Biology for IGCSE (Chapters 2-6)

Question 1

Define cells

Answer 1

The smallest units from which all organisms are made

Question 2

Too see smaller things inside a cell, a/n _____________ microscope is used. A picture taken with it is called a/n ____________________

Answer 2

Electron, electron micrograph

Question 3

What part of a cell is located around the outside?

Answer 3

Cell membrane

Question 4

What is meant by, “A cell membrane is said to be partially permeable”?

Answer 4

It means that a cell membrane will let some substances through but not others

Question 5

What are cell walls in plants made up of?

Answer 5

Cellulose

Question 6

What is cytoplasm?

Answer 6

The jelly-like material that fills a cell

Question 7

What is a vacuole?

Answer 7

A fluid-filled space inside a cell which is surrounded by its own membrane

Question 8

What is the name of the solution of sugars and other substances that fills a vacuole?

Answer 8

Cell sap

Question 9

What is the name for the small vacuoles in animal cells, which also contain solutions?

Answer 9

Vesicles

Question 10

What is the importance of the nucleus in a cell?

Answer 10

It is where the genetic information is stored.

Question 11

What is genetic information kept on in a nucleus?

Answer 11

Chromosomes, which are inherited from the organism’s parents.

Question 12

What are chromosomes made of?

Answer 12

DNA (deoxyribonucleic acid)

Question 13

If chloroplasts are never found in animal cells, where are they found?

Answer 13

Within the cells of all auto-trophic organisms

Question 14

What is the mitochondrion?

Answer 14

A small structure in a cell, where aerobic respiration releases energy from glucose; it is the powerhouse of the cell

Question 15

Can mitochondria be seen via a light microscope?

Answer 15

No, they are so small that they can only be seen with an electron microscope.

Question 16

What are ribosomes?

Answer 16

Very small structures in a cell that use information on DNA to make protein molecules

Question 17

Name some features of bacterial cells

Answer 17

• They always have a cell wall; this wall is not made of cellulose, but instead peptidoglycan
• A partially permeable cell membrane is pressed tightly against the inside of a bacterial cell wall
• They have cytoplasm and ribosomes
• They do not have mitochondria or chloroplasts
• They do not have a definite nucleus; instead, a circle of DNA. This is sometimes called a bacterial chromosome
• They also have one or two small circles of DNA, called plasmids

Question 18

What is a tissue?

Answer 18

A group of similar cells that work together to perform a particular function

Question 19

What is an organ?

Answer 19

A group of different tissues that carry out a function together

Question 20

What is an organ system?

Answer 20

Several organs that work together to perform a particular function

Question 21

What is the formula for magnification?

Answer 21

Size of image
————————
Size of object

Question 22

What is diffusion?

Answer 22

The net movement of particles down a concentration gradient.

Question 23

What is osmosis?

Answer 23

The diffusion of water molecules through a partially permeable membrane

Question 24

What is meant by high water potential?

Answer 24

An area where there are a lot of water molecules—a dilute solution

Question 25

What is meant by low water potential?

Answer 25

An area where there are not many water molecules—a concentrated solution

Question 26

What is meant by water potential gradient?

Answer 26

A difference in water potential between the two areas

Question 27

Explain what happens to animal cells when they are placed in pure water (3 marks)

Answer 27

The cells _burst_ because _water enters_ by _osmosis_

Question 28

Why does a plant cell not burst in pure water?

Answer 28

Because the strong cell wall stops it from bursting

Question 29

What is meant by turgid?

Answer 29

A description of a plant cell that is tight and firm

Question 30

What is turgor pressure?

Answer 30

The pressure of the water pushing outwards on a plant cell wall

Question 31

What is meant by flaccid?

Answer 31

A description of a plant cell that is soft

Question 32

What is meant by plasmolysed?

Answer 32

A description of a cell in which the cell membrane tears away from the cell wall

Question 33

What is active transport?

Answer 33

The movement of molecules or ions **against** a concentration gradient using energy from respiration

Question 34

What are carrier proteins?

