cell structure & function

Question 1

what is the cell theory

Answer 1

1. cells are the smallest unit of life
2. all living things are made up of one or more cells
3. all cells arise form pre-exisiting cells by cell division

Question 2

2 types of cells

Answer 2

prokaryotes and eukaryotes

Question 3

describe the 2 types of cells

Answer 3

prokaryotes:
- lacks membrane-bound organelles
- lacks a nuclues so DNA is free-lying
eukaryotes:
- contains membrane-bound organelles
- has a nucleus enclosed by a nuclear envelope
- DNA is usually organised into numerous chromosomes

Question 4

nucleus structure (3) and function (2)

Answer 4

stucture:
- the largest organelle and can be seen easily under a light microscope
- spherical in shape and measures an average of 5µm in diameter
- contains DNA, where most genes that control the activities of cell are found
functions:
- contain cell’s DNA
- directs cellular activities (direct protein synthesis, to direct DNA replication during cell division)

Question 5

nuclear envelope structure (2) and function (2)

Answer 5

Structure:
- Composed of double membranes
- perforated by nuclear pores
Function:
- separates DNA in nucleus from cytoplasm
- regulate entrance and exit of small polar molecules and macomolecures

Question 6

nucleolus structure and function

Answer 6

s: largest structure in nucleus
f: site of rRNA synthesis (contains genes coding for rrna and site of t/c of genes for rrna) , site of ribosomal subunits formation

Question 7

rer structure and function

Answer 7

s: consists of networks of sheets (flattened cisternae) , ribosomes present on rer memb , er memb is continuous with outer memb of nuclear envelope
f: site of protein synthesis, intracellular transport system, modifications of proteins

Question 8

ser structure and function

Answer 8

s: consists of networks of tubules, ribosomes absent on memb of ser
f: synthesis of lipids, involved in carbohydrate metabolism, detoxification of drugs and alcohol, stores calcium ions

Question 9

golgi body structure and function

Answer 9

s: consists of a stack of flattened memb-bound sacs called cisternae, together with associated golgi vesicles
f: further protein modification, sorting, packaging of proteins ,
formation of secretory vesicles containing matured proteins which move to and fuse w CSM , releasing their contents out of cell via exocytosis
formation of lysosomes containing hydrolysis enzymes
during synthesis of new plant cell walls, vesicles containing cell wall materials fuse to form new cell plate

Question 10

lysosome structure and function

Answer 10

s: single memb bound vesicles containing hydrolysis enzymes
f: intracellular digestion, autophagy, autolysis

Question 11

mitochondrion structure and function

Answer 11

s: enclosed by double membrane, inner memb is highly folded to form cristae
contains a matrix with a few ribosomes, ds circular dna and phosphate granules
f: sute of aerobic respiration, heat production

Question 12

chloroplast structure and function

Answer 12

s: disc shaped, enclosed by a double membrane ; inner memb enclosed a fluid filled space called stroma
thylakoid -> grana -> granules , joined by intergranal lamellae
containing hydrolysis enzymes photosynthetic pigments and ds circular DNA
f: site of photosynthesis, involved in important biosynthetic processes

Question 13

ribosome structure and function

Answer 13

s: consists of small ribosomal subunit and large ribosomal subunit
f: site of polypeptide synthesis

Question 14

centrioles structure and function

Answer 14

s: exists as a pair of rod-like structures made up of 9 triplets of microtubules arranged in a ring, centriole pair is positioned at right angles to each other
f: play a role in nuclear division by acting as microtubule organising centre (MTOC)