AOS 2 Unit 1 Chapter 5 Bio

The purpose of the endocrine system

• responsible for the production and secretion of hormones, which regulate body processes such as:

• Growth and development

• Metabolism

• Reproduction

• Homeostasis

signalling molecule

 a molecule which can interact with and initiate a response in a target cell

When is a signalling molecule used?

If one cell detects a change in the environment, communication allows other cells to respond.

-signalling molecules can be used

hormone 

a signalling molecule released from endocrine glands that regulates the growth or activity of target cells

• They travel to target cells, where they bind to specific receptors.

• This binding triggers a specific cellular response such as:

  • Altering gene expression

  • Changing enzyme activity

  • Regulating transport across membranes

Only cells with the correct receptor respond to a hormone.

How the Endocrine System Works

1. Endocrine gland produces hormone

2. Hormone released into bloodstream

3. Travels throughout body

4. Binds to receptors on target cells

5. Causes a specific response

gland 

a group of cells that secretes chemical substances to regions of the body or discharges them into the surroundings

Which glands are located in the brain

Hypothalamus

Pituitary gland

Pineal gland

Glands in neck

Thyroid gland (butterfly shaped gland)

Parathyroid glands base of neck 4 small glands

Hypothalamus ( small region in brain)

Maintains homeostasis (e.g. temperature) and regulates the pituitary gland via releasing hormones

Pituitary gland (pea sized area in brain)

“Master gland”; secretes hormones that control other endocrine glands (e.g. thyroid, adrenal glands, gonads)

Pineal gland

Secretes melatonin; regulates sleep–wake cycles and circadian rhythms

Thyroid gland (butterfly shaped gland in neck)

Produces thyroxine; regulates metabolic rate, growth, and development

Parathyroid glands (base of neck) (4 small glands)

Regulate calcium levels in blood, important for muscle contraction and nerve function

Thymus (between lungs)

Produces thymosin; involved in development of immune cells (active mainly before puberty)

Pancreas (sits across the back of the abdomen)

Regulates blood glucose levels via insulin and glucagon; also has digestive (exocrine) functions

(Found above the kidneys)

Adrenal glands

Produce hormones (e.g. adrenaline, cortisol) involved in stress response, metabolism, blood pressure, and immune function

Ovaries

Produce oestrogen; regulate female reproductive system and secondary sexual characteristics

Testes

Produce testosterone; regulate male reproductive system and secondary sexual characteristics

Placenta

Produces hormones that maintain pregnancy and support foetal development

Growth hormone (Pituitary)

Stimulates protein synthesis, cell division, and growth of bones and muscles

Thyroxine (Thyroid)

Increases metabolic rate by stimulating cellular respiration

Increases ATP production

Adrenaline(adrenal glands)

Increases heart rate, blood pressure, breathing rate; redirects blood to muscles

Insulin Pancreas (beta cells)

Promotes uptake of glucose into cells and storage as glycogen, lowering blood glucose

Glucagon (Pancreas (alpha cells))

Stimulates breakdown of glycogen to glucose in liver, increasing blood glucose

Nephron

Hormone Types

• Protein (peptide) → hydrophilic, cannot cross membrane (e.g. insulin)

• Steroid (lipid) → hydrophobic, can cross membrane (e.g. testosterone)

Endocrine vs Nervous

• Endocrine = slow but long-lasting

• Nervous = fast but short-lived

Hormones travel in blood → widespread effects

Kidney

Purpose of Excretory system

• Removes waste substances from the body

• Maintains homeostasis (stable water + ion balance)

What is the excretory system?

• Removes waste substances from the body

Maintains homeostasis (stable water + ion balance)

What is Nitrogenous waste?

• Proteins are broken down into amino acids, which are used to build new proteins (e.g. muscle, enzymes).

• Excess amino acids cannot be stored and must be removed quickly, as they become toxic if they accumulate.

• Nitrogenous waste is produced from the breakdown of proteins.

• It is the role of the excretory system to remove this waste before it damages cells.

Process of amino acids being excreted

• In the liver, amino acids undergo deamination:

  • The amine group (–NH₂) is removed

  • Forms ammonia (NH₃) + energy

• Ammonia is highly toxic and requires large amounts of water to excrete.

• In humans, ammonia is converted into urea (less toxic) in the liver.

Urea is transported in the blood to the kidneys, where it is filtered and excreted as urine

The urinary tract

 the series of channels in which urine is produced and excreted from the body

Liver

large organ found in the abdomen that is involved in many metabolic processes including the breakdown of toxins

urea 

the main nitrogenous product of protein breakdown in mammals. Excreted in urine 

kidneys 

a pair of bean-shaped organs that are responsible for removing waste substances from the blood and the production of urine

-The role of the kidneys is to filter blood, reabsorb the useful substances within the filtrate, and secrete the unwanted ones.

urine 

a fluid formed by the kidneys and stored in the bladder. One of the body’s major ways to remove excess water, solutes, and waste substances from the blood

renal arteries

arteries that deliver blood from the heart to the kidneys

afferent capillary

incoming capillaries that deliver blood to the glomeruli of nephrons

efferent capillary

 outgoing capillaries that carry blood away from the glomeruli of nephrons

Nephron structure

Glomerulus → Bowman’s capsule → PCT → Loop of Henle → DCT → Collecting duct

Kidney has 2 main regions:

• Cortex (outer layer) → contains:

  • Glomerulus

  • Bowman’s capsule

  • Proximal Convoluted Tubule (PCT)

  • Distal Convoluted Tubule (DCT)

• Medulla (inner layer) → contains:

  • Loop of Henle

  • Collecting Duct

Renal Capsule

thin protective layer covering the kidney’s outer surface.

