Cells as the basis of life: Topic 1

Question 1

Describe the cell theory.

Answer 1

Everything is made of cells. Biogenesis, all cells come from other cells. The smallest organisational unit.

Question 2

Distinguish between prokaryotic cells and eukaryotic cells.

Answer 2

Prokaryotic cells do not have a nucleus or organelles. Eukaryotic cells do.

Question 3

Recite the basic cell inclusions.

Answer 3

Cell membrane
Cytoplasm
DNA
Ribosomes

Question 4

What is the purpose of organelle membranes?

Answer 4

Allows enzymes and reactants to be concentrated in particular organelles of the cell. Maintains the right conditions for enzymes and reactants to function. Allows incompatible chemical reactions to take place simultaneously within the cell. Reduces the cell’s vulnerability to environmental changes.

Question 5

What is the cell membrane?

Answer 5

Fluid structures composed of a
phospholipid bilayer, with associated protein, carbohydrate and cholesterol molecules. It seperates the extracellular fluid from the intracellular fluid. It regulates what moves in and out of the cell. It has receptors for intercellular communication.

Question 6

Distinguish between hydrophilic and hydrophobic.

Answer 6

Hydrophilic is water loving. Hydrophobic is water hating.

Question 7

Define lipophilic.

Answer 7

Loves fat.

Question 8

Describe cholesterol.

Answer 8

Stabilizes the membrane without affecting the fluidity.

Question 9

Describe proteins.

Answer 9

They are restricted in the cell membrane.
Integral protein - permanent
Peripheral protein - temporary
Transmembrane proteins go through the whole width of the membrane.

Question 10

What do integral proteins do?

Answer 10

Transport channels for ions and molecules (enzymes). Are involved in signal transduction. Function incell-cell recognition. Connect cells to each other. Act as attachments to cytoskeleton and extracellular matrix.

Question 11

Describe Carbohydrates.

Answer 11

Recognition and adhesion between cells, and in the
recognition of antibodies, hormones and viruses by cells.

Question 12

Define permeablity.

Answer 12

Where molecules and fluids can flow through other cells and membranes. Selective permeability is where the cell or membrane decides what can come in and out.

Question 13

Define Diffusion.

Answer 13

Movement of substances from a region of high concentration to a region of low concentration until dynamic equilibrium is reached.

Question 14

Define osmosis.

Answer 14

The movement of water molecules from a region of high concentration to a region of low concentration through a semi-permeable membrane until dynamic equilibrium is reached.

Question 15

What is a hypertonic solution?

Answer 15

Solution in which there is a higher concentration of solute particles/ lower
water concentration than the surrounding medium. Cell will take in water and become turgid (swollen).

Question 16

What is an isotonic solution?

Answer 16

When the equilibrium is reached; the concentration in the solute is equal to the surrounding medium.

Question 17

What is a hyptonic solution?

Answer 17

Solution in which there is a lower concentration of solute particles/ higher
water concentration than the surrounding medium. Cell will lose water and become flaccid (shrink).

Question 18

Descibe facilitated diffusion.

Answer 18

When the molecule cannot diffuse on its own, it’ll need the help of a protein channel or carrier proteins.

Question 19

Distinguish between passive and active transport.

Answer 19

Active transport is the net movement of dissolved substances into or out of cells through a concentration gradient. It requires energy. Passive transport does not use energy and uses osmosis, diffusion and faciliated diffusion.

Question 20

Define concentration gradient.

Answer 20

The process of particles, which are sometimes called solutes, moving through a solution or gas from an area with a higher number of particles to an area with a lower number of particles.

Question 21

Define bulk transport.

Answer 21

The movement of macromolecules such as proteins or polysaccharides into or out of the cell is called bulk transport. There are two types of bulk transport, exocytosis and endocytosis, and both require the expenditure of energy (ATP).

Question 22

Describe organelles.

Answer 22

The compartments of a cell that perform specific functions. They are kept in cytosol (fluid) in the cell membrane. They only exist in eukaryotic cells.

Question 23

Describe the nucleus.

Answer 23

Contains the DNA, kept in the chromosomes. The nucleolus responsible for the assembly of ribosomes.

Question 24

Describe the ribosomes.

