Cell Level Systems

What Cell Level Systems covers

Cell Level Systems is examined in Paper 1 (Biology). It covers microscopy and sub-cellular structures; DNA as a polymer of nucleotides and its double helix; enzyme action and investigating enzymes; cellular respiration as an exothermic process; aerobic and anaerobic respiration compared; the synthesis and breakdown of carbohydrates, proteins and lipids; producers and the process of photosynthesis; photosynthesis as an endothermic reaction and investigating it; and limiting factors in photosynthesis.

The 9 subtopics

Each one has its own page.

• Microscopy, and sub-cellular structuresThe parts of a light microscope and preparing and staining slides, calculating magnification, where genetic material and plasmids sit in plant, animal and bacterial cells, the jobs of mitochondria, chloroplasts, the membrane and its receptors, and ribosomes, resolution and what electron microscopes revealed, converting between millimetres, micrometres and nanometres in standard form, estimating cell sizes, and significant figures.Open →
• DNA structure: polymer, double helix and nucleotidesWhat a polymer is, why DNA is a polymer built from nucleotides, how monomers and polymers differ, how the chain is built, and the two strands twisted into a double helix and why that shape stores genetic information stably.Open →
• Enzyme action, and investigating enzymesMeasuring the rate of an enzyme reaction with amylase and catalase, controlling pH and temperature, the active site and lock and key model, and how temperature, pH and concentration change the rate.Open →
• Cellular respiration as an exothermic processWhat cellular respiration and ATP are, why respiration is universal and continuous, the processes that depend on its ATP, the mitochondrion, how respiration differs from breathing, why it is exothermic, the germinating seeds experiment and its control, and how respiration keeps mammals and birds warm, heats the body in exercise and warms a compost heap.Open →
• Aerobic and anaerobic respiration comparedThe word equations for aerobic and anaerobic respiration, their difference in oxygen and ATP yield, the products in yeast and muscle, lactic acid and fatigue, and yeast in bread and brewing.Open →
• Synthesis and breakdown of carbohydrates, proteins and lipidsHow glucose builds starch and glycogen and why they are stored and broken down, amino acids as the monomers of proteins and why about twenty of them give so many proteins, the roles of proteins, lipids built from fatty acids and glycerol and broken down by lipase, why lipids store energy and their other uses, and the Benedict's, biuret and emulsion food tests.Open →
• Photosynthesis: producers and the processWhy photosynthetic organisms are the main producers of biomass, algae and phytoplankton as producers, where the carbon and energy in consumers come from, why life depends on photosynthesis and food chains start with producers, the word equation, chloroplasts and chlorophyll, where the reactants come from, the two stages, and what happens to the glucose made.Open →
• Photosynthesis as endothermic, and investigating itEndothermic reactions and where the energy in photosynthesis ends up, how it compares with respiration, measuring the rate in pondweed with a lamp, and testing a leaf for starch to show light is needed.Open →
• Limiting factors in photosynthesisHow light intensity, carbon dioxide concentration and temperature each change the rate of photosynthesis, why the rate stops rising in very bright light and falls when too hot, why growers heat, light and burn fuel in greenhouses, and slow photosynthesis on a cold bright day.Open →

What you need to know

Answer each one before you reveal it.

Take Cell Level Systems further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Magnification vs Resolution

  Magnification: how many times larger the image is than the real specimen. Resolution: smallest distance between two points still seen as separate.

• Aerobic respiration vs Anaerobic respiration

  Aerobic respiration: breakdown of glucose with oxygen to carbon dioxide and water. Anaerobic respiration: partial breakdown of glucose without oxygen to lactic acid or ethanol.

• Exothermic reaction vs Endothermic reaction

  Exothermic reaction: process that transfers energy out to the surroundings, usually warming them. Endothermic reaction: process that takes in energy from its surroundings.

Questions from this topic

Each one with the model answer underneath.

1. 1

   Which part of a light microscope supplies the light that passes up through a specimen?

   Model answer

   The lamp, positioned beneath the stage.

2. 2

   What is the flat platform called that a prepared slide rests on, and how is the slide held still?

   Model answer

   The stage, where the slide is held in place by clips.

3. 3

   Through which two lenses does light travel after leaving the specimen and before reaching the eye?

   Model answer

   First the objective lens, then the eyepiece lens.

4. 4

   Why is a cover slip lowered gently at an angle onto a specimen rather than dropped flat?

   Model answer

   So that air bubbles are not trapped underneath, because bubbles obscure the cells being viewed.

5. 5

   Why must many biological specimens be stained before they are viewed under a light microscope?

   Model answer

   Most cells are colourless and almost transparent, so a stain adds contrast and makes the structures visible.

6. 6

   How can stains be used to tell different structures or tissues apart within one section?

   Model answer

   Different stains are taken up by different structures, so each one takes on a different colour.

What is inside Levo

Six ways to work the same material.

Cell Level Systems revision questions

What does Cell Level Systems cover in OCR GCSE Combined Science Biology?

9 subtopics: microscopy, and sub-cellular structures, dna structure: polymer, double helix and nucleotides, enzyme action, and investigating enzymes, cellular respiration as an exothermic process, aerobic and anaerobic respiration compared, synthesis and breakdown of carbohydrates, proteins and lipids, photosynthesis: producers and the process, photosynthesis as endothermic, and investigating it and limiting factors in photosynthesis. Each one has its own page with questions and model answers.

How is Cell Level Systems organised?

By the OCR J250 specification, subtopic by subtopic, so it matches the order you are taught it in.