High School Entrance Exam
Science High School Entrance Exam Review Questions
Ace the Science section of your high school / grade 7 entrance exam with these review questions. The answer for each question is discussed, with tips, facts, and trivia to help you remember better.
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Practice Exam Questions: Characteristics of Life, The Cell, Prokaryotes vs. Eukaryotes
1
Which of these statements is incorrect?
a. All living things need energy to carry out life processes.
b. All living things are composed of one or more cells.
c. All living things reproduce.
d. All living things maintain a stable external environment.
Let’s look at these statements one by one.
Letter A. All living things need energy to carry out life processes. This is correct. In fact, this is why we eat. Animals get energy from plants, or from other animals that eat plants, and plants get energy from the sun.
Letter B. All living things are composed of one or more cells. This is also correct. Some living things have only one cell, such as prokaryotes, while others have many cells, such as humans, who have trillions of cells. But all living things are made up of one or more cells.
Letter C. All living things reproduce. This is also correct. The ability to reproduce is one of the characteristics of life. There may be some individuals within a species that don’t reproduce, for example, worker bees or those who are infertile. But, as a whole, all species of life are able to reproduce to keep themselves from going extinct.
Letter D. Now, if you look at this statement closely, it says external environment. But what living things actually do is maintain a stable internal environment while adjusting to changing external conditions. As much as possible, we try to keep stable things like our temperature, our oxygen levels, the amount of water in our body. This is what is known as homeostasis. But because the statement in letter D says “external environment” then letter D is the incorrect statement.
2
A _____ is the smallest structural and functional unit of an organism.
a. cell
b. tissue
c. organ
d. organ system
The answer is A. CELL. A cell is the smallest structural and functional unit of an organism. A group of cells that perform the same job is called a tissue. A group of tissues form an organ. A group of organs that work together is an organ system. And, as you know, a group of organ systems – like the digestive system, respiratory system, cardiovascular system, and all the other systems of the body – are what make up an organism such as you and me.
3
Which statement is incorrect?
a. There are two basic types of cells: prokaryotic cells and eukaryotic cells.
b. Prokaryotic cells do not have DNA.
c. Prokaryotic cells do not have a nucleus.
d. Eukaryotic cells have a nucleus where their DNA is stored.
There are two basic types of cells, prokaryotic cells and eukaryotic cells, so letter A is correct.
The main difference between them is that prokaryotic cells don’t have a nucleus or other membrane-bound organelles such as mitochondria or endoplasmic reticulum. So: letter C is correct; prokaryotes don’t have nuclei.
In contrast, eukaryotic cells do have a nucleus and that’s where their DNA is stored, so letter D is also correct.
How about letter B? Prokaryotes, even though they don’t have a nucleus, are living things, and all living things have DNA. So: letter B is wrong. Prokaryotic cells do have DNA; they just aren’t stored in a nucleus.
Letter B is the incorrect statement.
4
Which statement is incorrect?
a. All prokaryotes are unicellular.
b. Bacteria and archaea are all prokaryotes.
c. All eukaryotes are multicellular.
d. All multicellular organisms are eukaryotes.
First of all, what is the difference between prokaryotes and eukaryotes? Eukaryotes have a nucleus and other membrane-bound organelles while prokaryotes don’t – that is their main difference.
Under prokaryotes, there are two domains, bacteria and archaea, while eukaryotes are a separate domain all by themselves. So: letter B is correct; bacteria and archaea are both prokaryotes.
Now, remember this: all prokaryotes are unicellular, while eukaryotes can be unicellular or multicellular.
All prokaryotes are unicellular, so letter A is correct.
There are no multicellular prokaryotes. If an organism is multicellular, it’s a eukaryote. So: letter D is correct. All multicellular organisms are eukaryotes.
However, the reverse isn’t true. Not all eukaryotes are multicellular. Some eukaryotes are unicellular. Amoeba, for example, is only single-celled, but it has a nucleus, so it’s a eukaryote. Therefore, the incorrect statement is letter C.
