Lecture 7 Flashcards
What is an organelle?
- 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
are ribosomes organelles
Ribosomes are not considered to be organelles: 1) no membrane or fluid 2) Continuously disassemble & reassemble.
Ribosomes are called complexes
Present in eukaryotes & prokaryotes
The number of each organelle may differ depending on?
the cell type and
the activity of that cell
Plant central vacuoles can take up to ..% cell volume
Can take up to 80% of cell volume (Huge !)
plants central vacuole function
Water storage
Digestion
Store toxins or pigments
Can contain poisons/kill predators
what are Chromoplasts
make & store pigments
what are Amyloplasts
store starch
what do Chloroplasts do
photosynthesis
Make & store sugar (as starch)
contain Chlorophyll (green): main pigment that traps light energy
do all plant cells have chloroplasts
no, only the ones doing photosynthesis
which organelle does cell. resp
mitochondria
transfer chemical energy in carbs, aa, fatty acids, into chemical energy in ATP
what is the nucleus surrounded by
Surrounded by nuclear envelope: double cell membrane with nuclear pores (molecules enter & leave)
Nuclear pores allow for passage of materials into & out of the nucleus (ex RNA, ribosome subunits)
function of nucleus
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
what are chromosomes made up of
dna + protein
function of Nucleolus
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
(both animal and plant cells)
ribosomes are complexes made up of?
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
where are ribosomes located in the cell?
In Eukaryotes can be on the rER or free in cytoplasm.
In Prokaryotes: free in cytoplasm
function of free ribosomes and the ones on the rER
Free ribosomes: proteins for the cytoplasm: ex cytoskeleton, enzymes in the nucleus…
Ribosomes on the rER:
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)
diff between rough and smooth ER
Smooth:
No ribosomes
Makes lipids
Drug detoxification (fyi ex, morphine & some pesticides) Stores Ca2+
Rough:
Ribosomes on surface
Make proteins: ex transport proteins in plasma membrane
functions of Golgi (apparatus)
- Modifies proteins & lipids (ex attach a CHO, phosphates..)
- Sorts: proteins made on the rER passes to the Golgi, which then directs the protein to other organelles or to the plasma membrane
- Golgi is also part of the pathway that makes lysosomes
what are Peroxisomes
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
function of Mitochondria
(Glucose) + ADP + P + O2 → ATP + CO2 + heat
Glucose, Fatty acids, Amino acids + Oxygen
give
ATP (40%) + CO2 + Heat (60%)
Energy in food per gram
Carbohydrates: 4 kcal (4 Calories)
Proteins: 4 kcal (4 Calories)
Fats: 9 kcal (9 Calories)
When you exercise:
Why do you breathe faster?
Why do you get hot? Why does your heart rate increase?
Why do you breathe faster? BRING IN MORE OXYGEN AND GET RID OF EXCESS CO2
Why does your heart rate increase? BRING YOUR GLUCOSE, FA (REACTANTS) TO THE CELLS. BLOOD SHOULD FLOW MORE IN THE LUNGS AND ACTIVE MUSCLES.
Why do you get hot? MAKE MORE ATP AND MORE HEAT (MORE CELLULAR RESPIRATION)
true or false? plants do both photosynthesis and cellular respiration
true.
function of lysosomes
break down excess or worn-out cell parts. They may be used to destroy invading viruses and bacteria.
do plant cells have lysosomes
no.
what is the cause of the Tay-Sach’s disease
Missing an enzyme (Hex-A) in lysosomes
Can’t break down lipids in nerve cells
what are Centrioles and what is their function
Composed mainly of a protein (called tubulin)
Not an organelle
The main function of centriole is to help with cell division in animal cells
do plant cells have centrioles
no.
…, …, and … are present in cell membranes.
proteins (including glycoproteins), cholesterol, and carbohydrates are present in cell membranes.
functions of the cell membrane proteins
form channels or are carriers/pumps; are hormone or neurotransmitter receptors; can be enzymes; some are molecules involved in cell recognition, others hold one cell to another, allowing the formation of tissues.
what does it mean that the plasma membrane is selectively permeable
Selectively permeable means a membrane allows the passage of some molecules or ions and inhibits the passage of others.
why lipid-soluble molecules can pass more easily than non-lipid soluble molecules
Because of the chemical and structural nature of the phospholipid bilayer (hydrophobic core), only lipid-soluble molecules and some small molecules are able to freely pass through the lipid bilayer.
what molecules can pass through the plasma membrane
Only the smallest molecules like water, carbon dioxide, and oxygen can freely diffuse across cell membranes.
