Lecture 6: INTRO Cell structure and function

Question 1

What is cell theory?

Answer 1

1. All living organisms are composed of one or more cells
2. The cell is the basic unit of structure and organisation
3. All cells arise from pre existing cells (via mitosis or meiosis)

Question 2

What are the common features of prokaryotes and eukaryotes?

Answer 2

Both have cell surface plasma membrane
Have ribosomes
Have cytosol
Have DNA, RNA and protein

Question 3

What are the differences between prokaryotes and eukaryotes

Answer 3

Eukaryotes have membrane bound organelles and are larger

Prokaryotes have no membrane bound organelles and are smaller

Question 4

What is cytoplasm?

Answer 4

Everything inside the plasma membrane including the organelles, but not including the nucleus

Question 5

What is cytosol?

Answer 5

The fluid in the cytoplasm - composed of water and dissolved substances (ions, ATP, proteins, lipids)

Question 6

What is the endomembrane system?

Answer 6

The organelles of a cell involved in packaging, labelling, and shipping molecules around the cell

Made up of:
Nucleus
ER smooth and rough
Golgi apparatus
Lysosomes

Question 7

Plasma membrane function

Answer 7

The plasma membrane is a selectively permeable barrier controlling the passage of substances in and out of the cell

Question 8

Plasma membrane structure

Answer 8

Double layer of phospholipids with embedded proteins

Question 9

Phospholipid structure

Answer 9

Made up of a hydrophilic phosphate head and two hydrophobic fatty acid tails arranged as a tail to tail bilayer

Question 10

What are integral proteins

Answer 10

proteins embedded partially or fully in the plasma membrane

Question 11

What are transmembrane proteins

Answer 11

Type of integral protein that spans the whole membrane coming in contact with extracellular and cytoplasmic areas

Question 12

What are peripheral membrane proteins

Answer 12

Associated with the membrane but not embedded in them

Question 13

What is function of peripheral membrane proteins

Answer 13

Cell to cell identification and facilitate intercellular communication

Question 14

What is function of integral proteins

Answer 14

Mediate movement of hydrophilic substances

Question 15

What are 6 functions of plasma membrane proteins?

Answer 15

Transport
Enzymatic activity
Signal transduction
Cell-cell recognition
Intracellular joining
Attachment to cytoskeleton and extracellular matrix

Question 16

Nucleus function

Answer 16

House DNA in eukaryotic cells
Make RNA and assemble ribosomes
pores regulate movement of substances (protein and mRNA) in and out
molecule segregation to allow temporal and spatial control of cell function

Question 17

Nucleus structure

Answer 17

The largest distinct structure in the cell
Made up of:
nucleolus
nuclear envelope
nuclear pores

Question 18

What is nucleolus

Answer 18

Dark region of nucleus where rRNA are produced later forming ribosomes

Question 19

What is nuclear pores?

Answer 19

Gaps in the nuclear envelope controlling exit and entry into nucleus

Question 20

What is nuclear envelope

Answer 20

Membrane surrounding nucleus

Question 21

What is DNA

Answer 21

Deoxyribonucleic acid - encodes our phenotype

Question 22

What is a histone

Answer 22

Protein which DNA binds to

Question 23

What is nucleosome

Answer 23

Structure formed from DNA wrapped twice around 8 histone proteins

Question 24

What is chromatin

Answer 24

A length of nucleosomes (structures with DNA wrapped around 8 histone proteins)

Question 25

What is chromosome

Answer 25

Fully condensed form of DNA where chromatin condenses further to chromatin fiber which condenses into loops then stacking to form chromosomes

Question 26

What are genes

Answer 26

A length of DNA that codes for a phenotype/function

Question 27

What is diploid organism

Answer 27

Organisms with two sets of chromosomes

Question 28

What determines accessibility of DNA in the nucleus

Answer 28

Extent of coiling - more coiling reduces accessibiltiy

Question 29

What are ribosomes

Answer 29

Two subunits, small and large made up of rRNA in complex with many proteins Assembled in nucleolus and exited through nuclear pores

Question 30

What do ribosomes do

Answer 30

Protein synthesis, they are found in two places free in the cytoplasm- making cytosol proteins attached to RER- making endomembrane proteins

Question 31

What is ER

Answer 31

An extensive network of tubes and tubules, extending from the nuclear membrane

Question 32

What are the 2 types of ER

Answer 32

Rough and smooth

Question 33

What is rough ER

Answer 33

Extension of nuclear membrane dotted with attached ribosomes

Question 34

What is rough ER function

Answer 34

Ribosomes produce proteins which enter the lumen of ER for folding. Then rough ER membrane surrounds protein forming transport vesicles destined for golgi Production of secreted proteins, membrane proteins, organelle proteins

Question 35

What is smooth ER

Answer 35

Extension of rough ER with no ribosomes

Question 36

What is smooth ER function

Answer 36

Lipid synthesis Storage of cell-specific proteins Function of smooth ER varies a lot from cell to cell

Question 37

What is golgi appartus

Answer 37

A complex made up of 3-20 flattened membranous sacs called cisternae stacked on top of one another

Question 38

What is golgi apparatus function

Answer 38

Modify sort package and transport proteins from rough ER using enzymes present in each cisternae Formation of vesicles (3types): secretory vesicles membrane vesicles transport vesicles

Question 39

What are lysosomes

Answer 39

Vesicles produced by golgi apparatus containing digestive enzymes Highly acidic due to constant pumping of H+ ions via membrane proteins

Question 40

What is lysosome function

Answer 40

Digestion of: substances entering cell cell components entire cells

Question 41

What are mitochondria

Answer 41

Membrane bound organelles that generate ATP through cellular respiration Made of inner and outer membrane where the inner membrane folds to form cristae. Inside of mitochondria is filled with fluid called mitochondrial matrix Carry own genome Number of mitochondria depend on ATP needs

Question 42

How does mitochondria produce ATP

Answer 42

ATP -> ATP + phosphate Energy is released in this process

Question 43

What is cytoskeleton

Answer 43

Structural support system of cell - determines size shape integrity of cell

Question 44

What is cytoskeleton function

Answer 44

Act as scaffolding across cell | Involved in intracellular transportation and cell movement

Question 45

What are the 3 types of fibers that make up cytoskeleton

Answer 45

Microfilaments Intermediate filaments Microtubules

Question 46

What is the diameter of microfilaments

Answer 46

7 nm

Question 47

What are microfilaments and where are they found

Answer 47

Comprised of actin molecules assembled in two long chains, twisted around each other Found around the periphery and lining the interior of cell

Question 48

What is microfilament function

Answer 48

Bear tension and weight by anchoring cytoskeleton to plasma membrane proteins Promote amoeboid motility if required (movement of cell)

Question 49

What is the diameter of intermediate filaments

Answer 49

8-12nm

Question 50

What are intermediate filaments and where are they found

Answer 50

Comprised of diverse range of different materials and found in cytoplasm

Question 51

What is intermediate filament function

Answer 51

Bear tension and weight throughout the cell | Act as scaffold for cellular organelles

Question 52

What is the diameter of microtubules

Answer 52

A tubular structure, 25nm in diameter with a central lumen of 15nm

Question 53

What is microtubule

Answer 53

Comprised of tubulin dimers coiled to form a tube | Extends from centriole into cytoplasm/nucleus

Question 54

What are functions of microtubules

Answer 54

Support cell shape and size Guide for movement of organelles Chromosome organisation - cell division Support and movement of cillia and flagella