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BCH1002 Biochemical Aspects of Health and Disease. BIOMOLECULES AND METABOLISM 2. From Systems to Cells and Biomolecules. Prof. K. M. Chan Dept. of Biochemistry Chinese University Rm 513B, Basic Medical Sciences Building Tel: 3163-4420; Email: kingchan@cuhk.edu.hk ; chankingming@gmail.com.

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bch1002 biochemical aspects of health and disease

BCH1002Biochemical Aspects of Health and Disease

BIOMOLECULES AND METABOLISM2. From Systems to Cells and Biomolecules

Prof. K. M. Chan

Dept. of Biochemistry

Chinese University

Rm 513B, Basic Medical Sciences Building

Tel: 3163-4420;

Email: kingchan@cuhk.edu.hk; chankingming@gmail.com

Reference: On-Line Biology Book

http://www.estrellamountain.edu/faculty/farabee/biobk/biobooktoc.html

contents
Contents:
  • Biological Systems
  • Organizations of Cells
  • Organelles and their functions
  • Nucleic Acids: DNA and RNA
  • Proteins and amino acids
  • Sugars and carbohydrates
  • Fatty acids, lipids & membranes
  • Conclusions and revision exercises.
2 1 from systems to cells
2.1 From Systems to Cells
  • Systems> Organs> Tissues> Cells.
  • Various systems for specific life functions: Reproductive, cardiovascular (circulation), respiratory, nervous, digestive, endocrine, immune, etc.
  • Organs: specialized tissues for a unique function are to form an organ, e.g. pancreas, liver, lung, heart, intestine, brain, etc.
  • Tissues: Different cell-types for one unique task, e.g. pituitary gland to produce hormones, muscles (skeletal, cardiac, smooth muscles) to control movement, etc.
  • Cells: Specific cell type for one sole function, e.g. somatotroph is for growth hormone production and secretion, βcells in pancreas for insulin production and secretion.
slide5

Human Body Systems A Pathfinder for science students; visit this site to view different systems:http://pio.wsd.wednet.edu/library/body/bodypf.html

The Endocrine System

Hormone receptor

http://www.estrellamountain.edu/faculty/farabee/biobk/BioBookENDOCR.html

the reproductive systems
The Reproductive Systems

http://www.estrellamountain.edu/faculty/farabee/biobk/BioBookREPROD.html

slide7

Neuron

Bone

http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookAnimalTS.html#Muscle%20Tissue

Skeletal Muscle

2 2 molecular organization of cells
2.2 Molecular Organization of Cells
  • Cells are basic units of function and structure
  • Robert Hooke (1665) first used cells (tiny boxes) to describe the structure which he observed inside a slice of cork under a microscope.
  • All cells are now known to be enclosed by a membrane that control the materials to go in and out of the cells.
  • All cells contain DNA as their genetic materials. Viruses could use either RNA or DNA as their genetic materials.
slide9

http://www.estrellamountain.edu/faculty/farabee/biobk/BioBookCELL2.htmlhttp://www.estrellamountain.edu/faculty/farabee/biobk/BioBookCELL2.html

size range of cells
Size Range of Cells
  • Small molecules (chemicals) < 1 nm (10-9 m)
  • Proteins and lipids- biomolecules < 10 nm
  • Ribosomes= 20 nm; viruses < 100 nm
  • Bacteria nm, 1 µm to 10 µm (10-6 m)
  • Mitochondrion, 2 µm; Nucleus, 7 µm
  • Plant and animal cells: 10-100 µm
  • Frog egg, 2 mm; salmon egg, 6 mm
  • Chicken egg, 4-5 cm
  • Length of muscle and nerve cells: 50-70 cm.
slide11

Bacterial cells with thick cell wall made of carbohydrates, could be differentiated as Gram + and – cells by Gram’s stain.

