cells, enzymes etc.

Describe the structure of the cytoplasm.

Fluid component of the cell containing organelles, enzymes, and dissolved ions and nutrients.

What is the function of the cytoplasm?

Site of cellular reactions, e.g., first stage of respiration.

What is the function of the cell membrane?

Controls the entry and exit of materials into and out of the cell.

List the organelles found in prokaryotic cells.

Chromosomal DNA, Plasmid DNA, Cell wall, Cell membrane, Ribosomes, Flagella.

Describe how egg cells are adapted to their function.

Haploid nucleus contains genetic material; mitochondria in cytoplasm produce energy for the developing embryo; cytoplasm contains nutrients; cell membrane hardens after fertilisation.

How does a light microscope work?

Passes a beam of light through a specimen which travels through the eyepiece lens, allowing the specimen to be observed.

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

As temperature increases, molecules have more kinetic energy, movement increases, probability of successful collisions increases, and more enzyme-substrate complexes form.

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

As substrate concentration increases, the number of substrate molecules increases, probability of successful collisions increases, more enzyme-substrate complexes form, and the rate of reaction increases until all active sites are full.

Why must large organic molecules be broken down into smaller, simpler molecules in the body?

Large molecules are too big to be absorbed across the surface of the gut wall.

What is calorimetry?

A method of measuring the heat transfer during a chemical reaction.

What molecules enter and leave cells via simple diffusion through the cell membrane?

Small molecules e.g. oxygen, water, glucose, amino acids.

What are the two types of cells?

Eukaryotic (animals and plants) and prokaryotic

What is the difference between a eukaryotic and prokaryotic cell?

A eukaryotic cell contains a nucleus and membrane-bound organelles; a prokaryotic cell does not.

List the components of both plant and animal cells.

Nucleus, Cytoplasm, Cell membrane, Mitochondria, Ribosomes

How is genetic information stored in a eukaryotic cell?

Within the nucleus, arranged in chromosomes.

What is the function of the nucleus other than storing genetic information?

Controls cellular activities.

Which organelles are found in plant cells only?

Large, permanent vacuole, Cell wall, Chloroplasts.

What is the cell wall made of?

Cellulose.

Why do chloroplasts appear green under a light microscope?

They contain chlorophyll, a green pigment.

What is a haploid cell?

A cell that contains a single copy of each chromosome (half the number of chromosomes), e.g., 23 chromosomes in humans.

What is a diploid cell?

A cell that contains two copies of each chromosome (full set of chromosomes), e.g., 46 chromosomes in humans.

Describe the function of ciliated epithelial cells lining the airways.

Move in synchronised waves to beat mucus (containing dirt and pathogens) up to the back of the throat where it can be swallowed.

Name the two types of electron microscope.

Transmission electron microscope (TEM) and Scanning electron microscope (SEM).

How do you convert from m to mm?

Multiply by 1000 (× 10^3).

How do you convert from m to µm?

Multiply by 1,000,000 (× 10^6).

Convert 1.527 m to µm. Write your answer in standard form (higher).

1.527 m × 1,000,000 = 1.527 × 10^6 µm.

Why are enzymes described as having a 'high specificity' for their substrate?

Only substrates with a specific, complementary shape can fit into an enzyme's active site.

How is a percentage change in mass calculated?

Percentage change in mass is calculated by the formula: ((final mass - initial mass) / initial mass) x 100.

What is the function of the mitochondria?

Site of later stages of aerobic respiration in which ATP is produced.

What is the function of the ribosomes?

Joins amino acids in a specific order during translation.

What is the function of the cell wall?

Provides strength and prevents the cell from bursting when water enters by osmosis.

What does the permanent vacuole contain?

A solution of salts, sugars, and organic acids.

What is the function of the permanent vacuole?

Supports the cell, maintaining its turgidity.

What is the function of the chloroplasts?

Site of photosynthesis.

How is genetic information stored in a prokaryotic cell?

Found free within the cytoplasm as chromosomal DNA (single large loop of circular DNA) and plasmid DNA.

What are plasmids?

Small, circular loops of DNA found free in the cytoplasm and separate from the main DNA; carry genes that provide genetic advantages, e.g., antibiotic resistance.

What is the prokaryotic cell wall composed of?

Peptidoglycan.

What is a flagellum?

Long, rotating, 'whip-like' protrusion that enables bacteria to move.

What are gametes?

Reproductive cells (e.g., egg and sperm cells); they are haploid cells.

Describe sexual reproduction in terms of chromosome number.

Two haploid gametes fuse; the resulting embryo has two chromosomes for each gene and two copies of each allele, thus diploid.

