Chapter 2- Cells Flashcards
prototypical cell
-a generalized cell
combines features from many different cells for teaching
3 basic parts of human cells
1) plasma (cell) membrane
2) cytoplasm
3) nucleus
cell membrane
- thin outer border of cell
- selective physical/chemical barrier deciding what comes into/leaves the cell
- regulates passage of gases, nutrients, and wastes between internal and external environment of cell
intracellular
inside cell
extracellular
outside cell
composition/structure of cell membrane
composed of 2 molecular components: 1) lipids
2) proteins
membrane lipids
- 2 layers: inner and outer
- insoluble in water (by hydrophiic and hydrophobic ends)
types of lipid membranes
1) phospholipids- polar & non-polar ends
2) cholesterol- strengthens and stabilizes against extreme temps
3) glycolipids- have carbohydrates attached (glycocalyx)
functions of cell membrane (4)
- communication
- intercellular connection
- physical barrier
- selective permeability
protein specific functions of cell membrane (6)
- transport
- intercellular connection
- anchors the cytoskeleton
- enzyme activity
- cell-cell recognition
- signal transduction
passive membrane transport
- does not require energy from cell
- materials move from higher concentration down to area of lower concentration (diffusion)
- free
active membrane transport
- requires energy from cell (ATP)
- materials are moved up/against concentration gradient OR material is not soluble in membrane
- costs ATP
exocytosis
moving things from inside to outside of cell
endocytosis
moving things from outside to inside of cell
cytoplasm
- all materials between cell membrane and nucleus
- cytosol
- inclusions
- organelles
cytosol
viscous fluid containing different dissolved substances like:
- ions
- nutrients
- proteins
- carbohydrates
- amino acids
inclusions
large storage aggregates of complex molecules found in cytosol
a) melanin- brown pigment in skin cells
b) glycogen- long chains of sugars in liver & skeletal muscles
organelles and functions
- “little organs”
- a type of division labour
- the type and # of organelles within a cell is the reflection of the cells function
2 classifications of organelles
1) membrane-bound
2) non-membrane-bound
membrane-bound organelles (5)
- biochemical activity in organelles is isolated from cytosol and other organelles
- endoplasmic reticulum
- Golgi apparatus
- lysosomes
- peroxisomes
- mitochondria
non-membrane-bound organelles (5)
- in direct contact with cytosol
- ribosomes
- cytoskeleton
- centrosomes and centrioles
- cilia and flagella
- microvilli
endoplasmic reticulum
- network of intracellular membrane-bound tunnels
- enclosed spaces are called cisternae
2 types of endoplasmic reticulum
1) smooth endoplasmic reticulum (SER)
2) rough endoplasmic reticulum (RER)
Smooth endoplasmic reticulum
- walls have smooth appearance
- continuous with RER
functions of SER
1) synthesis, transport, and storage of lipids (steroid hormones)
2) metabolism of carbohydrates
3) detoxification of drugs, alcohol, and poisons
rough endoplasmic reticulum
- walls appear rough due to attachment of ribosomes on outside of RER membrane
- ribosomes synthesize protein
functions of RER
1) secretion by the cell
2) incorporation into the plasma membrane
3) creation of lysosomes
Golgi apparatus
stacked cisternae whose lateral edges bulge, pinch off, and give rise to small transport and secretory vesicles
function of Golgi apparatus
- to receive proteins and lipids from RER for modification, sorting, and packaging
- receiving region is cis-face
- shipping region is trans-face
lysosomes
-vesicles generated by Golgi apparatus
lysosomes functions
- contains enzymes used to digest & remove waste products and damaged organelles within cells (autophagy)
- when a cell is dying it releases lysosomal enzymes that digest the cell (autolysis)
autophagy
an ordered and purposeful digestion of cellular components
autolysis
when digestive enzymes leak out of lysosomes and start destroying the cell
peroxisomes
- vesicles smaller than lysosomes
- use oxygen and and enzyme (catalase) to detoxify harmful molecules taken into cell
mitochondria
- bean-shapes organelle with double membrane
- inner membrane folds into shelf-like cristae
- internal fluid= matrix
- cells that require more energy have more mitochondria than those requiring less energy
function of mitochondria
produce a high energy containing molecule called ATP on the cristae
ribosomes
- large and small subunit
- responsible for proteins synthesis
- free ribosomes float unattached
- fixed ribosomes are attached to outer surface of RER
cytoskeleton
-proteins organized in cytosol as solid filaments or hollow tubes
protein types of cytoskeleton
1) microfilaments
2) intermediate filaments
3) microtubules
microfilaments
- 7nm thick
- maintain and change cell shape
- participate in muscle contraction and cell division
intermediate filaments
- 8-12nm thick
- provide structural support and stabilize junctions between adjacent cells
microtubules (6)
- 25nm thick hollow tubes
- radiate for centrosome
- fix organelles in palce
- maintain cells shape and rigidity
- direct movement of organelles in cell
- allow cell mobility in cilia and flagella
cilia and flagella
projections of cell containing cytoplasm and microtubules capable of movement
cilia
grouped on cells that move objects across their surface
ex: respiratory tree and oviduct
flagella
longer, usually singular, to propel a cell
ex: sperm
microvilli
- extensions of cell, not capable of motion
- smaller than cilia
- increase surface area to increase absorption of food
- on surface of cells of small intestine
lumen
hollow cavity on inside of any organ or tissue
nucleus
- control centre for cellular activity
- contains DNA
DNA
- deoxyribonucleic acid
- when not dividing, nuclear DNA is unwound into fine filaments called chromatin
- during cell division chromatin coils tightly to for chromosomes
nuclear envelope
- double membrane structure
- controls entry and exit of molecules from nucleus and cytoplasm
- outer membrane in continuous with endoplasmic reticulum
nuclear pores
selectively permeable channels that allow some molecules in or out of the nucleus
nucleoli
- dark staining bodies within the nucleus
- responsible for making the components of the small and large units of the ribosome
life cycle of cell
always in either interphase or mitotic phase
interphase
- maintenance (resting) phase between cell divisions where the following activities occur:
- normal activities
- prep for cell division
- majority of life in this phase
mitotic phase
when the cell divides
steps of protein flow through Golgi apparatus
1) protein-containing vesicles pinch off rough ER and migrate to fuse with membranes of Golgi apparatus
2) proteins are modified within Golgi compartments
3) proteins are packaged within different vesicles depending on their destination
pathways of protein flow through Golgi apparatus
A) vesicle contents destined for exocytosis
B) vesicle membrane to be incorporated into plasma membrane
C) lysosome containing acid hydrolyses enzymes