Mesosome is infolding of membrane for specialized functions

Cell wall

Capsule

http://www.bact.wisc.edu/themicrobialworld/structure.html

Mesosome

Membrane

Nucleoid (DNA) region

Ribosomes

Contains lipo- polysaccharides (LPS) which are endotoxins of animals; but Gram-neg cells are sensitive to pennicillin and lysozyme.

Flagella

2 2 1 compare and contrast prokaryotic cells and eukaryotic cells
Prokaryotic cells

Small (1-5 μm diameter)

No intracellular membrane organelles.

Nucleoid with circular genomic DNA in cytoplasm, transcription and translation occur together.

Often with cell wall for protection.

E.g. bacterial cells

Eukaryotic cells

Larger and more complex cell (10 – 100 μm in length)

Membraneous organelles for specific functions, e.g. mitochondria for respiration.

Nucleus contains nuclear membrane, and genetic materials of DNA. After transcription, mRNA is processed and sent out of the nucleus for translation.

Intracellular cytoskeletons.

E.g. human, animal, plant and yeast cells.

2.2.1 Compare and contrast prokaryotic cells and eukaryotic cells
2 2 2 animal cells and plant cells
Compare (both are)

Eukaryotic cells

Contain organelles, for specific function

Contain mitochondria

Cytoskeleton (protein molecules) to hold up shape and structures

Nucleolus in nucleus for rRNA synthesis

Both contain rough endoplasmic reticulum and rough endoplasmic reticulum

2.2.2 Animal cells and plant cells
animal cells and plant cells
Contrast

Plants cells and fungal cells have cell wall which is made of carbohydrate.

Plant cells have mitochondria and chloroplast is only found in plants

Vacuole and storage granules in plant cells for water control and nutrient storage

Animal cells have lysosomes for digestion, microtubules, microfilaments, and centrioles for intracellular transport and cell division.

Animal cells and plant cells
slide15

Adapted from Molecular Expression (http://micro.magnet.fsu.edu/cells/plantcell.html)

slide16

Mitosis and cell cycle

http://teachline.ls.huji.ac.il/72373/substance_x/cell-cycle2.jpe

http://www.cancerquest.org/index.cfm?page=58

slide17

Differentiation

Adapted from the Merck Manuals On-line Medical Library: http://www.merck.com/mmhe/sec01/ch001/ch001b.html#sec01-ch001-ch001b-6

2 3 organelles and their functions
2.3 Organelles and their functions
  • Cell is the basic unit of life defined by cell boundary set with membrane
  • In eukaryotic cells, membranes also define cellular organelles to carry out different specific functions at a well defined location: compartmentation.
  • Membrane is a selectively permeablebarrier between the cell and the external environment.
  • The lipid bilayer structure defines inner membrane and outer membrane sides. Two sides of the membrane show different properties.
  • Homeostasis- selective permeability allows the cell to maintain a constant internal environment.
  • Each organelles carry out a specific function
2 3 1 the nucleus
2.3.1 The Nucleus
  • Bound by double membrane envelope that continues with endoplasmic reticulum.
  • There are nuclear pores to communicate with outside of the nucleus. “Gating” is necessary to ensure the various events impinging on gene transcription and cell signaling.
  • Luminal subunits in between the outer and inner membrane of the nucleus control the nuclear pores with a ring structure and nuclear cage.
  • Nucleolus is a structure inside the nucleus with chromatin actively transcribing ribosomal RNAs.
slide20

Nuclear translocator protein (vehicle)

Architectures of nucleus

Pore complex

Outer membrane

Inner membrane

Luminal subunit

Chromatin: DNA with histones and non-histone proteins

Nuclear pores

Ribosome: RNA translated to protein

Inner membrane

Outer Nuclear membrane

Rough Endoplasmic Reticulum

Nucleolus: ribosomal RNA genes being transcribed.

