Review for Cells Unit Test: The Origin, Structure and Function of Cells ANSWERS

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Review for Cells Unit Test: The Origin, Structure and Function of Cells ANSWERS

**Make sure you read through all your notes and homework to prepare for the test as well**

1 . Recognize and understand the definitions and meanings of the following terms.

phospholipid bilayer gene neutral mutation

prokaryotic cell chromosome point mutation

eukaryotic cell helicase frameshift mutation

intracellular fluid codon chromatin

extracellular fluid endocytosis mutation

nucleic acids Endosymbiosis Theory nucleotide

DNA polymerase 2. Regarding the cell membrane:

a) Explain how the structure of phospholipid molecules is ideal for the formation of membranes.

• The molecules have a polar and non-polar end. This causes them to naturally form a double layer (phospholipid bilayer) due to the hydrophilic and hydrophobic regions of the molecules

b) Explain how the structure of cell membranes is critical to the function of cells.

• Cells need to be filled with fluid (ICF) as well as surrounded by fluid (ECF). The polar regions of the membrane allow this to happen, while the non-polar middle region of the membrane stops other polar molecules from getting through, while allowing other small molecules (like water) through. It is semi- permeable.

c) Why are ‘modern’ cell membranes described as a ‘fluid mosaic’?

• They are fluid since the phospholipid bilayer is flexible and malleable, and mosaic due to the many different proteins that are embedded within the membrane.

d) What three MAIN ways can substances move into, and out of, cells? Describe each.

• Passive transport – moves particles across the membrane with diffusion (with the concentration gradient so, therefore no energy required)

• Active transport – moves particles across the membrane against diffusion (against the concentration gradient so, therefore energy is required)

• Bulk transport – moves large particles or droplets of fluid into and out of the cell (requires energy) 3. Regarding Endosymbiosis Theory:

a) What is the main idea of Endosymbiosis Theory?

• The theory that some of the earliest eukaryotic cells engulfed simple prokaryotic cells, which continued to live on inside them creating chloroplasts and mitochondria

b) Briefly describe the steps that may have happened, according to Endosymbiosis Theory.

• A eukaryotic cell would have engulfed an aerobic bacteria cell through phagocytosis

• After being engulfed, the bacteria would have continued to live, and would have provided energy to the host cell (in the form of glucose if it was a chloroplast, or ATP if it was a mitochondria)

• The host cell provided protection and nutrients for the prokaryotic cell, creating a symbiotic relationship

c) Which two organelles were most likely incorporated into eukaryotic cells by endosymbiosis?

• Mitochondria and chloroplasts

d) What are three pieces of evidence that support Endosymbiosis Theory?

• Mitochondria and chloroplasts are about the same size as a simple bacteria

• Both these organelles are surrounded by two membranes (suggesting they were engulfed by endocytosis)

• They have their own ribosomes and DNA which is similar to bacteria, and they reproduce independently of the host cell

4. Give three significant differences between prokaryotic and eukaryotic cells.

• Eukaryotic cells have a nucleus while prokaryotic do not

• Eukaryotic have organelles, which prokaryotic do not

• Eukaryotic are larger cells, prokaryotic are smaller cells 5. Draw a Venn diagram to compare the organelles that are found

in only plant cells, only animal cells and both plant and animal cells.

• See the other file attached on the website (Organelle review solutions) for a breakdown on which organelles are in plants and animals.

Plant only Animal only

Both

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6. Label the following generalized diagrams of typical bacterial, animal and plant cells (assume that the cell membranes are phospholipid bilayers) SEE YOUR NOTES FOR FILLED IN VERSIONS OF THESE DIAGRAMS

7. Compare and contrast the following terms (that is, know the similarities AND differences between the groups of terms):

a) prokaryotic and eukaryotic cells

• Both have a cell membrane and DNA

• Eukaryotic cells have a nucleus while prokaryotic do not

• Eukaryotic have organelles, which prokaryotic do not

• Eukaryotic are larger cells, prokaryotic are smaller cells b) positive and negative mutation

• both are a change in the DNA nucleotide sequence

• a positive mutation can have a good effect (helps the cell/organism)

