Ultrastructure of Cells

Question 1

Prokaryotes…

Answer 1

simple cell structure w/out compartmentalisation

Question 2

Eukaryotes…

Answer 2

much more complex and compartmentalised cell structure

Question 3

How do prokaryotes divide?

Answer 3

Binary fission

Question 4

Eukaryotic cells (including plant and fungi) have:

Answer 4

cell wall

Question 5

Organelles in exocrine gland cell of pancreas:

Answer 5

Nucleus - Structure: Large organelle w/ double membrane (perforated by pores) that contains chromosomes & one+ nucleoli within it. Function: Chromosomes contain DNA which controls the synthesis of proteins. Ribosomes are formed in the nucleolus.
Endoplasmic reticulum - Structure: complex network of cisternae (flattened, membrane-bound sacs). often has ribosomes on cytoplasmic side. Attached to nucleus.
Function: Forms system of channels for transporting materials through cytoplasm.
Rough endoplasmic reticulum: Has ribosomes on its surface, & is site of protein synthesis.
Smooth endoplasmic reticulum: Has no ribosomes, & is where steroids and other lipids are synthesised.
Golgi apparatus - Structure: Stack of cisternae (flattened, membrane-bound sacs) in cytoplasm. Function: Receives proteins synthesised on ER & prepares them for secretion from cell. Involved in adding carbohydrate to proteins to make them into glycoproteins.
Ribosome - Structure: Very small organelle not bound by membrane, consisting of large & small subunit. Made of protein and RNA. Function: Uses info in nucleic acid to synthesise proteins.
Free ribosomes: Located in cytoplasm, produce proteins for cell.
Bound ribosomes: Attached to ER, produce proteins that are transported out of cell.
Lysosome - Structure: vesicle containing digestive enzymes. Function: Responsible for destroying worn-out organelles & for digesting contents of vacuoles formed by phagocytosis.
Centrioles - Structure: pair of short cylinders. Each cylinder made up of nine fibres. Function: Forms spindle-shaped structure of protein fibres, in which chromosomes move to during cell division.
Plasma membrane - Structure: phospholipid bilayer w intrinsic & extrinsic protein molecules. Function: partially permeable barrier which controls substances passing in and out of cell.
Vacuole - Structure: sac bounded by single membrane. Contains cell sap; solution of mineral salts, pigments, organic acids & other substances. Function: Stores waste products & other substances. Changes in volume affect turgidity of cell.
Mitochondrion - Structure: Has an outer & inner membrane, folded to form cristae. Inside inner membrane: matrix, containing enzymes, circular DNA molecule & ribosomes. Function: Site of aerobic respiration & responsible for producing most of ATP in a cell.

Question 6

Organelles in palisade mesophyll of leaf

Answer 6

Plasma membrane - Structure: phospholipid bilayer w intrinsic & extrinsic protein molecules. Function: partially permeable barrier which controls substances passing in and out of cell.
Vacuole - Structure: sac bounded by single membrane. Contains cell sap; solution of mineral salts, pigments, organic acids & other substances. Function: Stores waste products & other substances. Changes in volume affect turgidity of cell.
Nucleus - Structure: Large organelle w/ double membrane (perforated by pores) that contains chromosomes & one+ nucleoli within it. Function: Chromosomes contain DNA which controls the synthesis of proteins. Ribosomes are formed in the nucleolus.
Mitochondria - Structure: Has an outer & inner membrane, folded to form cristae. Inside inner membrane: matrix, containing enzymes, circular DNA molecule & ribosomes. Function: Site of aerobic respiration & responsible for producing most of ATP in a cell.
Cell wall - Structure: Consists of cellulose microfibrils & other polysaccharides. Function: Provides mechanical support & protection, & prevents cell from bursting.
Chloroplast - Structure: Surrounded by 2 membranes & contains stroma (a matrix) which has system of membranes running through it. Has grana; membranes stacked in places, which contain chlorophyll. stroma contains circular DNA, ribosomes & starch grains.
Function: Photosynthesis takes place, by pigments capturing energy of sunlight & transferring it to chemical bonds.