Midterm Review

Question 1

Function of Lysosomes

Answer 1

hydrolysis / digestion / breaks down material (macromolecules) - including damaged organelles, pathogens and food materials

Question 2

Function of Golgi Apparatus

Answer 2

synthesis / sorting / processing / modifying / transporting / secretion of cell products

Question 3

Function of Rough Endoplasmic Reticulum

Answer 3

site of synthesis of proteins (to be secreted) / intracellular / transport of polypeptides to Golgi apparatus

Question 4

Function of Smooth Endoplasmic Reticulum

Answer 4

synthesizes lipids (phospholipids, steroids, triglycerides)

Question 5

Function of Mitochondria

Answer 5

(aerobic) respiration / generates ATP (chemical used by all cell processes)

Question 6

Function of Chloroplast

Answer 6

photosynthesis (produces glucose needed by the mitochondria to produce ATP)

Question 7

Function of Nucleus

Answer 7

controls cell activities / mitosis / replication of DNA / transcription of DNA (to RNA) / directs protein synthesis

Question 8

Function of Centriole

Answer 8

only found in animal cells. Made up of microtubules - responsible for mitotic spindle production for mitosis and positioning of nucleus

Question 9

Function of Peroxisomes

Answer 9

filled with enzymes / helps digest fat / enzymes depend on peroxisome function

Question 10

Function of Ribosome

Answer 10

synthesize proteins / found in rough ER and free floating in cytoplasm

Question 11

Function of Cytoplasm

Answer 11

site of chemical reactions (metabolic activity) in the cell. Liquid solution. Holds the cells organelles. Water, ions, glucose, proteins, and other organic molecules.

Question 12

Function of Cell Membrane

Answer 12

regulates the entrance and exit of molecules between the cell and its environment

Question 13

Function of Cell Wall

Answer 13

only in plant cells, found in prokaryotes, composed of cellulose. Bacteria cell wall is made up of different material

Question 14

Function of Cytoskeleton

Answer 14

Microfilaments, intermediate filaments, microtubules. Used for cell shape and structure and movement of substances. Found in both plants and animals.

Question 15

Organize from largest to smallest

enzyme, ribosome, plasma membrane, E. Coli, virus, paramecium, mitochondria, carbon atom, chloroplast????

Answer 15

plasma membrane, ribosome, enzyme, virus, E. Coli, mitochondria, chloroplast, paramecium, carbon atom????

Question 16

Distinguish between the structure of plant and animal cells

Answer 16

Plant: have cell walls, have plastids, chloroplasts, large vacuole, store starch, have plasmodesomata
Animal: have centrioles, have cholesterol in membrane, have a fixed shape (rounded), store glycogen

Question 17

Prokaryotes vs eukaryotes

Answer 17

P is smaller in size, E is larger/ both have cytoplasm/ P has no true nucleus, has nucleotide region / P has only DNA, E has DNA with proteins, P has no membrane bound organelles, E has some membrane bound organelles, E has mitochondria, flagella, P has pili and plasmids P has 70s ribosomes and E has 80s, P has cell wall, E has centrioles

Question 18

Explain how the surface area to volume ratio influences cell sizes

Answer 18

Small cells have larger ratio/ ratio decreases as size increases/ membrane must be large enough to absorb nutrients / oxygen/ membrane must be late enough to excrete/ pass out waste products/ cells divide when they reach a certain size

Question 19

How to calculate power of magnification of an image

Answer 19

Magnification = image size / actual size
Ex. 7mm / 100nm = 7 000 000nm/100nm
=70 000x

Question 20

Describe he importance of stem cells in differentiation

Answer 20

stem cells are undifferentiated cells, embryo cells are stem cells , stem cells are multipoint and can differentiate int specific tissues/cells. Differentiation involves expressing some genes but not others, stem cells can be used to repair/replace tissues/heal wounds

Question 21

List the functions of membrane proteins

Answer 21

cell to cell recognition, transport of substances, enzymatic activity, cell attachment to ECM and other cells and signal transduction

Question 22

Distinguish between diffusion and osmosis

Answer 22

diffusion is the movement of molecules from an area of high concentration to an area of low concentration, osmosis is the diffusion of water across of water across a partially permeable membrane

Question 23

Describe how the properties of phospholipids help to maintain the structure of the cell surface membrane

Answer 23

hydrophilic head groups point outward, hydrophobic tails form a lipid bilayer, forms a phospholipid bilayer, ions and polar molecules cannot pass through hydrophobic barrier, helps the cell maintain internal concentration and exclude other molecules, hydrophobic tails found in centre away from water, stability to membrane brought about by attraction between hydrophobic tails / between hydrophilic heads and water

Question 24

State the composition and the function of the plant cell wall

Answer 24

cellulose, structural support / protection / maintain turgor pressure

Question 25

Explain the various methods cells use to transport materials across membranes

Answer 25

Through endocytosis large particles are brought into cells across the membranes, through exocytosis large particles are removed from cells, by the formation of vesicles, active transport requiring ATP, uses protein pumps to move materials against concentration gradients , the molecules are too large or too charged to diffuse directly through the membrane, small polar and non-polar molecules / gases, can diffuse directly through the membrane from an area of high concentration to an area of low concentration / down the concentration gradient, osmosis is the passive movement of water molecules across a partially / selective permeable membrane from a region of lower solute concentration to a region of higher solute concentration