• a negative mutation has a negative effect (harms the cell/organism) c) frameshift and point mutation

• frameshift mutation adds or deletes a nucleotide affecting all of the codons from that point forward in a gene

• point mutation substitutes one nucleotide for another one in only one location (this may or may not change the resulting amino acid from that codon)

d) DNA and RNA

• Both are forms of nucleic acid

• DNA is double stranded while RNA is single stranded

• DNA contains deoxyribose, and RNA contains ribose

• DNA contains A, T, C, G, while RNA replaces the Thymine with Uracil (U instead of T) e) DNA and chromatin

• DNA refers to the single double helix molecule that makes up nucleic acid

• Chromatin is the form that nucleic acid takes in the nucleus during interphase. It is wound around histone proteins in order to condense it so it fits in the nucleus.

8. Regarding nucleic acids:

a) What are nucleotides?

• Nuclotides are the subunit that makes up nucleic acids.

b) What three molecules make up nucleotides?

• They consist of a sugar, phosphate and a nitrogen base

c) What are three significant differences between the structures of DNA and RNA?

• DNA is double stranded while RNA is single stranded

• DNA contains deoxyribose, and RNA contains ribose

• DNA contains A, T, C, G, while RNA replaces the Thymine with Uracil (U instead of T)

d) Give three reasons why the structure of the DNA molecule is so well suited to its function.

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• The sugar phosphate backbone is strong and stable which makes it an excellent molecule to store important information

• The sequence of base pairs allows it to store coded information to create proteins

• The complementary base pairs allow the molecule to replicate itself with great accuracy e) Describe the steps in DNA replication. Include the names of two enzymes.

• The enzyme helicase unwinds and unzips the DNA molecule

• Complimentary nitrogen bases are added onto each separate strand of the DNA

• DNA polymerase chemically bonds together the backbone and nitrogen bases

• The DNA is wound up back into a double helix

f) A sample of DNA contains 20% cytosine. What are the percentages of the other nucleotides in this DNA?

• Since Cytosine bonds with guanine they must both be present in the same amounts o Cytosine = 20%, guanine = 20%

• That leaves 60 % left for Adenine and thymine o Adenine = 30%, thymine = 30%

9. Write the letter of the appropriate cell part beside each description. Some cell parts may not be used.

Description of Cell Part or Function Cell Parts

___T__ The organelle that manufactures proteins. A.

B.

C.

D.

E.

F.

G.

H.

I.

J.

K.

L.

M.

N.

O.

P.

Q.

R.

S.

T.

U.

V.

W.

cell membrane cell wall central vacuole chloroplast(s) chromatin chromoplast(s) cilia

cytoplasm cytoskeleton flagellum Golgi apparatus leucoplast(s) lysosome(s) mitochondria nuclear pore(s) nucleolus nucleus peroxisome(s) plastids ribosome(s) rough ER smooth ER vacuole(s) ___L__ Organelles that store starch. They do not contain coloured pigments.

___I__ The microtubules and microfilaments that give cells their shape.

___E__ Uncoiled chromosomes. The form that DNA takes when the cell is not dividing.

___M__ Vesicles that contain digestive enzymes and break down and recycle worn out organelles.

___G__ Small hair-like projections on the cell surface that move with a sweeping motion.

___K__ Flattened stacks of membranes that process and then package proteins into secretory vesicles.

___O__ Small openings that connect the nucleus with the cytoplasm.

___C__ The organelle that stores water, salts and sugars in plant cells.

___P__ The area in the cell where ribosomes are manufactured.

___Q__ The membrane-bound structure where the majority of a cell’s DNA is found.

___V__ A series of membranes and tubules where steroids and phospholipids are made.

___R__ A specialized vesicle for breaking down long chain fatty acids and alcohol.

___A__ This structure controls the movement of substances into and out of the cell.

___F__ These organelles contain colourful pigments in only certain parts of plants.

___U__ A series of membranes which has ribosomes embedded on its surface.

___J__ Long, whip-like projections which are used for locomotion by animal cells.

___W__ Small vesicles in animal cells, which are used for storage.

____H_ The contents of the cell, excluding the nucleus.

___D__ Organelles that contain DNA, ribosomes and chlorophyll.

___N__ The organelle where cellular respiration takes place and ATP is produced.

10. Regarding mutations:

a) Define or explain what is meant by a mutation.

