L5 - Intro To Cell

Question 1

Cell theory

Answer 1

1) All living organisms are composed of 1+ cells forming collaborative, functional networks
2) The cell is the basic unit of structure and organisation as well as the smallest unit that makes use of survival needs of the body to undertake all functions necessary for life
3) All cells arise only from pre-existing cells
4) The total function of all cells in the body reflect the total function of the body

Question 2

Eukaryotic vs. prokaryotic cells

Answer 2

Membrane-bound organelles/nucleus

Question 3

Eukaryotic and prokaryotic cells similarities

Answer 3

have plasma membrane, cytosol, DNA, RNA, protein and ribosomes

Question 4

Endomembrane system

Answer 4

Work with plasma membrane to package, label and ship molecules

• INCLUDES; nucleus, endoplasmic reticulum, Golgi apparatus, lysosomes
• EXCLUDES: mitochondria (lots of membranes), ribosomes (don’t have a membrane)

Question 5

Types of plasma membrane proteins

Answer 5

Integral (including transmembrane), peripheral

Question 6

Functions of plasma membrane proteins

Answer 6

Transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, attachment to cytoskeleton and ECM

Question 7

Cell-cell recognition

Answer 7

• Some glycoproteins serve as identification tags/molecular signatures of the extracellular side of the cell that are specifically recognised by other cells
• More short-lived than intercellular joining proteins

Question 8

Components of nucleus

Answer 8

Nuclear envelope, nuclear lamina, nuclear pores, nucleolus

Question 9

Nucleus function

Answer 9

• House/protect DNA in eukaryotic cells
• Make RNA and assemble ribosomes
• Pores regulate movement of substances (e.g protein and mRNA) in and out of nucleus
• Molecule segregation to allow temporal and spatial control of cell function

Question 10

Condensing of DNA

Answer 10

Double helix, histones, nucleosomes, chromatin, chromatin fibres, looped domains, chromosomes

Question 11

Ribosomes

Answer 11

• made of rRNA
• small and large subunits
• protein production
• free in cytoplasm (cytosolic/non-endomembrane proteins) or attached to RER (non-cytosolic/endomembrane proteins)

Question 12

Endoplasmic reticulum

Answer 12

Extensive networks of tubes and tubules (cisternae) stretching out from nuclear membrane

Question 13

Cisternae function

Answer 13

Serves the biosynthesis of new lipids and of membrane anchored or secretory proteins

Question 14

Rough ER function

Answer 14

Production of:

• Secreted proteins (which leave cell via exocytosis)
• Membrane proteins
• Organelle proteins

Question 15

Rough ER

Answer 15

• Continuous with nuclear enevlope
• Dotted with attached ribosomes (synthesis proteins)
• Proteins enter lumen within rough ER for folding
• Rough ER membrane surrounds protein to form transport vesicle destined for Golgi

Question 16

Smooth ER

Answer 16

• Extends from rough ER

- Lacks ribosomes as they don’t make/synthesis proteins

Question 17

Smooth ER function:

Answer 17

• Housing unit/storage for proteins and enzymes
• Synthesise lipids (including steroids and phospholipids)
• Storage of cell-specific proteins (as not all cells make all proteins)

Question 18

Golgi apparatus structure

Answer 18

3-20 cisternae stacked on top of each other

Question 19

Golgi function

Answer 19

• Modify, sort, package and transport proteins received from rough ER using enzymes in each cisternae (each cisternae contain enzymes for different functions)
• formation of:
  — Secretory vesicles (proteins from exocytosis)
  — Membrane vesicles (plasma membrane molecules that fuse to the membrane)
  — Transport vesicles (molecules to mature lysosome)

Question 20

Golgi process

Answer 20

1) Proteins received from rough ER via the convex cis face
2) Modifications occur within each sac (formation of glycoproteins, glycolipids, lipoproteins)
3) Proteins move from sac to sac and mature at exit cisternae (concave trans face)

Question 21

Lysosomes

Answer 21

• Vesicles formed from Golgi membrane
• Contain powerful digestive enzymes (highly acidic inside)
  — Membrane proteins pump H+ in to maintain acidic pH
  — Rest of cell protected by membrane

Question 22

Lysosome function

Answer 22

• Destroying/breaking down a variety of cellular components, pathogens and antigens
• digestion of:
  — Substances that enter cell
  — Cell components (e.g organelles) - autophagy
  — Entire cells - autolysis
• Once digested, all building blocks (amino acids, lipids etc.) are recycled

Question 23

Components of mitochondria

Answer 23

• outer mitochondrial membrane
• inner mitochondrial membrane with folds (cristae)
• mitochondrial matrix
• inter membrane space
• small genome (37 genes) encoding mitochondrial specific products

Question 24

Cytoskeleton

Answer 24

• structural support system of cell

- act as scaffolding across cell: fibres/filaments help maintain cell shape, size and integrity

Question 25

Cytoskeleton function

Answer 25

Involved in/support: - Intracellular transportation - Cell movement - Contractibility - Tensile strength of cell structure

Question 26

Types of cytoskeleton

Answer 26

Microfilaments, intermediate filaments, microtubules

Question 27

Microfilaments structure

Answer 27

Two intertwined long chains/strands of ACTIN

Question 28

Microfilaments location

Answer 28

Around periphery and lining of cell interior

Question 29

Microfilaments function

Answer 29

Cell shape Bear tension and weight by anchoring cytoskeleton to plasma membrane proteins Promote amoebic mobility (crawling movement of cells) if required Support microvilli Muscle contraction Division of animal cells Cytoplasmic streaming in plant cells

Question 30

Intermediate filaments structure

Answer 30

Fibrous protein (KERATIN) coiled into cables

Question 31

Intermediate filament location

Answer 31

In cell cytoplasm

Question 32

Intermediate filament function

Answer 32

- Bear tension and weight through cell (e.g during cell anchoring) - Act as scaffold for cellular organelles (e.g nucleus) - Formation of nuclear lamina

Question 33

Microtubules structure

Answer 33

Hollow tubes formed by coiled TUBULIN (globular protein) dimers (alpha and beta)

Question 34

Microtubules location

Answer 34

Extends from centriole into cytoplasm/nucleus

Question 35

Microtubules function

Answer 35

- Support cell shape and size (compression resisting “girders”) - Guide for movement of organelles E.g vesicles from Golgi to membrane: motor proteins attach to receptors on vesicles and transport them by ‘walking’ along microtubules (and microfilaments in some cases) - Chromosome movement/organisation in cell division - Support and movement of cilia/flagella - cell motility

Question 36

Dynamic cytoskeleton structures

Answer 36

Microfilaments and microtubules (intermediate filaments are the most permanent of the three) - can be assembled/disassembled as required

Question 37

Cell-cell recognition glycoprotein composition

Answer 37

carbohydrates-oligosaccharides + protein

Question 38

Cell-cell recognition glycoprotein example

Answer 38

major histocompatibility (MHC) proteins