Cortex

granular tissue forming the outer portion, between capsule and medulla; where filtration starts (glomerulus, PCT, DCT).

Medulla

inner portion; contains Loop of Henle and Collecting Duct, where urine is concentrated

Nephron Processes 1.Filtration (Bowman’s capsule)

The renal artery delivers blood to the kidney for filtration.

1.Filtration (Bowman’s capsule)

Filtration occurs at the glomerulus, where high pressure forces small molecules into the Bowman’s capsule,

forming primary filtrate

(Only small molecules pass:

• ✔ water, glucose, ions called  glomerular capillaries. 

• ✖ proteins, blood cells remain in   glomerular capillaries.

2. Reabsorption (PCT, Loop, DCT, Collecting duct)

The filtrate enters the proximal convoluted tubule (PCT), where the majority of reabsorption occurs:

• Glucose, amino acids, ions → active transport

• Water → osmosis

3.Loop of Henle

• Descending limb → water reabsorbed via osmosis

• Ascending limb → ions pumped out (no water)
  👉 creates concentration gradient

4.. Secretion (= DCT, Collecting duct)

• Selective reabsorption and secretion occurs depending on the body’s needs

• water

• Excess ions

• Toxins

5.Collecting duct

-Further fine-tunes filtrate composition.

-May reabsorb more water.

• Secretes waste like ammonia into the duct. urea and then urine forms

Other Excretory Organs

Organ	Waste Removed
Lungs	CO₂ + water vapour
Skin	Sweat (water, salts, small urea)
Liver	Detoxifies, produces urea
Digestive tract	Some waste in faeces

Purpose of the digestive system

• Breaks down food into small molecules for absorption by cells.
  
  

• Provides energy (from carbohydrates, fats, proteins) and nutrients (vitamins, minerals) for survival, growth, and reproduction.
  
  

• Animals are heterotrophs – they cannot make their own food so eat other organisms to obtain organic molecules

Carbohydrates

Provide a source of immediate energy

Provide a source of immediate energy

Provide a source of immediate energy

Proteins

Structural components of cells, cell receptors, enzymes

Vitamins

While required in small amounts, many vitamins are used to make enzymes

Minerals

While required in small amounts, minerals are used in many structural components of organisms

digestion

The process of breaking down a substance into its basic components

digestive system 

the collection of specialised tissues and organs responsible for the digestion of food and absorption of nutrients 

Physical (or mechanical) digestion

the processes whereby the mechanical movement of organs and tissues causes this breakdown of food into smaller pieces.

-These movements include chewing, muscle contractions and peristalsis.

Chemical digestion

 -food pieces undergo chemical digestion by enzymes and stomach acid, producing smaller molecules that are capable of being absorbed.

The three major types of digestive enzymes

amylases (which act on carbohydrates), proteases (proteins), and lipases (lipids).

What do enzymes do?

split food molecules in hydrolysis reactions, by adding water molecules.

subunit of amylase

amino acids

subunit of protease

amino acids

subunit of lipase

fatty acids and glycerol

Steps of Digestion IDAE i dig all eggs

1. Ingestion – taking food in (mouth: teeth, saliva, tongue).

 The teeth physically break down food into smaller pieces, whilst  enzymes in the saliva chemically break down the food pieces into a soft mass that  can be swallowed.

2.Digestion – occurs along the digestive tract, where the soft mass travels from the mouth into the body of the organism chemically and physically

3.Absorption – nutrients absorbed through plasma membranes into blood. Energy used by body

4.Elimination/Egestion – undigested food removed as faeces.

Name all 12 organs

oral cavity (mouth)

salivary glands

oesophagus

stomach

liver

gallbladder,

pancreas

small intestine

large intestine

appendix

rectum

anus

Oral cavity

-The beginning of the digestive system

--site of ingestion

-Teeth mechanically break food into small pieces

-digestive amylase enzymes in saliva start the breakdown of carbohydrates,

-lipase enzymes in the mouth start the breakdown of fats. 

-The chewing of food occurs here. 

Salivary glands

that produces and releases saliva into mouth and oesophagus

Oesophagus

foods pushed down A hollow tube connecting the oral cavity to the stomach 

 by (peristalsis)

Stomach

-A temporary storage tank where food is mixed by muscular movements known as churning.

