Cells

Question 1

Viruses/HIV

Answer 1

• Attachment protein
(binds to a receptor on
host cell e.g. CD4 in
HIV)
• Enzymes e.g. reverse
transcriptase
• Genetic Material
(RNA in HIV)
• Lipid Envelope
• Protein Capsid

Question 2

Mitosis

Answer 2

• DNA is replicated in S-phase of interphase
• Prophase – Chromosomes condense and become visible, nuclear
membrane dissolves
• Metaphase – Chromosomes line up at the middle of the cell
• Anaphase – Sister chromatids are pulled to the opposite poles of the
cell
• Telophase – Chromosomes decondense and the nuclear envelope
starts to reform around the two nuclei
• Cytokinesis – The cytoplasm and surface membrane splits forming
two new cells that are genetically identical

Question 3

Binary fission

Answer 3

• Bacteria an prokaryotes reproduce by binary fission
• First the DNA (and plasmids) are replicated
• Then the cytoplasm and cell membrane divides in two
• Each daughter receives on copy of the circular DNA (and variable
number of plasmids if present)

Question 4

Organelles in a eukaryote

Answer 4

• Nucleus (and Nucleolus)
• Chloroplasts (plants)
• Mitochondria
• Rough Endoplasmic reticulum
• Smooth endoplasmic reticulum
• Golgi apparatus/body
• Lysosomes
• Vacuoles
• Ribosomes
• Cell Wall (plants)

Question 5

Organelles bound by a double membrane

Answer 5

• Nucleus (and Nucleolus)
• Chloroplasts
• Mitochondria

Question 6

Organelles bound by a single membrane

Answer 6

• Rough Endoplasmic reticulum
• Smooth endoplasmic reticulum
• Golgi apparatus/body
• Lysosomes
• Vacuoles

Question 7

Organelles with no membrane

Answer 7

• Ribosomes
• Cell Wall

Question 8

Mitochondria

Answer 8

• site of aerobic respiration
• release energy
• produce atp
• Surrounded by a double membrane
• Inner membrane has folds called
cristae
• Matrix is the bulk of the
mitochondrion
• Contain their own DNA
• The cristae are folded to increase
surface area for aerobic respiration.

Question 9

Nucleus

Answer 9

• contains genetic information and carries out protein synthesis
• Surrounded by the double nuclear
envelope
• Contain nuclear pores to allow
substances in and out
• Nucleoplasm– jelly like material of
the nucleus
• Contain chromosomes– linear DNA
wrapped around proteins
• Nucleolus– small and stains dark,
manufactures ribosomes and
ribosomal RNA

Question 10

Rough Endoplasmic reticulum

Answer 10

• Single folded
membranes
• Studded with
ribosomes for protein
synthesis
• Contribute to the
transportation
pathways in cells

Question 11

Smooth ER

Answer 11

• Single folded membranes
• No ribosomes
• Synthesis and transport of lipids and carbohydrates
• Contribute to the
transportation pathways in cells

Question 12

Golgi apparatus

Answer 12

• for processing, packaging, transport
• Surrounded by a single
membrane
• Made of flattened sacs called
cisternae – large surface area
• Modifies proteins by adding
carbohydrates
• Modified proteins are packaged
in vesicles for transport
• Modification and transport of
lipids
• Transport of carbohydrates
• Form lysosomes

Question 13

Lysosomes

Answer 13

• hydrolyse material e.g. worn out organelles/pathogens
• Surrounded by a single membrane
• Made by the Golgi apparatus
• Contain enzymes that hydrolyse substances

Question 14

Ribosomes

Answer 14

• protein synthesis
• 80S – found in eukaryotes
• 70S – (smaller) found in prokaryotes
• Made of protein and ribosomal RNA
• Produced in the nucleolus

Question 15

Chloroplasts

Answer 15

• site of photosynthesis
• Surrounded by a double membrane – chloroplast envelope
• Grana– stacks of membrane disks called thylakoids, the chlorophyll is here. Grana provide a large surface area for harvesting light energy
• Stroma– the remaining matrix of the chloroplast contains enzymes for photosynthesis
• Has its own DNA

Question 16

Cell wall

Answer 16

• for stability, to resist osmotic changes
• Made of cellulose in plant cells
• Water can move freely through the cell wall
• Some have plasmodesmata to allow other substances through
• The middle lamella marks where one plant cell wall meets another.
• Made of chitin in fungi

Question 17

Vacuole

Answer 17

• supports plant cells, stores sugars and amino acids
• Surrounded by a single membrane called the tonoplast
• For storage and support

Question 18

Producing and secreting proteins and
lipids by exocytosis

Answer 18

Proteins and lipids are synthesised by the RER and SER. They are then sent to the Golgi in vesicles where they are modified by adding carbohydrate groups and packaged into vesicles for transport. The vesicles move to the membrane,
where they fuse with it allowing the contents to be released out of the
cell by exocytosis.

Question 19

Squamous epithelium cells

Answer 19

• Control blood vessel
permeability, absorption and
secretion
• Flattened cells – diffusion distance
is shorter
• Smooth cells – less friction, blood flows
smoothly

Question 20

Ciliated epithelium cells

Answer 20

•Move/sweep away
secretions/foreign bodies
such as dust
•Lots of cilia to waft away mucus
from lungs
•Lots of mitochondria to release energy for cilia movement

Question 21

Red blood cell

Answer 21

•Transport oxygen to respiring
cells/tissues
•No nucleus – more space to carry
haemoglobin – more oxygen
•Biconcave shape – larger surface area –
transport more oxygen

Question 22

White blood cell

Answer 22

•Protect body from pathogens
•Lobed nuclei/flexibility to engulf
pathogens
•Many ribosomes/RER/Golgi &
mitochondria to produce proteins
(Antibodies)

Question 23

Root hair cell

Answer 23

•Absorb water and minerals
ions
•Projections increases the surface
area
•Many mitochondria for active transport of ions

Question 24

Palisade cell

Answer 24

•Photosynthesis to produce
glucose
•Long thin cells to increase the
surface area to collect light
•Many chloroplasts pushed to edges of
cells by vacuole for photosynthesis

Question 25

Guard cell

Answer 25

•Control gas exchange & rate
of transpiration
•Chloroplasts – respond to light to
open stomata
•Thickened edges (cellulose)allow
chloroplasts to open/close

Question 26

Prokaryotes

Answer 26

• cell surface membrane
• no membrane bound organelles
• peptidoglycan cell wall
• 70s ribosomes
• dna in cytoplasm, circular dna, can contain plasmids
• some have flagella
• can have a capsule

Question 27

Temporary mount

Answer 27

•Samples must be sliced thinly - to let light pass through them.
•A drop of water is typically added.
•Often stains are applied to make them darker – iodine and methylene blue
are examples.
•Usually, a cover slip is applied gently at an angle.
•The light passes through and when it hits the specimen it appears darker.