eukaryotic cell structures

Question 1

what structures are found within the nucleus?

Answer 1

• nuclear envelope- double membrane
• nuclear pores
• chromosomes (protein bound, linear dna)
• nucleolus (site of rna production &makes ribosomes)
• nucleoplasm (granular jelly like material)

Question 2

what is the function of the cell nucleus?

Answer 2

• site of DNA replication & transcription (making mRNA)
• contains the genetic code for each cell

Question 3

describe the structure of endoplasmic reticulum

Answer 3

rough and smooth ER
- have folded membranes called cisternae
- rough has ribosomes on cisternae

Question 4

what are the roles of eukaryotic organelles in protein production?

list eukaryotic organlles and what they do - only ones involved in prote

possible exam question

Answer 4

• ribosomes/RER - site of protein synthesis
• mitchondria produce ATP for protein synthesis
• golgi apparatus package/ modify proteins OR add carbohydrate to produce glycoprotein
• vesicles transport + fuse with membrane to release contents

Question 5

what is the function of ER (endoplasmic reticulum)

hint: smooth and rough have different functions

Answer 5

RER- protein synthesis (because it contains ribosomes)
SER- synthesis and store lipids and carbohydrates

Question 6

what is the structure of golgi apparatus?

golgi apparatus often look very similar to endoplasmic reticulum, but are smaller

Answer 6

• folded membranes making cisternae
• vesicles pinch off from cisternae

Question 7

what is the function of golgi apparatus?

how do vesicles link into this?

Answer 7

• package and modify proteins
• adds carbohydrates to proteins to form glycoproteins
• produces secretory enzymes
• forms lysosomes
• moleclues are labelled with their destination (e.g. adding on a receptor)

how do vesicles link?
- finished products transported to cell surface in golgi vesicles , they fuse with membrane + contents release

Question 8

describe the structure of lysosomes?

Answer 8

• bags of digestive enzymes

Question 9

what is the function of lysosomes?

Answer 9

• hydrolyse phagocytic cells (in phagocytosis)
• breaks down dead cells (in autolysis)
• exocytosis - releases enzymes, lysozymes, to destory material
• digests worn out organells for reuse of material

Question 10

describe the structure of mitochondria

Answer 10

• double membrane (creates compartments for aerobic respiration)
• innner membrane called cristae (provide large surface area)
• mitochondrial matrix
• loop of mitochondrial DNA

Question 11

what is the function of mitochondria?

Answer 11

• site of aerobic respiration
• site of ATP production
• loop of DNA codes for enzymes needed for respiration

Question 12

describe the structure of ribosomes

Answer 12

• small
• made up of two sub-units of protein + rRNA
• eukaryotic= 80s
• prokaryotic= 70s

Question 13

what is the function of ribosomes?

Answer 13

site of protein synthesis

Question 14

describe the structure of a vacuole

vacuoles are only found in plant cells

Answer 14

• filled with fluid surrounded by a single membrane (called tonoplast)

Question 15

what is the function of a vacuole?

Answer 15

• makes cells turgid, provided structural support
• temporary store of sugars and amino acids
• pigments can colour petals to attract pollinators

Question 16

describe the structure of a chloroplast

chloroplasts are only found in plant cells

Answer 16

• surrounded by double membrane
• contain thylakoids (folded membranes containing pigment)
• fluid filled stroma contains enzymes for photosynthesis

Question 17

what is the function of chloroplasts?

Answer 17

site of photosynthesis

Question 18

describe the structure of a cell wall

cell walls are only found in plants + fungi

Answer 18

in plants:
- made of microfibrils of cellulose

in fungi:
- made of chitin, (a nitrogen containing polysaccharide)

Question 19

what is the function of a cell wall?

Answer 19

provides structural strength to the cell

Question 20

Describe the structure of the plasma membrane?

Answer 20

phospholipid bilayer
- hydrophobic tails facing inward
- hydrophillic heads facing outwards

• proteins:
• embedded or attached to bilayer
• involved in transport and cell recognition

cholesterol:
- maintains membranes fluidity

membrane is partially permeable:
- small non polar molecules e.g. oxygen, co2 can diffuse through lipid bilayer
- large polar molecules must pass through transport proteins
- ions cannot pass through, must rely on ion channels

Question 21

what is the function of the plasma membrane?

Answer 21

• controls the entrance and exit of molecules

Question 22

compare prokaryotic and eukaryotic cells (5 marks)

Answer 22

• prokaryotic cells have no nucleus (dna free in cytoplasm) , whereas, eukaryotic cells have dna enclosed in nucleus
• prokaryotic cells have smaller 70s ribosomes, whereas, eukaryotic cells have larger 80s ribosomes
• prokaryotic cells dont contain membrane bound organelles, whereas, eukaryotic cells do contain membrane bound organelles
• prokaryotic cells are smaller than eukaryotic cells
• both prokaryotic and eukaryotic contain dna, ribosomes, and cytoplasm