 -Protease enzymes Eg pepsin are secreted by the stomach and begin the digestion of protein .

- Digestive juices HCL are released by the stomach membrane, which creates an acidic environment. 

-Peristalsis of the stomach muscles helps push food along to the small intestine.

liver functions and process

The liver is the site of bile production

roles in regulating metabolism, toxin removal, and processing nutrients. 

-The liver stores excess glucose in the form of glycogen, which can be converted back to glucose when needed for energy. 

6. Gallbladder 

After being produced in the liver, bile is stored and further concentrated in the gallbladder before it is released into the small intestine

7. Pancreas 

-Digestive enzymes (insulin and glucagon) are produced in the pancreas and are released when food reaches the first part of the small intestine. 

-regulates blood sugar levels and is responsible for secreting bicarbonate, which neutralises acids in chyme.

8. Small intestine 

The main function of the small intestine 

(divided into three sections: the duodenum, the jejunum, and the ileum) is to absorb nutrients from food. (why it has enormous surface area)

function: enzymes produced in small intestine + enzymes from pancreas + bile from gallbladder AID the breakdown of food in chyme

-further breakdown of carbohydrates, proteins and fats

9.large intestines

(cecum, colon and rectum) function and process

final absorption of water, minerals and vitamins

process:

- water is reabsorbed from undigested food

- food becomes more solid and compact

- faeces ready for egestion

10Appendinix

ocation: sits at the junction between small and large intestines.

role: acts as a 'safehouse' for beneficial gut bacteria and immune cells.

11.rectum

final area of the large intestine that stores faeces for elimination.

12.anus

the end of the digestive tract where faeces are expelled from the body.

chyme

 mixture of partially digested food and digestive juices that passes from the stomach to the small intestine

peristalsis 

 coordinated muscular contractions and relaxations of the digestive tract wall that move food along the system

Digestion Process (Pizza Example)

. Ingestion (Mouth → Oesophagus)

• Teeth physically break pizza into smaller pieces.

• Saliva (amylase + lipase) starts chemical digestion (carbs + fats).

• Food swallowed → moves down oesophagus by peristalsis.

---

2. Digestion (Stomach → Small Intestine)

• Stomach:

  • Churning = physical digestion

  • Acid (pH 1–3) + proteases break down proteins

  • Forms chyme

• Small intestine (duodenum):

  • Bile (liver → gallbladder) → breaks fats into smaller droplets

  • Pancreas:

    • Enzymes → digest carbs, proteins, fats

    • Bicarbonate → neutralises acid

---

3. Absorption (Small Intestine)

• Nutrients fully broken down:

  • Carbs → glucose

  • Proteins → amino acids

  • Fats → fatty acids + glycerol

• Absorbed into bloodstream through villi & microvilli (↑ surface area)

---

4. Elimination (Large Intestine → Anus)

• Water + remaining nutrients absorbed

• Waste becomes faeces

• Stored in rectum → exits via anus

omnivores

medium digestive tract

- digest plant + animal material

Carnivores digestive system?

Shorter, meat easy to digest

Herbivores digestive system?

Long, specialised for cellulose digestion

alimentary canal digestive tract

What do large plants need to move water, minerals and glucose

specialised tranport systems amd is achieved through vascular tissues

xylem and pholem

The importance of water in plants

-photosynthesis metabolic processes

-transport of nutrients and waste

-cooling via evaporation (transpiration)

-maintaing turgor pressure (prevents wiliting/dehydration)

-maintaining correct cell toncity

What is the xylem tissue?

Tubes that transport water and minerals in 1 direction from the roots to the leaves of a plant.

What is the phloem tissue?

Tubes that transport sugars and other nutrients around a plant in 2 directions.

Vascular bundles

Xylem+pholem grouped

Location

-roots >centre

-stems> near outer layer (under bark)

-Leaves>veins

Roots do what?

Provide structure and are a anchor in a ground preventing them from toppling over

Adapation for absorbption

-highly branched roots for increases surface area to volume ratio

root hair cells-cell with hair like extensions that absorb water/minerals from soil into root

What are the 2 pathways in the root system that water and nutrients can move through?

1) Extracellular pathway
2) Cytoplasmic pathway

What is the extracellular pathway?

Pathway with water and solutes dissolved in it, diffuses into gaps between cells

-roots absorb the majority of water from the soil.

-reaches hydrophobic casparian strip, water and solutes forced to enter cells

Fast passive diffusion

What is the cytoplasmic pathway?

-The pathway by which roots absorb the majority of nutrients and essential minerals from the soil.

- mineral ions (and bit of water) diffuse into the cytoplasm

Via

-Diffusion-passive

-Active transport

Ion concentration inside root cells can be 100x higher

This helps draw water via osmosis

Casparian strip

-Water proof barrier in roots

-forces selective entry into xylem

-ensures harmful substances filtered out

What is the equation for photosynthesis?

6CO2 + 6H2O ------> C6H12O6 + 6O2

What is transpiration?

evaporation of water from plant leaves/pores/surface/stoma