• Any accidental change in the sequence of nucleotides in a piece of DNA b) What are two common types of mutations? Describe what happens in each type of mutation.

• Base pair substitution (point mutation) – one nucleotide is replaced by another nucleotide

• Frameshift mutation – a nucleotide is deleted or an extra one is added, which affects all the codons from that point on in a gene

c) If a mutation occurs during DNA replication, how will this affect the cell?

• Positively – the cell can benefit from the mutation

• Negatively – the cell can be harmed by the mutation

• Neutral – the cell may see no change at all from a mutation

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11. Be able to perform microscope calculations for total magnification, FOV and estimate the size (width and/or length) of a cell seen under the microscope.

a)

FOV low = 3.5mm = 3500μm FOV high = 1750μm

Width = 1/5 x 1750μm = ~350μm Length = ¾ x 1750 = ~1312μm

b)

FOV low = 5mm = 5000μm FOV medium = 2500μm

Width = 1/3 x 2500μm = ~833μm Length = same as width!

Practice Multiple Choice Questions

1. Which of the following are found in the cell membrane?

i) phospholipids ii) cholesterol

iii) proteins iv) DNA

a) i and ii only b) i and iii only c) i, ii and iii only d) i, ii, iii and iv 2. Cell membranes are composed mainly of:

a) sugars and phosphates c) carbohydrates and cellulose

b) phospholipids and proteins d) nucleotides and carbohydrates

3. The function of the rough endoplasmic reticulum is to:

a) process and package proteins c) manufacture long chain fatty acids

b) make ribosomes d) all of the above

4. The organelle which is important in plant cells for storing water, salts and sugar is the:

a) centrosome b) peroxisome c) lysosome d) central vacuole 5. In animal cells, the centrosome is made up of:

a) the nucleus, nucleolus and chromatin c) both the smooth and rough ER

b) two centrioles d) vesicles and vacuoles

Microscope Information:

Ocular lens = 10X Objective Lenses:

low power = 10X high power = 20X high power = 40X Field of View (Low Power) Onion Cells (High Power)

Microscope Information:

Ocular lens = 10X Objective Lenses:

low power = 5X med. power = 10X Field of View (Low Power) Amoeba (Medium Power)

**Remember that these calculations are

estimations. Your answers may be close,

but not exactly the same**

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6. Which of the following are found ONLY in plant cells?

i) centrioles ii) cell wall iii) flagella iv) chloroplasts v) mitochondria

a) i, ii and iv only b) i and iv only c) ii and iv only d) iv only 7. Which of the following parts of the cell contain DNA:

i) chloroplasts

ii) ribosomes iii) mitochondria iv) lysosomes v) nucleus

a) i, ii and iii only b) i, iii and v only c) iii and v only d) i, ii, iii, iv and v 8. Ribosomes are:

a) surrounded by a membrane c) important in making fatty acids and lipids b) manufactured in the nucleolus d) all of the above

9. Pancreatic cells make and secrete large quantities of proteins (enzymes). They must have a large number of:

a) nuclei b) Golgi apparatus c) lysosomes d) peroxisomes

10. In what way do mitochondria resemble bacteria? They both contain:

a) the same type of ribosomes c) chlorophyll for photosynthesis

b) a loop of DNA d) both a) and b)

11. Which part of a plant would most likely contain chromoplasts?

a) the roots b) the stem c) the flower d) all of the above

12. A protein is manufactured and will be secreted outside of the cell. It will travel from the:

a) rough ER → smooth ER → Golgi → transport vesicle → outside the cell b) rough ER → transport vesicle → Golgi → secretory vesicle → outside the cell c) smooth ER → transport vesicle → Golgi → secretory vesicle → outside the cell d) ribosome → cytoplasm → secretory vesicle → outside the cell

