OCR Gateway GCSE Biology: B1 Cell Level Systems

What is magnification?

How much larger a displayed image is compared with the original object.

What is resolution?

The ability to distinguish between two points.

Why is staining used?

To highlight different structures, increase contrast, and because some specimens are colourless.

What is the formula to calculate magnification from image size and actual size?

Image size = Actual Size x Magnification.

How do you calculate total magnification?

Total magnification = Eyepiece magnification x Objective lens magnification.

How is a light microscope set up?

Place the specimen on a slide, cover it with a cover slip, illuminate with a lamp, and view using the eyepiece.

What are 5 parts of an animal cell?

Nucleus, cytoplasm, mitochondria, ribosomes, and the cell membrane.

What are 2 functions of the nucleus?

Controls the cell and contains genetic material found in the form of chromosomes.

What is the function of the cytoplasm?

It is where most of the cell's chemical reactions take place.

What is the function of mitochondria?

They are the site of aerobic respiration.

What is the function of ribosomes?

They are the site of protein synthesis.

What are 3 organelles only found in plant cells?

Cellulose cell wall, permanent vacuole, and chloroplasts.

What is the function of the cell wall and what is it made of?

It provides strength and support and is made of cellulose.

What is the function of the permanent vacuole and what does it contain?

It supports the cell and contains cell sap, a solution of sugars and salts.

What is the function of chloroplasts?

They are the site of photosynthesis.

What are 3 differences between prokaryotic and eukaryotic cells?

Prokaryotic cells have no nucleus, have plasmid loops of DNA, and have no mitochondria.

Describe the image produced by an electron microscope.

The image is black and white, can be 2D or 3D, and has a very high magnification and resolution.

Why are electron microscopes better than light microscopes?

They produce images with enough detail to see structures inside cells and have a higher resolution and higher magnification.

What is the structure of DNA?

DNA is a polymer made of many nucleotide monomers and consists of 2 strands in the shape of a double helix.

What is the structure of a nucleotide?

A nucleotide contains a 5 carbon sugar, phosphate group, and nitrogenous base.

What are the 4 bases in DNA?

Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).

How do the bases in DNA pair up?

Adenine pairs with Thymine (A with T) and Cytosine pairs with Guanine (C with G).

What are the steps of transcription?

1) DNA unzips. 2) Complementary mRNA nucleotides bind and are joined together. 3) mRNA detaches and leaves the nucleus.

What are the steps of translation?

1) mRNA travels to a ribosome. 2) Carrier molecules carry amino acids to the ribosome based on the mRNA sequence. 3) The amino acids are joined together.

How does the sequence of DNA affect protein synthesis?

DNA is a triplet code where 3 bases code for one amino acid, and the order of amino acids determines the protein produced.

What are enzymes?

Enzymes are biological catalysts that speed up the rate of metabolic reactions.

What is the structure of enzymes?

Enzymes are proteins that contain an active site that fits a specific substrate.

What is the lock and key hypothesis?

A substrate that fits the specific active site of the enzyme binds, a reaction occurs (catalyzed by the enzyme), and then the products are released.

What are 4 factors that affect enzyme function?

Temperature, pH, substrate concentration, and enzyme concentration.

How does temperature affect the rate of an enzyme-controlled reaction?

As the temperature increases, so does the rate of reaction. Once the temperature exceeds the optimum, the enzyme denatures and the rate of reaction decreases.

What is the purpose of respiration?

To produce energy in the form of ATP from larger molecules (like sugars)

What type of reaction is respiration?

Respiration is an exothermic reaction

When does aerobic respiration take place?

When there is plenty of oxygen available

What is the word equation for aerobic respiration?

Glucose + Oxygen → Carbon dioxide + Water (+ energy)

What is the symbol equation for aerobic respiration?

C6H12O6 + 6O2 → 6CO2 + 6H2O (+energy)

When does anaerobic respiration take place?

When there is no oxygen available

What does anaerobic respiration in animals produce?

Lactic acid and energy

What does anaerobic respiration in yeast produce?

Ethanol (alcohol), carbon dioxide and energy

Which type of respiration produces more ATP?

Aerobic respiration which produces 36 ATP compared to anaerobic respiration which produces only 2 ATP

What is the oxygen debt?

The extra oxygen that is needed to break down the lactic acid formed in anaerobic respiration

What type of molecules are carbohydrates and proteins?

They are polymers

What are the monomers that make up proteins?

Amino acids

What type of enzymes break down carbohydrates?

Carbohydrases

What type of enzymes break down proteins?

Proteases

What type of enzymes break down lipids and what are they broken down into?

Lipids are broken down by lipases into glycerol and fatty acids

What type of organisms use photosynthesis to make their own food?

Producers

What type of reaction is photosynthesis?

Photosynthesis is an endothermic reaction.

Where does photosynthesis take place?

Photosynthesis takes place in the chloroplasts.

What is the word equation for photosynthesis?

Carbon dioxide + Water → Glucose + Oxygen.

What is the symbol equation for photosynthesis?

6CO2 + 6H2O → C6H12O6 + 6O2.

What is the effect of temperature on the rate of photosynthesis?

As temperature increases, so does the rate of photosynthesis. Once the temperature exceeds the optimum, the rate of photosynthesis decreases as enzymes begin to denature.

What is the effect of light intensity on the rate of photosynthesis?

As the light intensity increases, the rate of photosynthesis increases.

What is the inverse square law?

As the distance from the light source doubles, the light intensity quarters. Light intensity ∝ 1 / distance².

What is the effect of carbon dioxide concentration on the rate of photosynthesis?

As the concentration of carbon dioxide increases, the rate of photosynthesis increases.

What is a limiting factor?

A factor that limits the rate of a reaction when there is not enough of it.