Year 11 Biology · Unit 2: Cells and Multicellular Organisms Detailed Study Guide

Comprehensive vocabulary flashcards covering the key definitions across all units of Year 11 Biology Unit 2: Cells and Multicellular Organisms, directly extracted from the detailed study guide.

Open system

A system that exchanges matter and energy with its surroundings

Flux

The movement of a substance across a boundary in a given time

Secretory cell

A cell that makes and releases a product, such as an enzyme or hormone

Phospholipid

A lipid with a hydrophilic head and two hydrophobic tails

Hydrophilic

Attracted to water

Hydrophobic

Repelled by water

Selectively permeable

Allowing some substances to cross and not others

Concentration gradient

A difference in concentration between two regions

Water potential

A measure of the tendency of water to move; water moves from higher to lower water potential

Turgid

A plant cell swollen with water, pressing against its wall

Flaccid

A plant cell that has lost water and no longer presses against its wall

Surface area to volume ratio

Surface area divided by volume; falls as size increases

Diffusion distance

The thickness of the barrier a substance must cross

Permeability

How easily a substance can cross a barrier

Active transport

Movement against a concentration gradient using a carrier protein and ATP

Endocytosis

Bulk transport into a cell in a vesicle formed from the membrane

Exocytosis

Bulk transport out of a cell when a vesicle fuses with the membrane

Prokaryote

A cell with no nucleus and no membrane-bound organelles

Eukaryote

A cell with a nucleus and membrane-bound organelles

Endosymbiosis

One organism living inside the cells of another

Resolution

The ability to distinguish two points as separate

Rough ER

Endoplasmic reticulum with ribosomes, where proteins for export are made

Golgi apparatus

Stacked membranes that modify, sort and package proteins into vesicles

Activation energy

The energy needed to start a reaction

Active site

The region of an enzyme where the substrate binds

Denaturation

A permanent change in the shape of a protein, so it can no longer function

Inhibitor

A molecule that reduces the activity of an enzyme

ATP

The molecule that carries usable energy in the cell

Glycolysis

The first stage of respiration, in the cytosol, splitting glucose into pyruvate

Fermentation

Anaerobic breakdown of glucose that yields only the ATP from glycolysis

Chlorophyll

The green pigment in chloroplasts that absorbs light

Limiting factor

The factor in shortest supply, which sets the rate

Compensation point

The light intensity at which photosynthesis and respiration run at the same rate

Tissue

A group of similar cells carrying out a shared function

Organ

A structure made of several tissues working together

Differentiation

The process by which a cell becomes specialised by expressing particular genes

Epidermis

The outer layer of cells of a plant organ

Palisade mesophyll

Tall leaf cells, packed with chloroplasts, below the upper epidermis

Spongy mesophyll

Loosely packed leaf cells with air spaces between them

Alveolus

A tiny air sac at the end of the airways, wrapped in capillaries

Ventilation

Moving air in and out of the lungs by bulk flow

Haemoglobin

The protein in red blood cells that binds oxygen

Villus

A finger-like fold of the small intestine lining

Lacteal

A lymph vessel in each villus that receives absorbed fats

Bile

A liquid made by the liver that emulsifies fats

Nephron

The functional unit of the kidney

Filtrate

The fluid filtered from the blood into Bowman's capsule

Reabsorption

The return of useful substances from the filtrate to the blood

Aquaporin

A channel protein that lets water cross a membrane

Capillary

The narrowest blood vessel, with a wall one cell thick

Tissue fluid

The fluid that surrounds the body's cells

Pulmonary circuit

Heart to lungs and back

Systemic circuit

Heart to the body's tissues and back

Bulk flow

The movement of a whole fluid together, driven by a pressure difference

Diaphragm

The sheet of muscle separating the chest and abdominal cavities

Stoma

A pore in the epidermis, between two guard cells

Guard cell

A specialised epidermal cell that opens and closes a stoma

Transpiration

The loss of water vapour from a plant, mainly through the stomata

Cuticle

A waxy, waterproof layer over the epidermis

Xylem

Tissue carrying water and ions up from the roots

Phloem

Tissue carrying sugars from source to sink

Plasmodesmata

Channels connecting the cytoplasm of neighbouring plant cells

Lignin

A rigid substance that strengthens xylem walls

Cohesion

The attraction of water molecules to each other

Adhesion

The attraction of water molecules to other surfaces, such as xylem walls

Translocation

The movement of sugars in the phloem from source to sink

Source and sink

Where sugars enter the phloem, and where they leave it

Dialysis

A treatment that removes urea, excess water, and ions by passing blood over a partially permeable membrane with dialysis fluid on the other side