§-Unit

Unit 1: How do organisms regulate their functions?

9 dot points, in syllabus order. Each dot point has a focused answer, with exam-style questions and worked answers where available.

How do cells function?

apoptosis as a regulated process of programmed cell death, including the role of caspases, and the consequences of disruption to the regulation of the cell cycle and apoptosis with reference to the development of cancer

Apoptosis and cancer. Covers programmed cell death through initiator and effector caspases, the intrinsic and extrinsic pathways, and how loss of checkpoint control (mutations in tumour suppressor genes such as p53, or activation of proto-oncogenes) leads to cancer.

11 min read →

the characteristics of the plasma membrane as a semi-permeable boundary between the internal and external environments of a cell and the movement of hydrophilic and hydrophobic substances across it, including water (osmosis), simple diffusion, facilitated diffusion, active transport, endocytosis and exocytosis

Plasma membrane. Covers the fluid mosaic model (phospholipids, proteins, cholesterol, carbohydrates) and the mechanisms of crossing it: simple and facilitated diffusion, osmosis, active transport, endocytosis and exocytosis.

12 min read →

the binary fission of prokaryotic cells and the eukaryotic cell cycle, including interphase (G1, S and G2), mitosis (prophase, metaphase, anaphase and telophase) and cytokinesis in plant and animal cells, with reference to checkpoints that regulate the cycle

Cellular reproduction. Covers prokaryotic binary fission, the eukaryotic cell cycle (G1, S, G2, M), the four phases of mitosis (PMAT), cytokinesis in plant and animal cells, and the checkpoints that regulate the cycle.

12 min read →

the structure and specialisation of plant and animal cell organelles for distinct functions, including chloroplasts and mitochondria, and the suggested origins of mitochondria and chloroplasts as described by the endosymbiotic theory

Cell organelles. Covers the structure and function of the nucleus, ribosomes, ER, Golgi, mitochondria, chloroplasts, lysosomes, vacuole, cytoskeleton and cell wall, and the endosymbiotic theory for the origin of mitochondria and chloroplasts.

13 min read →

surface area to volume ratio as an important factor in the limitations of cell size and the need for internal compartments (organelles) with specific cellular functions

Surface area to volume ratio. Covers why SA:V decreases as cells get larger, why diffusion becomes inefficient, and why eukaryotes rely on internal membrane compartments (organelles) to maintain rapid exchange.

9 min read →

cells as the basic structural feature of life on Earth, including the distinction between prokaryotic and eukaryotic cells

Cells as the basic unit of life. Covers the cell theory, the distinction between prokaryotic and eukaryotic cells, and the structural features (nucleus, membrane-bound organelles, ribosomes, cell wall) that separate them.

10 min read →

How do plant and animal systems function?

specialisation and organisation of animal cells into tissues, organs and systems with specific functions: digestive, endocrine and excretory

Animal systems. Covers the four primary tissue types, the hierarchy of organisation (cells, tissues, organs, systems), and the structure and function of the digestive, endocrine and excretory systems.

13 min read →

specialisation and organisation of plant cells into tissues for specific functions in vascular plants, including intake, movement and loss of water

Plant tissues and water transport. Covers root hair cells, xylem and phloem, the cohesion-tension theory of water movement, stomata and transpiration, and how vascular plants move water from roots to leaves.

11 min read →

structural, physiological and behavioural adaptations of plants and animals that enhance survival and allow life to exist in a wide range of environments, including extreme environments

Adaptations. Covers the distinction between structural, physiological and behavioural adaptations, and worked examples of plant and animal adaptations to extreme environments (desert, polar, deep-sea).

10 min read →