Chapter 2- Cells Flashcards
What do microscopes do?
Microscopes make small objects appear bigger. With a microscope you can zoom in and see the cells that make up living things.
What are animals, plants and other living things made of?
Animals, plants and other living things are made up of tiny cells.
What is the function of a compound light microscope?
These microscopes use light and a number of lenses to form an imageThe specimen (the object being observed) is placed on a rectangular piece of glass called a microscope slide. The specimen needs to be very thin so that light can pass through it. A small, thin piece of glass called a coverslip is placed on top of the specimen. Light is made to pass through the object and the glass lenses, which bend the rays of light. A magnified image of the part of the specimen directly under the objective lens is formed..
What is a microscope called with one eyepiece?
The microscope at right has only one eyepiece; it is a monocular microscope.
What is a microscope called with two eyepieces?
Some school microscopes have two eyepieces; they are called binocular microscopes.
What are microscopes with built-in lights?
These microscopes do not have a mirror at the bottom; they have a light.
What do most microscopes have a selection of?
Most microscopes have a selection of objective lenses, and a revolving nosepiece allows the user to switch from one objective lens to another and thus change the magnification.
How can you calculate the magnification?
You can calculate the magnification by multiplying the eyepiece magnification by the objective lens magnification.
Does changing the objective lens change the size of the image?
It is important to note that changing the objective lens does not change the size of the image; it just shows a tinier part of the specimen at a greater magnification.
What can a typical school microscope magnify up to?
Typical school microscopes can magnify up to 400 times.
What is the microscope measured in?
The measurements of objects viewed under a microscope are usually expressed in microns or micrometres.
1 micron or micrometre (µm) = 0.000 001 m = 0.001 mm
What are the main rules for handling a microscope?
Rules for handling a microscope
- Always use two hands when carrying a microscope: one on the arm of the microscope and the other under the base.
- Place the microscope securely on a flat surface, away from the edge. • Never shine sunlight directly up the microscope tube. You could damage your eyes.
- Use only lens tissues to clean microscope lenses; never use your fingers.
What are the hints for using a microscope?
More hints for using a microscope •
Look down the microscope with one eye, but keep both eyes open — don’t squint.
• Begin focusing a microscope on the lowest magnification.
• Focus a microscope by beginning with the coarse focus. Look from the side and adjust the objective lens so that it is just above the microscope slide.
• Turn the coarse focus knob to move the tube up until the object comes into view.
• Turn the fine focus to make the image of the object as clear as possible.
What is a digital eyepiece?
You can take photos of microscopic objects using a digital eyepiece. This is a special digital camera that works with a microscope.
How can a digital eyepiece be viewed?
Instead of looking through the eyepiece to see the image, the digital eyepiece is connected to a computer and the image can be viewed on a computer screen. The image can be saved, annotated and manipulated in the same way as any digital photo.
What is a stage in a microscope?
Where the slide is placed
What is the function of eyepiece lens?
Used to adjust the amount of light reaching the eyepiece
What is the function of the coarse focus knob?
Makes large adjustments to the distance between the stage and the objective lens; brings the image into focus
What is the function of the fine focus knob?
Makes small adjustments to the distance between the stage and the objective lens; brings the image into focus
What is the function of the stage slide clip?
Holds the slide in place
What is the function of the mirror?
Directs the light towards the specimen
What is the function of the iris adjustment?
Used to adjust the amount of light reaching the eyepiece
What is the function of the slide?
Thin piece of glass where the specimen is placed
What is the function of the revolving nosepiece?
Can be turned to change objective lens
What is the function of the objective lenses?
Magnifies the image
What is a graticule?
This grid is also called a graticule; it is on a glass disc that is often inserted into the eyepiece of a microscope to help measure small objects.
How is the stereomicroscope used?
A stereomicroscope is useful to provide a magnified view of the surface of thicker objects such as rocks, crystals, insects and small flowers.
How much magnification do the stereomicroscopes provide?
These microscopes do not provide as much magnification but they have the advantage that the specimen does not need to be sliced thinly.
How is the hand-held microscope produced?
Like the stereomicroscope, it can be used to view the surface of thick objects, but it plugs into a computer. The image is displayed on the computer screen and can be saved and edited. These devices are cheaper and more portable than stereomicroscopes, but they cannot be used without a computer.
What can the best light microscopes magnify up to?
