Cell Structure and Composition

Question 1

Definition of a cell

Answer 1

The basic unit from which living organisms are made, consisting of an aqueous solution of organic molecules enclosed by a membrane. All cells arise from existing cells, usually by a process of division.

Question 2

Predominant types of molecules found in cells

Answer 2

Soluble proteins, ions, sugars, nucleotides, amino acids, mRNA, tRNA, lipids, cholesterol, peptides.

Question 3

Size of cells

Answer 3

10-20 micrometres diameter

Question 4

Mass of a cell

Answer 4

1 nanogram

Question 5

Size of a virus

Answer 5

10 nanometres

Question 6

Small protein

Answer 6

40 nanometres

Question 7

Unit of measurement for cell volume

Answer 7

Nanolitres

Question 8

Size of molecules

Answer 8

0.2 nanometres in diameter

Question 9

Function of nucleus

Answer 9

Contain the genetic information for the cell, coordinate the activity of the cell

Question 10

Function of nucleolus

Answer 10

Contains genes for rRNA production

Question 11

Function of nuclear envelope

Answer 11

Contain the nucleus

Question 12

Function of mitochondrion

Answer 12

ATP synthesis

Question 13

Function of rough ER

Answer 13

Synthesis and packaging of proteins

Question 14

Function of smooth ER

Answer 14

Synthesis of lipids

Question 15

Function of ribosomes

Answer 15

Synthesis of protein

Question 16

Function of golgi apparatus

Answer 16

Modification of proteins and packing into vesicles

Question 17

Function of secretory granules

Answer 17

Contain and release contained molecules

Question 18

Function of plasma membrane

Answer 18

Contain and define limits of the cell

Question 19

Function of cytoskeletal components

Answer 19

Provide organisation and control of components of intracellular matrix

Question 20

Essential characteristics of prokaryotic cells

Answer 20

• No membrane bound organelles
• No nucleus
• Some have flagella
• Lesser degree of organisation within cell
• Some have peptidoglycan cell walls
• 70s ribosomes

Question 21

Essential characteristics of eukaryotic cells

Answer 21

• Membrane-bound organelles
• Nucleus
• Some have cilia/microvilli
• Cytoskeleton - high degree of organisation
• No cell wall, only cell membrane
• 80s ribosomes

Question 22

Structural components of phospholipids (in descending order)

Answer 22

Hydrophilic choline head
Phosphate
Glycerol
Two fatty acid tails

Question 23

Explain the formation of phospholipid bilayers in aqueous environments

Answer 23

Hydrophobic tails form hydrophobic core of bilayer, pointing towards the inside of the bilayer. Hydrophilic heads form the two hydrophilic surfaces of the bilayer, facing outwards from the inside of the bilayer. Form a micelle.

Question 24

Permeability properties of phospholipid bilayer membrane

Answer 24

• Selectively permeable
• Impermeable to large molecules and charged molecules
• Permeable to water molecules and small uncharged molecules

Question 25

Functions of membrane proteins

Answer 25

• Increase fluidity of membrane
• Transport of molecules
• Transmission of signals
• Anchors linking intracellular actin filaments to extracellular matrix
• Receptors for hormones
• Cell recognition and adhesion
• Electron carriers
• Enzymes

Question 26

Simple diffusion

Answer 26

Movement of a particle down its concentration gradient

Question 27

Facilitated diffusion

Answer 27

Movement of charged particles through channel proteins down their concentration gradient

Question 28

Active transport

Answer 28

Movement of a particle against its concentration gradient, using ATP in the process.

Question 29

Example of simple diffusion

Answer 29

O2/CO2 molecules through lipid bilayer

Question 30

Example of facilitated diffusion

Answer 30

K+ diffusion through its gated channel protein

Question 31

Example of active transport

Answer 31

Na+/K+ pump, both ions moving against their electrochemical gradients