SP1 Key Concepts in Biology

Question 1

Define an electron microscope

Answer 1

uses electrons to see smaller things in much more detail - has a higher magnification and resolution

Question 2

Define a light microscope

Answer 2

pass light through the specimen to show us things like nuclei and chloroplasts

Question 3

Define resolution

Answer 3

How well a microscope distinguishes between two points that are close together. A higher resolution means that the image can be seen more clearly

Question 4

Why can some cells be seen with an electron but not a light microscope?

Answer 4

Electron microscopes see things in more detail

Question 5

Formula for total magnification

Answer 5

total magnification = eyepiece lens magnification x objective lens magnification

Question 6

Formula for sizes and magnification

Answer 6

magnification = image size / real size

Formula triangle with image size on top

Question 7

List the units and conversions

Answer 7

Millimetre (mm) x1000 = Micrometre (um) x1000 = Nanometre (nm) x 1000 = Picometre (pm)

Question 8

List 5 parts to an animal cell

Answer 8

Nucleus, Cytoplasm, Cell membrane, Mitochondria, Ribosomes

Question 9

List 3 additional parts to a plant cell

Answer 9

Rigid cell wall, Vacuole, Chloroplasts

Question 10

Define ribosomes

Answer 10

these are involved in the translation of genetic material in the synthesis of proteins

Question 11

Define large vacuole

Answer 11

contains cell sap and maintains the internal pressure to support the cell

Question 12

Define mitochondria

Answer 12

where most of the reactions for respiration take place

Question 13

Define chloroplasts

Answer 13

where photosynthesis occurs - they contain a green substance called chlorophyll

Question 14

Define cytoplasm

Answer 14

gel-like substance where most chemical reactions occur in the cell - it also contains enzymes

Question 15

Define nucleus

Answer 15

contains genetic material that controls the activities of the cell

Question 16

How are sperm cells adapted to their function?

Answer 16

• has long tail to help it swim
• lots of mitochondria to provide it with energy to swim
• acrosome at front of head, where it stores enzymes needed to digest its way through membrane of egg
• haploid nucleus

Question 17

How are egg cells adapted to their function?

Answer 17

• contains nutrients in cytoplasm to feed embryo
• haploid nucleus
• straight after fertilisation, its membrane changes structure to stop any more sperm getting in. This makes sure the offspring has the right amount of DNA

Question 18

How are ciliated epithelial cells adapted to their function?

Answer 18

Cilia are on the top surface of the cell; the cilia beat to move substances upwards, moving mucus up to the throat where is can be swallowed and doesn’t reach the lungs

Question 19

List 5 parts to a bacterial cell

Answer 19

Chromosomal DNA, Ribosomes, Cell membrane, Plasmid DNA, Flagellum

Question 20

Define plasmid DNA

Answer 20

small loops of extra DNA that aren’t part of the chromosome. Plasmids contain genes for things like drug resistance, and can be passed between bacteria

Question 21

Define flagellum

Answer 21

hair-like structure that rotates to make a bacterium move away from harmful substances or towards beneficial things like nutrients

Question 22

Define eukaryotes

Answer 22

complex cells

Question 23

Define prokaryotes

Answer 23

smaller, simpler cells that make single-celled organisms

Question 24

Define enzymes as biological catalysts

Answer 24

Enzymes are catalysts in the body used to speed up chemical reactions

Question 25

Why are enzymes important as catalysts for life processes?

Answer 25

Enzymes speed up chemical reactions in the body, and reduces the need for high temperatures

Question 26

Test for Starch

Answer 26

Add iodine : if starch is present, the sample will turn from browny-orange to a dark blue-black colour

Question 27

Test for Sugars

Answer 27

Use Benedict’s Reagent : higher conc. of sugar, the further the colour change will go from blue - green - yellow - orange - brick red

Question 28

Test for Proteins

Answer 28

Use the Biuret Test : add some potassium hydroxide to make solution alkaline. Then add some copper sulfate. If there is protein, the solution will turn purple. No protein = stays blue

Question 29

Test for Lipids

Answer 29

Emulsion Test : shake test substance with ethanol and pour into water. If lipids are present, they will precipitate and show up as a milky emulsion