The best light microscopes can magnify up to 2000 times at the most.
Is the light microscopes sufficient to see viruses
This is sufficient to see bacteria, but viruses are so tiny that they cannot be seen even with the best quality light microscope.
How is the electron microscope used?
An electron microscope is required. These use a beam of particles called electrons, rather than light, to produce an image with up to 2 million times magnification.
How to prepare specimens for view in electron microscopes?
Preparing specimens for viewing is tricky. A specimen needs to be dehydrated and may be coated with a thin layer of metal, so it is not possible to observe living organisms.
What do the images look like when being produced?
The images produced (called electron micrographs) are black and white, although sometimes colours are added later to make particular features stand out or enhance the appearance of the image.
What are the types of electron microscopes?
Scanning electron microscopes (SEM) and transmission electron microscope (TEM).
What does SEM do?
Scanning electron microscopes (SEM) scan the surface of an object and can produce an image of the surface of the object.
What does TEM do?
In a transmission electron microscope (TEM), the electrons pass through a thin section of an object and so the image is a cross-section of the specimen.
What are organelles?
Cells contain ‘little organs’ or organelles. There are different types of organelles and each organelle has a particular function or job. Plant and animal cells appear quite different and contain different organelles.
What is inside an animal cell?
Animal cells are enclosed by a cell membrane that controls the movement of substances in and out of the cell. Inside the cell membrane there is a runny, jelly-like substance called cytosol and a darker area called the nucleus. The nucleus is the control centre of the cell. It contains DNA, a chemical substance that holds the instructions for making particular proteins. These proteins determine what the cell does.
What is mitochondria?
Mitochondria are organelles that can be seen only with a very high-quality light microscope or an electron microscope.
What happens inside mitochondria?
In the mitochondria, glucose reacts with oxygen to release energy. This process is called respiration.
What are plant cells like?
Plant cells tend to be larger and have a more regular shape with some straight edges. This is because they contain a large, water-filled vacuole and are enclosed by a rigid cell wall. The vacuole stores water and minerals.
What are chloroplasts?
Chloroplasts are the oval-shaped organelles found only in plant cells.
What do chloroplasts contain?
Chloroplasts contain a green substance called chlorophyll.
What is the function of chloroplasts?
Chloroplasts use energy from the sun to make food.
Where are chloroplasts found?
Not all plant cells contain chloroplasts. They are found only in leaf and stem cells.
What is the vacuole?
The vacuole is an organelle used to store water and dissolved substances.
What do vacuoles look like?
Vacuoles can look empty, like an air bubble. Plant cells usually have one large vacuole.
What is the function of vacuoles?
The mixture inside a plant’s vacuoles is called cell sap. The red, blue and violet colours that you often see in plant leaves and flowers are due to the substances stored in vacuoles. Most animal cells don’t have vacuoles.
What is the cell wall?
The tough covering around plant cells is the cell wall.
What is the function of the cell wall?
It gives plant cells strength and holds them in shape. Water and dissolved substances can pass through the cell wall.
What are cell walls made of?
Cell walls are made of a substance called cellulose.
What is the cell membrane?
The thin layer that encloses the cytoplasm is the cell membrane.
What is the function of the cell membrane?
It keeps the cell together and gives it its shape. Some substances, such as water and oxygen, can pass through the cell membrane but other substances cannot. The cell membrane controls what enters and leaves the cell.
What is the nucleus?
The nucleus is the control centre of the cell.
What is the function of the nucleus?
It contains DNA in the form of chromosomes and it controls what the cell does and when.
What is the cytosol?
The jelly-like substance inside cells is the cytosol.
What does the cytosol contain?
It contains many important substances, such as glucose, that are needed for chemical reactions that occur inside cells.
What is the cytoplasm?
Cytoplasm = cytosol + all organelles except nucleus
What do plant cells contain?
Plant cells contain cytosol, a nucleus, mitochondria and a cell membrane, just like animal cells. They also contain green organelles called chloroplasts.
What is photosynthesis?
Photosynthesis, a process that uses energy from the sun to convert carbon dioxide and water into glucose and oxygen.
What are the points to remember for sketching a microscope?
Some points to remember
- Use a sharp lead pencil.
- Draw only the lines that you see (no shading or colouring).
- Your diagrams should take up about a third to half a page each.
- Record the magnification next to each diagram.
