Cells and organelles

Question 1

What is a cell?

Answer 1

the basic structural and functional unit of a living organism consisting of an aqueous solution of organic molecules enclosed by a membrane

Question 2

How do cells become specialised?

Answer 2

Particular genes are switched on triggered by signals from their immediate environment - produces mRNA - produces protein -creates enzymes which induce the formation of specialised organelles

Question 3

What does polarity mean?

Answer 3

A structure that has an inherent asymmetry so one end can be distinguished from the other (unequal distribution of organelles)

Question 4

How big are cells in diameter?

Answer 4

10-100 micrometres in diameter

Question 5

What is the size of a flu virus?

Answer 5

80 nanometres

Question 6

How big is a small protein?

Answer 6

10 nanometres

Question 7

How big are bacteria?

Answer 7

1 micrometre

Question 8

How does transmission electron microscopy work?

Answer 8

Uses a beam of electrons and magnetic coils to focus the beam and electron-dense heavy-metal contrast is used to absorb electrons, removing them from the beam as it passes through specimen

Question 9

Definition of organelles

Answer 9

separate, recognisable sub-cellular structures that perform specialised functions within the cell

Question 10

Functions of nucleus, nucleolus and nuclear pores

Answer 10

Nucleus - contains genetic material, enclosed within two concentric membranes
Nucleolus - ribosomal RNA is transcribed here and ribosomal subunits are assembled (found in the nucleus)
Nuclear pores - specialised protein complexes which filter molecules moving between nucleus and cytosplasm

Question 11

Function of mitochondria

Answer 11

Membrane-enclosed organelle that carries out oxidative phosphorylation and produces ATP in eukaryotic cells

Question 12

Functions of vesicles and secretory granules

Answer 12

Small membrane-enclosed organelles in the cytoplasm destined for secretion are stored prior to release

Question 13

Function of Golgi apparatus

Answer 13

Membrane-enclosed organelle where proteins and lipids made in endoplasmic reticulum are modified and sorted for transport to other sites in cell

Question 14

Functions of centriole

Answer 14

short cylindrical array of microtubules found in pairs at the centre of a centrosome and found at the base of cilia and flagella

Question 15

Functions of ribosome

Answer 15

Particle composed of rRNA and ribosomal proteins that associate with mRNA and catalyses synthesis of protein (translation)

Question 16

Functions of cytoskeleton

Answer 16

system of protein filaments in the cytoplasm that gives the cell shape and capacity for directed movement; contains actin filaments, microtubules and intermediate filaments

Question 17

Functions of lysosome

Answer 17

intracellular membrane-enclosed organelle containing digestive enzymes

Question 18

Functions of liposomes

Answer 18

Artifically prepared vesicles made from the lipid bilayer

Question 19

Functions of plasma membrane

Answer 19

membrane that surrounds a living cell

Question 20

Functions of cilia

Answer 20

Hairlike extensions on the surface of a cell with a core bundle of microtubules and capable of performing repeated beating movements which drive the movement of fluid over epithelial sheets, as in the lung

Question 21

Function of endoplasmic reticulum

Answer 21

membrane-enclosed component where lipids are secreted and membrane-bound proteins are made

Question 22

Functions of smooth, rough and sarcoplasmic endoplasmic reticulum

Answer 22

Smooth ER - region of ER not associated with ribosomes but involved in synthesis of lipids
Rough ER - region of ER associated with ribosomes and involved in synthesis of lipids and membrane-bound proteins
Sarcoplasmic ER - specialist form of ER found in smooth and striated muscle

Question 23

Definition of cytosol

Answer 23

Contents of the main compartment of the cytoplasm, e.g. intracellular fluid, site of many chemical reactions including manufacture of proteins and glycolysis, includes soluble proteins, sugars, ions, nucleotides etc.

Question 24

What is a basement membrane?

Answer 24

Thin sheet of fibre that underties the epithelium or endothelium; acts as a selective barrier for macromolecules, type VI collagen network, laminas, type XV collagen (provides strength in membranes)

Question 25

What is extracellular fluid?

Answer 25

Complex network of polysaccharides (e.g. cellulose) and proteins (e.g. collagen) secreted by cells; structural component of tissues that also influences development and physiology; consists of ions, soluble proteins, carbohydrates and sugars, vitamins, amino acids, nucleotides, lipids, plasma, saliva etc.

Question 26

Outline characteristics of all cells

Answer 26

all have a cell membrane, DNA, RNA molecules and proteins, composed of the same basic chemicals (carbohydrates, proteins, nucleic acids, fats etc.), regulates flow of nutrients and wastes, reproduce, require a supply of energy and are affected and respond to reactions that occur in them and many environmental conditions around them

Question 27

Definition of prokaryote

Answer 27

living cells distinguished by the absence of a nucleus and other membrane-bound organelles; single-celled organisms comprising the kingdoms archaea and bacteria

Question 28

Definition of eukaryote

Answer 28

living organism composed of one or more cells with a distinct nucleus and other membrane-bound organelles; includes all forms of life except archaea, bacteria and viruses

Question 29

Distinguish between prokaryotes and eukaryotes

Answer 29

Prokaryotes - no organelles, has a nucleoid region with naked DNA, has external whip-like flagella for locomotion and hair-like pili for adhesion, smaller, cell walls contain peptidoglycan

Eukaryotes - membrane-bound organelles present, nucleus with DNA associated with proteins, may have cilia or microvilli on surface of cell membrane, cytoskeleton, no cell wall (if animal cell)

Question 30

Outline importance of movements of molecules, organelles and cells

Answer 30

Molecules move spontaneously by diffusion and Brownian motion; some movements require energy from hydrolysis of ATP: active transport, movement of cell membranes, nerve growth, muscle contraction etc.; all require specialised motor proteins

Question 31

What is a motor protein?

Answer 31

Proteins, such as myosin or kinesin, that uses energy derived from ATP hydrolysis to propel itself along a protein filament

Question 32

What is cancer?

Answer 32

Cancer is a disease caused by abnormal and uncontrolled cell division resulting in localised growths, or tumours, which may spread throughout the body

Question 33

What mutations can lead to cancer?

Answer 33

• Switch on “divide” signals or switch off “don’t divide” signals
• Loss of correction mechanism on DNA copying
• Loss of escape mechanism from cell division
• Ability to evade body defence mechanisms
• Ability to recruit blood vessels to growing tumour
• Ability to establish tumours in the “wrong” tissue