structure of eukaryotic cells (plant & animal)

Question 1

what are organelles?

Answer 1

organelles are specialised sturctures within a cell that perform distinct functions necessary for the cell’s survival and operation.
they are often referred to as the “organs” of the cell.

Question 2

what are the key organelles in eukaryotic cells?

Answer 2

• nucleus
• mitochondria
• ribosomes
• endoplasmic reticulum (ER)
• golgi apparatus
• lysosomes
• peroxiscomes
• cytoskeleton
• plasma membrane
• vacuoles
• chloroplasts (plants)
• cell wall (plants)

Question 3

what is the structure of the cell membrane?

Answer 3

the membrane consists of a phospholipid bilayer. the hydrophilic ends face into the cytoplasm and the environment, whilst the hydrophobic ends face wach other in the centre of the membrane.

Question 4

what is a phospholipid?

Answer 4

a phospholipid is a lipid that contains phosphate groups.
a lipid is a water insoluble substance that contains carbon, hydrogen & oxygen.
one end is hydrophilic and the other is hydrophobic.

Question 5

what is the function of the cell membrane?

Answer 5

the cell membrane is semi-permeable, allowing some molecules to pass through and not others.
it allows food (glucose/nutrients), water & oxygen gas (in animals) in, and removes waste and waste gases (carbon dioxide).
the regulation of movement is based on size, bacteria and viruses are too big to pass through.
lareg molecules that are needed are tranpsported by proteins.

Question 6

what is the fluid mosaic model?

Answer 6

it is a model used to represent the structure of cell membranes, since they’re like a mosaic of different protein molecules mixed with phospholipids.
carbohydrate molecules are attached to the proteins and lipids on the side facing the external environment, and the complex molecules are called glycoproteins and glycolipids.

Question 7

what are the different proteins attached to or embedded in the phospholipid bilayer?

Answer 7

intergral (transmembrane) proteins : span the entire membrane and are involved in transporting molecules across the membrane (e.g channels).
peripheral proteins: located on the inner or outer surface of the membrane, attached to intergral proteins or to phospholipids. they assist in signalling, structural support and cell shape.

Question 8

what are the functions of carbohydrates attached to the cell membrane?

Answer 8

glycoproteins and glycolipids are carbohydrates which are often attached to proteins (forming glycoproteins) or lipids (forming glycolipids) on the external surface of the membrane.
they play a role in cell reconition, cell signalling & adhesion.

Question 9

what are the functions of cholesterol attached to the cell membrane?

Answer 9

cholesterol molecules are interspersed with the bilayer, particularly animal cells.
it plays a key role in membrane fluidity and stability.

Question 10

what is passive transport?

Answer 10

osmosis & diffusion.
passive transport doesn’t use energy (ATP) and relies on the concentration gradient.

Question 11

what is diffusion?

Answer 11

diffusion is the movement of any molecules from high to low concentration, eventually resulting in an equilbrium.
lipid soluble molecules and very small molecules like oxygen and carbon dioxide can diffuse directly through the lipid bilayer.

Question 12

what is osmosis?

Answer 12

osmosis is the movement of water across a semi-permeable membrane, from highn to low concentration.
it works the same as diffusion.

Question 13

what are hypertonic solutions?

Answer 13

hypertonic solutions have a greater solute concentration outside of the cell than inside, causing water to move out of the cell and make it shrink.
when animal cells are exposed, they shrivel up, which is why drinking salt water is bad.

Question 14

what are hypotonic solutions?

Answer 14

hypotonic solutions have a lower solute concentration than inside the cell, causing water to move into the cell and the cell expands.
when they are exposed they can burst.

Question 15

what are isotonic solutions?

Answer 15

they have the same concentration as the inside of the cell.
its the “ideal conditions”.

Question 16

what is active transport?

Answer 16

active transport requires the cell membrane and uses energy (ATP). substances are often transported from low to high concentration, against concentration gradients.

Question 17

what is endocytosis?

Answer 17

endocytosis is when the cell membrane changes its shape to surround a large particle and engulf it.

Question 18

what is endocytosis called if a solid particle is engulfed?

Answer 18

its called phagocytosis

Question 19

what is endocytosis called if a fluid is engulfed?

Answer 19

its called pinocytosis.

Question 20

what is exocytosis?

Answer 20

exocytosis is the process by which waste products are moved out of the cell.

Question 21

what are factors that affect the exchange of materials across membranes?

Answer 21

• the chemical properties of a substance.
• the size and shape of molecules.
• the relative concentration of substances on either side of the membrane.
• the SA:V ratio

Question 22

what is the nucleus?

Answer 22

it’s the control centre of the cell, housing the cell’s DNA, which contains genetic instructions for making proteins and controlling cell activities.

it is surrounded by a double membrane called the nucleur envelope, and contains the nucleolus, where ribosomal RNA (rRNA) is made.