5
The following are found in both prokaryotes and eukaryotes EXCEPT _____.
a. cytoplasm
b. ribosomes
c. DNA
d. mitochondria
Do you remember what the difference is between prokaryotic and eukaryotic cells?
Prokaryotic cells do NOT have a nucleus or other membrane-bound organelles, while eukaryotic cells do.
Now let’s look at letter A. The cytoplasm is the fluid that fills the inside of a cell. It is not a membrane-bound organelle, so it can also be found in prokaryotes.
How about letter B? Ribosomes are where proteins are made. They are organelles, but they are NOT membrane-bound, so they can also be found in prokaryotes.
Letter C. DNA. All living things have DNA, and prokaryotes are living things, so prokaryotes do have DNA. The DNA just isn’t stored in a nucleus but it is still present in prokaryotic cells.
That leaves us with letter D. The mitochondria is often nicknamed the powerhouse of the cell because it is where the cell produces energy. It is an organelle and it is membrane-bound, so it can only be found in eukaryotes.
The answer, the exception, is letter D. Mitochondria are NOT found in both prokaryotes and eukaryotes. They are only found in eukaryotes.
6
Which cell organelle is in charge of producing and assembling ribosomes?
a. Smooth endoplasmic reticulum
b. Golgi apparatus
c. Lysosome
d. Nucleolus
The answer is D. NUCLEOLUS. The nucleolus is the spherical structure inside the nucleus that is where ribosomes are made.
The smooth endoplasmic reticulum (ER) is where lipids are produced. It’s called “smooth” because it doesn’t have ribosomes sticking to it. The ER that is covered with ribosomes is the rough ER, and that’s the ER involved with processing proteins. So: smooth ER for lipids, rough ER and ribosomes for proteins.
The Golgi apparatus is the organelle that receives proteins from the rough ER, packages them, and sends them off to other places in the cell.
And the lysosomes are in charge of dealing with the cell’s waste, generally by using digestive enzymes to break the waste down into recyclable parts.
Again, the organelle responsible for the production of ribosomes is the nucleolus.
Practice Exam Questions: Photosyhthesis
1
Photosynthesis is the process by which plant cells convert _____ into chemical energy in the form of glucose.
a. hydrocarbons
b. the sun’s energy
c. water and oxygen
d. nitrogen, phosphorus, and potassium
Well, we know for sure that it’s not hydrocarbons because the word “hydrocarbon” refers to things like methane and coal and petroleum, so it’s definitely not letter A.
The word “photosynthesis” itself gives us a clue. “Photo-” is from the Greek word for light. In photosynthesis, sunlight splits the water molecules in the leaves of a plant into its components hydrogen and oxygen. The oxygen is released by the plant into the air and the hydrogen that’s left combines with carbon dioxide to produce glucose. It’s a very simple way of looking at a complicated process but that’s the basics of it.
In this process of photosynthesis, oxygen is produced – it’s not the one being converted into something else – so the answer is not letter C. And nitrogen, phosphorus, and potassium, even though they’re nutrients needed by plants, are not directly involved in photosynthesis, so it’s not letter D either.
The answer is letter B. The light energy from the sun sets off a reaction that results, among other things, in chemical energy being stored as glucose.
2
Which of these plant cell organelles are involved in photosynthesis?
a. Vesicles
b. Vacuoles
c. Centrioles
d. Chloroplasts
The answer is D. CHLOROPLASTS. A chloroplast is an organelle found within the cells of plants and algae. It has a high concentration of chlorophyll and serves as the site of photosynthesis.
What about vesicles, vacuoles, and centrioles? Vesicles are small sacs that transport materials around the cell – sort of like vehicles, but with an s. Vacuoles are the cells’ storage centers and centrioles are organelles involved in cell division. All of them play important roles within the cell, but only chloroplasts are the organelles of photosynthesis.
Practice Exam Questions: Nutrients
1
Photosynthesis is the process by which plant cells convert _____ into chemical energy in the form of glucose.
a. hydrocarbons
b. the sun’s energy
c. water and oxygen
d. nitrogen, phosphorus, and potassium
Well, we know for sure that it’s not hydrocarbons because the word “hydrocarbon” refers to things like methane and coal and petroleum, so it’s definitely not letter A.
