Cells structure

Question 1

Define the terms eukaryotic and prokaryotic

Answer 1

Eukaryotic: DNA is contained in a nucleus, contains membrane-bound specialised organelles.
Prokaryotic: DNA is ‘free’ in cytoplasm, no organelles e.g. bacteria & archaea

Question 2

State the relationship between a system and specialised cells.

Answer 2

Specialised cells –> tissues that perform specific function –> organs made of several tissue types –> organ systems

Question 3

Describe the structure and function of the cell-surface membrane

Answer 3

‘Fluid mosaic’ phospholipid bilayer with extrinsic & intrinsic proteins embedded.
. Isolates cytoplasm from extracellular environment
. Selectively permeable to regulate transport of substances.
. Involved in cell signalling/ cell recognition

Question 4

Explain the role of cholesterol, glycoproteins & glycolipids in the cell-surface membrane

Answer 4

Cholesterol: steroid molecules connect phospholipids & reduces fluidity
Glycoprotein: cell signalling, cell recognition (antigen), & binding cells together
Glycolipids: cell signalling & cell recognition

Question 5

Describe the structure of the nucleus

Answer 5

. Surrounded by nuclear envelope, a semi-permeable double membrane.
. Nuclear pores allow substances to enter/exit.
. Dense nucleolus made of RNA& proteins assembles ribosomes.

Question 6

Describe the function of the nucleus

Answer 6

. Contains DNA coiled around chromatin into chromosomes.
. Controls cellular processes: gene expression determines specialisation & site of mRNA transcription, mitosis, semiconservative replication.

Question 7

Describe the structure of a mitochondrion

Answer 7

. Surrounded by double membrane folded inner membrane forms cristae: site of electron transport chain
. Fluid matrix: contains mitochondrial DNA, respiratory enzymes, lipids, proteins.

Question 8

Describe the structure of a chloroplast

Answer 8

. Vesicular plastid with double membrane
. Thylakoids: flattened discs stacks to form grana; contain photosystems with chlorophyll
. Intergranal lamellae: tubes attach thylakoids in adjacent grana.
Stroma: fluid-filled matrix

Question 9

State the function of mitochondria and chloroplasts

Answer 9

. Mitochondria: site of aerobic respiration to produce ATP
. Chloroplasts : site of photosynthesis to convert solar energy to chemical energy

Question 10

Describe the structure and function of the Golgi-apparatus

Answer 10

Planar stack of membrane-bound, flattened sacs cis face align with rER.
Molecules are processed in cisternae vesicles bud off trans face via exocytosis:
. modifies & packages proteins for rapport
. synthesises glycoproteins

Question 11

Describe the structure and funtion of a lysosome

Answer 11

Sac surrounded by single membrane embedded H+ pump maintains acidic conditions contains digestive hydrolase enzymes glycoprotein coat protects cell interior:
. digests contents of phagosome
. exocytosis of digestive enzymes