2 3 2 endoplasmic reticulum er
2.3.2 Endoplasmic Reticulum (ER)
  • It spans the entire cell and attaches with numerous ribosomes for protein translation (Rough ER).
  • The proteins made in the ER are folded, may be glycosylated (post-translational modifications by adding sugars), and sorted to various parts of the cell.
  • ER also produces phospholipids (smooth ER).
  • It is also a depot of calcium ions (smooth ER) in the cell for controlling the signalling of cellular processes.
slide22

Rough ER dedicated for protein production

http://cellbio.utmb.edu/cellbio/ribosome.htm#Ribosome-Endoplasmic%20Reticulum

From RER to Golgi Apparatus

http://cellbio.utmb.edu/cellbio/golgi.htm

2 3 3 the golgi apparatus
2.3.3 The Golgi Apparatus
  • Proteins made in the RER are sorted and processed in the Golgi apparatus.
  • They enter the Golgi at the cis face from vesicles formed at the ends of the ER.
  • In the cisternae, proteins are labelled (secondary modification), sorted and delivered to the trans face of the Golgi apparatus.

http://sun.menloschool.org/~birchler/cells/animals/golgi/structure.html

protein sorting trafficking
Protein sorting (trafficking)
  • As vesicles formed in the Golgi, they are sent to proper locations for specific function to be carried out in other organelles or stored as secretory vesicles.
  • Proteins in vesicles would accumulate and wait for signal to be exported out by exocytosis (either regulated or constitutively secreted out of the cells.
  • Some proteins are delivered to and kept on cell membrane.
slide25

Rough Endoplasmic Reticulum and Golgi Apparatus

Lysosome

Early endosome

Rough Endoplasmic Reticulum

Engulfed materials

Regulated secretory pathways

Vesicle

Trans Golgi apparatus

Constitutive secretory pathway

Cis-Golgi apparatus

Golgi Apparatus

Proteins are further modified and sorted in the Golgi apparatus

2 3 4 the lysosome
2.3.4 The Lysosome
  • An intracellular digestive organ with acidic condition to digest and remove unwanted materials or break down materials for cellular uptake or re-use.
  • It contains digestive enzymes (primary lysosome).
  • After bud off from the Golgi, the enzymes may be released outside of the cellular membrane or fused with autophagic vesicles to form phagocytic vacuoles (secondary lysosomes) or endosomes).
  • Autophagy: degradation of intracellular components in lysosomes.
  • The debris could be discarded outside of the cell or kept as granules or recycle to cytoplasm.
2 3 5 the mitochondrion
2.3.5 The MITOCHONDRION
  • Has double membrane: inner and outer.
  • The inner membrane fold to create the matrix space and inter-membrane space in between inner and outer membrane.
  • The matrix contains enzymes to oxidize metabolites
  • The inter-membrane has potential gradient generated by pumps at the inner membrane, energy released from the gradient produce ATP energy.
slide28

Outer membrane, with channel forming proteins but only permeable to 5 kDa molecules or less. Other enzymes on this membrane facilitate metabolism of lipid for use in matrix and transport of specially required protein in the mitochondrion.

MAJOR FUNCTION OF MITOCHONDRION: OXIDATIVE PHOSPHORYLATION (oxidation of NADH to produce ATP)

Matrix, internal space with enzymes for oxidation of pyruvate and fatty acids and for the citric acid cycle (Kreb’s cycle).

Cristae in boxed region

Intermembrane space, for enzymes using ATP passing out of the matrix to phosphorylate other nucleotides.

Inner membrane, folded into numerous cristae to increase total surface area for electron-transport chain (respiratory enzymes), ATP synthase and transporters for metabolites going through the matrix.

2 4 dna and rna
2.4 DNA and RNA

Translation

Transcription

Protein

RNA

DNA

Reverse Transcription

The Central Dogma of Life

Replication

transmission of genetic information

Specific

Cellular Function

Transmission of Genetic Information

Polypeptides

RNA

RNA polymerase

Amino acids

DNA

Replication

Semi-conservative

Translation

or

Protein Synthesis

Transcription

or

RNA synthesis

2 4 1 differences between dna and rna
2.4.1 Differences between DNA and RNA

DNA, 2-deoxyribose sugar linked with A, G, C, or T bases.

