Active Transport & Homeostasis

Life Science: Molecular

Membrane ProteinsTransporters are transmembrane proteins that use energy to move molecules across a membrane.

Active TransportLow Concentration

Cell Membrane

High Concentration

Low Concentration

Cell Membrane

High Concentration

Active transport is the movement of molecules through a membrane against a concentration difference.

Protein pumps use energy to move molecules such as calcium, potassium, and sodium ions across the membrane against a concentration gradient. – sodium-potassium pump

• pumps sodium out • pumps potassium in

Transmembrane Pumps

Active Transport

Active TransportLarger molecules can be transported by movements of the cell membrane known as bulk transport. – Endocytosis is the process of taking material into the

cell by infolding of the cell membrane. • phagocytosis - cell eating • pinocytosis - cell drinking

– Exocytosis is a process of releasing large amounts of materials from the cell.

Active Transport

Homeostasis• Homeostasis means maintaining a constant

internal environment. • Cells need to maintain a narrow range of

conditions to stay alive. – temperature – pH – salinity – minerals – glucose

Hypothalamus• Hypothalamus = master nerve control center

➡ receives information about internal conditions from nervous system

➡ releases hormones to maintain homeostasis

• Pituitary gland = master endocrine gland ➡ secretes broad range of hormones

to regulate other glandsin the body hypothalamus

pituitary

Chemical Controls➡ Neurotransmitters released by neurons ➡ Hormones released by endocrine glands

axon

endocrine gland

receptor proteins

target cell

receptor proteins

hormone carried by blood

neurotransmitter

Feedback• There are two ways to maintain homeostasis

– Positive feedback – Negative feedback

Maintaining Homeostasis

high

low

hormone 1

lowersbody condition

hormone 2

gland

specific body condition

raisesbody condition gland

Negative FeedbackModel

Blood Osmolarity

Osmoregulation

osmoreceptors inhypothalamus

nephron

nephron

ADH

promoteswaterreabsorption

increase thirst

renin

promotessodiumreabsorption

high salt

pituitary

angiotensin

adrenalgland

aldosterone

nephron (JGA)

low blood pressureJuxtaGlomerular Apparatus