Biology - Unit 4 - Cells Part 2

Cytoskeleton Structure

-strands/fibers made of protein
-all throughout cell
-Three types:
1. Actin filaments
-Thinnest
2. Intermediate filaments
-Medium
3. Microtubules
-Thicketst

Cytoskeleton Structure

Strength, structure, and motility
1. Actin filaments
-cell movement
-muscle contraction
2. Intermediate filaments
-support organelles
3. Microtubules
-vesicle transport
-cell motility
-many other functions

Centriole structure

-bundles of microtubules

Centriole Function

-help organize microtubules
-only active during mitosis and cell division

Centrosome Structre

-2 centrioles = 1 centrosome
-made of microtubules

Centrosome Function

-functional during mitosis and cytokinesis
-organize microtubules
-move chromosomes

Mitsos

nuclear division

Cytokinesis

cell division

Spindle Apparatus

-microtubules lengthen the cell and pull chromosomes to either side
-demonstrated how the centrosome and cytoskeleton work together

Lysosome Structure

-membrane bound
-contains digestive (hydrolytic) enzymes
-low pH (acidic)
-made by golgi body

Lysosome Function

-digests worn out cell parts (biomolecules, organelles)
-Digests ingested particles/food
Assists with apoptosis

Apoptosis

programed cell death

Why would a cell want to die?

-unfixable DNA damage
-removal of tissues
-organ sculpting

Peroxisome Structure

-membrane bound
-special enzymes
-requires special proteins and lipids to form (ribosomes and ERs play a role)

Peroxisome Formation

-form from ribosomes and ER
-can divide on their own

Peroxisome Function

-breaks down lipids
-breaks down hydrogen peroxide
-peroxisomes contain oxidase and catalase

Oxidase

creates H2O2C

Catalase

breaks down hydrogen peroxide (toxic to cells)

Enzymes

-special proteins
-perform chemical reactions in cells
-catalysts
-reusable
-found in small amounts

Enzymes are biological catalysts

they reduce activation energy and speed up the reaction rate of a reaction

Enzymes have a special shape that lets them work

-active site: where the enzyme does chemistry
-Substrate: the reactant
Products: the end result of the reaction

What do enzymes need to function?

-optimal temperature
-optimal pH

Enzymes can.....?

denature (unfold)
-the active site is no longer functional; the reaction cannot proceed

Low temperatures...

slow down enzymatic activity; move slower

High temperatures and different pH levels...

denatures enzymes

Cilia Structure:

-short hairlike projections
-on surface of cell
-made of protein (microtubules)
-only in eukaryotes

Cilia Function:

-helps cells move
-helps move fluid around cells
-back and forth movements
-helps keep lungs clear of debris

Flagella Structure

-long, whiplike projections
-made of protein (microtubules in eukaryotes)

Flagella Function

-moves cells

Mitochondria Structure

-double membrane (inner and outer)
-internal folds = cristae
-internal space = matrix
-contains own ribosomes and DNA in matrix

Mitochondria Function

-performs cellular respiration

Chloroplasts Structure:

-double membrane (inner and outer)
-disks = thylakoid disk
-stacks on disks = granum
-fluid = stroma
-contains own ribosomes and DNA

Chloroplasts Function

-performs photosynthesis

Chloroplasts contain chlorophyll

-found in proteins in the thylakoid membrane
-green pigment
-reflect green light

Endosymbiotic theory

states eukaryotic cells formed from symbiotic relationships between primitive prokaryotic cells

Endocytosis

taking in matter from outside of the cell

How did endosymbiosis happen?

-membrane folds in
-forms membrane-enclosed system
-consumes aerobic bacterium (becomes mitochondria)
-consumes photosynthetic bacterium (becomes chloroplasts)

Membrane (evidence for endosymbiosis)

mitochondria and chloroplasts have an interior membrane (their own) and an outer membrane (from endocytosis)

DNA (evidence for endosymbiosis)

mitochondria and chloroplasts have their own DNA (not nuclear) and ribosomes (different from cell)

Reproduction (evidence for endosymbiosis)

mitochondria and chloroplasts replicate independently of the cell; resembles binary fission

Size (evidence for endosymbiosis)

mitochondria and chloroplasts have a similar size to prokaryotes

Did mitochondria or chloroplasts evolve first?

Mitochondria - because all eukaryotic cells have mitochondria and only plant cells have chloroplasts

Nucleoid Structure and Function

contains prokaryotic DNA (circular)
-used for transcription
-translation happens at free-floating ribosomes

Plasmids

-in prokaryotes
-small species of circular DNA
-can be transferred from one bacterium to another

Cytoplasm Structure

-dense, water-based gel (cytosol)
-contains dissolved substances, enzymes, ribosomes, and membrane bound organelles

Cytoplasm Function

-cushions and surrounds organelles
-location of some types of metabolism and translation
-allows movement of molecules

Cytosol

-the fluid in the cell
-made mostly of water

Prokaroytes

-all unicellular
-nucleoid region for DNA
-cell wall (peptidoglycan)
-no membrane bound organelles
-includes bacteria

Eukaryotes

-uni- or multicellular
-nucleus stores DNA
-plants: cellulose cell wall
-have membrane bound organelles
-includes animals, plants, fungi, protists

Both Prokaryotes and Eukaryotes

-DNA
-Ribosomes
-Membrane
-Cytosol
-Cytoskeleton

Large Central Vacuole Structure

-membrane bound (tonoplast)
-large container

Large Central Vacuole Function

Stores: water, nutrients, enzymes/proteins, waste
-helps the cell maintain turgor pressure
-fullof water = strong cell

Small Vacuole Structure and Function

-small vesicles (membrane bound)
-contain food or waste
-not always present

Cell Wall Structure

-made of carbohydrates and proteins
-plant cells = cellulose (fibers)
-fungal cells = chitin
-prokaryotic cells = peptidoglycan

Cell Wall Function

-structural support
-protection