Answer 24

Made of proteins and RNA. Where protein synthesis is performed. They are either attached to the ER (endoplasmic reticulum) or roam free. They take mRNA and turn it into proteins.

Question 25

Distinguish between rough ER and smooth ER.

Answer 25

Rough ER has ribosomes; secretes synthesised proteins. Smooth ER synthesises molecules; no ribosomes.

Question 26

Descibe the golgi body.

Answer 26

Involved in modifying the proteins formed in the rough ER for use by the cell or for use outside the cell, for example as hormones. Secretory cells have more golgi bodies.

Question 27

Describe lysosomes.

Answer 27

They are specialized vesicles that digest unwanted matter. Lysosomes are formed when transport vesicle from the golgi body fuses with an endosome
which has material brought into the cell by endocytosis.

Question 28

Describe mitochondria.

Answer 28

Are involved in the energy transformations that release energy from organic molecules
for use by the cell. Active cells have more mitochondria.

Question 29

Describe chloroplasts.

Answer 29

Involved with photosynthesis. They contain chlorophyll. Consists of three membranes – outer membrane, inner membrane and the
thylakoid system. Chloroplast traps light energy which splits water
into H and O2. H combines with CO2 to form glucose C6H12O6.

Question 30

Describe vacuoles.

Answer 30

Vacuole is surrounded by the tonoplast. Used to store water and other
substances. Plays a supportive role in plant cells through turgor pressure.

Question 31

Describe plastids.

Answer 31

Consists of chloroplasts, chromoplasts and leucoplasts (amyloplasts). Involved in the synthesis and storage of different chemical compounds.

Question 32

Descibe the cell wall.

Answer 32

Only in plant cells; composed of cellulose. Allows water and dissolved substances to move freely into and out of cell. Has a supportive function. Lignin in woody stems provides
additional support.

Question 33

Describe the cytoskeleton.

Answer 33

Supports the cell’s structure, allows the cell to move and assists in the
transport of organelles and vesicles within the cell.

Question 34

How is energy stored?

Answer 34

Chemical energy is stored in the bonds between
elements in compounds like glucose C‐C bonds &
C‐H bonds.

Question 35

Compare autotrophs and heterotrophs.

Answer 35

Autotrophs – (producers) ‐ make glucose from
inorganic compounds during photosynthesis Heterotrophs –(consumers) ‐ obtain glucose from their food. Both autotrophs and heterotrophs use glucose as a source of energy.

Question 36

Describe glycolysis.

Answer 36

Glucose breaks down to form pyruvate and release
4 ATP molecules in cytoplasm. 2 ATP are used to start glycolysis again. Doesn’t need O2.

Question 37

Describe the krebs cycle.

Answer 37

Takes place in the matrix; pyruvate undergoes a series of reactions to produce 2 ATP and also several molecules of NADH and FADH2.

Question 38

Define electron transport.

Answer 38

The loaded acceptors are
moved across the membranes within the mitochondria.
The acceptors react with oxygen and lose their hydrogen atoms over a number of steps and this releases 32 ATP.

Question 39

List and describe the steps of cellular respiration.

Answer 39

The first stage (glycolysis)
occurs in the cytoplasm The second stage of cellular respiration, the Krebs cycle,takes place in the matrix. The third stage, electron transport, takes place on the inner membrane.

Question 40

Describe fermentation.

Answer 40

The breakdown of a nutrient molecule, such as glucose, without oxygen. Anaerobic respiration.

Question 41

Descibe enzymes.

Answer 41

Biological catalysts for chemicals in the body. Acts on the substrate; lowering the activation energy for a reaction.

Question 42

Describe catalysts.

Answer 42

Changes the rate of a reaction. Doesn’t change the aim of a reaction.

Question 43

Describe an active site.

Answer 43

Active sites are where enzymes will most prominently act on.

Question 44

Describe coenzymes.

Answer 44

Cannot be synthesised by organisms; assist enzymes. I.e vitamins.

Question 45

What factors can alter an enzymes performance?

Answer 45

pH (can change shape)
Temperature (can kill them)
Concentration (Only a very small number of enzyme molecules is usually involved in a reaction and these produce a given amount of product per unit time.)

Question 46

List the organic compounds.

Answer 46

Carbohydrates
Lipids
Proteins
Nucleic acids

Question 47

Describe lipids.

Answer 47

Fats and oils.