Cell Organelles + Functions

Question 1

Structure of nucleus

Answer 1

Surrounded by a nuclear envelope, a semipermeable double membrane

Nuclear pores allow substances to enter/exit

Dense nucleolus made of RNA + proteins assembles ribosomes

Question 2

Function of nucleus

Answer 2

Contains DNA coiled around chromatin into chromosomes
Controls cellular processes: gene expression determines specialisation + sire of MRNA transcription, mitosis, semiconservative replication

Question 3

Structure and function of Endoplasmic Reticulum

Answer 3

Cisternae = network of tubules and flattened sacs extend from cell membrane + connects to nuclear envelope

Rough ER = many ribosomes attached for protein synthesis and transport
Smooth ER = lipid synthesis

Question 4

Structure + function of Golgi Apparatus

Answer 4

Structure :
- Planar stack of membrane-bound, flattened sacs, cis face aligns with rER

Function:

• molecules are processed in the cisternae.
• vesicles bud off trans face via exocytosis
• modifies and packages proteins for export
• synthesises glycoproteins

Question 5

Structure + Function of Ribosomes

Answer 5

Formed of protein and rNA

large subunit which joins amino acids
small subunit which with mRNA binding site

Question 6

Describe the relationship between the organelles involved in the production and secretion of proteins

Answer 6

The ribosomes that synthesise proteins are attached to the rER. The Golgi apparatus, which modifies proteins for secretion, aligns with the rER

Question 7

Structure + Function of mitochondrion

Answer 7

Structure:

• surrounded by double membrane
• folded inner membrane forms cristae (site of electron transport chain)
• fluid matrix: contains mitochondrial DNA, respiratory enzymes, lipids proteins

Function:
- site of aerobic respiration to produce ATP

Question 8

Structure + Function of Chloroplasts

Answer 8

Structure:

• vesicular plastid with double membrane
• thylakoids = flattened discs stack form grana, contain photo systems with chlorophyll
• intergranal lamellar = tubes attach thylakoids in adjacent grana
• Stroma = fluid filled matrix

Function:
Site of photosynthesis to convert solar energy to chemical energy

Question 9

Structure + Function of Lysosome

Answer 9

Structure:

• sac surrounded by single membrane
• embedded H+ pump maintains acidic conduits
• contains digestive hydrolyse enzymes
• glycoprotein coat protects cell interior

Function:

• digests contents of phagosome
• exocytosis of digestive enzymes

Question 10

Structure + Function of Plant Cell Wall

Answer 10

Made of cellulose microfibrils for mechanical support
Plasmodesmata form part of apoplast pathway to allow molecules to pass between cells.
Middle lamella separates adjacent cell walls

Question 11

Bacterial cell walls are made of…

Answer 11

… peptidoglycan (murein)

Question 12

Fungal cell walls are made of…

Answer 12

… chitin.

Question 13

Structure + Function of Centrioles

Answer 13

Structure:

• spherical group of microtubules arranged in triples
• located in centrosomes

Function:
- migrate to opposite poles of cell during prophase + spindle fibres form between them

Question 14

Structure + Function of Cell-surface Plasma Membrane

Answer 14

Structure:
- Fluid mosaic phospholipid bilayer with extrinsic + intrinsic proteins embedded

Function:

• isolates cytoplasms from extracellular environment
• selectively permeable to regulate transport of substances
• involved in cell signalling/ cell recognition

Question 15

Role of cholesterol in cell-surface membrane

Answer 15

Steroid molecule

Connects phospholipids and recuses fluidity

Question 16

Glycoproteins’ role in cell-surface membrane

Answer 16

Cell signalling
Cell recognition (antigens)
Binding cells together

Question 17

Glycolipids

Answer 17

Cell signalling

Cell recognition

Question 18

Structure + function of flagella

Answer 18

Structure:
- hollow helical tune made of the protein flagellin

Function:
- rotates to propel (usually unicellular) organism

Question 19

Structure + Function of Cilia

Answer 19

Structure:
- hairlike structure on eukaryotic cells

Function:
- move back and forth rhythmically to sweep foreign substances EG dust or pathogens away / enable cell to move

Question 20

Why is the cytoskeleton important

Answer 20

Provides mechanical strength
Aids transport within cells
Enables cell movement

Question 21

Similarities between eukaryotic and prokaryotic cells

Answer 21

Cell membrane
Cytoplasm
Ribosomes

Question 22

Contrast eukaryotic and prokaryotic cells (eukaryotic)

Answer 22

Larger cells, often multicellular
Always have organelles and nucleus
Linear chromosomes associated with histones
80s ribosomes
Mitosis + meiosis - sexual and/or asexual reproduction
Murein cell walls
No capsule, no plasmids, always cytoskeleton

Question 23

Contrast eukaryotic and prokaryotic cells (prokaryotic)

Answer 23

Small cells, always unicellular
No membrane-bound organelles
No nucleus
Circular DNA not associated with proteins
70s ribosomes
Binary fission - always asexual reproduction
Cellulose cell wall (plants) / chitin (fungi)
Capsule, sometimes plasmids + cytoskeleton