Question 26

Explain how vesicles are used in cells, including the way in which they form and are reabsorbed

Answer 26

vesicle is made by pinching off a piece of membrane, fluidity of membrane allows this, vesicles can be used to transport material around inside cells, proteins are transported in vesicles, from the rough ER to the Golgi Apparatus, from the Golgi apparatus to the plasma membrane, formation of vesicle from plasma membrane allows material to be taken in, endocytosis / phagocytosis / phagolysosome is absorption of material using a vesicle, fusion of vesicle with plasma membrane allows the material to be secreted / passed out, exocytosis is secretion of material using a vesicle, named example of endocytosis

Question 27

What happens in an Isotonic Solution

Answer 27

A solution that has the same salt concentration as cells and blood. Isotonic solutions are commonly used as intravenously infused fluids in hospitalized patients.

Question 28

What happens in a Hypertonic Solution

Answer 28

If concentrations of dissolved solutes are greater outside the cell, the concentration of water outside is correspondingly lower. As a result, water inside the cell will flow outwards to attain equilibrium, causing the cell to shrink. As cells lose water, they lose the ability to function or divide. Hypertonic environments such as concentrated brines or syrups have been used since antiquity for food preservation because microbial cells that would otherwise cause spoilage are dehydrated in these very hypertonic environments and are unable to function.

Question 29

What happens in a Hypotonic Solution

Answer 29

If concentrations of dissolved solutes are less outside the cell than inside, the concentration of water outside is correspondingly greater. When a cell is exposed to such hypotonic conditions, there is net water movement into the cell. Cells without walls will swell and may burst (lyse) if excess water is not removed from the cell. Cells with walls often benefit from the turgor pressure that develops in hypotonic environments.

Question 30

Outline the process of endocytosis and exocytosis

Answer 30

endocytosis- an energy-using process by which cells absorb molecules (such as proteins) by engulfing them. It is used by all cells of the body because most substances important to them are large polar molecules that cannot pass through the hydrophobic plasma or cell membrane

exocytosis- a process in which an intracellular vesicle (membrane bounded sphere) moves to the plasma membrane and subsequent fusion of the vesicular membrane and plasma membrane ensues.

Question 31

State one type of secondary structure of a protein

Answer 31

alpha helix or beta pleated sheets

Question 32

Outline the differences between globular and fibrous proteins, giving one named example of each.

Answer 32

fibrous proteins have a long and narrow shape, globular protein have rounded shapes, fibrous mostly insoluble in water, globular protein soluble in water, fibrous: collagen / silk / keratin, globular: immunoglobulin / hemoglobin / catalase / named enzyme /

Question 33

Explain the significance of polar amino acids for membrane proteins.

Answer 33

polar amino acids are hydrophilic / “water loving”, polar amino acids form hydrophilic proteins / channels allowing hydrophilic / polar / charged particle acids on the surface proteins make them water soluble

Question 34

Describe the supercoiling of DNA to form chromosomes

Answer 34

DNA wraps around 8 histone proteins 1.65 times, and remains bound via hydrogen bonds and an H1 linker protein. This complex is known as a nucleosome. Nucleosomes condense some more to create chromatin which eventually condenses even more to form chromosomes.

Question 35

Define the term: gene

Answer 35

a gene is “a locatable region of genomic sequence, corresponding to a unit of inheritance, which is associated with regulatory regions, transcribed regions, and or other functional sequence regions. Segments of DNA carry codes for specific proteins and thus code for various biological traits. The region of the chromosome at which a particular gene is located is called its locus.

Question 36

Distinguish between single copy genes and repetitive sequence genes.

Answer 36

Single copy genes are found only once and code for proteins, while repetitive sequence genes are found multiple times and do not code for proteins.

Question 37

Define Enzyme and Active Site

Answer 37

enzymes are high molecular mass soluble globular proteins that act as catalysts as living systems, increasing the rate of the reaction they catalyze without being used up.

Question 38

Define enzyme-substrate specificity

Answer 38

enzymes possess an active site where substrate binds to form an enzyme-substrate complex which induces stress in the substrate thereby lowering the energy required for the reaction. They are very efficient catalysts that cause very high reaction rates at low temperatures. The active site has a particular shape and enzymes can therefore only react with substrates that have a certain shape and can enter a bind with the active site. They are specific to either one substrate where only a single substrate can bind or a chemical group where a particular chemical group can bind

Question 39

Explain the effects of temperature, pH and substrate concentration on enzyme activity

Answer 39

They have optimum conditions of temperature and pH for maximum activity and activity can be lowered or cease altogether in extreme conditions.
The rate of reaction also depends upon concentrations of enzyme, substrate, product and inhibitor.
As proteins, they denature temporarily or permanently at higher temps. Temperature and pH changes cause bond changes affecting conformation of the protein molecule and therefore the shape of the active site, the substrate can no longer bind to the site and the reaction is no longer catalyzed.

Question 40

Define denaturation

Answer 40

Denaturation is a change in the shape of an enzyme which prevents it from fulfilling its function. Enzymes can be denatured by heat, pH changes, or certain chemicals.