Anatomy of the Cell

Question 1

Cell

Answer 1

Basic structural unit of all living organisms

Question 2

Composition of a Cell

Answer 2

Water = 80%
Protein = 15%
Lipid = 2.5%
Carbohydrate = 1.5%
Inorganic = 1.0%

Question 3

Plasma Membrane - Function (3), Composition, Properties (2)

Answer 3

Controls entry and exit of cell
Protects the cell
Separates cytoplasm from external environment
Bimolecular layer of amphiphatic phospholipid molecules with hydrophilic heads and hydrophobic tails
Fluid - change shape, membrane proteins can diffuse laterally in membrane
Selectively-permeable - molecules like water/oxygen/hydrophobic molecules can pass, but molecules like ions and large molecules can’t
Trilaminar

Question 4

Cytoplasm - Composition, Properties,

Answer 4

Solution of proteins, electrolytes and carbohydrates
Fluid and gel-like properties

Question 5

Cytoskeleton

Answer 5

Determines shape and fluidity of cell
Includes –> MIcrofilaments, Intermediate filaments
Microtubules

Question 6

Organelles

Answer 6

Membrane-bound subcellular structures within the cytoplasm
Small intracellular organs with specific function and structural organisation

Question 7

Inclusions (3)

Answer 7

Other structures in cytoplasm which may or may not be bound by a membrane
Dispensable and may be present only as transients
Components synthesised by the cell itself or taken up from the extracellular environment

Question 8

Integral Proteins

Answer 8

Within the plasma membrane
Movement of signals across (signal transduction)
I.e. Receptors, Channels, Transporters, Enzymes, Cell Attachment

Question 9

Nucleus

Answer 9

Contains the genetic code (DNA)
Nucleolus - 1-3um, rRNA transcribed
Nuclear membrane - pores present
Inner membrane
Outer membrane - studded with ribosomes, continuous with RER
mRNA and tRNA transcribed in nucleus
Euchromatin - open, uncondensed, active
Heterochromatin - closed, condensed, inactive

Question 10

Mitochondria

Answer 10

Energy production
Cellular respiration - electron transport chain
ATP production - via OXPHOS
Synthesis of some lipids/proteins
Oblong, cylindrical organelles
0.5-2um length
Outer Membrane
Inner membrane - folded into cristae (increase SA)
Mitochondrial DNA

Question 11

Ribosomes

Answer 11

Formed in nucleolus
Protein synthesis
Small 40S subunit - binds RNA
Large 60S subunit - catalyses peptide bond formation

Question 12

Endoplasmic Reticulum

Answer 12

Network of Interconnecting membrane-bound compartments in cell

Question 13

Rough ER

Answer 13

Studded with ribosomes
Protein synthesis - destined for membrane insertion or secretion
Glycoprotein formation
High RER = Metabolically active cell
Low RER = Metabolically inactive cell

Question 14

Smooth ER

Answer 14

Cholesterol and Lipid synthesis/detoxification
Continues protein processing from RER
Most cells have little SER

Question 15

Golgi Apparatus

Answer 15

Modification & Packaging of macromolecules - adds sugars, cleavage, vesicle sorting
Flattened membrane bound cisternae
Sub-compartments
Transport vesicles arrive from ER
Cis- and trans-Golgi

Question 16

Lysosome

Answer 16

Contains hydrolytic enzymes for intracellular digestion

Question 17

Microfilaments - Diameter, Globular, Filamentous, Assembly

Answer 17

7nm diameter
Actin
Globular actin polymerises to form FIlamentous actin
Assemble into filaments then disassemble (dynamic)

Question 18

Intermediate FIlaments

Answer 18

> 10nm diameter
6 Main Proteins
BInd intracellular elements together and to membrane
More than 50 types - neurofilaments, desmin, cytokeratins, vimentin, lamin, etc

Question 19

Microtubules

Answer 19

25nm diameter
Alpha and Beta-tubulin proteins
Hollow tubule
Assembled and Disassembled
Originate from centrosome and include MAPs (stabilising proteins)
Important in Cilia, Flagella and Mitotic Spindle
Dynein and Kinesin attach and move along - associate with organelles and vesicles

Question 20

Intracellular Junctions

Answer 20

Specialised membrane structures which link individual cells together into a functional unit
Prominent in epithelia

Question 21

Occluding Junctions/ Tight Junctions

Answer 21

Prevent diffusion
Focal region of close apposition between adjacent cells
Contain occludin and claudin

Question 22

Anchoring Junctions/ Zonula Adherens

Answer 22

Link submembrane actin bundles of adjacent cells
Transmembrane cadherin bind to each other in the extracellular space and to the actin of the cytoskeleton (link molecules)

Question 23

Desmosomes/ Macula adherens

Answer 23

Link submembrane intermediate filaments of adjacent cells
Common in skin - mechanical stability
Desmocollin and Desmoglein

Question 24

Communicating Junctions/ Gap Junctions

Answer 24

Selective diffusion
Each junction is a circular patch studded with several hundred pores
Connexon proteins
Found in epithelia and also some smooth muscle and cardiac muscle (excitation spread)

Question 25

Junctional Complex

Answer 25

Close association of several types of junctions found in certain epithelial tissues
ZO –> ZA –> MA

Question 26

Transport in and out of the cell

Answer 26

Diffusion
Transport Proteins - pumps or channels
Vesicles - endocytosis, phagocytosis

Question 27

Endocytosis

Answer 27

From extracellular space to intracellular space of the cell
Membrane invaginates, fuses and newly made endocytotic vesicle buds into the cell
Receptor-mediated

Question 28

Exocytosis

Answer 28

Material moves from the intracellular space to the extracellular space

Question 29

Phagocytosis

Answer 29

Bacteria or larger material from extracellular space incorperated into cell
Bacterium binds to cell surface receptors –> cell extensions –> Engulfment of bacterium –> Phagosome –> Binds to Lysosome –> Phagolysosome