Carbs and lipids

What are the two learning objectives of this lecture?

Explain where lipids and carbohydrates are found in the body and their functions; summarise a disorder associated with lipids and carbohydrates.

What is selective diffusion?

Selective passage of molecules through membrane proteins.

What is active transport?

Energy-dependent movement of molecules across membranes.

What is facilitated diffusion?

Movement of molecules through membrane proteins without energy expenditure.

Where are lipids primarily found in the body?

Plasma, adipose tissue, and biological membranes.

Why are biological membranes essential for life?

They store energy, maintain gradients, separate cellular compartments, and permit information transduction.

What membrane lipids are found in addition to phospholipids?

Glycolipids and cholesterol.

Why is there no cellular life without lipids?

Lipids are essential for membrane formation and cellular compartmentalisation.

What are fatty acids?

Long hydrocarbon chains with a terminal carboxyl group.

What is a saturated fatty acid?

A fatty acid containing no double bonds.

What is a monounsaturated fatty acid?

A fatty acid containing one double bond.

What is a polyunsaturated fatty acid?

A fatty acid containing two or more double bonds.

What are essential fatty acids (EFAs)?

Fatty acids required for maintaining normal bodily functions and homeostasis.

Which part of a fatty acid is hydrophobic?

The hydrocarbon tail.

What drives spontaneous formation of lipid bilayers?

Hydrophobic interactions between lipid tails.

What forces help stabilise lipid bilayers?

Van der Waals forces, electrostatic interactions and hydrogen bonding.

In what form are fatty acids primarily stored?

Triglycerides.

Why are triglycerides important?

They are an efficient energy storage molecule.

How does triglyceride energy storage compare to glycogen?

1 g of triglyceride stores about 6 times more energy than glycogen.

What are the two main types of adipose tissue shown in the lecture?

Brown fat and white fat.

What enzyme in the paracrine pathway is a target of NSAIDs?

COX-2.

What is the role of COX-2?

It is involved in inflammation and pain.

What does NSAID stand for?

Non-steroidal anti-inflammatory drug.

Why is cholesterol important?

It is essential for cellular structure and function.

Which steroid hormones are derived from cholesterol?

Cortisol and aldosterone.

Which sex hormones are derived from cholesterol?

Progesterone, oestrogen and testosterone.

What vitamin is derived from cholesterol?

Vitamin D.

What digestive compounds are derived from cholesterol?

Bile acids/bile salts.

How is cholesterol transported after intestinal absorption?

In chylomicrons.

What is an atheroma?

A fatty deposit on the inside of an artery.

How can a small atheroma affect blood flow?

It can significantly reduce blood flow and cause tissue hypoxia.

What is hyperlipidaemia?

Abnormally high levels of lipids in the blood.

What is found in the core of an atheroma?

Lipid-rich material.

Why are atheromas often called plaques?

They are dynamic structures containing cells that can grow, die, degenerate and calcify.

What happens when an artery wall weakens?

The radius increases and the wall balloons outward.

What is an aneurysm?

Abnormal ballooning of an artery due to wall weakness.

What is a common site for an aneurysm?

The aorta.

Where do aneurysms commonly occur in the brain?

Cerebral arteries.

Why are cerebral arteries prone to aneurysms?

Their twisted structure creates additional wall stress.

What is a berry aneurysm?

An aneurysm that forms at branch points in cerebral arteries.

How can cerebral aneurysms present clinically?

Incidental discovery, rupture causing subarachnoid haemorrhage, or symptoms from mass effect.

What type of homeostatic process controls blood pressure rapidly?

Negative feedback.

What are the main blood pressure sensors?

Baroreceptors.

Where are the major baroreceptors found?

In the carotid sinus.

What happens when blood pressure increases?

Baroreceptors stretch and increase action potential frequency.

Where do baroreceptor signals travel?

To the medulla oblongata in the brainstem.

What brain region is responsible for blood pressure control?

The nucleus of the solitary tract (NTS) near the medulla oblongata.

What is located next to the carotid sinus?

The carotid body.

What is found in the carotid body?

Chemoreceptors.

How can atheroma formation affect baroreceptor sensitivity?

It stiffens the arterial wall and reduces receptor sensitivity.

How may reduced baroreceptor sensitivity contribute to hypertension?

Blood pressure is regulated at a higher-than-normal set point.

How might atheromas contribute to hypertension through the brainstem?

They may cause hypoxia in the medulla, which can promote hypertension.

What are carbohydrates composed of?

Carbon, hydrogen and oxygen.

What is the elemental ratio of carbohydrates?

1:2:1.

What is the major dietary function of carbohydrates?

Providing energy.

What is a monosaccharide?

A single sugar molecule.

Name four monosaccharides.

Glucose, fructose, galactose and mannose.

What is a disaccharide?

Two monosaccharides joined by a glycosidic bond.

What sugars make up sucrose?

Glucose and fructose.

What sugars make up maltose?

Glucose and glucose.

What sugars make up lactose?

Galactose and glucose.

What is an oligosaccharide?

A carbohydrate containing 3–10 monosaccharides.

Give two examples of oligosaccharides.

Heparin and blood group antigens.

What is a polysaccharide?

A carbohydrate composed of many monosaccharides.

What is glycogen?

A polysaccharide storage form of glucose.

What type of bond joins glucose units in glycogen?

Alpha-1,4 glycosidic bonds.

What type of bond joins glucose units in cellulose?

Beta-1,4 glycosidic bonds.

What protein forms the core of glycogen?

Glycogenin.

What hormone is secreted when blood glucose rises after a meal?

Insulin.

What enzyme does insulin stimulate in liver cells?

Glycogen synthase.

What does glycogen synthase do?

Adds glucose molecules to glycogen chains.

What enzyme breaks down glycogen?

Glycogen phosphorylase.

What is released when glycogen is broken down?

Glucose.

What diabetic complications are associated with activation of the polyol pathway?

Damage to nerves, retina and kidneys.

What accumulates during excessive polyol pathway activation?

Sorbitol and reactive oxygen species.

What is the first pathological microvascular change in diabetes?

Vasoconstriction.

What happens to capillaries as diabetes progresses?

Basement membrane thickening occurs.

How common is neuropathy after more than 10 years of diabetes?

Up to 50% of patients develop it.

What type of nerve damage is typical in diabetic neuropathy?

Distal sensory nerve fibre degeneration.

What causes diabetic neuropathy?

Hyperglycaemia-induced nerve damage and reduced blood flow.

What symptoms can peripheral diabetic neuropathy cause?

Muscle weakness and loss of reflexes.

What foot problems can develop from diabetic neuropathy?

Foot deformities, blisters and ulcers.

Why do diabetic foot ulcers occur?

Injuries go unnoticed because of sensory loss.

What may happen if diabetic foot infections spread to bone?

Amputation may be required.

What does autonomic neuropathy affect?

Digestion, bowel function, bladder function, sexual response and perspiration.

How can autonomic neuropathy affect the cardiovascular system?

It can affect heart function and blood pressure control.

What is diabetic retinopathy?

Damage to retinal blood vessels caused by diabetes.

What is HbA1c?

A form of glycated haemoglobin used to measure long-term blood glucose control.

What does a high HbA1c indicate?

Poor blood glucose control.

What disease complications are associated with elevated HbA1c?

Cardiovascular disease, kidney damage and retinopathy.

How often should HbA1c typically be monitored in diabetic patients?

Every 3 months.

Why is lowering HbA1c beneficial?

It reduces the risk of diabetic complications.

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