4.1 - Cell biology
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146 Terms
What are the three basic structures in animal cells?
Nucleus, cytoplasm and cell membrane.
What is the function of the nucleus?
Contains genetic material and controls cell activities.
What is the function of the cytoplasm?
Where most chemical reactions occur.
What is the function of the cell membrane?
Controls movement of substances into and out of the cell.
What is the function of mitochondria?
Site of aerobic respiration.
What is the function of ribosomes?
Site of protein synthesis.
Which structures are found in plant cells but not animal cells?
Chloroplasts, cellulose cell wall and permanent vacuole.
What is the function of chloroplasts?
Site of photosynthesis; contain chlorophyll.
What is the function of the permanent vacuole?
Contains cell sap and helps maintain cell rigidity.
What is the function of the cellulose cell wall?
Strengthens and supports the cell.
What is a prokaryotic cell?
A cell without a nucleus, such as a bacterium.
How is bacterial DNA different from eukaryotic DNA?
It is a single DNA loop, not enclosed in a nucleus.
What are plasmids?
Small rings of DNA found in bacterial cells.
What is a eukaryotic cell?
A cell with genetic material enclosed in a nucleus.
How do bacterial cells differ from animal cells?
Bacteria have no nucleus and have a cell wall and plasmids.
What is a specialised cell?
A cell adapted to carry out a particular function.
How is a sperm cell adapted for its function?
Tail for movement, many mitochondria for energy and enzymes to penetrate the egg.
How is a nerve cell adapted for its function?
Long axon carries electrical impulses over long distances.
How is a muscle cell adapted for its function?
Contains many mitochondria to provide energy for contraction.
How is a root hair cell adapted?
Large surface area for absorbing water and mineral ions.
How is a xylem cell adapted?
Hollow, dead cells with lignin-strengthened walls form tubes.
How is a phloem cell adapted?
Forms tubes allowing dissolved sugars to be transported.
What is cell differentiation?
The process where cells become specialised for different functions.
When do most animal cells differentiate?
At an early stage of development.
How does plant cell differentiation differ from animal cells?
Many plant cells can differentiate throughout the plant's life.
What is the difference between magnification and resolution?
Magnification enlarges; resolution shows detail between two close points.
Why are electron microscopes better than light microscopes?
They have much higher magnification and resolution.
What is the magnification equation?
Magnification=Actual sizeImage size
How do you rearrange the magnification equation?
Actual size=MagnificationImage size
What happens before a cell divides by mitosis?
DNA replicates and the cell grows, increasing organelles.
What happens during mitosis?
Chromosomes separate and one set moves to each end of the cell.
What are the products of mitosis?
Two genetically identical daughter cells.
Why is mitosis important?
Growth, development, repair and replacement of cells.
What is a stem cell?
An undifferentiated cell that can produce different cell types.
Where are stem cells found in adult humans?
Mainly in bone marrow.
What can embryonic stem cells become?
Most different types of human cells.
What can bone marrow stem cells become?
Many types of cells, including blood cells.
Where are plant stem cells found?
In meristem tissue.
What is therapeutic cloning?
Producing an embryo genetically identical to a patient for stem-cell treatment.
What is a risk of using stem cells?
Viral infection can be transferred.
Why might stem-cell treatment be controversial?
Some people have ethical or religious objections.
What is diffusion?
Net movement of particles from high to low concentration.
What three factors affect diffusion rate?
Concentration gradient, temperature and surface area.
Why do single-celled organisms exchange substances efficiently?
They have a large surface-area-to-volume ratio.
Why do multicellular organisms need exchange surfaces?
Their smaller surface-area-to-volume ratio makes diffusion insufficient.
How is an exchange surface adapted for efficient diffusion?
Large surface area and thin membrane; animals also have blood supply.
What is osmosis?
Movement of water from dilute to concentrated solution through a partially permeable membrane.
What is a partially permeable membrane?
A membrane allowing some substances through but not others.
What happens to a plant cell in a dilute solution?
Water enters by osmosis; the cell becomes turgid.
What happens to a plant cell in a concentrated solution?
Water leaves by osmosis; the cell becomes plasmolysed.
What is active transport?
Movement from low to high concentration using energy from respiration.
Why does active transport require energy?
It moves substances against the concentration gradient.