Usually double stranded

For storage of genetic information

RNA, ribose sugar linked with A, G, C, or U bases.

Usually single stranded

For gene expression, but some viruses use RNA as genetic materials

PO4

PO4

5

5

CH2

CH2

O

O

Base

1

Base

4

2

3

3

OH

OH

OH

H

slide32

2.4.2 Formation of 5’ – 3’ Phosphodiester Bond

PO4

RNA

5

CH2

DNA

O

O-

1

Base

5

4

2

OCH2

3

P

O-

Hydroxides can attack phospho-diester bond and cleave RNA, hence DNA is more stable.

O

1

Base

O-

O

OH

4

2

3

O

P

= O

PO4

OH

Phosphodiester bond linkage

H

O

OH

5

5

CH2

CH2

O

O

1

Base

1

Base

4

4

2

2

3

3

OH

H

OH

H

2 4 3 dna structure
2.4.3 DNA Structure
  • Watson-Crick double helix (B-DNA)
  • Anti-parallel strands going opposite direction
  • A-T and G-C base pairing with hydrogen bonds (2 bonds for A=T, 3 bonds for G C)
  • A gene is a segment of DNA that controls and directs the synthesis of a polypeptide
  • Chromosome is a much larger structure with histones and other proteins packing up the DNA molecules with functional and structural DNAs.
the dna double helix

Double helical structure of DNA and chromatin

The DNA Double Helix

5’

3’

Anti-parallel stranded with hydrogen bonds between bases to join the helixes together

11 nm in diameter

H1

2 nm in diameter

H2A

H2B

H3

H4

Histone protein

3’

5’

Nucleosome core has 4 histones wrapped with one and three-quarters turns of DNA; H1 histone stays in between core; forming condensed fiber of 30 nm in chromatin structure. Each chromosome is 1 μm in diameter. Histones protect DNA from degradation by enzymes.

bases at and gc pairing
Bases: AT and GC pairing

Pyrimidines:

C, T

NH

Guanine

H

O

N

H

C

Purines: A, G

HC

C

C

C

N

C

HC

HN

N

Cytosine

C

N

C

N

HN

O

H

Hydrogen bond distance: 0.28 – 0.30 nm

Adenine

H

CH3

HN

N

O

H

C

Thymine

C

C

C

C

N

C

HC

HN

N

C

N

C

N

H

O

1.08 nm

slide36

2.4.4 Genetic Information can be decoded by transcription

Eukaryotes: genes have introns and exons

Prokaryotes: polycistronic, co-translation

exon

mRNA

Introns, intervening region (uncoding)

AAAAA

RNA splicing

AAAAA

Mature messenger RNA

AAAAA

Nucleus

Cytoplasm

Translation in rough endoplasmic reticulum or polysomes area

Proteins made

Polycistronic: one mRNA codes for several proteins

2 4 5 rna ribonucleic acids
2.4.5 RNA, ribonucleic acids
  • All cellular RNAs are copied (transcribed) from a DNA template in the process of gene transcription.
  • Only messenger RNAs are further translated to make proteins.
  • Ribosomal RNAs and transfer RNAs do not make proteins directly but they form the translational machinery for protein synthesis.
  • Micro RNAs are small RNA molecules for gene regulation, they bind and cleave mRNAs to control gene expression.
slide38

Types and structures of RNAs

O

Uracil

H

H

N

  • RNAs use uridine instead of thymine
  • Uracil could be produced by deamination of cytosine
  • RNAs are single stranded
  • They form secondary structures
  • They may form hairpins in G+C rich or A+U regions

