Active Transport and Material Exchange

Active transport is a crucial process in cellular biology, involving the movement of particles against their concentration gradient. This section of the GCSE Biology B1 Cell Biology revision notes explores the mechanics and importance of active transport in various biological contexts.

Definition: Active transport is the movement of particles from an area of lower concentration to an area of higher concentration, against their concentration gradient, requiring energy from respiration.

The notes highlight two key examples of active transport in biological systems:

1. Root hairs: These structures take up water and mineral ions from the soil. Active transport is necessary because mineral ions often have a higher concentration in the root hair cells than in the soil.

2. The gut: Substances like glucose and amino acids move from the gut to the bloodstream. Active transport is required when the concentration of these molecules is lower in the gut than in the blood.

Example: In the gut, when sugar concentration is lower than in the blood, active transport moves sugar molecules against the concentration gradient into the bloodstream.

The section also covers material exchange in other biological processes:

• Gas exchange in alveoli: Oxygen diffuses into red blood cells, while carbon dioxide diffuses out into the alveoli.
• Digestion: Small molecules from digestion are absorbed into the blood in the small intestine.

Highlight: Understanding active transport is crucial for comprehending how cells maintain homeostasis and acquire essential nutrients against concentration gradients.

Prokaryotic and Eukaryotic Cells

This section of the AQA GCSE Biology revision notes delves into the fundamental differences between prokaryotic and eukaryotic cells, providing a comprehensive overview of cell structures and their functions.

Definition: Prokaryotic cells are cells that do not have a nucleus, while eukaryotic cells are cells that do have a nucleus.

The notes provide detailed descriptions of both plant and animal cells, which are eukaryotic:

Plant Cell Features:

• Cell membrane
• Nucleus
• Cytoplasm
• Mitochondria
• Ribosomes
• Cellulose cell wall
• Chloroplasts
• Permanent vacuole

Animal Cell Features:

• Cell membrane
• Nucleus
• Cytoplasm
• Mitochondria
• Ribosomes

Vocabulary: Cytoplasm is the gel-like substance where most chemical reactions occur in the cell, containing enzymes that control these reactions.

The section also explains the unique features of bacterial cells, which are prokaryotic:

• Single circular strand of DNA floating in the cytoplasm instead of a nucleus
• One or more small rings of DNA called plasmids
• Absence of chloroplasts and mitochondria

Highlight: Understanding the differences between prokaryotic and eukaryotic cells is crucial for grasping the diversity of life forms and their cellular organization.