BGCSE Human & Social Biology flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

MRS GREN

A mnemonic listing the seven life processes: movement, respiration, sensitivity, growth, reproduction, excretion and nutrition. All living organisms show these characteristics.

Osmosis

The movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration, without requiring energy.

Active transport

Movement of dissolved substances against a concentration gradient across a cell membrane, using energy released by respiration and carrier proteins.

Enzyme active site

The specific region of an enzyme where the substrate binds. Its shape is complementary to the substrate; high temperature or extreme pH changes the shape and denatures the enzyme.

Balanced diet components

The seven dietary components: carbohydrates, proteins, fats, vitamins, minerals, water and fibre. Each is needed in the correct proportion for health.

Bile function

Bile is made in the liver and stored in the gall bladder. It emulsifies fats into small droplets to increase surface area for lipase and neutralises acidic stomach contents.

Villi

Finger-like projections of the small intestine lining. Their thin walls, large surface area and rich blood supply speed absorption of digested nutrients into the blood.

Aerobic respiration

The breakdown of glucose using oxygen to release energy, producing carbon dioxide and water. It releases much more energy per glucose molecule than anaerobic respiration.

Anaerobic respiration in muscle

Breakdown of glucose without oxygen, producing lactic acid and a small amount of energy. Lactic acid builds up and causes oxygen debt after vigorous exercise.

Alveoli

Tiny air sacs in the lungs where gas exchange occurs. They are thin-walled, moist, numerous and surrounded by capillaries, giving a large surface area.

Double circulation

Blood passes through the heart twice in one complete circuit: once to the lungs and once to the body. This keeps oxygenated and deoxygenated blood separate.

Capillary structure

Capillaries have walls one cell thick, a narrow lumen and branch through tissues, allowing rapid exchange of gases, nutrients and waste between blood and cells.

Red blood cell function

Red blood cells contain haemoglobin, which binds oxygen in the lungs and releases it in respiring tissues. They lack a nucleus, giving more space for haemoglobin.

ADH

Antidiuretic hormone, released by the pituitary gland. It increases water reabsorption in kidney tubules, producing smaller, more concentrated urine when the body is dehydrated.

Dialysis

A treatment for kidney failure in which blood passes through a machine containing a partially permeable membrane that removes urea and excess salts and water.

Negative feedback

A control mechanism in which a change from the normal level triggers a response that reverses the change, restoring the internal environment to its set point.

Insulin

A hormone released by the pancreas when blood glucose is high. It causes liver and muscle cells to convert glucose to glycogen, lowering blood glucose concentration.

Reflex arc

The pathway of a reflex action: receptor, sensory neurone, relay neurone in the spinal cord, motor neurone and effector, producing a rapid involuntary response.

Meiosis

Cell division producing four haploid gametes with half the normal chromosome number. It creates genetic variation through crossing over and independent assortment.

Ovulation

Release of a mature egg from an ovary, usually around day 14 of a 28-day menstrual cycle. The egg travels along the oviduct where fertilisation may occur.

Placenta

An organ in the uterus where fetal and maternal blood come close together, allowing oxygen and nutrients to pass to the fetus and waste to be removed.

Meristem

A region of unspecialised plant cells capable of continuous mitosis. Meristems at root and shoot tips allow plants to grow throughout their lives.

Metamorphosis

A change in body form during development, such as a tadpole becoming a frog or a caterpillar becoming a butterfly. Complete metamorphosis includes a pupal stage.

Germination requirements

Seeds need water, oxygen and a suitable temperature to germinate. Water softens the seed coat and activates enzymes; oxygen is needed for respiration.

Dominant allele

An allele whose characteristic appears in the phenotype even when only one copy is present. Recessive alleles only show when two copies are inherited.

Genotype and phenotype

Genotype is the combination of alleles an organism carries; phenotype is the observable characteristic that results from the genotype and environmental influences.

Natural selection

Organisms with alleles better suited to their environment survive and reproduce more successfully, so advantageous alleles become commoner in later generations.

Continuous variation

Variation showing a range of values between two extremes, such as height or mass, controlled by many genes and affected by the environment.

Vaccination

Introducing weakened or dead pathogens so the immune system makes antibodies and memory cells, giving protection against later infection by the same pathogen.

Antibiotic resistance

Bacteria with alleles giving resistance survive antibiotic treatment and reproduce, so resistant strains spread. This makes infections harder to treat.

Eutrophication

Fertiliser runoff raises nitrate levels in water, causing algal blooms. Decomposers use up oxygen, so fish and other organisms die.

Sustainable development

Meeting the needs of the present generation without compromising the ability of future generations to meet their own needs, for example by using renewable resources.