The word “photosynthesis” itself gives us a clue. “Photo-” is from the Greek word for light. In photosynthesis, sunlight splits the water molecules in the leaves of a plant into its components hydrogen and oxygen. The oxygen is released by the plant into the air and the hydrogen that’s left combines with carbon dioxide to produce glucose. It’s a very simple way of looking at a complicated process but that’s the basics of it.
In this process of photosynthesis, oxygen is produced – it’s not the one being converted into something else – so the answer is not letter C. And nitrogen, phosphorus, and potassium, even though they’re nutrients needed by plants, are not directly involved in photosynthesis, so it’s not letter D either.
The answer is letter B. The light energy from the sun sets off a reaction that results, among other things, in chemical energy being stored as glucose.
2
Which of these plant cell organelles are involved in photosynthesis?
a. Vesicles
b. Vacuoles
c. Centrioles
d. Chloroplasts
The answer is D. CHLOROPLASTS. A chloroplast is an organelle found within the cells of plants and algae. It has a high concentration of chlorophyll and serves as the site of photosynthesis.
What about vesicles, vacuoles, and centrioles? Vesicles are small sacs that transport materials around the cell – sort of like vehicles, but with an s. Vacuoles are the cells’ storage centers and centrioles are organelles involved in cell division. All of them play important roles within the cell, but only chloroplasts are the organelles of photosynthesis.
3
Nutrients are chemicals needed by our body that are found in food. There are five types of nutrients: carbohydrates, proteins, vitamins, minerals, and _____.
a. collagen
b. rice
c. lipids
d. sugars
Well, we know that rice and sugars are carbohydrates, so the answer isn’t letter B or D. Collagen, on the other hand, is a protein – in fact, it’s the most abundant protein in our body – so the answer isn’t letter A either.
The answer is letter C. LIPIDS. Lipids are fatty or waxy substances that perform a variety of functions in our body. Their roles include moving and storing energy, making hormones, and absorbing vitamins, and they are an important part of our cell membranes.
4
Among the five types of nutrients, our main source of energy is _____.
a. carbohydrates
b. proteins
c. vitamins
d. minerals
The answer is A. CARBOHYDRATES.
Our digestive system breaks down carbohydrates into glucose, which our cells then convert to the form of energy used by our bodies at cellular level, ATP. This process of transforming glucose to ATP is called cellular respiration. It takes place in the mitochondria (and cytoplasm) of every cell in our body, which is why the mitochondria is nicknamed the “powerhouse of the cell.”
5
The following are complex carbohydrates except _____.
a. starch
b. fiber
c. galactose
d. none – all are correct
The answer is C. GALACTOSE.
So, there are two types of carbohydrates: simple carbohydrates and complex carbohydrates.
Simple carbohydrates, also known as simple sugars or monosaccharides, are the simplest forms of carbs. Examples of monosaccharides include glucose, fructose, and galactose. Simple sugars are the building blocks from which all other carbohydrates are built. For example, when you put glucose and fructose together, you get sucrose, which is your table sugar.
Complex carbohydrates are larger in structure than simple carbohydrates. Our bodies break them down more slowly compared to simple carbs, so they can give us energy more steadily and for a longer period of time. This is why it’s better for us if more of the carbohydrates in our food are complex, and not simple, carbohydrates. Examples of complex carbohydrates include starch, glycogen, and fiber.
So, going back to the question, starch and fiber are complex carbohydrates, but galactose is a simple sugar like glucose and fructose. Therefore, the answer to this question is galactose.
6
Proteins are made up of smaller molecules called_____.
a. fibrins
b. amino acids
c. proteases
d. carnitines
The answer is B. AMINO ACIDS.
In the same way that you put LEGO blocks together to make, say, a car or a building, amino acids are strung and folded together to make proteins. That’s why they are called the “building blocks” of proteins, while monosaccharides are the building blocks of carbohydrates, and fatty acids and glycerol are the building blocks of lipids.