- State the name of the specimen and the date of observation.
- A written description is also often of considerable value.
- When you are viewing many cells at one time, it is often useful to select and draw only two or three representative cells for each observation.
Why are specimens stained?
Many objects are colourless when viewed down the microscope, so specimens are often stained to make them easier to see.
What are examples of commonly used stains?
Methylene blue, iodine and eosin are some examples of commonly used stains. Each stain reacts with different chemicals in the specimen. For example, iodine stains starch a blue-black colour.
What is respiration?
Respiration, a chemical process that releases energy, occurs in the mitochondria. Respiration is a chemical reaction where glucose, a type of sugar, reacts with oxygen to produce a gas, called carbon dioxide, and water.
It can be summarised by the following equation:
glucose + oxygen → carbon dioxide + water
Why is respiration a very important process?
Respiration is a very important process because this is how living things convert the energy locked up in glucose into a useful form.
What is one important difference between animals and plants?
One important difference between animals and plants, though, is the source of glucose and oxygen that they use in respiration.
Where does respiration take place?
Respiration takes place in the cells of animals, fungi, plants and many microscopic organisms.
Which cells contain the most mitochondria?
Cells that have a high demand for energy, such as muscle cells in animals, contain many mitochondria.
How do animals obtain glucose for respiration?
Animals obtain the glucose needed for respiration by ingesting food.
How does food digest in humans and animals?
In humans and many other animals the food passes through a digestive system where the complex chemicals that make up the food are broken down into smaller chemicals, including glucose. The small chemicals pass through the walls of the small intestine and into the bloodstream and are delivered to all the cells of the body. The bloodstream thus brings glucose from the food we eat to the cells that need glucose for respiration.
How do plant cells obtain glucose?
Plants can make their own glucose. Plant cells contain chloroplasts where photosynthesis occurs. Photosynthesis produces glucose, so plant cells do not need to ingest food.
How do plant cells perform respiration?
Photosynthesis can occur only when there is light. During the day, plants usually make more glucose than they need for respiration. Some of the glucose is converted to other chemicals, such as the cellulose that plant cell walls are made of. Some glucose is converted to starch and stored in various parts of the plant, including the roots. At night, the plant continues to carry out respiration. When it starts to run out of glucose, some of the starch is converted back into glucose so that respiration can continue.
How does fungi obtain glucose?
Fungi do not eat food either; nor do they carry out photosynthesis. They obtain glucose and the other chemicals they need for survival from the material on which they grow.
How does fungi obtain chemicals from the materials on which they grow?
The substances needed to break down this material move out through the cell membrane and cell wall of the fungus; the chemicals resulting from this breakdown that the fungus needs then move into the cells of the fungus.
What is the hydra?
The hydra is a tiny animal, about 1 cm long, that lives in rivers and streams.
What is diffusion?
The water in which it lives contains small amounts of dissolved oxygen. The oxygen moves into the hydra through its skin. This is known as diffusion.
What are some examples of how animals get oxygen into their bodies?
Fish and many other aquatic animals have gills to extract oxygen from their environment. Insects get oxygen into their bodies via little holes, called spiracles, along the sides of their bodies. These holes lead to tubes that bring the outside air into the body of the insect, so that oxygen can diffuse into the cells that need it.
How does the respiratory system work?
Air is breathed into the lungs. Oxygen moves across the walls of the air sacs in the lungs and into the bloodstream so it can be delivered to cells.
What are the products of the respiration?
The products of respiration are water and carbon dioxide.
Why does carbon dioxide need to be moved from animal cells?
Water is used in various processes in living cells, but carbon dioxide can be a problem if it builds up to high levels. Animal cells cannot use up the carbon dioxide produced in respiration, so it needs to be removed from the cells and taken out of the body.
What are multicellular organisms?
Animals and plants are made up of many cells; they are multicellular organisms.
What are unicellular organisms?
Some microscopic organisms, including bacteria, are unicellular; they are made of just one cell.
What are the types of unicellular organisms?
There are two main types of unicellular organisms: those that have a nucleus (the protists) and those that do not have a nucleus (mainly bacteria).
What are the examples of protists?
Examples of protists include Amoeba, Paramecium and Euglena.
What is Amoeba?
Amoeba look like blobs but they can move about and they can engulf food.
What is Paramecium?
Paramecium have small hairs that beat to enable them to move.
