cell structure

what is the structure of nucleus

• Spherical organelle

• Contains nucleolus  + chromatin 

• Surrounded by nuclear envelope

what is the function of nucleus?

1. Contains hereditary material (DNA) + enzymes

• Enzymes that participate in:

1. DNA replication

2. RNA processing

3. Transcription 

1. Control cell activities by regulating protein synthesis

what is the structure of nucleolus?

Contain large amount of DNA and rRNA and protein

what is the function of nucleolus?

1. Synthesize rRNA

2. Site assembly of rRNA and proteins (that are exported from the cytoplasm)

• Form large and small ribosomal subunits

what is the structure of chromatin?

Long and elongated threads of DNA coiled around histone protein

what are the 2 types of chromatin?

1. Euchromatin

   • Transcriptionally active  

2. Heterochromatin

   • Transcriptionally inactive 

what is the function of chromatin?

DNA contains genes that will be transcribed to mRNA and translated into polypeptides when it is exported out of the nucleus

what is the structure of RER?

• Flattened sacs : cisternae 

• Has ribosomes on outer surface

• Continuous with outer membrane of nuclear envelope

what is the function of RER?

1. Transport protein

   • Which are synthesised by ribosomes on the surface to Golgi via transport vesicles

2. Fold

   • Allow protein to fold into their native conformation 

3. Glycosylated proteins  → glycoproteins

what is the structure of SER?

• Tubular sacs: cisternae 

• No ribosomes

what is the function of SER?

1. Synthesise carbohydrates and lipids 

2. Detoxify drugs and poison

   • abundant at liver 

3. Store Mg2+

what is the structure of Golgi Apparatus?

• Flattered sacs: cisternae 

• Forms “trans” and “cis” face 

what is the function of Golgi Apparatus?

1. Glycosylated protein+lipid ⇒ glycolipid + glycoprotein 

2. Modify existing glycoproteins/lipids by cleaving exiting sugar chain

3. Lysozyme (form)

4. Sort + package protein into transport vesicles and target them to different parts of the cell for secretion out of the cell 

5. Synthesis polysaccharides 

   • E.g: pectin

   • To transport it via transport vesicle out of the cell

what is the structure of lysozyme?

Membranous sacs containing hydrolytic enzymes

what is the function of lysozyme?

1. Digest material taken in by cell via endocytosis 

2. Digest unwanted/worn out organelles 

3. Release enzymes via exocytosis out of the cell for extracellular digestion

4. Self destruct cell that undergoing cell death

what is the structure of mitochondria?

• Rod shaped structure 

• Double membrane:

  a. Outer membrane

  • Smooth  

  b. Inner membrane

  • Highly folded membrane: cisternae 

• ATP synthetase complex in inner membrane projects into matrix

what is the function of mitochondria?

1. Site of aerobic respiration to generate energy in the form of ATP 

   a. Inner mitochondrial membrane 

   • Increased surface area = ⬆oxidative phosphorylation 

   b. Mitochondrial matrix

   • Site of Kreb cycle and Link Reaction

Mitochondrion vs mitochondria

Singular vs plural

what is the structure of chloroplast?

• Len shape structure 

• Double membrane 

  a. Internal membrane 

  • Contain flattened sac: (thylakoid)

  • Stack of thylakoid (granum) 

• Fluid in the chloroplast = stroma

• Chlorophyll molecules are located on thylakoid membrane 

• ATP synthetase complex in thylakoid membrane projects into stroma

what is the function of chloroplast?

• Contains chloroplast that converts solar energy → light energy through photosynthesis 

  a. Site of light-independent reaction

  • stroma

  b. Site light-dependent reaction 

  • Thylakoid  membrane

what is the structure of ribosome?

• Large and small subunit made of rER and protein 

• Found freely floating in cytosol/bound to rER

what is the function of ribosome?

Site of protein synthesis

what is the structure of centrioles?

• A pair of hollow cylinder made of 9 triplets of microtubules 

• Found in centrosomes

what is the function of centrioles?

• Organise spindle fibres during nuclear division 

• Determine polarity of the cell

compare prokaryotes VS eukaryotes:

size

1. pro

   • small (0.5-5)

2. eu

   • large (10-100)

compare prokaryotes VS eukaryotes:

nucleus

1. pro

   • no true nucleus

2. eu

   • nucleus + nuclear envelope

compare prokaryotes VS eukaryotes:

DNA

1. pro

   • Linear DNA + histone like protein 

     • Plasmid present

2. eu

   • Circular dna + histones 

     • No plasmid

compare prokaryotes VS eukaryotes:

membrane-bound organelles

1. pro

   • no

2. eu

   • yes, many

compare prokaryotes VS eukaryotes:

ribosomes for protein synthesis

1. pro

   • 70s – freely roaming around cytoplasm

2. eu

   • 80s

     • Either attached to the rough endoplasmic reticulum 

     • Freely floating around cytoplasm

compare prokaryotes VS eukaryotes:

cell wall

1. pro

   • peptidoglycan

2. eu

   • cellulose cell wall