What about the other choices? Fibrins and proteases are just examples of proteins. Fibrin is involved in blood clotting and proteases are enzymes that break down protein. Carnitine, on the other hand, is a specialized kind of amino acid that helps the body turn fat into energy. So, again, the answer to this question – the building block of proteins – is amino acids.
7
Which nutrient stores energy, protects nerves, cushions internal organs, and makes up the membranes that surround our cells?
a. carbohydrates
b. lipids
c. vitamins
d. minerals
The answer is B. LIPIDS.
The lipids in our body play many important roles. Their functions include wrapping around and protecting our vital organs, forming an integral part of the membranes of all our cells, and acting as an energy reserve that we tap when we’re running low on carbohydrates. Of course, too much of a good thing is…not good anymore. An excess of lipids can lead to problems like heart disease and stroke, and so, as with everything else, we need to consume lipids in moderation.
8
Which vitamin is incorrectly paired with its role in the body?
a. Vitamin A – for good vision
b. Vitamin B1 – for healthy nerves
c. Vitamin C – for blood clotting
d. Vitamin D – for healthy bones and teeth
The answer is C.
The vitamin closely involved in blood clotting is actually vitamin K.
See, when our skin gets cut, for example, it will bleed, but the bleeding eventually stops because our bodies react immediately and form a clot so that we don’t lose too much blood. The process of forming a clot involves proteins called clotting factors, which are produced by our liver. Without vitamin K, there are clotting factors that our liver would not be able to produce, so vitamin K is very important for healthy blood clotting.
9
Which mineral is incorrectly paired with its role in the body?
a. Calcium – for strong bones and teeth
b. Iron – for making hemoglobin, which carries oxygen in red blood cells
c. Potassium – for muscles to work properly
d. None of the above
Let’s look at these statements one by one.
First, calcium. Did you know that 99% of all the calcium in our body is found in our bones and teeth? Calcium is a very important part of the structure of our bones and teeth, so letter A is correct.
Next, iron. You probably know that our blood distributes oxygen throughout our body. Specifically, our red blood cells contain a protein called hemoglobin. Oxygen sticks to the iron in hemoglobin and that’s how it gets transported from our lungs to our cells. So: letter B is also correct.
Finally, potassium. Our body needs potassium for lots and lots of different things but its importance is especially obvious in the workings of our muscles. When we are low in potassium, our muscles will tend to feel weak and we get cramps. So: letter C is also correct.
That means the answer to this question is letter D. All of the statements from A to C are correct so none of them are incorrect.
Practice Exam Questions: Digestive System
1
The _____ is the system that is in charge of breaking down the food we eat into a form that can be absorbed by our cells.
a. respiratory system
b. circulatory system
c. digestive system
d. excretory system
The answer is C. DIGESTIVE SYSTEM.
Our cells need energy to work and raw materials to make into things that our body needs. We get all these from the nutrients in our food. However, the food that we eat can’t just be shoved into our cells. They need to be broken down into very small bits and transformed into molecules that our cells are able to accept. This is the role of our digestive system.
The respiratory system, on the other hand, is the system in charge of getting the oxygen that we need. The circulatory system transports the oxygen and nutrients to our cells and picks up waste products for elimination. And the excretory system is in charge of getting rid of those waste products.
Again, the system that is in charge of breaking down food into absorbable nutrients is our digestive system.
2
What type of digestion is the process of physically breaking down the food we eat into smaller pieces? It is also known as physical digestion.
a. Chemical digestion
b. Mechanical digestion
c. Cellular digestion
d. Indigestion
Well, the answer obviously isn’t indigestion!
But, first of all, what is digestion? Digestion is the process of breaking down the food we eat into a form that can be absorbed by our cells. This involves two separate processes: mechanical digestion and chemical digestion.