O

N

H

PO4

Ribose

OH

OH

U

U

U

U

U

C

G

C

C

G

C

G

C

G

C

G

C

G

AAUUUU

UUUUUUU

rnas have specific functions
RNAs have specific functions
  • Messenger RNAs carry information for amino acid sequence of a polypeptide chain to the ribosomes for translation for protein synthesis
  • Transfer RNAs are small molecules of 80 nucleotides that form three-dimensional structure and carry amino acids individually for translation
  • Ribosomal RNAs are part of the ribosomes with large size to form ribonuleoproteins for protein synthesis
  • Small nuclear RNAs and small cytoplasmic RNAs are for splicing, gene regulation, and control of gene expression.
slide40

Methionein

3’

ACC

Amino acid attachment site

5’

microRNA to cleave RNA at specific sites

3’-OH

Anticodon

ACC

UAC

3’

5’

5’

AUGAGC

3’

Codon

5’

Acceptor Stem

TψC loop

DHU loop

Extra Arm

Anticodon

2 5 proteins and amino acids
2.5 Proteins and Amino acids
  • Proteins are polypeptides.
  • Polypeptides is a polymer of amino acids connected in a unique sequence.
  • Amino acids are organic molecules possessing both carboxyl and amino groups with a side chain carrying different functional groups.
  • The carboxyl group of an amino acid is linked with the amino group of another amino acid and thus the amino acids are linked a polymer of polypeptide.
  • Different polypeptides can further linked together to make a larger protein complex.
2 5 1 an overview of protein functions
2.5.1 An overview of protein functions
  • Structural and support
  • Storage of amino acids or useful chemicals
  • Transporters
  • Hormones (messenger)
  • Receptors (membrane or cellular)
  • Contractile and movement
  • Enzymes
  • Antibodies for recognition
  • Transcription factors for DNA interactions

2.4 Proteins and Amino acids

2 5 2 amino acids
At the center of the amino acid is an asymmetric carbon atom called alpha (α) carbon.

The side-chain differs with amino acids.

The R group may be as simple as hydrogen in glycine, or a carbon skeleton with functional groups attached as in glutamine.

Peptide bond CO-NH is formed by dehydration.

2.5.2 Amino acids

H

O

H

C

C

N

OH

H

R

Amino

Group

Carboxyl end

Side Chain

  • Polar, e.g. cysteine
  • Non-polar, e.g. glycine
  • Acidic, e.g. aspartic acid
  • Basic, e.g. lysine, arginine

2.4 Proteins and Amino acids

slide44

http://www.estrellamountain.edu/faculty/farabee/biobk/BioBookCHEM2.htmlhttp://www.estrellamountain.edu/faculty/farabee/biobk/BioBookCHEM2.html

slide45

http://www.estrellamountain.edu/faculty/farabee/biobk/BioBookCHEM2.htmlhttp://www.estrellamountain.edu/faculty/farabee/biobk/BioBookCHEM2.html

slide46

http://www.estrellamountain.edu/faculty/farabee/biobk/BioBookCHEM2.htmlhttp://www.estrellamountain.edu/faculty/farabee/biobk/BioBookCHEM2.html

2 5 3 synthesis of polypeptide
2.5.3 Synthesis of polypeptide

stop

3’

5 ‘

Start

Termination

Elongation

40 S 60 S

Initiation

In a polypeptide, the amino acids are joined with peptide bond between acid group of one amino acid and the amino group of another.

slide48

http://www.estrellamountain.edu/faculty/farabee/biobk/BioBookPROTSYn.htmlhttp://www.estrellamountain.edu/faculty/farabee/biobk/BioBookPROTSYn.html

aminoacyl trna synthetase reaction
Aminoacyl-tRNA synthetase reaction
  • The synthetase forms aminoacyl-AMP for the amino acid to be added to the 3’ end of the tRNA with the pyrophosphate.
  • Each amino acid would have their specific aminoacyl-tRNA synthetase.

ribosome

ATP

mRNA

2.4 Proteins and Amino acids

slide50

A; anterior; P: posterior; E: exit sites

P site

Recognition of codon

E site

A site

mRNA for translation

Peptidyltransferase

Peptide Bond Formation and moving onto P site, making the previous tRNA leave the P site and the A site for incoming tRNA-aa, until the stop codon appears. tRNA moves to E site to exit.

