cells

Question 1

Nucleus

Answer 1

• contains coded genetic information in the form of DNA molecules
• DNA contained within a double membrane
• nuclear envelope contains nuclear pores for molecules to move in and out
• DNA associates with histone proteins to form chromatin, which coils and condenses to form chromosomes

Question 2

Nucleolus

Answer 2

• area within the nucleus
• responsible for ribosome production
• composed of RNA and proteins

Question 3

Mitochondria

Answer 3

• Site of the later stages of aerobic respiration
• double membrane organelle
• inner membrane folded to form cristae
• inner fluid= matrix
• contains small amount of mitochondrion DNA
• can produce own enzymes and reproduce themselves

Question 4

Vesicles

Answer 4

• membranous sacs
• roles in transport and storage
• single membrane with fluid enclosed
• transport minerals into cells

Question 5

Lysosomes

Answer 5

• forms of vesicles containing hydrolytic enzymes
• break down waster material in cells, including old organelles
• break down pathogens in immune system
• role in programmes cell death/apoptosis

Question 6

Cilia

Answer 6

• hair like structures
• extension from some cell types
• shorter but more frequent compared to flagella
• mobile or stationary
• arranged in a 9+2 = 2 central microtubules, surrounded by 9 pairs arranged like a wheel
• parallel pairs of microtubules slide over each other

Question 7

roles and function of the cytoskeleton

Answer 7

• present throughout the cytoplasm of eukaryotes
• network of fibres essential for shape and stability
• holds organelles in place
• controls cell movement
• controls organelle movement within cells

Question 8

Key components of the cytoskeleton

Answer 8

• microfilaments
• microtubules
• intermediate fibres

Question 9

Microfilaments

Answer 9

• contractile fibres formed from actin
• responsible for cell movement, and cell contraction in cytokinesis

Question 10

Microtubules

Answer 10

• globular tubulin proteins
• polymerise to form tubes
• determine cell shape
• act as tracks for movement of organelles

Question 11

Intermediate fibres

Answer 11

• give mechanical strength to cells
• maintain cell integrity

Question 12

Centrioles

Answer 12

• component of cytoskeleton
• present in most eukaryotic cells
• 2 associated centrioles form the centrosome
• involved in assembly and organisation of spindle fibres during division
• made of microtubules
• role in positioning of flagella and cilia

Question 13

Flagella

Answer 13

• whip like structures
• extension from some cell types
• longer but less frequent than cilia
• used to enable cell motility (movement)
• used as a sensory organelle in some cells (detects changes)

Question 14

what is protein synthesis in cells, what organelles does in use

Answer 14

• protein synthesis key cell function for internal use and secretion
• uses significant proportion of internal structure
• cytoskeleton plays role in co-ordinating protein synthesis
• involves ribosomes, RER, SER, Golgi apparatus
• organelles co-ordinated to produce and prepare proteins

Question 15

Endoplasmic reticulum, smooth and rough

Answer 15

• a network or membranes, enclosing flattened sacs called cisternae
• connected to the outer membrane of the nucleus
• SMOOTH= responsible for lipid and carbohydrate synthesis and storage, no ribosomes
• ROUGH- ribosomes bound to surface, responsible for synthesis sand transport of proteins

Question 16

Ribosomes

Answer 16

• free floating in the cytoplasm or attached to RER
• not surrounded by a membrane
• constructed of RNA molecules, made in the cell nucleolus
• the site of protein synthesis
• (also present in mitochondria, chloroplasts, prokaryotic cells)

Question 17

Golgi apparatus

Answer 17

• similar structure to SER
• compact structure formed of cisternae
• role in modifying and ‘packaging’ proteins into vesicles

Question 18

Process of protein production

Answer 18

1. proteins are synthesised on ribosomes attached to RER
2. proteins pass into cisternae, and are packaged into transport vesicles
3. vesicles move towards and fuse with the Golgi apparatus
4. proteins enter Golgi apparatus ,are structurally modified
5. secretory vesicles carry proteins towards the cell surface membrane
6. vesicles fuse with cell surface membrane, release content by exocytosis
7. some vesicles form lysosomes, which contain enzymes for use in the cell

Question 19

Plant Cell walls

Answer 19

• plant only
• cellulose in plants
• surround cell surface membrane
• freely permeable
• gives the cell shape
• rigid as cell content press against cell wall
• supports the plant and the cell
• defence mechanism from pathogens

Question 20

Vacuoles

Answer 20

• membrane lined sacs in cytoplasm
• plant cells only
• large vacuoles maintain turgor as contents push against
• vacuole membrane= tonoplast
• selectively permeable

Question 21

Chloroplasts

Answer 21

• plant cells only
• responsible for photosynthesis
• double membrane
• stroma= enclosed fluid
• thylakoid= internal network membrane
• granum= thylakoid stacks
• lamellae= join grana together
• pigments contained within grana
• contain own DNA and ribosomes
• internal membrane provides large sa for enzymes, proteins and pigment

Question 22

Prokaryotic cells DNA

Answer 22

• generally 1 supercoiled molecule of DNA in the form of a chromosome
• plasmids= rings of DNA

Question 23

Prokaryotic cell walls

Answer 23

• peptidoglycan (polymer of amino acids and sugar)

Question 24

Prokaryotic ribosomes

Answer 24

• 70s (smaller)

Question 25

Prokaryotic flagells

Answer 25

• thinner than eukaryotic, no 9+2
• chemiosmosis provides energy to rotate filament forming flagella, compared to ATP in eukaryotes
• flagellum attached to cell membrane of a bacterium by a basal body
• rotated by a molecular motor