Mechanical digestion involves making the food smaller and smaller and smaller. Obviously, it begins in the mouth, as we chew our food. For example, if we take a bite of fried chicken, obviously that bite won’t fit into our cells. But it’s our cells that need the nutrients that are in the fried chicken. So what our body does is it makes it smaller and smaller and smaller.
But it’s not enough that we end up with very tiny bits of fried chicken. That still won’t get through the walls of our intestines into our blood and into our cells. That’s where chemical digestion comes in.
Chemical digestion involves changing the actual chemical structure of the food into a form that can go through our cell membranes. So, for example, from a bite of fried chicken – which might include bread crumbs as well as the chicken meat itself – enzymes break down the carbohydrates in the bread crumbs into glucose, and the protein in the chicken meat into amino acids. Our cells can then use the glucose for energy and the amino acids for making other proteins that our body needs such as antibodies and hormones.
So: digestion involves both mechanical and chemical digestion, and that part of digestion where the food is physically broken down into very tiny pieces is called mechanical digestion.
3
An enzyme is a protein that speeds up chemical reactions in the body. Digestive enzymes play a huge role in which type of digestion?
a. mechanical digestion
b. chemical digestion
c. both
d. neither
The first thing we need to know is: what is mechanical digestion? And what is chemical digestion? We need to know what they are so we can tell if enzymes are involved in one of them or both of them or none of them.
Mechanical digestion is the process of breaking down the food we eat into smaller and smaller pieces. It is purely physical; it doesn’t involve chemical changes. There is only a change in size. For example, if you eat fried chicken, by the end of mechanical digestion, it’s still chicken – just very, very, very tiny.
Chemical digestion, on the other hand, involves changing the actual chemical structure of our food into a form that can be absorbed by our intestines. The chicken, for example, is acted upon by digestive juices in the stomach and intestines, such that by the end of chemical digestion, it’s no longer chicken and instead has been thoroughly broken down into a bunch of amino acids and minerals and whatnot.
So: are enzymes involved in mechanical digestion? No – because mechanical digestion doesn’t involve chemical processes; it’s purely physical. That means the answer isn’t letter A or letter C.
Are enzymes involved in chemical digestion? Definitely. They are the ones that carry out the chemical changes. In fact, many of what we call “digestive juices” are enzymes and you can tell they’re enzymes because they usually end in -ase. For example, lipases act on lipids. Proteases act on proteins. The protein in your chicken will have been acted on by enzymes such as pepsin and several proteases and turned into amino acids by the end of the process of digestion.
So: the answer to this question is B. CHEMICAL DIGESTION.
4
Which of these statements about digestive enzymes is incorrect?
a. Protease breaks down proteins.
b. Lipase breaks down fats.
c. Carbohydratase breaks down carbohydrates.
d. None – all are correct
Let’s look at these statements one by one.
Do proteases break down proteins? Yes, they do. They do this by snapping the peptide bond that joins amino acids together in proteins. So letter A is correct.
Do lipases break down fats? Actually, they do. Lipases are the enzymes in charge of breaking down fats and other lipids. So letter B is also correct.
Do carbohydratases break down carbohydrates? Well, proteins are broken down by proteases and lipids are broken down by lipases. That makes sense, right? However, there is no such thing as carbohydratases. Enzymes that break down carbohydrates include amylase, which acts on starch; maltase, which converts maltose to glucose; sucrase, which splits sucrose into glucose and fructose; and lactase, which breaks down lactose into glucose and galactose.
The incorrect statement is C.
Practice Exam Questions: Excretory System
1
Which organ is part of the excretory system?
a. Lungs
b. Skin
c. Kidneys
d. All of these
Well, we know that the lungs are part of the respiratory system, right? And the skin is part of the integumentary system. And the kidneys are part of the urinary system. So…?
Actually, one of the most distinctive things about the excretory system is that all its organs are actually part of other major organ systems in the body. In fact, unlike most other systems, the organs of the excretory system are not even really next to each other. But as long as they perform excretion – that is, the removal of excess and waste products from the body – then they are considered part of the excretory system.
Let’s take a look at the lungs. The lungs are in charge of taking in oxygen, but they are also in charge of getting rid of carbon dioxide. So: the lungs are part of the excretory system.
