AQA GCSE Combined Science Biology Overview

eukaryotic cell

A cell with a nucleus and other membrane-bound organelles. Examples include animal and plant cells.

prokaryotic cell

A cell without a nucleus or membrane-bound organelles. Examples include bacteria.

main organelles in an animal cell

Nucleus, cell membrane, cytoplasm, mitochondria, ribosomes.

additional organelles in plant cells

Chloroplasts, cell wall, permanent vacuole (in addition to organelles found in animal cells).

function of the nucleus

Contains genetic material (DNA) and controls the cell's activities.

function of mitochondria

Site of aerobic respiration, where energy is released from glucose.

function of chloroplasts

Site of photosynthesis, where light energy is used to make glucose.

function of the cell membrane

Controls what substances enter and leave the cell (selectively permeable).

function of ribosomes

Site of protein synthesis.

function of the cell wall

Provides structural support and protection for the cell.

function of the permanent vacuole

Contains cell sap to help maintain turgor pressure.

stem cell

An undifferentiated cell that can develop into many different cell types.

differentiation

The process where cells develop to become specialized for specific functions.

diffusion

The movement of particles from an area of higher concentration to an area of lower concentration.

osmosis

The diffusion of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.

active transport

The movement of particles from an area of low concentration to an area of high concentration, requiring energy.

binary fission

The asexual reproduction method in prokaryotic cells where one cell divides to form two identical cells.

mitosis

A type of cell division that results in two identical daughter cells, used for growth and repair.

chromosomes

Thread-like structures made of DNA found in the nucleus of cells.

tissue

A group of cells with similar structures working together to perform a shared function.

organ

A structure made up of different tissues working together for a specific function.

organ system

A group of organs working together to perform a particular function.

four main tissues in plants

Epidermal, palisade mesophyll, spongy mesophyll, and xylem and phloem (vascular tissues).

function of the xylem

Transport water and dissolved mineral ions from the roots to the rest of the plant.

Phloem

Transport dissolved sugars from the leaves to the rest of the plant.

Human digestive system parts

Mouth, esophagus, stomach, small intestine, large intestine, rectum, anus, plus accessory organs like the pancreas, liver, and gallbladder.

Enzyme

A biological catalyst that speeds up chemical reactions in living organisms.

Three main digestive enzymes

Carbohydrase (e.g., amylase), protease, and lipase.

Amylase

Breaks down starch into sugars; produced in the salivary glands and pancreas.

Protease

Breaks down proteins into amino acids; produced in the stomach and pancreas.

Lipase

Breaks down lipids (fats) into fatty acids and glycerol; produced in the pancreas.

Function of bile

Emulsifies fats (breaks large fat droplets into smaller ones) and neutralizes stomach acid.

Function of the heart

Pumps blood around the body.

Four chambers of the heart

Right atrium, right ventricle, left atrium, left ventricle.

Difference between arteries and veins

Arteries carry blood away from the heart (usually oxygenated), have thick walls, small lumen. Veins carry blood to the heart (usually deoxygenated), have thin walls, large lumen, and valves.

Capillaries

Tiny blood vessels that connect arteries to veins, where exchange of substances occurs.

Function of red blood cells

Transport oxygen from the lungs to body tissues.

Function of white blood cells

Protect the body against infection and disease.

Function of platelets

Help blood clot to prevent excessive bleeding.

Plasma

The liquid component of blood that carries blood cells, nutrients, hormones, and waste products.

Pathogen

A microorganism that causes disease.

Types of pathogens

Bacteria, viruses, fungi, and protists.

How bacteria cause disease

They reproduce rapidly inside the body and produce toxins.

How viruses cause disease

They invade cells and replicate, damaging or destroying the host cells.

First line of defense against pathogens

Physical and chemical barriers (skin, mucus, stomach acid, etc.).

Function of white blood cells in immune response

They can phagocytose (engulf) pathogens, produce antibodies, and produce antitoxins.

Antibodies

Proteins produced by white blood cells that recognize and bind to specific antigens on pathogens.

Antigen

A molecule on the surface of a pathogen that stimulates an immune response.

vaccine

A preparation containing dead or weakened pathogens that stimulates the immune system to produce antibodies.

immunity

The ability to resist infection due to the presence of antibodies or cells that attack specific pathogens.

active immunity

Develops when your body produces its own antibodies.

passive immunity

When antibodies are transferred to you from another source.

antibiotics

Medicines that kill bacteria or inhibit their growth but are not effective against viruses.

antibiotic resistance

When bacteria evolve to survive the effects of antibiotics.

painkiller

A drug that relieves pain without treating the cause of the pain.

monoclonal antibodies

Identical copies of antibodies that are made in a laboratory to target specific antigens.

photosynthesis

The process where plants use light energy to convert carbon dioxide and water into glucose and oxygen.

word equation for photosynthesis

Carbon dioxide + water → glucose + oxygen (using light energy and chlorophyll)

chemical equation for photosynthesis

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

chloroplasts

Where photosynthesis takes place in plants, mainly in the palisade mesophyll cells of leaves.

factors that limit the rate of photosynthesis

Light intensity, carbon dioxide concentration, and temperature.

uses of glucose produced in photosynthesis

For respiration, converted to starch for storage, converted to cellulose for cell walls, converted to proteins for growth, and converted to lipids for storage.

respiration

The process of releasing energy from glucose, which occurs in all living cells.

word equation for aerobic respiration

Glucose + oxygen → carbon dioxide + water (+ energy)

chemical equation for aerobic respiration

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (+ energy)

aerobic respiration location

It begins in the cytoplasm and is completed in the mitochondria.

anaerobic respiration

Respiration that occurs without oxygen, producing less energy than aerobic respiration.

equation for anaerobic respiration in humans

Glucose → lactic acid (+ energy)

equation for anaerobic respiration in plants and yeast

Glucose → ethanol + carbon dioxide (+ energy)

fermentation

Anaerobic respiration in yeast, producing ethanol and carbon dioxide.

oxygen debt

The amount of extra oxygen needed to break down lactic acid after anaerobic respiration.

body response to exercise

Increased breathing rate, increased heart rate, and increased stroke volume to deliver more oxygen to muscles.

metabolism

The sum of all the reactions that occur in a cell or the body.