Describe how sperm cells are adapted to their function.

Haploid nucleus contains genetic information; tail enables movement; mitochondria provide energy for tail movement; acrosome contains enzymes that digest the egg cell membrane.

Where are ciliated epithelial cells found?

Lining the surface of structures such as the respiratory tract and uterus.

What is magnification?

The number of times bigger an image appears compared to the size of the specimen.

How can the total magnification of an image be calculated from lens powers?

Multiply the power of the objective lens by the power of the eyepiece lens.

How can the magnification of an image be calculated?

magnification = size of image / size of specimen

What is resolution?

The smallest distance between two objects that can be distinguished.

What are the advantages of light microscopes?

Inexpensive, easy to use, portable, observe both dead and living specimens.

What is the disadvantage of light microscopes?

Limited resolution.

How does an electron microscope work?

It uses a beam of electrons which are focused using magnets. The electrons hit a fluorescent screen which emits visible light, producing an image.

What is the advantage of electron microscopes?

Greater magnification and resolution.

Why do electron microscopes have a greater magnification and resolution?

They use a beam of electrons which has a shorter wavelength than photons of light.

How have electron microscopes enabled scientists to develop their understanding of cells?

Allow small sub-cellular structures (e.g., mitochondria, ribosomes) to be observed in detail, enabling scientists to develop more accurate explanations about how cell structure relates to function.

What are the disadvantages of electron microscopes?

Expensive, large so less portable, require training to use, only dead specimens can be observed.

How do you convert from m to nm?

Multiply by 1,000,000,000 (× 10^9).

How do you convert from nm to m?

Divide by 1,000,000,000 (× 10^-9).

How do you convert from m to pm?

Multiply by 1,000,000,000,000 (× 10^12).

Write 0.005 in standard form (higher).

5 × 10^-3.

Write 10382 in standard form (higher).

1.0382 × 10^4.

What are enzymes?

Biological catalysts that increase the rate of a chemical reaction without being permanently altered themselves.

What is an advantage of enzymes in the body?

They enable cellular reactions to take place at lower temperatures.

What is the active site of an enzyme?

The region of an enzyme to which a substrate molecule binds and the reaction takes place.

Describe the 'lock and key' model.

Substrate collides with the active site of an enzyme, binds, forms an enzyme-substrate complex, is converted to products, and products are released.

What factors affect the rate of an enzyme-controlled reaction?

Temperature, pH, substrate concentration.

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

Increased vibrations break bonds in the enzyme's structure, changing the shape of the active site, denaturing the enzyme, and decreasing the rate of reaction.

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

Enzymes have an optimum pH; shifts from this pH alter bonds in the enzyme's structure, change the shape of the active site, denature the enzyme, and decrease the rate of reaction.

how can the rate of an enzyme controlled reaction be calculated when given a value for time?

rate = 1/time

What are the units for rate of reaction?

s⁻¹.

Give an example of the breakdown of large molecules into smaller molecules in plants.

Starch is broken down by enzymes into simpler sugars which are respired to release energy.

What type of molecules are proteins and carbohydrates?

Polymers.

What are the monomers of carbohydrates?

Simple sugars.

Which group of enzymes catalyses the breakdown of carbohydrates?

Carbohydrases.

Which type of carbohydrase catalyses the breakdown of starch?

Amylase.

What are the monomers of proteins?

Amino acids.

Which type of enzyme catalyses the breakdown of proteins?

Proteases.

What is the function of lipases?

Enzymes which catalyse the breakdown of lipids into fatty acids and glycerol.

Why are small molecules synthesised into larger organic molecules in the body?

Large molecules are used for storage or to build structures.

Which enzyme catalyses the formation of glycogen from glucose?

Glycogen synthase.

How can the amount of energy contained in food be measured?

Measured using calorimetry.

Describe the method used to measure the amount of energy in a sample of food.

Add a set volume of water to a boiling tube, record initial temperature, record mass of a small sample of food, light the food sample, hold it under the boiling tube until it burns, record the maximum temperature reached by the water, and record the final mass of the food sample.

How can the amount of energy in the food sample be calculated?

Calculate based on the temperature change and mass of the food sample.

What is simple diffusion?

The net movement of molecules from an area of high concentration to an area of low concentration down a concentration gradient.

What factors affect the rate of diffusion?

Temperature, concentration gradient, surface area of cell membrane.

Define osmosis.

The net movement of water molecules from an area of high water concentration to an area of low water concentration through a partially permeable membrane.

What is active transport?

The movement of molecules across a cell membrane from an area of low concentration to an area of high concentration, against the concentration gradient, using energy.

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