How about the skin? The skin has a lot of different functions – including being our first line of defense against infection, helping regulate our temperature, and basically keeping us together – but it also performs an excretory function. Our sweat glands, which are part of our skin, help us get rid of water, salts, and other substances through our sweat. So: the skin is also part of the excretory system.
Finally, the kidneys. Our kidneys filter our blood and remove salts, urea, and excess water, excreting them in the form of urine, so they are definitely also part of the excretory system.
That means the answer to this question is letter D. The lungs, skin, and kidneys are all part of the excretory system.
2
Our bodies lose water through the following processes, except _____.
a. sweating
b. breathing
c. urination
d. none – all are correct
Well, we know for sure that there’s water in our sweat and our pee, so we definitely lose water through sweating and urination.
How about breathing? Well, the air we breathe out is a gas, right? But actually, it also contains water in the form of water vapour. In fact, that’s why we can see our breath when we’re outside in very cold air, or why a mirror mists up when we breathe on it – because the cold air or the cold surface causes the water vapour in our breath to condense. That means our bodies also lose water, though in very small amounts, when we breathe.
And since we lose water through sweating, breathing, and urination, the answer to this question is D. NONE – ALL ARE CORRECT.
Practice Exam Questions: Immune System
1
The _____ forms a physical barrier between the body and the outside world. For this reason, it is the body’s first and most important line of defense against infection.
a. white blood cells
b. muscles
c. skin
d. lymph nodes
Let’s look at these choices one by one.
Our white blood cells do help us fight infection in many ways, including recognizing foreign particles, “eating” them, and making antibodies. However, they are located deep within our body and do not form a physical barrier between our body and the outside world, so they are not our first line of defense.
The same goes for lymph nodes. They help us fight infection by acting as “filters” that trap germs and activate the creation of antibodies. If our lymph nodes are swollen, that’s actually a sign that they’re currently very active and that they’re probably trying to fight off an infection. However, again, they’re deep inside our bodies, so they can’t physically be our first line of defense.
As for our muscles, well, they don’t really have much to do with our immune system. They have very important roles in our body but fighting off infection isn’t really one of them.
How about our skin? Well, when you think about it, it is literally, physically, what stands between our bodies and the outside world. First of all, it’s waterproof, and as long as it’s intact, our skin is very tough for germs to get through. Our sweat contains enzymes that can break down the cell walls of bacteria to kill them. And our skin even has resident good bacteria that help us fight off harmful bacteria. You can think of our skin as the thick wall around a castle or town. Without it, invaders would find it very easy to get in and take over. So: the answer to this question is C. SKIN.
2
True or False – Hydrochloric acid, which is also known as muriatic acid and is used in many household cleaning solutions, is also used by the body to protect itself against pathogens.
a. True
b. False
This is actually true!
The cleaning solution that we call muriatic acid – which we use for stuff like cleaning our bathrooms and removing stains and mold from various parts of our house – is more formally known as hydrochloric acid.
This acid is also present in our stomach. There are cells in our stomach called parietal cells and it’s actually their job to produce muriatic acid every day. Which is kinda mind-blowing, right? If you have muriatic acid at home, you’ll know it looks really toxic and has a really strong, unpleasant smell. And this is something that we naturally have in our stomach!
The hydrochloric acid in our gastric juices helps us digest food, particularly protein, AND it kills most of the germs that enter our body in the food we eat. In this way, it is a very important component of our immune system.
As you can tell from its smell, hydrochloric acid is a very strong acid and so it can be dangerous. Our stomach protects itself from its own acid by secreting mucus, which forms a protective layer around the cells that line the insides of our stomach. Obviously, this doesn’t mean that we can just drink hydrochloric acid if there are germs in our body that we want to get rid of. Let’s not be stupid. Our stomach environment is very delicately balanced such that we have just enough acid at just the right times. Our entire body, in fact, is all about keeping the right balance and the right timing of things, so let’s leave the muriatic acid to household cleaning.
