1
State the three principles of cell theory.
All living things are made of cells; cells are the basic unit of structure and function; all cells come from pre-existing cells.
What is the function of the cell membrane?
It selectively controls substances entering and leaving the cell.
Put these in order from simplest to most complex: organ, cell, organ system, tissue.
Cell → tissue → organ → organ system.
What is the difference between positive and negative tropism?
Positive tropism is growth toward a stimulus. Negative tropism is growth away from it.
A student walks 60 m east in 20 s. Calculate their average velocity.
v = Δd ÷ Δt = 60 ÷ 20 = 3.0 m/s [E].
A microscope has a 10× eyepiece and a 4× objective. What is its total magnification?
40×
What is a concentration gradient?
A difference in a substance’s concentration between two regions.
Why is a leaf considered an organ?
It contains different tissues working together for photosynthesis, gas exchange, and transport.
What is the difference between phototropism and gravitropism?
Phototropism is growth in response to light. Gravitropism is growth in response to gravity.
A student walks at 3.0 m/s east for 15 s. Calculate their displacement.
Δd = v × Δt = 3.0 × 15 = 45 m [E].
What is the difference between biogenesis and abiogenesis?
Biogenesis means life comes from existing life. Abiogenesis means life originates from non-living matter.
What does “fluid mosaic” mean when describing a cell membrane?
A flexible phospholipid bilayer containing proteins and other molecules, many of which can move sideways.
How many cells are in the human body?
37 trillion cells
Calculate the surface area and volume of a cube with 2 cm sides. Use SA = 6s² and V = s³.
Surface area = 24 cm². Volume = 8 cm³.
A skateboarder speeds up from 2.8 m/s north to 9.4 m/s north in 4.0 s. Calculate their average acceleration.
a = (9.4 − 2.8) ÷ 4.0 = 1.65 m/s² [N], or 1.7 m/s² [N].
What is the main difference between prokaryotic and eukaryotic cells?
Prokaryotic cells lack a nucleus and membrane-bound organelles. Eukaryotic cells have both.
Which parts of a phospholipid are attracted to water, and which parts avoid water?
Hydrophilic heads are attracted to water; hydrophobic tails avoid water.
What are stomata, and how do guard cells control them?
Stomata are pores that allow gas exchange and water vapour loss. Guard cells open and close them.
A cube has a surface area of 96 cm² and a volume of 64 cm³. Calculate its surface-area-to-volume ratio.
1.5:1.
A student pushes a box 5.0 m with a force of 30 N in the direction of motion. How much work does the student do on the box?
W = Fd = 30 × 5.0 = 150 J.
State the function of each: nucleus, ribosome, mitochondrion, and chloroplast.
Nucleus: contains DNA and controls cell activities. Ribosome: makes proteins. Mitochondrion: produces ATP through cellular respiration. Chloroplast: carries out photosynthesis.
A root cell absorbs minerals from soil even though the cell already has a higher mineral concentration. Identify the process and explain why energy is needed.
Active transport. It uses ATP to move minerals against their concentration gradient, from lower to higher concentration.
Where are vascular bundles found in a leaf, root, and stem?
Leaf: in the veins. Root: in the central vascular cylinder. Stem: in a ring near the outside in dicots, or scattered throughout in monocots.
A 10 kg box accelerates at 2.0 m/s². What net force acts on the box?
F = ma = 10 × 2.0 = 20 N.
On a velocity–time graph, what do these represent: a horizontal line above zero, a line rising from zero, a line falling from positive velocity to zero, and the slope?
Horizontal: constant positive velocity. Rising: speeding up. Falling: slowing to a stop. Slope: acceleration.