13. Cell walls:

a) are made of a polysaccharide c) control how substances move into and out of cells b) replace the cell membrane in plant cells d) all of the above

14. Cilia are:

a) found on the outer surface of some animal cells c) a type of vesicle b) important in making proteins d) all of the above 15. Which of the following is/are vesicles?

a) lysosomes b) peroxisomes c) vacuoles d) all of these 16. Which of the following organelles is responsible for breaking down long chain fatty acids and some drugs?

a) lysosomes b) peroxisomes c) ribosomes d) Golgi apparatus

17. Nuclear pores allow:

a) only water to enter the nucleus c) DNA to enter and leave the nucleus b) only proteins to enter and leave the nucleus d) ribosomes to leave the nucleus 18. Which cell part(s) most closely resemble bacteria in their size and composition?

a) lysosomes b) nuclei c) plastids d) Golgi apparatus

19. The ___________ gives shape and internal organization to all eukaryotic cells.

a) nucleus b) cytoskeleton c) endoplasmic reticulum d) cell wall

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20. Which organelle contains enzymes that digest worn out organelles?

a) nucleus b) ribosome c) lysosome d) Golgi apparatus 21. Which organelle is important in organizing the filaments and tubules that form an animal cell’s cytoskeleton?

a) centrioles b) nucleolus c) lysosomes d) vacuoles 22. Cells such as muscle cells which require large amounts of energy will have large numbers of:

a) centrioles b) lysosomes c) chloroplasts d) mitochondria 23. The chemical reactions that take place in lysosomes are classified as:

a) photosynthesis reactions c) cellular respiration reactions

b) anabolic reactions d) catabolic reactions

24. The cell’s cytoskeleton is composed, in part, of:

a) plastids b) cytoplasm c) microtubules d) chromatin 25. Which organelle functions as a storage and packaging site?

a) ribosomes b) lysosomes c) mitochondria d) Golgi apparatus 26. Plant cells have:

a) chloroplasts instead of mitochondria c) cell walls instead of cell membranes

b) smooth ER instead of rough ER d) a large central vacuole instead of smaller vacuoles 27. In which of the following organelles is light energy used to produce simple sugars?

a) lysosomes b) chloroplasts c) endoplasmic reticulum d) mitochondria 28. Which of the following organelles is correctly matched with its product?

a) nucleolus & DNA c) mitochondria & ATP

b) Golgi apparatus & ribosomes d) smooth endoplasmic reticulum & glucose 29. When a protein is ready to leave the rough endoplasmic reticulum, it travels to the Golgi bodies in:

a) transport vesicles b) secretory vesicles c) lysosomes d) vacuoles 30. The fluid-mosaic membrane model describes the cell membrane as a:

a) sheet of protein around a cell c) sugar-phosphate backbone around the cell

b) phospholipid bilayer and proteins d) network of cellulose that surrounds the cell 31. In which of the following organelles is a large membrane surface area important?

a) chloroplasts b) mitochondria c) endoplasmic reticulum d) all of these 32. Ribosomes:

a) are made of two equally sized subunits c) are enclosed in a phospholipid membrane b) are found by the thousands in eukaryotic cells d) all of the above

33. Plant cells are green because they:

a) are surrounded by a green cell wall c) contain chlorophyll

b) contain leucoplasts d) have chloroplasts instead of mitochondria 34. Which organelle is responsible for producing the majority of the ATP needed by a cell?

a) chloroplasts b) lysosomes c) leucoplasts d) mitochondria 35. Most eukaryotic cells have only one:

a) nucleus b) mitochondria c) centriole d) all of the above 36. Which of the following organelles can be seen using an ordinary light microscope (like those at school)?

a) mitochondria b) leucoplasts c) cytoskeleton d) ribosomes

Answers:

1. c 11. c 21. a 31. d

2. b 12. b 22. d 32. b

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3. a 13. a 23. d 33. c

4. d 14. a 24. c 34. d

5. b 15. d 25. d 35. a

6. c 16. b 26. d 36. b

7. b 17. d 27. b

8. b 18. c 28. c

9. b 19. b 29. a

10. d 20. c 30. b

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