Also, while our stomach is protected by a thick mucus layer, our skin and our eyes don’t have that protection, so hydrochloric acid can cause irritation to our skin and our eyes. In high concentrations, it can even result in severe chemical burns and eye damage, so we should be very careful when using it.
3
True or False – A fever can help the body fight infection.
a. True
b. False
Actually, this is correct!
We have this tendency to think of fever as an illness and that’s understandable because fevers tend to make us feel really bad. But, actually, it’s a sign that our body is trying to fight off an illness or infection. It’s actually our immune response that intentionally raises the temperature of our body.
Why does it do this?
Well, most of the viruses and bacteria that infect us operate really well and reproduce fastest at our normal body temperature. By raising our temperature, our immune system “stresses out” pathogens and slows down the rate at which they reproduce. At the same time, the higher temperature gets our immune cells to work better and move faster. All of this gives our immune system a better chance at being able to contain and eventually kill off the viruses and bacteria that infect us.
So it’s true – fever does help the body fight infection.
4
There are certain kinds of white blood cells that go to areas of inflammation and “eat” pathogens, foreign particles, and dead cells. The cells that do this are called _____.
a. lysozymes
b. erythrocytes
c. myocytes
d. phagocytes
Let’s look at the choices one by one.
The word “erythrocytes” is just another term for red blood cells so they are, obviously, not white blood cells and so the answer is not letter B.
In the same way, “myocyte” is just another term for a muscle cell, so the answer is not letter C either.
(By the way, you’ll notice that the presence of “-cyte” usually means that it’s a type of cell.)
Next. Lysozymes actually do have something to do with fighting off pathogens but they are not cells. Rather – and the “-zymes” part of their name might have given you a clue – lysozymes are enzymes found in our sweat, mucus, tears, and saliva that help us fight off infection by breaking down the cell walls of pathogens. Again, they are enzymes, not cells, much less white blood cells, so the answer also isn’t letter A.
The answer is letter D. PHAGOCYTES. The term “phago-” actually comes from the Greek word for eating and, of course, “-cyte” means cell. They’re called “eating cells” because they ingest – that is, they wrap themselves around – pathogens and other foreign particles and use different ways to kill them.
It’s estimated that one litre of human blood contains about six billion phagocytes. The process by which they engulf pathogens is called phagocytosis. And did you know that there are actually several types of phagocytes? If you’re a phagocyte and you’re very good at phagocytosis, you’re called a “professional phagocyte,” but if you’re not very good at it, then unfortunately you’re just a “non-professional phagocyte.” Seriously.
Practice Exam Questions: Integumentary System
1
The following are part of the integumentary system except _____:
a. bones
b. hair
c. nails
d. skin
The integumentary system is the system of our body that forms a physical barrier between our internal environment and our external environment. In simple terms, it’s our skin – which covers our entire body – and the things that are in or right next to our skin. That includes our hair and our nails, both of which grow from our skin, as well as our glands and our hypodermis.
Our bones are part of our skeletal system. They have very important roles in the way our body works but they are not part of our integumentary system. So: the answer is A. BONES.
2
True or False – The epidermis does not have any blood vessels.
a. True
b. False
This is actually true!
This is why, sometimes, when you have a shallow paper cut, or any cut that isn’t very deep, it can hurt very much but not bleed.
That’s because, as you probably remember, the skin has two layers: (1) the outer part, which is the epidermis, and (2) the layer underneath, which is the dermis. Sensory nerve endings, which detect things like pain, pressure, and temperature, are found in both the epidermis and the dermis. However, blood vessels, which are what bleed when they get cut, are found only in the deeper layer, the dermis.
So, if your cut isn’t deep, if it’s only up to the epidermis, then it may reach the nerve endings in the epidermis, and that makes you feel pain. But it doesn’t reach the dermis, so it doesn’t reach the blood vessels, and that’s why it doesn’t bleed.
Of course, if you do have a cut that’s deep enough, then it will definitely bleed and hurt. Either way, make sure that you clean your cut and cover it to reduce the risk of infection.