Give an example of active transport in plants.
Root hair cells absorb mineral ions from dilute soil.
Give an example of active transport in humans.
Sugar is absorbed from the gut into blood against its concentration gradient.
What is the key difference between diffusion and active transport?
Diffusion needs no energy; active transport requires energy.
What is the key difference between osmosis and diffusion?
Osmosis is water movement through a partially permeable membrane.
What is the equation for percentage change in mass?
Percentage change=Original massChange in mass×100
What does a negative percentage change in mass show?
The tissue lost mass, so water left by osmosis.
What does a positive percentage change in mass show?
The tissue gained mass, so water entered by osmosis.
What is Required Practical 1?
Use a light microscope to observe, draw and label plant and animal cells.
What must be included when drawing cells from Practical 1?
Labels and a magnification scale.
What is Required Practical 2?
Investigate how salt/sugar concentration affects plant tissue mass.
What should be calculated in the osmosis practical?
Percentage gain or loss of mass.
What does the point where percentage mass change is zero represent?
The concentration where there is no net movement of water.
Why should repeats be done in the osmosis practical?
To identify anomalies and calculate a reliable mean.
Why does a larger surface-area-to-volume ratio increase diffusion?
More surface is available for exchange relative to the cell's volume.
Why does a steeper concentration gradient increase diffusion rate?
There is a greater difference in particle concentration, increasing net movement.
Why does higher temperature increase diffusion rate?
Particles gain kinetic energy and move faster.
Why does a thin exchange surface increase diffusion rate?
It gives particles a shorter distance to travel.
Why are multicellular organisms unable to rely only on diffusion?
Their low surface-area-to-volume ratio makes diffusion too slow for their needs.
Why does active transport allow mineral absorption when soil concentration is lower?
Energy moves ions against their concentration gradient.
Why does a plant cell not burst when placed in dilute solution?
The cellulose cell wall resists expansion and prevents bursting.
Why does osmosis cause a plant cell to become turgid?
Water enters, increasing pressure against the cell wall.
Why does an electron microscope reveal more cell structures?
Its higher resolution distinguishes smaller structures.
Why are stem cells useful in treating damaged tissues?
They can differentiate into specialised cells that replace damaged cells.
What is the function of mitochondria?
Site of aerobic respiration.
What is the function of ribosomes?
Site of protein synthesis.
Which structures are found in plant cells but not animal cells?
Chloroplasts, cellulose cell wall and permanent vacuole.
What is the function of chloroplasts?
Site of photosynthesis; contain chlorophyll.
What is the function of the permanent vacuole?
Contains cell sap and helps maintain cell rigidity.
What is the function of the cellulose cell wall?
Strengthens and supports the cell.
What is a prokaryotic cell?
A cell without a nucleus, such as a bacterium.
How is bacterial DNA different from eukaryotic DNA?
It is a single DNA loop, not enclosed in a nucleus.
What are plasmids?
Small rings of DNA found in bacterial cells.
What is a eukaryotic cell?
A cell with genetic material enclosed in a nucleus.
How do bacterial cells differ from animal cells?
Bacteria have no nucleus and have a cell wall and plasmids.
What is a specialised cell?
A cell adapted to carry out a particular function.
How is a sperm cell adapted for its function?
Tail for movement, many mitochondria for energy and enzymes to penetrate the egg.
How is a nerve cell adapted for its function?
Long axon carries electrical impulses over long distances.
How is a muscle cell adapted for its function?
Contains many mitochondria to provide energy for contraction.
How is a root hair cell adapted?
Large surface area for absorbing water and mineral ions.
How is a xylem cell adapted?
Hollow, dead cells with lignin-strengthened walls form tubes.
How is a phloem cell adapted?
Forms tubes allowing dissolved sugars to be transported.
What is cell differentiation?
The process where cells become specialised for different functions.
When do most animal cells differentiate?
At an early stage of development.
How does plant cell differentiation differ from animal cells?
Many plant cells can differentiate throughout the plant's life.
What is the difference between magnification and resolution?
Magnification enlarges; resolution shows detail between two close points.
Why are electron microscopes better than light microscopes?
They have much higher magnification and resolution.
What is the magnification equation?
Magnification=Actual sizeImage size
How do you rearrange the magnification equation?
Actual size=MagnificationImage size