Lecture 6: Cell structure and function

Question 1

What are the 3 components that make up the cytoskeleton: in order from smallest to biggest

Answer 1

Microfilaments, Intermediate filaments and microtubules

Question 2

Microfilaments : materials made from, function and location, permanence

Answer 2

made of actin and myosin. Anchors the cytoskeleton to plasma membrane proteins, therefore found lining the periphery of the cell. Assembled and disassembled as required

Question 3

Intermediate filaments : materials made from, function and location, permanence

Answer 3

made of keratin mostly. Bears tension and weight throughout the cell, stabilising position of organalles therefore found in cytoplasm. Most permanent of cytoskeleton

Question 4

Microtubules: materials made from, function and location, permanence

Answer 4

made from alpha and beta tubulin dimers. They guide the movement of organelles and chromosomes. Support the movement of cillia and flagella. They extend from the centre of cell.

Question 5

List the functions of membrane proteins

Answer 5

Transport, Enzymatic activity, signal transduction, cell to cell recognition, intercellular joining and attachment of the Cytoskeleton and ECM.

Question 6

What is an integral protein

Answer 6

one that is embedded partially or fully into the membrane but doesn’t span it.

Question 7

Describe the levels of DNA packaging in the Nucleus from smallest to biggest

Answer 7

DNA, the double helix < wrapped around 8 histones = nucleosome < nucleosomes linked together = chromatin < 3 or more chromatin strands = chromatin fiber < looped domains of chromatin fibre < chromosome

Question 8

What is the nucleolus

Answer 8

this is the middle of the nucleus which is the site of synthesis and assembly of ribosomes.

Question 9

Where is DNA housed in the nucleus

Answer 9

Between the nuclear lamina (lining of the nuclear envelope) and the nucleolus.

Question 10

Which form of DNA is the most inaccessible but easiest to organise

Answer 10

chromosomes

Question 11

Which form of DNA is the most accessible but hardest to organise

Answer 11

chromatin

Question 12

What is the smooth ER: where is it and function

Answer 12

Part of the RER that lacks ribosomes so doesn’t make proteins but stores cell specific proteins and enzymes and synthesises lipids (steroids and phospholipids).

Question 13

What is the structure and function of the Golgi apparatus

Answer 13

3-20 flattened membranous sacs called cisternae. It makes combinations of glyco, lipid, proteins. and modifies proteins, packaging them for transport to their destination.

Question 14

is the mitochondria part of the endomembrane system ?

Answer 14

no

Question 15

What are the 4 things that prokaryote and eukaryote cells have in common

Answer 15

plasma membrane, ribosomes, cytosol, (DNA,RNA and protein)

Question 16

What are the differences between prokaryote and eukaryote cells

Answer 16

prokaryote cells are smaller and lack membrane bound organelles (no nucleus) compared to eukaryotes which have membrane bound organelles.

Question 17

What are peripheral membrane proteins

Answer 17

proteins associated with the membrane but not actually embedded in it.

Question 18

What is the intercellular joining function of transmembrane proteins

Answer 18

Linkers anchoring proteins in the other cells plasma membrane together with or to protein filaments inside or outside the cell

Question 19

What is cell to cell recognition function of transmembrane

Answer 19

Glycoprotein dots are cell identity markers allowing cells to recognise same cells during tissue formation and also recognise foreign cells that are dangerous

Question 20

What is attachment function of transmembrane proteins

Answer 20

Microfilaments of the cytoskeleton or fibres of the ECM may be attached to the transmembrane proteins to maintain structure shape and fixed location of membrane proteins. Proteins adhered to the ECM can also coordinate extra and intracellular change.

Question 21

What is an attachment transmembrane protein

Answer 21

fibronectin