1.2 - Cell Structures

Question 1

(a)

Mitochondria

Answer 1

Function- site of aerobic respiration to produce ATP.
Structure- cylindrical in shape, folded inner membrane forms cristae.
Found in animal and plant cells

Question 2

(a)

Mitochondria structure

Answer 2

Matrix: A fluid-filled space
Internal membrane: Folded into cristae

Question 3

(a)

Why do mitochondria differ in appearance?

Answer 3

• They are cut in different plane/angles
• Size
• Age

Question 4

(a)

Vacuole

Answer 4

Function- water storage, maintain PH
Structure- surronded by a single membrane, tonoplast and contains cell sap
Found in plant cells

Question 5

(a)

Endoplasmic Reticulum (ER):

Answer 5

Function- lipid synthesis (smooth)
protein synthesis and transport (rough)
Structure- a series of flatterned sacs double membraned cisternae leading from the nuclear envelope
Found in animal and plant cells

(rough-spiky, smooth-seaweed)

Question 6

(a)

Role of rough endoplasmic reticulum

Answer 6

Production of protein synthesis on ribosomes
Transport to golgi body

Question 7

(a)

Ribosomes

Answer 7

Function- site of protein syntheis (translation)
Structure- made from rRNA and proteins
Found in animal and plant cell

* (around the er)

Question 8

(a)

Golgi body

Answer 8

Function - modifies and packages proteins
Structure - planar stack of membrane-bound, flattened sacs
Found in animal and plant cells

Question 9

(a)

Lysosomes

Answer 9

Function- role in phagocytosis, digest unwanted materials in the cytoplasm
Structure - fluid-filled vesicles surronded by a single membrane, contain enzymes (*)
Found in animal cells

Question 10

(a)

Centrioles

Answer 10

Function- form the spindle in cell division
Structure- 2 cylinders of microtubules
Found in animal cells

Question 11

(a)

Chloroplast

Answer 11

Function- site of photosynthesis
Structure- disk shaped surronded by double membrane
Found in plant cells

Question 12

(a)

Nucleus

Answer 12

Function- contains DNA which codes for protein synthesis
Structure - surronded by nuclear envelope which is semi-permeable and double membraned.
Nuclear pores allows transport of ribosomes
Dense nucleolus (made of RNA and proteins) assembles ribosomes.

Question 13

(a)

Chromatin

Answer 13

Function- protein synthesis
Structure- DNA coils bound to protein codes
Found in animal cells

Question 14

(a)

Plasmodemata

Answer 14

Function- faciliate communication and symplastic transport
Structure- microscopic channels between plant cell walls
Found in plant cells

Question 15

(b)

Structure of prokaryotic cells

Answer 15

Prokaryotic cells (bacteria):
DNA
Mesosome
Ribosome
Cell membrane
Cytoplasm
Cell wall
Slime coat (in some, not all bacteria)
Plasmid
Flagellum

Question 16

(b)

Structure of viruses

Answer 16

Viruses:
Protein coat
Genetic material

Question 17

(c)

Cell theory

Answer 17

Cell theory states that new cells are
formed from other existing cells and
that the cell is a fundamental unit of
structure, function and organisation in
all living organisms.

Question 18

(c)

Similarities and differences in the cell structure of eukaryotes and prokaryotes

Answer 18

• Eukaryotic cells are bigger (10-100mm)
• Prokaryotic cells are smaller (1-10mm)
• DNA in nucleus (Eukaryotes)
• DNA free in cytoplasm (Prokaryotes)
• Cellulose in cell wall
• Peptidoglycan in cell wall
• Mitochondria for respiration
• Mesosome for aerobic respiration

Question 19

(c)

Similarities and differences in the cell structure of eukaryotes and prokaryotes
(2)

Answer 19

• Eurkaryotic- have a true nucleus that contain gentic material and have membrane bound organelle
• Prokaryotic- do not have a true nucleus or any membrane bound organelles
• Do not contain plasmids
• May contain plasmids

Question 20

(c)

Magnification formula

Answer 20

Magnification = image size / actual size

Question 21

(c)

Conversions for magnification

Answer 21

mm → µm (micrometres): × 1,000
µm → nm (nanometres): × 1,000

Question 22

(c)

A mitochondrion in an electron micrograph measures 45 mm in length. The scale bar on the image represents 500 nm and measures 20 mm on the paper. Calculate the actual length of the mitochondrion. Give your answer in micrometres (µm).

Answer 22

Scale bar magnification = 20 mm ÷ 500 nm
→ Convert units: 20 mm = 20,000 µm, 500 nm = 0.5 µm
→ Magnification = 20,000 ÷ 0.5 = 40,000×
Actual size = 45 mm ÷ 40,000
→ 45 mm = 45,000 µm
→ Actual size = 45,000 ÷ 40,000 = 1.125 µm
Final answer: 1.13 µm (to 2 decimal places)

Question 23

(d)

Cell

Answer 23

Basic unit of life

Question 24

(d)

Tissue

Answer 24

Cells near each other in the embryo often differentiate in the same way and group together.

Question 25

# (d) Organ

Answer 25

A group of tissues in a structural unit, working together and performing a specific function.

Question 26

# (d) Organ system

Answer 26

A group of organs working together with a particular role.

Question 27

# (d) Organisms

Answer 27

All the systems of the body work together, making an organism, which is a discrete individual.

Question 28

# (d) Epithelia tissue

Answer 28

Continuous layers of cells on internal and external surfaces

Question 29

# (d) Epithelia tissue - Cuboidal

Answer 29

Simplest, one cell thick Found in promixal convulted tububle (PCT) kidney

Question 30

# (d) Epithelia tissue - Columnar

Answer 30

Elongated, can have cilia Found in trachea

Question 31

# (d) Epithelia tissue - Squamous

Answer 31

Flattened Found in alveolar walls

Question 32

# (d) Muscle tissue

Answer 32

Tissue able to contract

Question 33

# (d) Muscle tissue - Skeletal

Answer 33

Striated (striped), voluntary, generates locomotion in mammals Found attached to bones

Question 34

# (d) Muscle tissue - Smooth

Answer 34

Spindle-shaped cells, no stripes, involuntary Found in skin and digestive tract

Question 35

# (d) Muscle tissue - Cardiac

Answer 35

Striated, short fibres, contracts without nerve stimulation. Does not tire Found in heart muscle

Question 36

# (d) Connective tissue

Answer 36

Separates tissues and organs