3.2.1.1

Question 1

Describe the structure of the cell surface membrane

Answer 1

-‘fluid mosaic’ phospholipid bilayer
-with extrinsic and intrinsic proteins embedded

Question 2

Describe the function of the cell surface membrane

Answer 2

-Isolates cytoplasm from extracellular environment
-Selectively permeable to regulate transport of substances
-Involved in cell signalling

Question 3

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

Answer 3

Cholesterol :
-steroid molecule connects phospholipids and reduces fluidity
Glycoproteins :
-cell signalling, cell recognition (antigens) and binding cells together
Glycolipids :
cell signalling and cell recognition

Question 4

Describe the structure of the nucleus

Answer 4

-surrounded by nuclear envelope, a semi permeable double membrane
-nuclear pores allow substances to enter/exit
-dense nucleolus made of RNA and proteins assembles ribosomes

Question 5

Describe the function of the nucleus

Answer 5

-Contains DNA coiled around chromatin into chromosomes
-controls cellular processes: gene expression determines specialisation and site of mRNA transcription, mitosis, semiconservative replication

Question 6

Describe the structure of a mitochondrion

Answer 6

-surrounded by a double membrane, folded inner membrane firms cristae: site of electron transport chain
-fluid matrix: contains mitochondrial DNA, respiratory enzymes, lipids, proteins

Question 7

State the function of mitochondria

Answer 7

-site of aerobic respiration to produce ATP

Question 8

Describe the structure of a chloroplast

Answer 8

-vesicular plastid with double membrane
-Thykaloids: flattened discs stack to form grana; contain photosystems with chlorophyll
-Intergranal lamelle: tubes attach thykaloids in adjacent grana
-Stroma: fluid filled matrix, contains starch grains

Question 9

State the function of chloroplasts

Answer 9

-site of photosynthesis to convert solar energy to chemical energy

Question 10

Describe the structure of the golgi apparatus

Answer 10

-planar stack of membrane-bound, flattened sacs or cisternae with small rounded hollow structures called vesicles

Question 11

Describe the function of the golgi apparatus

Answer 11

-modifies and packages proteins
-synthesises glycoproteins

Question 12

Describe the structure of a lysosome

Answer 12

-sac surrounded by single membrane
-membrane-bound organelle that releases hydrolytic enzymes
-embedded H+ pump maintains acidic conditions
-contains digestive hydrolase enzymed
-glycoprotein coat protects cell interior

Question 13

Describe the function of a lysosome

Answer 13

-digests contents of phagosome
-exocytosis of digestive enzymes

Question 14

Describe the structure of a ribosome

Answer 14

-formed of protein and rRNA
-free in cytoplasm or attached to ER

Question 15

Describe the function of a ribosome

Answer 15

Site of protein synthesis via translation :
-large subunit: joins amino acids
-small subunit: contains mRNA binding site

Question 16

Describe the structure and function of the endoplasmic reticulum

Answer 16

-cisternae: network of tubules and flattened sacs extends from cell membrane through cytoplasm and connects to nuclear envelope

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

Question 17

Describe the structure of the cell wall(plants)

Answer 17

-made of cellulose microfibrils
-plasmodesmata: allows molecules to pass between cells
-middle lamella - acts as boundary between adjacent cell walls

Question 18

State the function of the cell wall(plants)

Answer 18

-mechanical strength and support
-physical barrier against pathogens
-part of apoplast pathway to enable easy diffusion of water

Question 19

Describe the structure of the cell vacuole in plants

Answer 19

-surrounded by a single membrane called the tonoplast
-contains cell sap: mineral ions, water, enzymes, soluble pigments

Question 20

Describe the function of the cell vacuole in plants

Answer 20

-controls turgor pressure
-absorbs and hydrolyses potentially harmful substances to detoxify cytoplasm

Question 21

Explain some common cell adaptions

Answer 21

-folded membrane or microvilli increase surface area eg: for diffusion
-many mitochondria = large amounts of ATP for active transport
-Walls one cell thick to reduce distance of diffusion pathway

Question 22

State the structures in a eukaryotic cell that cannot be identified with an optical microscope

Answer 22

-mitochondria
-ribosomes
-ER
-lysosome
-cell surface membrane

Question 23

How are chloroplasts adapted to their function

Answer 23

-granal membranes: provide large surface area fir the attachment of chlorophyll, electron carriers and enzymes that carry out the first stage of photosynthesis
-the fluid of the stroma posses all the enzymes needed to make sugars in the second stage of photosynthesis
-chloroplasts contain both DNA and Ribosomes so they can manufacture some of the proteins needed for photosynthesis

Question 24

Outline the roles of organelles in the production, transport and release of proteins from eukaryotic cells

Answer 24

-DNA in nucleus is code for protein
-Ribosomes/RER produce protein
-mitochondria produce ATP for protein synthesis
-golgi apparatus packages/ modifies proteins
-Vesicles transport proteins

Question 25

What is the cell wall component of:
-plants
-algae
-fungi
-prokaryotes

Answer 25

Plants: cellulose
Algae: cellulose
Fungi: chitin
prokaryotes: murein