Answer 34

Protein molecules in cell membranes that can use energy to change shape and move ions or molecules into or out of a cell

Question 35

What are some examples of carbohydrates?

Answer 35

Starch, cellulose and sugar. More specific examples include: Glucose, etc.

Question 36

What are the linked-together glucose molecules in animals called?

Answer 36

Glycogen; it is used as an energy store in animal cells

Question 37

What is starch?

Answer 37

A carbohydrate that is used as an energy store in plant cells

Question 38

How can we detect the presence of starch?

Answer 38

By using iodine solution; it turns from brown to blue-black if starch is present

Question 39

Most sugars can be detected by _____________________

Answer 39

Benedict's solution

Question 40

What happens to Benedict's solution when heated with reducing sugars?

Answer 40

It changes from **blue** to **orange-red.**The colour change is gradual, so the blue solution becomes green and yellow before finally turning orange-red.

Question 41

What are fats?

Answer 41

Lipids that are solid at room temperature

Question 42

What are oils?

Answer 42

Lipids that are liquid at room temperature

Question 43

What are lipids?

Answer 43

They are substances containing carbon, hydrogen and oxygen that are used as energy stores in organisms. They are also insoluble in water.

Question 44

What are amino acids?

Answer 44

The building blocks of protein

Question 45

What are some of the functions of proteins in organisms?

Answer 45

- Antibodies, which help protect the body against pathogens. - Enzymes - Haemoglobin - Forming cell membranes - Keratin: the protein that forms hair and fingernails

Question 46

DNA is made of smaller molecules called __________________

Answer 46

Nucleotides

Question 47

What is a **base** in DNA?

Answer 47

One of the components of DNA; there are four bases, A, C, G, and T, and their sequence determines the proteins that are made in a cell

Question 48

What is **complementary base pairing?**

Answer 48

The way in which the bases of the two strands of DNA pair up; A always with T, and C with G

Question 49

Vitamin C is tested using ______________

Answer 49

DCPIP (Dichlorophenolindophenol)

Question 50

What is a catalyst?

Answer 50

A substance that increases the rate of a chemical reaction and is not changed by the reaction

Question 51

What is an enzyme?

Answer 51

Proteins that are involved in all metabolic reactions, where they function as biological catalysts

Question 52

What does an amylase do?

Answer 52

Catalyses the breakdown of starch to maltose

Question 53

What does protease do?

Answer 53

Catalyses the breakdown of protein to amino acids

Question 54

What does catalase do?

Answer 54

Catalyses the breakdown of hydrogen peroxide to water and oxygen

Question 55

The names of enzymes often end in -ase. Using this, name the enzyme that catalyses the breakdown of carbohydrates, lipids, and maltose.

Answer 55

- Carbohydrases - Lipases - Maltase

Question 56

The substance that an enzyme changes is called _______________

Answer 56

substrate

Question 57

Each enzyme has molecules with a very specific shape. The enzyme molecule has a ‘dent’ in it called ____________________

Answer 57

Active site

Question 58

What is the photosynthesis equation?

Answer 58

———————————-*sunlight* *and* *chlorophyll* carbon dioxide + water———> glucose + oxygen 6CO₂ + 6H₂ —> C₆H₁₂O₆ + 6O₂

Question 59

What are vascular bundles?

Answer 59

Collections of xylem tubes and phloem vessels running side by side, which form the veins in a leaf

Question 60

What is the epidermis?

Answer 60

The outer layer of tissue on a plant

Question 61

What is the cuticle?

Answer 61

A thin layer of wax that covers the upper surface of a leaf

Question 62

What is the palisade mesophyll?

Answer 62

The layer of cells immediately beneath the upper epidermis, where most photosynthesis happens

Question 63

What is the spongy mesophyll

Answer 63

The layer of cells immediately beneath the palisade mesophyll, where some photosynthesis happens; this tissue contains a lot of air spaces between the cells

Question 64

What are stomata?

Answer 64

Openings in the surface of a leaf, most commonly in the lower surface; they are surrounded by pairs of guard cells, which control whether the stomata are open or closed. Guard cells are the only cells in the epidermis that contain chloroplasts