Translocase

2.4 Proteins and Amino acids

2 5 4 selected antibiotics work as inhibitors of protein synthesis
2.5.4 Selected antibiotics work as inhibitors of protein synthesis

Tetracycline inhibits initiation by binding to the A site.

Initiation

Streptomycin, Neomycin, Kanamycin, they can sit into the P site

Recognition of codon

Chloramphenicol, Puromycin, Erythromycin

Peptidyltransferase

Translocase

Cycloheximide, Erythromycin, Fusidic acid

Termination

2 6 sugars and carbohydrates
2.6 Sugars and carbohydrates
  • Carbon fixation: Plants produce sugars and carbohydrates using CO2 and sun-light with Calvin Cycle.
  • Simplest carbohydrates are monosaccharides (single sugars) and disaccharides (double sugars).
  • Polysaccharides are polymers of sugars.
  • Open structure (straight-chain) and Harworth “ring” structure (2 conformers: cup or chair form).
  • They are used as energy source, structural supports, cell-cell communication or intercellular interaction (recognition).
2 6 1 monosaccharides
Aldoses

Triose sugars: glyceraldehyde

Pentose sugar: Ribose

Hexose sugars: glucose and galactose

Ketoses

Triose sugars: dihydroxyacetone

Pentose sugar: Ribulose

Hexose sugars: fructose

2.6.1 Monosaccharides

w/ a keto group

w/ an aldehyde group

2 6 2 disaccharides
2.6.2 Disaccharides
  • Maltose is 2 glucose linked with 1-4 glycosidic linkage)
  • Sucrose is a fructose linked with glucose with 1-2 glycosidic linkage)
  • We need to digest these sugars in the intestine into monosaccharides for uptake in gut via glucose transporters.

Disaccharides formed from dehydration (condensation).

2 6 3 polysaccharides
2.6.3 Polysaccharides
  • Starch (amylose and amylopectin) in plants and glycogen (condensed glucose in muscle and liver) in animals are ENERGY storage polysaccharides.

The followings are structural polysaccharides:

  • Cellulose in plants’ cell wall and chitin in exoskeletons of arthropods are structural polysaccharides.
  • Dextran and peptidoglycan (with peptides added) are found in bacteria.
  • Agarose are found in algae as cell wall materials.
  • Hyaluronate is a glycosaminoglycan (acidic) found in vertebrates.
slide56

http://www.estrellamountain.edu/faculty/farabee/biobk/BioBookCHEM2.htmlhttp://www.estrellamountain.edu/faculty/farabee/biobk/BioBookCHEM2.html

2 7 fatty acids and lipids
2.7 Fatty acids and lipids
  • Lipids are hydrophobic (insoluble in water)
  • Fat molecule is triacylglycerol with ester linkages of three fatty acids with to a glycerol
  • Two types of fatty acids: saturated and unsaturated
slide58

Adapted from Alberts et al., 1998. Essential Cell Biology. An Introduction Biology of the Cell. Garland Pub.Inc.

2.6 Fatty acids and lipids

slide60

2.7.2 Common unsaturated fatty acids

Unsaturated fatty acids remain liquid at low temperatures and become denatured as the temperatures increase, however saturated fatty acids are more stable than unsaturated fatty acids at high temperatures. The membranes of psychrophilic (cold-loving) bacteria have high content of polyunsaturated fatty acids and thermophilic bacteria use mainly saturated fatty acids.

slide61

Melting points of saturated fatty acids increase with increasing molecular weight; melting points of unsaturated fatty acids are determined by the number of double bonds (trans C-C bonds rotate 120 O).

