Life at cellular level IA%%+(+

Question 1

Prokaryotic cells

Answer 1

• Lack Nuclear membrane
• No Mitochondria
• No membrane bound structures
• e.g Bacteria

Question 2

Eukaryotic cells

Answer 2

• Multicellular animals and plants
• Nucleus with membrane
• Membrane bound structures
• e.g Human cells

Question 3

Multipotent cell

Answer 3

•Cells that can differentiate into many cell type

Question 4

Pluripotent

Answer 4

Cells that can differentiate into all cell types

Question 5

Apoptosis

Answer 5

• Is a process of programmed cell death
• Is a central mechanism controlling multicellular development

Question 6

Cell membrane

Answer 6

• Selective barrier
• Detects chemical messengers and signalling molecules from surrounding cells or other organs
• Membrane lipids are amphipathic (hydrophilic head and hydrophobic tail)
• Membrane proteins (some span the membrane, others are embedded in the membrane)

Question 7

Diffusion

Answer 7

Passive diffusion

• Concentration gradient needed
• Lipid-soluble molecules pass freely (non-polar)

Facilitated diffusion

• Concentration gradient needed
• Requires carrier molecules

Question 8

endocytosis

Answer 8

Mechanisms for moving macromolecules across membranes without disrupting them.

There is an invagination (turned inside out) of the membrane to form a vesicle which eventually separates on the cytoplasmic (inside) surface of the membrane and migrates within the cell to its destination.

Question 9

Exocytosis

Answer 9

The merging of vesicles with the plasma membrane to release materials from the cell.

Question 10

Mitochondria

Answer 10

• Outer membrane contains pores (porin protein)
• Inner membrane has cristae
• Matrix contains binding sites for calcium and also most of the enzymes for oxidation of food molecules (e.g. Krebs cycle)

They also have:

• Their own circular DNA
• Ribosomes – similar to bacterial ribosomes
• Synthesise most of their own proteins
• Self-replicate

Question 11

Nucleus

Answer 11

• Contains DNA, nucleoprotein and some RNA
• Nucleoli are sites of ribosomal RNA synthesis and ribosomal assembly
• DNA tends to be one of two forms:Heterochromatin, Euchromatin

Nuclear Membrane (Envelope)

• Phospholipid bilayer
• Encloses the nucleus
• Contains pores
• Closely associated with the endoplasmic reticulum

Question 12

Endoplasmic reticulum and golgi apparatus

Answer 12

• Membrane bound
• Rough ER has ribosomes attached
• Protein modifications and transport coordinated by the RER and Golgi
• Smooth ER used mainly to breakdown compounds (e.g. drugs and glycogen) or synthesise some compounds (e.g. lipids)

Question 13

Lysosomes

Answer 13

• Used to separate enzymes from the rest of the cell
• Used in autophagy (digestion of cells own materials) or digestion of engulfed particles (e.g. bacteria)

Question 14

Cytoskeleton

Answer 14

• Supports and maintains cell shape
• Holds organelles in position
• Moves organelles
• Involved in cytoplasmic streaming (cytosol movement)
• Interacts with extracellular structures to hold cell in place

Question 15

Cell surface projections

Answer 15

Cilia and eukaryotic flagella are made of microtubules

Cilia

• short
• many present
• move with stiff power stroke and flexible recovery stroke

Flagella

• Longer
• usually one or two present
• movement is snakelike

Question 16

Nucleic acid

Answer 16

• They are polymers of nucleotide monomers linked by 3’,5’-phosphodiester bonds
• There are 2 kinds of base in nucleic acids

–Pyrimidines (flat, single rings CUT) – cytosine (C), uracil (U) and thymine (T)

–Purines (flat, double rings AG) – adenine (A) and guanine (G)

Question 17

D-glucose

Answer 17

• Reducing sugar
• The linear form (but not cyclic form) has an aldehyde group, which can be oxidised
• If this is oxidised then the other reactant would be reduced

Question 18

Triglycerides

Answer 18

• Storage lipids
• Non-polar
• 3 fatty acid chains linked to glycerol

Question 19

1st energy law

Answer 19

Energy can be converted from one form to another but the total energy of the universe remains constant

Question 20

2nd energy law

Answer 20

• All energy transformations ultimately lead to more disorder in the universe, i.e. increase the entropy
• As usable energy decreases and unusable energy increases, entropy increases
• Entropy is a gauge of randomness or chaos within a closed system. As usable energy is irretrievably lost, disorganization, randomness and chaos increase.

Question 21

Gibbs free energy

Answer 21

• Free energy change can be used to define the spontaneity of a reaction
• Spontaneous reactions can occur if a system:

-Gives up energy (water runs downhill spontaneously, giving up potential energy as it goes)

And/or

-Becomes more random and increases in entropy (complex structures decay spontaneously giving up potential energy)

Question 22

Reaction coupling

Answer 22

• Cells use a process called “energy coupling” to carry out thermodynamically unfavourable reactions
• Reaction coupled to energy-releasing reaction e.g catabolic ones

Question 23

Facts about certain Molecules

Answer 23

• Charged molecules are also water soluble (hydrophilic)
• Non-polar (uncharged) molecules are hydrophobic
• Amphipathic molecules contain both hydrophobic and hydrophilic parts e.g phospholopid
• CO₂ and O₂ are non-polar and poorly water soluble

Question 24

Water dissociation

Answer 24

• [H₂O] is very high in pure water, so it is essentially constant
• Kw is the ion product of water. Kw = 1 × 10-¹⁴ (mol/L)²

Question 25

Strong and weak acids

Answer 25

• Hydrochloric acid (HCl; produced in the stomach) fully dissociates into H+ and Cl- (chloride ion)
• Strong acids and bases fully dissociates
• Weak acids and bases are far more important in biological systems as they are only partially dissociated, which gives them some unique properties
• Lots of biomolecules (proteins, DNA) are affected by pH changes as their shape is often dictated by the pH of their environment

Question 26

Buffers

Answer 26

• Acids are defined as proton donors and bases as proton acceptors
• The stronger the acid the greater its tendency to lose its proton in (an aqueous environment) and vice versa
• A buffer is a mixture of a week acid and its conjugate base

Question 27

Buffers in the body

Answer 27

• In cells, the phosphate buffer system is important:
• And, in plasma, the bicarbonate buffer system is important:

Question 28

Metabolism, Catabolism and Anaobilism►

Answer 28

Metabolism

• Metabolism refers to the biochemical reactions that take place in an organism. It consists of two processes – Catabolism and Anabolism

Catabolism

• Catabolism deals with energy releasing processes.
• It breaks things and releases energy

Anabolism

• Anabolism is related to energy-using processes.
• It builds things and consumes energy

Question 29

Peroxisome

Answer 29

A major function of the peroxisome is the breakdown of very long chain fatty acids through beta-oxidation.

Question 30

5 chemical reactions►

Answer 30

–Redox reactions

–Making and breaking C-C bonds

–Internal rearrangements (isomers)

–Group transfers

–Condensation and hydrolysis reactions