Cell Biology and Signalling

Question 1

Definition of a cell

Answer 1

Semi-independent, living unit within the body

Question 2

Definition of an organelle

Answer 2

Subunit within a cell, with a defined structure and performing specific, integrated activities

Question 3

Definition of a tissue

Answer 3

Organised assembly of cells that carry out coordinated activites within the body

Question 4

Defintion of an organ

Answer 4

Assembly of tissues coordinated to perform specific functions within the body

Question 5

Normal range of volume for a cell

Answer 5

1,000-5,000 µm3

Question 6

What factors limit the size of a cell

Answer 6

-limited by rate of diffusion
-movement of metabolites within the cell
-uptake of oxygen from outside the cell
-movement of mRNA from the nucleus

Question 7

At what distance does diffusion become less efficent

Answer 7

Over 50µm

Question 8

What’s the solutions for less efficent diffusion distances

Answer 8

-use of the cytoskeleton to move things around
-creation of giant cells with multiple nuclei
-

Question 9

What can be resolved using a light microscope

Answer 9

Only nucleus and plasma membrane

Question 10

What is the benefit of an electron microscope and how are samples prepared

Answer 10

-An electron microscope is needed to visualise a full range of organelles
-Samples are dead, fixed and dehydrated

Question 11

Range resolveable by the unaided eye, light microscope and electron microscope

Answer 11

-Unaided eye: 0.2mm
-Light microscope: 10mm – 200nm
-Electron microscope: 10mm – 0.1nm

Question 12

Range of length for cells and organelles

Answer 12

Cells: 200µm - 1µm
Organelles: 10µm – 0.5µm

Question 13

Function of the plasma membrane

Answer 13

-defines the boundary of the cell
-regulates the entry and exit of chemicals

Question 14

What are the 3 types of protein polymers in the cytoskeleton

Answer 14

-actin filaments
-microtubules
-intermediate fibres

Question 15

What are the functions of the cytoskeleton

Answer 15

-mechanical strength of cells
-controls shape of cell
-guide movement of substances within cells

Question 16

Functions of the nucelus

Answer 16

-storage of chromosomes
-site of DNA replication
-site of gene expression

Question 17

Function of the nucleolus

Answer 17

-site of rRNA synthesis and ribosome biogenesis

Question 18

Structure of the nuclear membrane/ envelope

Answer 18

-made up of a double phospholipid bilayer
-contains perinuclear space between bilayers
-underneath the inner nuclear membrane is the nuclear lamina (a protein layer)

Question 19

What’s the function of the nuclear envelope

Answer 19

-regulates the entry and exit of mRNA and proteins into the nucleus
-maintains the integrity of the nucleus

Question 20

Structure of the mitocondria

Answer 20

-it is surrounded by a membrane
-the inner membrane folds into cristae that increase surface area

Question 21

Function of the mitocondria

Answer 21

-aerobic oxidation of glucose to produce ATP in the Krebs cycle
-components of the electron transport chain are located in the inner membrane

Question 22

Explain structure and functions of rough endoplasmic reticulum

Answer 22

-made of a membrane bilayer
-surrounded by endosomes (membrane bound vesicles)
-due to being coated with ribosomes, responsible for mRNA translation and synthesis of proteins
-proteins are folded, cys-cys bridges form, enclosed in vesicles and taken to the Golgi apparatus

Question 23

Explain the structure and function of the smooth endoplasmic reticulum

Answer 23

-bilayer membrane surrounded by endosomes
-biosynthesis of membrane lipids and steroids
-start of N-linked glycosylation
-detoxification of xenobiotics

Question 24

What’s the structure and function of a ribosome

Answer 24

-ribosomes are proteins
-responsible for the translation of mRNA and the synthesis of proteins

Question 25

Structure of Golgi apparatus

Answer 25

-made of 4-8 closely stacked membrane bound channels (cisternae)
-proteins delivered from rough endoplasmic reticulum

Question 26

What’s the function of the Golgi Apparatus

Answer 26

-directs proteins in vesicles to their correct location in the cell
-creates lysosomes
-site of glycolysation

Question 27

Function of secretory vesicles

Answer 27

-vesciles fuse with the inner surface of plasma membrane and release contents by exocytosis

Question 28

Describe structure and function of a lysosome

Answer 28

-vescile surrounded by a bilayer
-lysosomes contain hydrolytic enzymes for major cellular macromolecules
-PH5
-involved in organelle autophagy