Lecture 7

Question 1

What is an organelle?

Answer 1

Specialized structure within a cell that performs a specific function.

Membrane-enclosed: one or more cell membranes forms the boundary: see lecture 6

Contains fluid

Ribosomes are not considered to be organelles: 1) no membrane or fluid 2) Continuously disassemble & reassemble.
Ribosomes are called complexes
Present in eukaryotes & prokaryotes

Question 2

All eukaryotic cells have organelles, BUT

Answer 2

Cells of one organism vary to another depending of their function

The number of each organelle may differ depending on
the cell type and
the activity of that cell

Ex 1. Cells of leaves have chloroplasts, cells of roots do not
Ex 2. Liver cells have more sER than most cells (ex skin cells), and amount of sER in a liver cell will increase if that liver cell becomes exposed to more toxins (ex drugs)

Question 3

Plant central vacuoles

Answer 3

Can take up to 80% of cell volume (Huge !)

Water storage
Digestion
Store toxins or pigments
Can contain poisons/kill predators

Question 4

Platids (organelles) in plant cells

Answer 4

1) Chromoplasts: make & store pigments
2) Amyloplasts: store starch
(colorless)
3) Chloroplasts: photosynthesis

Question 5

Chloroplasts: photosynthesis

Answer 5

CO2 + H2O + sun’s energy → CHO + O2
Make & store sugar (as starch)

Chlorophyll (green): main pigment that traps light energy

Question 6

Are chloroplasts in all plant cells?

Answer 6

Cell wall & central vacuole in all plant cells BUT…Chloroplasts
only in plants that do photosynthesis

Question 7

Energy Transformers in plants

Answer 7

Chloroplasts do photosynthesis convert light energy to energy stored in sugar
Mitochondria do cellular respiration: transfer chemical energy in carbs, aa, fatty acids, into chemical energy in ATP

Both contain:
1 circular chromosome: DNA + protein
Ribosomes: where some of the proteins are made (rest made in the cytoplasm & transported into the organelle)

Question 8

Nucleus

Answer 8

Surrounded by nuclear envelope: double cell membrane with nuclear pores (molecules enter & leave)

Nucleus=Master

• Usually in center of cell
• Most prominent organelle
• Usually spherical or oval

Protects & stores DNA
Almost all DNA (genetic information) is here
Small amount of DNA also found in the mitochondria

DNA replication & transcription (mRNA, rRNA & tRNA) takes place here

Influences cell structure & function
Genes on DNA determine which proteins get made
Proteins determine cell shape and function

Question 9

Nuclear pores

Answer 9

Nuclear pores allow for passage of materials into & out of the nucleus (ex RNA, ribosome subunits)

Question 10

Nucleolus: inside the nucleus

Answer 10

(DNA transcribed → rRNA here)
Where proteins + rRNA put together to make a ribosomal subunit (which are then exported to cytoplasm)

Nucleolus is not enclosed by a membrane, not an organelle

Question 11

Ribosomes are complexes

Answer 11

Complex (not an organelle) made up of 2 different subunits

Each subunit contains:
rRNA
Proteins
that are need for translation to occur

Not surrounded by a membrane

Make proteins, Join amino acids together to make a protein

Question 12

In eukaryotes and prokaryotes, where are the ribosomes?

Answer 12

In Eukaryotes can be on the rER or free in cytoplasm.

In Prokaryotes: free in cytoplasm

Free ribosomes: site of translation for proteins for the cytoplasm: ex cytoskeleton, enzymes in the nucleus…

Ribosomes on the rER:
site of translation for
1) enzymes to be packaged into lysosomes or
2) proteins to be secreted (ex hormones)
3) proteins that will be inserted into the plasma membrane (receptors, cell junctions, protein channels)

Question 13

Endoplasmic reticulum (ER)
SLide 23

Answer 13

Organelle that forms an interconnected network of flattened, membrane-enclosed sacs or tube-like structures either with a smooth surface (smooth ER) or studded with ribosomes (rough ER)

Question 14

Endoplasmic reticulum: Smooth & Rough

Answer 14

Smooth: No ribosomes, makes lipids, drug detoxification, Stores Ca2+

Rough: Ribosomes on surface, make proteins ( transport proteins in plasma membrane)

Cells with prominent:
sER: Liver (detox), bone (store calcium)
rER: cells of digestive tract, cells of the pancreas: secrete hormones and enzymes

Question 15

Golgi (apparatus)

Answer 15

1. Modifies proteins & lipids (ex attach a CHO, phosphates..)
2. Sorts: proteins made on the rER passes to the Golgi, which then directs the protein to other organelles or to the plasma membrane
3. Golgi is also part of the pathway that makes lysosomes

Question 16

Endomembrane system

Answer 16

Collection of organelles & membranes that work together to make, package, label & ship proteins & other molecules.

Question 17

Peroxisomes

Answer 17

Peroxisomes are membranous sacs containing enzymes used to detoxify substances such as alcohol, & free radicals. Also breaks down long fatty acids into shorter ones for the mitochondria to use

Found in most cells but abundant in liver cells.

Question 18

Cellular respiration chemical equation (in mitochondria)

Answer 18

(Glucose) + ADP + P + O2 → ATP + CO2 + heat

Glucose                       
Fatty acids
Amino acids        
\+
Oxygen
→ ATP + CO2+ Heat

Question 19

Energy in food per gram and process digestion

Answer 19

Carbohydrates: 4 kcal (4 Calories)
Proteins: 4 kcal (4 Calories)
Fats: 9 kcal (9 Calories)

STEP 1: digest in digestive system

Once carbs, proteins, & fats are digested into glucose, amino acids, & fatty acids….
Mitochondria break the bonds of glucose, amino acids, & fatty acids
Energy from broken bonds used for this reaction: ADP + P → ATP

Question 20

Lysosomes (only in animal cells)

Answer 20

inside the lysosomes: enzymes and low pH

digest the macromolecules that would be in the cell

destroy damaged or old cell parts, bacteria

Good to keep separate b/c don’t want to randomly digest cell components

Sacs filled with DIGESTIVE (hydrolytic) enzymes

Question 21

Centrioles

Answer 21

Composed mainly of a protein
Not an organelle

The main function of centriole is to help with cell division in animal cells

Question 22

Plant vs animal cells

Answer 22

Only in animal cells = centrioles, lysosomes

Only in plant cells: rigid cell walls, large central vacuole, plastids

All other organelles are common to both