Cell Ultrastructure

Question 1

Structure of Nucleus

Answer 1

Contains:
Double nuclear envelope
Nuclear pores
Nucleolus
Chromatin

Question 2

Function of Nucleus

Answer 2

Nucleus - contains DNA (chromatin) which controls activity of cells and also allows replication and copy for cell division, Attached to rough endoplasmic reticulum allowing MRNA to go to ribosome for protein synthesis
Nucleolus - Made by RNA and protein - produces ribosomes
Nuclear envelope - Double membrane - compartmentalises DNA - protecting it from damage
Nuclear pores - Allows molecules to enter and leave nucleus

Question 3

Structure of Endoplasmic Reticulum

Answer 3

Rough Endoplasmic Reticulum -
System of interconnected hollow tubes and membrane bound sacs which stack to form sheets of cisternae
Attached to nucleus
Have ribosomes attached to them
Smooth Endoplasmic Reticulum -
System of interconnected hollow tubes and membrane bound sacs which stack to form sheets of cisternae
Do Not have ribosomes attached to them

Question 4

Function of Endoplasmic Reticulum

Answer 4

Rough Endoplasmic Recticulum - site of protetin synthesis

Smooth Endoplasmic Recticulum - Carbohydrate and lipid synthesis and storage

Question 5

Structure of Golgi Apparatus

Answer 5

Stack of flattened membrane bound sacs stacked to form sheets of Cisternae
Continuously formed from ER and constantly budding off as Golgi vesicles from the other end

Question 6

Function of Golgi Apparatus

Answer 6

Allows internal transport
receives protein from RER
Modifies and processes molecules (coming from ER) and after modifying them they package them into vesicles and send them to where they are needed.
Makes lysosomes - one kind of vesicle the Golgi apparatus can make - these stay in the cell
Makes Secretory vesicles - another kind of vesicle the Golgi apparatus can make - these leave the cell

Question 7

Structure of Ribosome

Answer 7

2 subunit organelle
Made from RNA and Protein
very small - 22nm
not membrane bound
Free floating in the cell or attached to the rough endoplasmic reticulum

Question 8

Function of Ribosome

Answer 8

Makes proteins - assemble amino acids to proteins in chains using mRNA

Question 9

Structure of Mitochondrion

Answer 9

Oval shaped
double membrane
inner membrane contains finger-like structures called cristae - increases surface area for reactions to happen quicker
Solution inside = matrix - contains enzymes for respiration
contains mitochondrial DNA - to replicate enzymes

Question 10

Function of Mitochondrion

Answer 10

Site of aerobic respiration 
Produces ATP (energy carrier in cells) - Because of respiration

Question 11

Structure of Lysosomes

Answer 11

Spherical sacs surrounded by single membrane

Question 12

Function of Lysosomes

Answer 12

Contains powerful hydrolytic digestive enzymes - called lysozomes
Lysozomes - break down worn out components, digest invading cells

Question 13

Structure of Centrioles

Answer 13

Component of cytoskeleton
Made of 9 rings of triplet microtubules
Small hollow cylinders - occur in pairs next to nucleus
Animal cells only

Question 14

Function of Centrioles

Answer 14

Copy itself during cell division and form the spindle in cell division

Question 15

Structure of Cilia

Answer 15

Hair-like extensions protruding from some animal cell types
In cross section they have an outer membrane and a ring of nine pairs of microtubules and two microtubles in the centre - 9+2 arrangement - allows movement

Question 16

Function of Cillia

Answer 16

Sensory function (e.g. nose)
beat creating a current to move
For locomotion

Question 17

Structure of Plasma Membrane

Answer 17

Found on surface of animal cells
Found inside cell wall of plant and prokaryotic cells
Phosholipid Bilayer - composed of proteins & Lipids
Contains cholesterol

Question 18

Function of Plasma Membrane

Answer 18

Regulate substances entering and leaving the cell

Receptor molecules allows hormones and reacts to hormones etc.

Question 19

Structure of Cytoskeleton

Answer 19

Has 3 structural components - Microfilaments (made of actin), Microtubules (made of tubulin), Intermediate Fibres

Question 20

Function of Cytoskeleton

Answer 20

Microfilaments - Actin - movement during cytokinesis
Microtubules - Tubulin - determine shape of cell by polymerising, act as tracks for movement for organelles
Intermediate Fibres - gives strength to cells, helps maintain integrity