junctions (gap junctions)

Answer 16

1.5-2 nm pores called connexons formed by connexins - helps pass action potentials

Ex: heart, neurons, retina

Question 17

Endoplasmic Reticulum

Answer 17

Site for synthesis of all transmembrane proteins and lipids for plasma membrane and cellular organelles

Smooth ER
Rough ER
Sarcoplasmic reticulum

Question 18

Smooth ER

Answer 18

NO ribosomes

Synthesizes steroid hormones or catabolism lipid solvable molecules

Also responsible for sequestering intracellular calcium ( role in apoptosis)

Question 19

Rough ER

Answer 19

Has ribosomes

Important role in protein and lipid synthesis

Question 20

Sarcoplasmic reticulum

Answer 20

Specialized smooth ER of muscle cells

Responsible for regulating muscle contraction

Question 21

Chaperones

Answer 21

Retain proteins in the ER until folding is complete

Question 22

Golgi apparatus

Answer 22

Proteins sent from ER to Golgi apparatus

Post office of the cell - receives synthesized proteins and shuttles them to target region

Question 23

Different types of waste disposal mechanisms in the cell

Answer 23

Lysosomes - Hererophagy and autophagy, uses acid to break down substances

Proteosomes- can onle degrade proteins, tab them with uB

Question 24

Heterophagy

Answer 24

Endoscopes or phagosomes rise with lysosomes to facilitate the degradation of their internalized contents

Comes from outside

Question 25

Autophagy

Answer 25

Senescent organelles or denatured proteins are encircled with a double membrane which fuses with the lysosome and degraded Self eating

Question 26

Process of protests oral degradation

Answer 26

Can handle only proteins Misfolded protein is tagged (ubiqinoine uses lighters to tag misfolded protein) and is chopped into fragments 6-12 AAs long Errors in this process can lead to diseases such as CF

Question 27

Origin of Mitochondria

Answer 27

Evolved from ancestral prokaryotes that were engulfed by primate eukaryotes (1.5 billion years ago) contain their own DNA

Question 28

Functions of Mitochondria

Answer 28

Oxidative phosphorylation - process by which we get energy Apoptosis - cytochrome C leaks enzyme to activate apoptosis Anabolism - mitochondria synthesize hemoglobin as heme, steroidalgenesis

Question 29

Reactive Oxygen species

Answer 29

Oxygen radicals that can cause damage to the cell, side product of chemical reactions Utilized by antioxidant system, but when there is an increase in ROS and cells are supersaturated then they acculturate and cause damage Hypoxia, toxic injury increase ROS - damage to DNA structure and cell cycle arrest or apoptosis

Question 30

Two types of cell death

Answer 30

Necrosis - always pathological, inflammation Apoptosis - pathological or physiological, no inflammation IRREVERSIBLE

Question 31

Necrosis

Answer 31

External agents such as toxins, ischemia or trauma, is always pathological Exposure to these agents affects ATP generation of the cell and the cell Bursts - mitochondrial membrane damage INFLAMMATION - always bad

Question 32

Apoptosis

Answer 32

External or internal agents (DNA damage or IC stress) could be physiological or pathological Leaky mitochondria 0 cytochrome c released - triggers apoptosis NO INFLAMMATION

Question 33

Purpose of cell signaling

Answer 33

Cells require basic signaling to survive and in the absence will undergo apoptosis Abnormal signaling - lead to unregulated growth or cancer or in an ineffective response to an extrinsic stress - shock

Question 34

Extracellular Matrix

Answer 34

Network of interstitial proteins that constitutes a significant proportion of Any tissue Cell interactions with ECM are critical for development and healing as well as maintaining normal tissue architecture (proper organ growth)

Question 35

Functions of ECM

Answer 35

Mechanical support Control of cell proliferation Support for tissue renewal ECM disruption - defective tissue regeneration and repair (liver cirrhosis) Tissue micro environment (basement membrane in kidney)

Question 36

Interstitial Matrix

Answer 36

Produced by mesenchymal cells such as fibroblasts, type I collagen Less organized, found in spaces between cells Main function is to provide support

Question 37

Basement membrane

Answer 37

Is the ECM that surround epithelial cells, endothelial cells and smooth muscle cells and separates them from muscle cells More organized then IM Type IV collagen and laminitis Main function is to separate epithelium and blood vessels from underlying tissue, performs specialized functions (kidney - filtration mechanism)