Cellular Aspects of Ageing

Question 1

What is ‘normal ageing’?

Answer 1

The gradual and spontaneous changes that occur in maturation from infant to young adult, these changes create a normal physiological decline seen in middle and late adulthood

Question 2

What are the consequences of ageing?

Answer 2

Reduced tissue/physiological function, decreased resistance to stress (physical and psychological) and increased susceptibility to disease (age-related diseases)

Question 3

What different levels does ageing occur on?

Answer 3

Molecular, cellular, tissues and organ systems

Question 4

What happens to the cells in cellular ageing?

Answer 4

Response to damage or stress can lead to apoptosis or arrested cell growth (senescence)

Question 5

Why is there a balance between cancer prevention and ageing?

Answer 5

Apoptosis and senescence are mechanisms which prevent the development of cancer, but also work to facilitate ageing

Question 6

What factors affect life expectancy?

Answer 6

Disease processes, medical treatment, lifestyle choices, nutrition, heredity

Question 7

What are the two main groups of ageing theories?

Answer 7

Programmed theories (ageing has an internal biological clock) and error theories (ageing is a result of assaults that damage cells or organs so they no longer function properly)

Question 8

What are telomeres?

Answer 8

Specialise DNA sequences at the end of chromosomes

Question 9

What is the base sequence of telomeres?

Answer 9

TTA GGG

Question 10

What is the role of telomerase?

Answer 10

The enzyme which fills the gap in word down telomeres by attaching bases to the end of chromosomes

Question 11

Describe the programmed senescence theory (telomeric theory of sensence) of ageing

Answer 11

Telomeres shorten with each cell division and when they become too short, this causes the cell to enter senescence; with ageing, telomerase levels decrease and the telomeres become shorter and shorter so more and more cells enter senescence

Question 12

Describe the endocrine theory of ageing

Answer 12

Biological clocks act through hormones to control the pace of ageing, the hormones affect growth, metabolism, inflammation, stress and temperature

Question 13

Describe the immunologic theory of ageing

Answer 13

A programmed decline in the immune system which leads to an increased vulnerability to disease, ageing and death

Question 14

What is a free radical?

Answer 14

A molecule with an unpaired, highly reactive electron which works to grab electrons from any molecule in its vicinity and whilst doing this causes damage to the other molecule

Question 15

What does the body have to defend against free radicals?

Answer 15

Natural antioxidants in the body e.g. Bilirubin, enzymes such as superoxide dismutase (SOD), catalase, and glutathione peroxidase and dietary antioxidants e.g. Vitamin E and C

Question 16

Where are reactive oxygen species predominantly produced?

Answer 16

Mitochondria in oxidative phosphorylation

Question 17

Describe the wear and tear theory of ageing

Answer 17

Years of damage to cells, tissues and organs eventually wears them out

Question 18

Describe the rate of living theory of ageing

Answer 18

The greater an organisms basal metabolic rate, the shorter the life span

Question 19

Describe the cross-linking theory of ageing

Answer 19

The accumulation of cross-linked proteins damages cells and tissue, and slows down bodily processes. There is loss of flexibility of connective tissue and there are micro vascular changes in arteries

Question 20

Describe the catastrophe theory of ageing

Answer 20

Any damage to the enzyme systems that synthesise proteins in the body cause improper protein synthesis and these faulty proteins continue to accumulate until they reach a level which damages the cell/tissue. When enough damage accumulates, this may result in cell malfunctioning, which eventually leads to death

Question 21

What is epigenetics?

Answer 21

Inherited and reversible modification to nucleotides or chromosomes that do not change the sequence but can alter gene expression

Question 22

What heart changes occur with ageing?

Answer 22

Valves thicken and stiffen, number of pacemaker cells decrease, fatty and fibrous tissue increases around the SAN (can slow HR slightly), hypertrophy of left ventricle, heart may fill more slowly (therefore an increased role of atrial contraction is often required)

Question 23

What changes in stem cells occur with ageing?

Answer 23

There is a decline in stem cell function with age, leading to stem cell exhaustion

Question 24

How does the body’s response to nutrients change with ageing?

Answer 24

•Nutrient sensing is a cell’s ability to recognise and respond to fuel substrates such as glucose but in old age, the homeostatic mechanisms involved in nutrient sensing decline which results in development of fat mass etc which have consequences for the development of other diseases e.g. Diabetes type II

Question 25

How may calorie restriction improve life length?

Answer 25

Calorie restriction postpones senescence, and may also play a role in prevention of disease. There is some evidence that caloric restriction induces levels of some antioxidant enzymes and downregulates IGF-1

Question 26

Describe the free radical theory of ageing

Answer 26

During ageing, damage produced by free radicals causes cells and organs to stop functioning, and these free radicals are predominantly produced as a result of oxidative phosphorylation in mitochondria (produces reactive oxygen species); as mitochondrial dysfunction occurs with ageing, this results in an increased production of reactive oxygen species