Eukaryotic Cell Ultrastructure

Question 1

what is the Cell Theory?

Answer 1

• cell is a basic unit of life
• organisms of single cells are unicellular and many cells are multicellular
• arise through cell division
• contains information for growth, development and functioning
• chemical reactions that maintain life take place in cells

Question 2

what does the cytoplasm include?

Answer 2

• cytosol; fluid component that contains essential ions
• cytoskeleton; supports the cell to maintain shape
• organelles; carries out functions to maintain the cell

Question 3

structure of the nucleus?

Answer 3

• double membrane known as nuclear envelope
• outer membrane continuous with the ER
• inner membrane in contact with nucleus contents
• nuclear pores in membrane
• one or more nucleolus
• contains almost all DNA
• largest organelle (10-20 micrometers)

Question 4

function of the nucleus?

Answer 4

• controls cellular activities
• basis of cell replication
• synthesis and partial assembly of ribosomes

Question 5

function of the cell surface membrane?

Answer 5

• partially permeable membrane
• barrier that protects cytoplasm from the surroundings
• prevents most water-soluble substances from passing through the membrane

Question 6

structure of the centrioles?

Answer 6

• only in animal cells
• cylindrical structures made of microtubules
• 2 centrioles are centrosome
• centrosome in animal cells
• centriole in cilia and flagella

Question 7

function of centrioles?

Answer 7

• produces spindle fibers that attach to chromosomes and split them up for cell division
• formation of flagella and cilia

Question 8

structure of ribosomes?

Answer 8

• no membranes
• made of protein and ribonucleic acid
• 20 nanometers as diameter
• attached to the rough endoplasmic reticulum
• free ribosomes in the cytosol

Question 9

function of ribosomes?

Answer 9

site of protein synthesis

Question 9

structure of endoplasmic reticulum?

Answer 9

• consists of network of membranous tubes and sacs called cisternae
• rough endoplasmic reticulum have ribosomes present on the surface
• smooth endoplasmic reticulum have no ribosomes present and more tubular

Question 10

function of endoplasmic reticulum?

Answer 10

• rough endoplasmic reticulum synthesizes proteins
• smooth endoplasmic reticulum synthesizes lipids

Question 11

structure of Golgi apparatus?

Answer 11

• flattened membrane-bound sacs called cisternae
• formed at cis face
• budded off at trans face

Question 12

function of Golgi apparatus?

Answer 12

• chemically modifies, sorts and transports molecules
• lysosome formation

Question 13

structure of lysosome?

Answer 13

• bound by a single membrane
• contains hydrolytic digestive enzymes

Question 14

function of lysosome?

Answer 14

• digestion of materials taken in by cells
• autophagy of improperly functioning organelles
• autolysis by release of contents

Question 15

structure of mitochondria?

Answer 15

• double membrane, outer and inner membrane separated by an inter-membrane space
• outer membrane is a smooth and continuous boundary
• inner membrane is folded to form cristae to project the matrix
• contains DNA, RNA and ribosomes

Question 16

function of mitochondria?

Answer 16

involved in cellular respiration to release energy

Question 17

structure of chloroplast?

Answer 17

• double membrane
• outer membrane is smooth and continuous
• inner membrane give rise to lamellae and thylakoids surrounded by stroma (gel-like)
• contains chlorophyll

Question 18

function of chloroplast?

Answer 18

site of photosynthesis

Question 19

structure of vacuole?

Answer 19

• single membrane filled with liquid
• surrounded by tonoplast and cell sap in plant cells
• are vesicles in animal cells

Question 20

function of vesicle?

Answer 20

• contains pigments
• act as food reserves
• accumulates waste products

Question 21

structure of cell wall?

Answer 21

• made of cellulose
• surrounds planet cells
• strong, rigid and permeable

Question 22

function of cell wall?

Answer 22

• mechanical support
• protective layer

Question 23

what are the steps of the protein secretory pathway?

Answer 23

1. ribosome bound to the RER synthesize polypeptide chains into RER
2. ER vesicle containing the protein buds off the RER
3. vesicle travels and fuses with the cis face of the Golgi apparatus
4. GA chemically modifies, sorts and transports the protein by budding of one cisterna and fusing with another
5. secretory vesicle buds off the trans face of the GA
6. secretory vesicle travels and fuses with the cell surface membrane and released out of the cell