Changes from a gel state to a liquid state at special melting temperature

90

20

Melting Point ºC

Melting Point ºC

80

10

70

0

60

The melting points of saturated fatty acid increase with increasing molecular weight

-10

50

40

-20

30

8 10 12 14 18 22 26 28

1 2 3 4

Number of carbon

Number of double bonds

fatty acids fas form the basic structures of phospholipids
Fatty acids (FAs) form the basic structures of phospholipids

2.7.3 Structure of lipid bilayer and phospholipids forming cell membranes

Phospholipid molecule

Hydrophilic head on surface

Polar group

Hydrophilic head

water

Phosphate

Hydrophobic core of lipid bilayer

Glycerol

Hydrophobic fatty acid tails

Fatty acid-(unsaturated)

Hydrophilic head to cytoplasm

Fatty acid (saturated)

cholesterol stays in between fatty acids with its rigid planar steroid ring
Cholesterol stays in between fatty acids with its rigid planar steroid ring

Polar Head

Polar Head

Phosphate

Glycerol

Fatty acid-(unsaturated)

Hydrophobic fatty acid tails

Rigid Planar Steroid Ring

Non polar hydrocarbon Tail

slide64

Lipids are water insoluble, fluid-like property, and amphipathic in nature.

Hydrophilic

hydrophobic

A liposome formed with micelles or lipid bilayer.

hydrophilic

Hydrophobic

water

Lipid on the surface of water

Bubbles with soap trapping a layer of water inside with the detergents at the outside: just the reverse of the lipid bilayer.

Lipid bilayer

hydrophobic

hydrophilic

water

hydrophilic

water

water

hydrophobic

slide65

The asymmetrical nature of plasma membrane: polar heads of phospholipids and carbohydrates of glycolipids vary on two sides of the lipid bilayer; protein orientations also vary but are fixed too.

carbohydrates

Cell Wall

Rotations occur

Lipid bilayer

Peripheral proteins

Integrated Protein (NO flip-flopping)

Fluid Mosaic Model of Plasma Membrane: Lipids and Proteins are free to rotate and move but can hardly flip-flop; some proteins are controlled by peripheral protein underneath of the membrane. The two sides of the membranes are not the same (asymmetrical).

2 8 conclusions
2.8 Conclusions:
  • We have reviewed the biomolecules in our body and the order of these chemicals in making up a dynamic cell.
  • Four different types of chemicals (nucleic acids, protein, carbohydrate, lipids) have different chemical properties, structures and functions.
  • From cells to tissues and organs, systems building up an organism in a coordinated way.
  • All cells have DNA as genetic materials that can be converted into messengers to produce proteins for specific function temporally and spatially.
  • These biomolecules follow basic chemical rules to make living organisms perform their biological activities.
revision exercises
Revision Exercises:
  • Compare and contrast the structures and chemical properties of DNA and RNA.
  • Explain the compositions of plasma membrane and how cholesterol could affect the membrane fluidity.
  • Why some antibiotics are specific to kill bacterial cells and some could kill fungal cells?
  • List the organelles and their specific functions.
  • Compare and contrast the structures and characteristics of eukaryotic cells and prokaryotic cells.
  • Compare and contrast the mechanisms of gene expression in prokaryotic cells and eukaryotic cells.
multiple choice questions
Multiple Choice Questions
  • Which ONE of the following chemical bonds is the major force in maintaining membrane structure and protein folding?

A. Hydrogen bonds

B. Ionic interactions

C. Hydrophobic interactions

D. Van der Waals interactions

E. Covalent bonding

  • Which ONE of the followings are structural polysaccharides found in the liver of animals?

A. Agarose

B. Hyaluronate

C. Cellulose

D. Dextran

E. Glycogen

  • Which ONE of the following statements on the properties of fatty acids is INCORRECT?

A. Unsaturated fatty acids remain liquid at low temperatures and become denatured as temperatures increase.

B. Saturated fatty acids are more stable than unsaturated fatty acids at high temperatures.

C. Thermophilic bacteria use mainly saturated fatty acids.

D. Melting points of saturated fatty acids decrease with increasing molecular weight.

E. Melting points of unsaturated fatty acids are determined by the numbers of double bonds, the more the double bond numbers the lower their melting points.