Biology

Characteristics of life

Movement, Responsiveness, Growth, Reproduction, Energy, Excretion, Nutrition

Homeostasis

The process by which living organisms maintain a stable internal environment despite changes in external conditions.

Cell membrane

A selectively permeable phospholipid bilayer composed mainly of proteins and lipids

Phospholipid bilayer

Two layers that lipids/proteins are arranged into that make up a single membrane.

Integral proteins

Permanently embedded proteins in the cell membrane

Peripheral proteins

Membrane-associated proteins that temporarily attach to the surface of the lipid bilayer or integral proteins without penetrating the hydrophobic core

Differentially permeable

Membrane selectively allows certain substances to pass through while blocking others, enabling cells to regulate their internal environment.

Passive transport

Movement of particles down the concentration gradient that does not require energy (ATP).

[types include diffusion, facilitated diffusion, and osmosis]

Active transport

Movement of particles against the concentration gradient that require the energy (ATP).

Diffusion

The passive movement of particles from high concentration to low concentration down the concentration gradient.

Concentration gradient

The difference in concentration between two areas that causes particles to move from high concentration to low concentration (diffusion).

Net diffusion

The overall movement of particles from high concentration to low concentration

Osmosis

The movement of water through a semi-permeable membrane, from high solvent concentration to low solvent concentration.

Osmotic pressure

The pressure needed to prevent water moving across a semi‑permeable membrane.

Water potential

The tendency of water to move from one area to another due to factors such as osmosis, gravity, and pressure.

[Denoted by Ψ and measured in kiloPascals (kPa]

Hypertonic solution

Greater concentration of solutes than another solution

Hypotonic

Lower concentration of solutes than another solution

Isotonic

Same concentration of solutes than another solution

Facilitated diffusion

Passive process in which water-soluble materials move with the concentration gradient, from high to low solute concentration

Active transport

Energy-dependent movement of molecules or ions across a cell membrane from a region of lower concentration to a region of higher concentration, against the concentration gradient.

ATP

Adenosine Triphosphate

Loop System

A circular situation where the body responds to a change or stimulus

Negative Feedback

The response reduces/removes the original stimulus to restore balance

Positive Feedback

The response reinforces/amplifies the original stimulus, pushing the system further

Stimulus

A change in the internal or external environment that disrupts the normal range of a physiological variable

Receptor

Detects changes in the internal and external environment

Modulator

Receives information from sensors, compares it to a set point, and sends signals to effectors to maintain internal stability

Effector

A muscle, gland, or organ that responds to signals from the control centre to restore balance and maintain homeostasis.

Feedback

The response that a system sends back to itself to change or reinforce the original stimulus.

Vasodilation

The widening of blood vessels, increasing blood flow.

Vasoconstriction

The narrowing of blood vessels, reducing blood flow

Insulin

Lowers blood glucose

[by helping glucose move from the bloodstream into the body’s cells for energy or storage]

Glucagon

Raises blood glucose

[by telling the liver to release stored glucose back into the bloodstream]

Excretion

The biological process in which organisms eliminate metabolic wastes such as urea, carbon dioxide, salts, etc to maintain internal balance (homeostasis)

Dialysis

Diverting the blood through an artificial kidney machine which cleans it, then returns the blood to the body

Neurons

Nerve cells which convey information in the form of nerve impulses

Nerve Impulses

Electrical messages sent along a neuron

Sensory/Afferent Neurons

Neurons with specialised receptors, which carry messages from receptor organs to the Central Nervous System

Connector/Relay Neurons

Neurons which transmit messages between neurons in the central nervous system

Motor neurons

Neurons which carry messages from the central nervous system to effectors (muscles and glands) that relay messages into action

Presynaptic cell

Sends signals by releasing neurotransmitters

Postsynaptic cell

Recieves signals by receptors binding to neurotransmitters

Chemoreceptors

Sensitive to chemicals (e.g. odour) and found in the nose and tongue

Mechanoreceptors

Sensitive to touch, pressure, sound and motion, and found in the skin, inner ears, and muscles

Pain receptors

Sensitive to chemical changes in damaged cells, and found in the body (mostly skin)

Thermoreceptors

Sensitive to change in temperature, and found in the skin

Photoreceptors

Sensitive to light, and found in the eyes.

Reflex

An involuntary, nearly instantaneous movement in response to stimulus