What is Euglena?
Euglena are interesting because they can take in food (like animals) and also carry out photosynthesis (like plants), depending on the availability of food and sunlight.
What are the examples of unicellular organisms?
Examples of unicellular organisms that do not have a nucleus include bacteria, cyanobacteria and bacteria-like organisms that are believed to be similar to the very first life forms to have evolved on Earth.
What happens in unicellular organisms?
When an organism is made of only one cell, it is necessary for that cell to carry out all the jobs needed to keep the organism alive. The cell cannot specialise.
What happens in multicellular organisms?
In multicellular organisms, on the other hand, certain cells can become specialised for a particular task.
Example of certain cells becoming specialised in a particular task?
Red blood cells specialise in carrying oxygen around the body, and nerve cells specialise in transmitting messages from one part of the body to another.
How do unicellular organisms reproduce?
First, the cell grows. When it reaches a certain size, it divides into two small cells, which in turn grow and eventually divide. In unicellular organisms that have a nucleus, the nucleus divides first, and then the cytoplasm divides.
What are complex organisms made up of?
Complex organisms such as humans are made up of many different types of cells, each with a special job to do. But these cells do not function independently; they are organised into tissues, organs and systems so that they can work efficiently together.
What make up tissues?
Groups of similar cells that carry out a particular job make up tissues.
What is the heart made up of?
The heart is made up of cardiac muscle tissue, fat and connective tissue.
What makes up organs and examples?
Different types of tissues form organs. The heart, brain, lungs, liver and eye are all organs.
What makes up systems and examples?
Organs, in turn, are organised into systems. The kidneys, ureters and urethra are all part of the excretory system. The ovaries, fallopian tube and uterus are organs of the reproductive system. Each body system has a particular role to play in keeping an organism functioning.
What do the central nervous system consist of?
The central nervous system consists of the brain and the spinal cord.
What is the function of the digestive system?
Breaks down the food we eat and moves nutrient particles into the bloodstream
What is the function of the respiratory system?
Moves air in and out of the lungs, takes oxygen from the air into the bloodstream and removes carbon dioxide from the blood
What is the function of the excretory system?
Filters out and removes some of the waste products from the bloodstream
What is the function of the reproductive system?
Is involved with making babies
What is the function of the nervous system?
Carries and processes messages from one part of the body to another along nerves
What is the function of the Musculoskeletal system?
Allows the body to move, and some bones also protect important organs
Why do cells vary in their shape, size and structure?
The cells of multicellular organisms are specialised for the particular job they carry out, so they vary in their shape, size and structure.
What are lung epithelial cells?
The cells that line your nose, windpipe and lungs are a type of lining cell. They have hair-like tips called cilia.
What is the function of the lung epithelial cell?
These cells help protect you by stopping dust and fluid from getting down your windpipe. The cilia can also move these substances away from your lungs. You remove some of these unwanted substances whenever you sneeze, cough or blow your nose.
What is the function of the adipose tissue cell?
Some cells store fat. Fat stores a lot of energy for cells to use later.
What does the adipose tissue cell look like?
Round shapes are good for holding a lot of material in a small space.
Where are adipose tissue cells found?
Fat cells are mostly found underneath your skin, especially in the chest, waist and buttocks.
What is the shape of the muscle cell?
Muscle cells are long and elastic. Long thin cells can slide further over each other to allow you to move.
What are some types of muscle cells?
There are different types of muscle cells. The walls of your blood vessels and parts of your digestive system have smooth muscle cells. The muscles that are joined to your bones are called skeletal muscles. Skeletal muscles work in pairs — one muscle contracts (shortens) and pulls the bone in one direction while the other muscle relaxes.
What is the function of bone cells?
Minerals such as calcium surround your bone cells. The minerals help make bone cells hard and strong.
What is the shape of bone cells?
Bone cells need to be hard so that they can keep you upright.
What is the shape of motor nerve cells?
Nerve cells are very long and have a star shape at one end
Why do nerve cells have their shape?
The long shape of nerve cells helps them detect and send electrical messages through the body at the speed of a Formula 1 racing car.
What is the function of a nerve cell?
There are nerve cells all over your body. They allow you to detect touch, smell, taste, sound, light and, unfortunately, pain.
What is the function of skin cells?
Special cells line the outside surfaces of your body. These are the cells that form your skin.
