AQA GCSE Combined Science Biology - Paper 1

What is the function of the nucleus?

Contains DNA to control the cell

What is the function of the cell membrane?

Controls entry and exit of substances

What is the function of the cell wall?

Provides structure and support

What is the function of mitochondria?

Carry out respiration to release energy

What is the function of ribosomes?

Protein synthesis

What is the function of chloroplasts?

Carry out photosynthesis

What is the function of a vacuole?

Contains cell sap

Define a prokaryote

A cell that does not have a nucleus

Define a eukaryote

A cell that has DNA in a nucleus

Name two cell structures that are in a eukaryote but not in a prokaryote

Nucleus, mitochondria, chloroplasts

What is a plasmid?

A small loop of DNA in bacteria

What is a plant cell wall made from?

Cellulose

How is DNA stored in a bacterial cell?

As a single, free-floating loop; also on plasmids

What is differentiation?

The process by which cells become specialised

What is the equation for magnification?

Magnification = Image Size ÷ Actual Size

A photograph of a cell is 15mm long. It has a magnification of 1100x. What is the actual size?

0.0136mm, or 13.6µm

A cell is 12µm wide. It is magnified by 450 times. How big is the image?

5400µm, or 5.4mm

If the image of a virus is 1.2mm, and its actual size is 0.2µm, how much has it been magnified by?

6000 times

Convert 38500µm into mm

38.5mm

How many µm are in 1mm?

1000

Write 17400m in standard form

1.74 x 10^4 m

Write 0.0034 in standard form

3.4 x 10^-3

How is a sperm cell adapted for its function?

It has a tail to swim to the egg

How is a nerve cell adapted for its function?

It has a long axon to conduct impulses over long distances

How is a muscle cell adapted for its function?

It can contract to cause movement

How is a root hair cell adapted for its function?

It has a large surface area to increase osmosis of water

How is a xylem cell adapted for its function?

It has hollow ends to transport water

How is a phloem cell adapted for its function?

It has sieve tubes to transport sugars

What is a stem cell?

An undifferentiated cell that can differentiate to become any type of specialised cell

Where are stem cells most commonly found in animals?

In embryos and in bone marrow

What is meristem tissue?

Plant tissue containing stem cells

When are plant cells able to differentiate?

Throughout the whole life of the plant

When do most animal cells differentiate?

At an early stage of development (as an embryo)

What is the "resolution" of a microscope?

Resolution is the smallest distance between two separate points

Why are electron microscopes better than light microscopes?

They have a higher resolution and higher magnification

Give an example of an organelle you could see with an electron microscope, but not with a light microscope?

Ribosomes

What shape is DNA?

Double helix

What molecule is DNA stored as?

Chromosomes

How are chromosomes usually found in body cells?

In pairs

What is a gene?

A small section of DNA that codes for a specific protein

What is mitosis?

Cell division

What are the two main purposes of mitosis?

To grow and to replace cells

What must happen in a cell before mitosis can take place?

It must replicate its DNA to form two copies of each chromosome

Once DNA has been replicated, what happens next in mitosis?

One set of chromosomes is pulled to each end of the cell and the nucleus divides

What are the products of mitosis?

Two genetically identical daughter cells

What is the cell cycle?

The stages in a cell as it grows and goes through mitosis

What conditions may stem cells be able to help with?

Diabetes and paralysis

How are most blood cells formed?

From stem cells in bone marrow

What is therapeutic cloning?

When an embryo is produced with the patient's genes so that stem cells from the embryo can be used

Why are stem cells made by therapeutic cloning more useful for medical treatments?

They contain the same genes as the patient, so are not rejected by the patient's body

Give two ways using stem cells to clone plants may be useful

For preventing the extinction of rare plant species, and for producing large numbers of identical disease-resistant crops

Define diffusion

The movement of particles from a high concentration to a low concentration down a concentration gradient

What factors affect the rate of diffusion?

Temperature, surface area, difference in concentration

How is the small intestine adapted for diffusion?

There are lots of villi to give a large surface area, villi contain lots of capillaries close to the surface so there is a short diffusion distance

How are the lungs adapted for diffusion?

Lots of alveoli give a large surface area, they have thin walls and capillaries are close so there is a short diffusion distance

How are fish gills adapted for diffusion?

Gills have lots of filaments to give a large surface area, there are lots of capillaries with a short distance for diffusion

How are plant roots adapted to absorb water?

Roots have lots of long root hair cells to give a large surface area for osmosis

How are plant roots adapted to absorb mineral ions?

Root hair cells have mitochondria to release energy for active transport of mineral ions

How are leaves adapted for gas exchange?

Leaves have lots of stomata on the underside to allow carbon dioxide to diffuse in

Define osmosis

The movement of water from a high water potential to a low water potential across a partially permeable membrane

How would you calculate % change in mass of a potato chip in sucrose solution?

(Change in mass ÷ Starting mass) x 100

Why should you blot a potato chip dry before taking its mass?

To remove excess water, so it doesn't increase the mass

Why do you calculate %change in mass of a potato chip rather than just change in mass?

So that you can compare different chips, as the starting mass of each potato may not be the same

Define active transport

The movement of particles from a low concentration to a high concentration against a concentration gradient, using energy

Explain one example of active transport in plants

Absorption of mineral ions in root hair cells

Explain one example of active transport in animals

Absorption of glucose in the small intestine

Define a tissue

A group of cells with similar structure and function

Define an organ

A group of tissues working together to perform a function

Deine an organ system

A group of organs working together

Give two examples of tissues in animals

Epithelial tissue, muscle tissue, nerve tissue, glandular tissue

Give two examples of tissues in plants

Palisade tissue, spongy mesophyll tissue, xylem tissue, phloem tissue

Give two examples of organs in animals

Heart, lungs, stomach, brain, liver

Give two examples of organs in plants

Leaf, root, stem, flower

Define an enzyme

A biological catalyst that carries out metabolic reactions in living organisms

What is a substrate?

A substance that is broken down by an enzyme

Where does a substrate bind to an enzyme?

Active site

What is formed when an enzyme binds to a substrate?

Enzyme-substrate complex

Why are enzymes specific?

Each type of enzyme has an active site that only fits one specific substrate

What are enzymes made of?

Protein

What conditions cause enzymes to denature?

High temperatures or pH that is too high or low

Define denature

When an enzyme cannot work because its active site has lost its specific shape so the substrate no longer fits

What is human body temperature?

37oC

What is the Lock and Key Theory?

A substrate is specific to one enzyme because of the specific shape of its active site (like a key fitting a lock)

What is the purpose of digestion

To break large, insoluble molecules into small, soluble molecules so they can be absorbed

Where is amylase made?

Salivary glands and pancreas

Where is protease made?

Stomach and small intestine

Where is lipase made?

Pancreas and Small intestine

What is the substrate of amylase?

Starch

What is the substrate of protease?

Protein

What is the substrate of lipase?

Lipids (fats)

What is the substrate of carbohydrase?

Carbohydrate

What are the products of amylase digesting starch?

Glucose

What are the products of protease digesting proteins?

Amino acids

What are the products of lipase digesting lipids?

Glycerol and fatty acids

Where is bile made?

Liver

Where is bile stored?

Gall bladder

Give two functions of bile

To emulsify fats, and to neutralise stomach acid

What is the purpose of emulsification

To break large fats into small droplets, to increase surface area for lipase

Why must hydrochloric acid from the stomach be neutralised by bile in the small intestine?

So that enzymes aren't denatured

What equipment is used to control temperature in an investigation?

Water bath