Core Concepts (Cell Structure and Organisation)

Question 1

Define eukaryotic cell

Answer 1

A type of cell that contains a true nucleus along with membrane-bound organelles.

Question 2

Describe the structure of the nucleus.

Answer 2

● Surrounded by nuclear envelope which is
semi-permeable and double membraned
● Nuclear pores allow substances to enter/exit
● Dense nucleolus (made of RNA and proteins)
assembles ribosomes

Question 3

Describe the function of the nucleus.

Answer 3

● Contains DNA coiled around chromatin into chromosomes
● Coordinates cellular activities

Question 4

Describe the function of the nucleus.

Answer 4

● Contains DNA coiled around chromatin into
chromosomes
● Coordinates cellular activities

Question 5

What is chromatin?

Answer 5

A DNA-protein complex found in
eukaryotic cells.

Question 6

Describe the structure of mitochondria.

Answer 6

● Surrounded by double membrane, mitochondrial envelope
● Folded inner membrane forms cristae (large surface area)
● Fluid matrix contains mitochondrial DNA, respiratory
enzymes, lipids and proteins

Question 7

Describe the function of mitochondria.

Answer 7

Site of aerobic respiration to produce ATP.

Question 8

Describe the structure of the
endoplasmic reticulum (ER).

Answer 8

● Series of flattened membrane-bound sacs
(cisternae) within the cytoplasm, continuous with
the nuclear envelope
● Two types: rough ER and smooth ER

Question 9

Describe the function of the smooth
endoplasmic reticulum (SER).

Answer 9

Lipid synthesis

Question 10

Describe the function of the rough
endoplasmic reticulum (RER).

Answer 10

Many ribosomes attached for protein
synthesis and transport.

Question 11

Describe the structure of ribosomes.

Answer 11

● Made from rRNA and proteins
● Found free in the cytoplasm or
associated with the RER

Question 12

Describe the function of ribosomes.

Answer 12

Site of protein synthesis (translation)
● Large subunit joins amino acids
● Small subunit reads RNA

Question 13

Describe the structure of the Golgi body.

Answer 13

● Planar stack of membrane-bound, flattened sacs
● Cis face aligns with RER
● Molecules are processed in cisternae
● Vesicles bud off trans face via exocytosis

Question 14

Describe the function of the Golgi body.

Answer 14

● Modifies and packages proteins for export
● Synthesises glycoproteins

Question 15

Describe the structure and function of
lysosomes.

Answer 15

● Fluid-filled vesicles surrounded by a single
membrane, contain enzymes
● Role in phagocytosis, digest unwanted materials
in the cytoplasm

Question 16

Describe the structure of centrioles.

Answer 16

● Cylindrical structure
● Organised into microtubules in a 9+0 pattern
● Found in pairs in centrosomes

Question 17

Describe the function of centrioles.

Answer 17

● Migrate to opposite poles of the cell during
prophase
● Involved in the organisation of spindle fibres

Question 18

Describe the structure of a chloroplast.

Answer 18

● Disk shaped surrounded by double membrane
● Thylakoids - flattened discs stacked to form grana
● Grana - contain photosystems with chlorophyll
● Intergranal lamellae - tubes attach thylakoids in adjacent
grana
● Stroma - fluid-filled matrix

Question 19

What is the function of a chloroplast?

Answer 19

Site of photosynthesis

Question 20

Describe the structure of the permanent
vacuole in plants.

Answer 20

● Surrounded by a single membrane, tonoplast
● Contains cell sap (mineral ions, water,
enzymes, soluble pigments)

Question 21

Describe the function of the permanent
vacuole in plants.

Answer 21

● Controls turgor pressure
● Water storage
● Isolates harmful waste products
● Maintains pH

Question 22

Define plasmodesmata

Answer 22

Microscopic channels between plant cell
walls that facilitate communication and
symplastic transport.

Question 23

Define prokaryotic cell

Answer 23

A type of cell that does not contain any
membrane-bound organelles or a true
nucleus.

Question 24

Describe the structure and function of
the flagella in prokaryotic cells.

Answer 24

● Long, whip-like protrusion made of flagellin
● Rotates to propel the organism
● Sensory organ

Question 25

How is genetic information stored in prokaryotes?

Answer 25

● Plasmids - small rings of DNA that carry non-essential genes, exchanged between bacterial cells via conjugation ● Loop of DNA - circular DNA stored in the nucleoid region of the cell

Question 26

Describe the structure and function of pili in prokaryotic cells.

Answer 26

● Hair-like microfibers made of pilin that extend through the cell wall ● Enable the attachment of bacteria to each other and to other surfaces

Question 27

Describe the structure and function of the mesosome.

Answer 27

● Infolds of the cell membrane ● Increase the surface area of the cell, aiding cellular respiration

Question 28

What is the function of the capsule in prokaryotic cells?

Answer 28

● Protective, slimy layer ● Helps the cell to retain moisture and adhere to other surfaces

Question 29

Which organelles are found in both eukaryotic and prokaryotic cells?

Answer 29

● Cell membrane ● Cytoplasm with a form of cytoskeleton (although cytoskeleton of eukaryotes is more significant) ● Ribosomes

Question 30

Contrast eukaryotic and prokaryotic cells.

Answer 30

Prokaryotic * Small, unicellular Large * No membrane-bound organelles, no nucleus * Circular DNA, not associated with proteins * 70S ribosomes 80S ribosomes * Reproduce via binary fission * Peptidoglycan cell wall * Extrachromosomal DNA in plasmids Eukaryotic * Often multicellular * Contain membrane-bound organelles and true nucleus * Linear chromosomes associated with histones * Reproduce via sexual or asexual reproduction * Cell wall made of cellulose (plants) or chitin (fungi) * Extra DNA in some organelles, e.g. mitochondria

Question 31

Contrast eukaryotic plant and animal cells.

Answer 31

Plant cells * Cellulose cell wall * Large permanent vacuole * Contain chloroplasts * No pseudopodia Animal cells * No cell wall * Small temporary vacuoles (vesicles) * No chloroplasts * Some may have pseudopodia

Question 32

What is a light microscope?

Answer 32

A type of microscope that uses a series of lenses to magnify the visible light reflecting off a specimen.

Question 33

What is magnification?

Answer 33

The number of times bigger an image appears compared to the size of the specimen.

Question 34

How can the magnification of an image be calculated?

Answer 34

image size / actual size

Question 35

Describe cell theory

Answer 35

● The cell is the fundamental unit of all life forms ● New cells can be formed from existing cells ● Cells contain genetic material which can be transferred to daughter cells

Question 36

What is a virus?

Answer 36

A non-living microorganism that consists of genetic material surrounded by a protein husk.

Question 37

How do viruses differ from prokaryotic and eukaryotic cells?

Answer 37

Virus * Non-living * Smaller and simpler in structure * Genetic material in the form of DNA or RNA * Can only reproduce within a host cell * No ribosomes Prokaryotic and eukaryotic cells * Living * Larger and more complex structure * Genetic material in the form of DNA * Independent cell division, sexual or asexual * Contain ribosomes

Question 38

How are multicellular organisms organised?

Answer 38

● Many cells make up a tissue ● Many tissues make up an organ ● Many organs make up an organ system

Question 39

Define tissue

Answer 39

A group of cells working together to carry out a specific function.

Question 40

Define organ

Answer 40

A group of tissues working together to carry out a specific function.

Question 41

Define organ system

Answer 41

A group of organs working together to carry out a specific function.