Question 23

what is the mitochondria?

Answer 23

the mitochrondia is the site of cellular respiration, where ATP is generated.
it contains its own DNA and has a double membrane; the inner membrane is folded into crstae to increase surface area for energy production.

Question 24

what are ribosomes?

Answer 24

ribosomes produce proteins by translating mRNA into amino acid sequences.
they can be found floating freely in the cytoplasm or attached to the endoplasmic reticulum.

Question 25

what is the endoplasmic reticulum (ER)?

Answer 25

it synthesizes proteins and lipids, and helps transport materials throughout the cell.
the rough ER is studded with ribosomes and involved in protein synthesis and folding.
the smooth ER lacks ribosomes and is involved in lipid synthesis, detoxification, and calcium storage.

Question 26

what is the golgi apparatus?

Answer 26

the golgi apparatus modifies, sorts, and packages proteins and lipids for storage or transport out of the cell.
it consists of flattened membrane-bound sacs called cisternae.

Question 27

what are lysosomes?

Answer 27

lysosomes are the cell’s waste disposal system. they contain enzymes that break down waste materials, cellular debris, and foreign invaders like bacteria.
the are membrane-bound vesicles filled with digestive enzymes.

Question 28

what are peroxisomes?

Answer 28

they break down fatty acids and detoxify harmful substances, like hydrogen peroxide.
they contain enzymes involved in metabolic reactions.

Question 29

what is the cytoskeleton?

Answer 29

the cytoskeleton provides structural support for the cell, facilitates cell movement, and assists in intracellular transport. it’s made up of microtubules, microfilaments, and intermediate filaments that maintain cell shape and enable movement.

Question 30

what are chloroplasts?

Answer 30

they carry out photosynthesis, converting sunlight into chemical energy (glucose). they contain green pigment chlorophyll and have a double membrane with internal structures called thykaloids.

Question 31

what is the cell wall?

Answer 31

the cell wall is made of cellulose and is located outside the plasma membrane. it provides additional support and protection to plant cells.

Question 32

what are nucleic acids?

Answer 32

nucleic acids are large macromolecules that contain carbon, hydrogen, oxygen, nitrogen and phosphorus.
the two types are DNA and RNA.

Question 33

what are the building blocks of RNA and DNA?

Answer 33

nucleotides.
each consist of a sugar, base and a phosphate.

Question 34

what is DNA (Deoxyribonucleic Acid)?

Answer 34

DNA is the fundamental molecule responsible for storing and transmitting genetic information, used in the growth, development, functioning, and reproduction of all living organisms and many viruses.
it provides the blueprint for making proteins, which perform most of the functions in cells.

Question 35

what is RNA?

Answer 35

RNA is a nucleic acid that plays an essential role in the expression of genetic information, the synthesis of proteins, and cellular regulation.

Question 36

what is the difference between DNA and RNA?

Answer 36

RNA and DNA are both nucleic acids but differe in structure, function and location.

Question 37

what is cellular respiration?

Answer 37

it is the breakdown of food molecules like glucose as a source to drive cellular metabolism.
glucose can be broken down in the presence of oxygen (aerobic) or the absense of oxygen (anearobic).
different products and amounts of energy are released in each process.

Question 38

what occurs during aerobic cellualr respiration?

Answer 38

it is a chain of many biochemical reactions that occur in the presence of oxygen. there are 20 different reactions, each catalysed by a specific enzyme.
the first is the breakdown of glucose in the process of glycolysis.
it occurs in the cytosol of the cell and produces pyruvate, this releases 2 ATP molecules.
the pyruvate then enters the mitochondria where the rest of the reactions happen.
the energy is released in the form of 3 ATP molecules.
In total, 36 ATP are produced for the breakdown of every glucose moelcule.

Question 39

how many ATP does the breakdown of a glucose moelcule produce?

Answer 39

36 ATP.

Question 40

what happens during anaerobic cellular respiration?

Answer 40

there are two other biochemical pathways that produce energy without oxygen.
alcohol fermentation, and lactic acid fermentation.

Question 41

how does alcohol fermentation work?

Answer 41

it involves the breakdown of glucose in the absence of oxygen to form ethanol and carbon dioxide.
two molecules of ATP are produced.
occurs in yeast, many bacteria, and plants

Question 42

how does lactic acid fermentation work?

Answer 42

it occrs in periods of strenuous exercise when the body can’t deliver enough oxygen to the muscles.
one molecule of glucose is broken down, to produce two molecules of lactic acid and two ATP molecules.
when the strenuous exercise is finished there will be more oxygen available and the lactid acid turns to pyruvate and is converted into carbon dioxide, water & ATP.