Topic 1 - Key Concepts in Biology

Question 1

What are the functions of the organelles in animal cells

Answer 1

Nucleus - stores genetic information
Mitochondria - site of aerobic respiration
Cell membrane - controls the exit and entry of substances in a cell
Cytoplasm - site of most metabolic reactions
Ribosomes - site of protein synthesis

Question 2

What are the functions of the organelles found in plant cells

Answer 2

Cell wall - provide protection and support; prevents cell from bursting
Chloroplasts - contain chlorophyll which absorbs light energy for photosynthesis
Vacuole - contains cell sap which helps to maintain the cell’s shape
Nucleus - stores genetic information
Mitochondria - site of aerobic respiration
Cell membrane - controls the exit and entry of substances in a cell
Cytoplasm - site of most metabolic reactions
Ribosomes - site of protein synthesis

Question 3

What are the functions of the organelles found in bacteria cells

Answer 3

Chromosonal DNA - a singular long chromosome that floats free in the cytoplasm
Flagellum - a hair-like structure that rotates to make the bacterium move
Plasmid DNA - small loops of extra DNA that can pass between bacteria for genetic variation
Cell membrane - controls the exit and entry of substances in a cell
Cell wall - provide protection and support; prevents cell from bursting
Ribosomes - site of protein synthesis
Cytoplasm - site of most metabolic reactions

Question 4

How are sperm cells adapted to their function

Answer 4

Acrosome - a vescicle containing hydrolytic enzymes to dissolve the egg cell
Nucleus - contains 23 chromosomes
Middle piece - contains mitochondria for energy released by aerobic respiration, for swimming
Tail - produces swimming movement

Question 5

How are egg cells adapted to their function

Answer 5

• Nucleus contains 23 chromosomes
• Cytoplasm provides nutrition to the growing zygote until implantation and attachment to the placenta in the uterus
• Jelly coating hardens after fertilization to prevent other sperm cells from entering the egg

Question 6

How are ciliated epithelial cells adapted to their function

Answer 6

• Cilia are hair-like cytoplasmic projections that are motile and help to move mucus (containing germs and dirt) away from the lungs and towards the mouth and nose
• Epithelium is found in the inner lining of organs, so these organs are protected

Question 7

What are the characteristics of optical microscopes

Answer 7

Resolution of 250nm
Magnification of x2000
Views the surface structure of live specimens

Question 8

What are the characteristics of electron microscopes

Answer 8

Resolution of 0.25nm
Magnification of x2,000,000
Views thin slices or sections of cells or tissues and dead materials

Question 9

What is the order of units from metre to picometre and theire conversion rates

Answer 9

Metre, m
Millimetre, mm
Micrometre, µm
Nanometre, nm
Picometre, pm

Multiply by 1000 to go down the scale

Question 10

What is the microscopy equation

Answer 10

Actual size = Image size÷Magnification

Question 11

What is the equation for total magnification

Answer 11

Eyepiece lens magnification x objective lens magnification

Question 12

Describe the core practical: investigate biological using microscopes, including magnification calculations and labelled scientific drawings from observations

Answer 12

1. Add a drop of water to the middle of a clean slide to secure the specimen in place
2. Cut up an onion and separate it out into layers. Use tweezers to peel off some epidermal tissue from the bottom of one of the layers.
3. Using the tweezers, place the epidermal tissue into the water on the slide.
4. Add a drop of iodine solution (a stain). This is used to add colour to objects in a cell, making them easier to see.
5. Place a cover slip over the specimen.
6. Clip the slide you’ve prepared onto the stage and select the lowest-powered objective lense. Look down the eyepiece.
7. Draw the observed specimen.