What is the shape of skin cells and why?
These cells have a flattened shape so they can better cover and protect your body.
What is the size of a red blood cell and why?
Red blood cells carry oxygen around the body. Their small size helps them move easily through blood vessels. The nucleus in a red blood cell dies soon after the cell is made. Without a nucleus, red blood cells live for only a few weeks.
Where are red blood cells made and why?
The body keeps making new blood cells to replace those that have died. Red blood cells are made in bone marrow at the rate of 17 million cells per minute! This is why most people can donate some of their blood to the Red Cross without harm.
What shape and function does the white blood cell have?
White blood cells, which are larger than red blood cells, are also made in the bone marrow. Their job is to rid the body of disease-causing organisms and foreign material.
What do sperm cells look like and why?
Sperm cells have long tails that help them swim towards egg cells. Only males have sperm cells.
What is the size of egg cells and why?
Egg cells are some of the largest cells in a human body. Their large round shape helps them store plenty of food.
Why do only females have egg cells?
Only females have egg cells. When a sperm cell moves into an egg cell, the egg cell is fertilised.
What are the examples of protists?
Examples of protists include Amoeba, Paramecium and Euglena.
What is Amoeba?
Amoeba look like blobs but they can move about and they can engulf food.
What is Paramecium?
Paramecium have small hairs that beat to enable them to move.
What is Euglena?
Euglena are interesting because they can take in food (like animals) and also carry out photosynthesis (like plants), depending on the availability of food and sunlight.
What are the examples of unicellular organisms?
Examples of unicellular organisms that do not have a nucleus include bacteria, cyanobacteria and bacteria-like organisms that are believed to be similar to the very first life forms to have evolved on Earth.
What happens in unicellular organisms?
When an organism is made of only one cell, it is necessary for that cell to carry out all the jobs needed to keep the organism alive. The cell cannot specialise.
What happens in multicellular organisms?
In multicellular organisms, on the other hand, certain cells can become specialised for a particular task.
Example of certain cells becoming specialised in a particular task?
Red blood cells specialise in carrying oxygen around the body, and nerve cells specialise in transmitting messages from one part of the body to another.
How do unicellular organisms reproduce?
First, the cell grows. When it reaches a certain size, it divides into two small cells, which in turn grow and eventually divide. In unicellular organisms that have a nucleus, the nucleus divides first, and then the cytoplasm divides.
What are plants made of?
Plants are made up of different types of cells, each suited to a particular function.
What are guard cells?
Guard cells are kidney-shaped cells found on the surface of leaves.
What is the function of guard cells?
They can change shape to either open or close the small hole between them.
What is stomata?
The small holes, called stomata (or stomates), allow substances such as carbon dioxide to enter the leaf. They also let water out of the leaf.
When do most plants open their stomata?
Most plants open their stomata at night; they close their stomata during the day (when it is hotter) to conserve water.
What do xylem cells form?
Xylem cells form xylem tubes, which carry water and dissolved minerals from the roots to all parts of the plant.
What are xylem tubes made up of?
They are made up of dead xylem cells joined end to end. When xylem cells die, the cell walls at each end of the cells dissolve, forming a long straw-like tube.
What happens when a xylem cells die?
When xylem cells die, the cell walls at each end of the cells dissolve, forming a long straw-like tube. They have thick cell walls with lots of cellulose to make the xylem tubes strong.
Describe phloem cells?
Like xylem cells, phloem cells form tubes. The tubes formed by phloem cells carry the food made in the leaves to all parts of the plant. Phloem cells do not need to die to do this job. The ends of phloem cells have holes and look like sieves.
What is the main function of leaf cells?
The main function of leaf palisade cells is to photosynthesise, so they are packed with chloroplasts and are usually green.
Where are epidermal cells found?
Epidermal cells are found on the outside of the plant. They form an outer skin for the plant and protect the cells underneath. This explains why they need a flat shape and why they interlock like tiles.
Do epidermal cells photosynthesise?
Epidermal cells do not usually photosynthesise so they lack chloroplasts. Light needs to pass through them, and they are usually transparent. The cells in the diagram below are onion epidermal cells.
What is the function of the root hair cells?
Root hair cells absorb water and dissolved minerals from the soil. They have small hairs, called root hairs, on their surface. This increases the surface area of the root cells so that they can soak up water more quickly.
