Cells and Cell Processes

Inside the cell

Cells are the building blocks of every living thing. Animal cells have a nucleus that controls the cell, cytoplasm where reactions happen, a cell membrane that controls what goes in and out, and mitochondria that release energy in respiration. Plant cells have all of these plus a cell wall for support, chloroplasts that trap light for photosynthesis, and a large vacuole of sap. Bacterial cells are simpler and have no nucleus. Cells rarely work alone: similar cells form tissues, tissues form organs, and organs form organ systems that build the whole organism. Substances move in and out of cells by diffusion, osmosis and active transport. Because cells are tiny, we use magnification to study them. This module covers cell structure, organisation, transport and magnification.

Cell words

Learn these before you match any part, and keep the three ways substances cross the membrane in mind.

Animal cell against plant cell

Plant and animal cells share several parts, but plant cells have extra features an animal cell lacks.

How substances cross the membrane

Whenever a substance moves in or out of a cell, ask two things: which way the concentration runs and whether energy is used. If particles drift from where there are many to where there are few, that is diffusion and it needs no energy. If it is water crossing a partially permeable membrane, that is osmosis. If the cell has to push a substance the hard way, from few to many, it must spend energy, and that is active transport. Name the direction and the energy, and the process names itself.

Match the cell part to its job

Which part is this?

A student finds a part that is present in plant cells but not animal cells and traps light to make food. Which part is it?

• A chloroplast.
• The nucleus.
• A mitochondrion.
• The cell membrane.

Transport across membranes

Select the TWO true statements about how substances cross the cell membrane.

• Diffusion moves particles from high to low concentration
• Active transport needs energy to move substances
• Osmosis moves large proteins across the membrane
• Diffusion needs a lot of energy

Work out the magnification

Magnification is the image size divided by the actual size. Under a microscope a cell image is 60 mm across, while the real cell is 3 mm across. Divide to find the magnification, as the number of times larger.

Order the levels of organisation

Put the levels of organisation in a living thing in order, smallest first.

• Cell
• Tissue
• Organ
• Organ system
• Organism

Complete the facts

Particles spreading from a high to a low concentration is _____. Water moving across a partially permeable membrane is _____. Moving a substance from low to high concentration using energy is _____ transport. The part that controls the cell and holds the genetic material is the _____.

Match the process to what it moves

Spot the true cell facts

Tap the TWO statements that are true about cells.

• Plant cells have a cell wall that animal cells lack
• Active transport moves substances using energy
• Animal cells contain chloroplasts
• The cell membrane holds the genetic material

Explain the cell

Read each case and choose the best response, with a reason.

• A cell is examined and found to have a cell wall, chloroplasts and a large vacuole. What type of cell is it?
• A root cell must take in a mineral that is already at a higher concentration inside than outside. How does it do this?
• A student says an image 60 mm wide of a 3 mm cell is magnified 3 times. How should this be corrected?

Explain cells and transport

A student is studying a plant cell under a microscope. Explain its structure and how substances move in and out of it.

• Name three parts a plant cell has that an animal cell does not
• Give the job of the nucleus and of the mitochondria
• Explain diffusion and osmosis
• Explain how active transport differs from diffusion
• Finish by explaining what magnification means