AP Biology: Cells

Two different types of cells

Prokaryotes and Eukaryotes

Prokaryotes traits

1) No membrane bound organelles
2) Unicellular
3) Domains: bacteria and archaea

Eukaryotes Traits

1) Membrane-bound organelles
2) Uni- or multi-cellular
3) Domain: Eukaryota (animals, plants, fungi, protista)

Prokaryotic Cells

1)No membrane bound organelles**
2) DNA in a "nucleoid" region
4) Unicellular
5) Small
6) Domains: Bacteria and Archaea

Eukaryotic Cells

1) Has membrane bound organelles**
2) Nucleus contains DNA
3) Unicellular or Multicellular
4) Larger: 10x bigger than prokaryotes
5) Domain: Eukarya

Nucleus

1) Contains genetic information in the form of chromosomes or chromatin
2) Has a nucleolus for ribosome production
3) Surrounded by a phospholipid nuclear membrane (envelope)
4) spherical shape
5) molecules pass in and out of the nucleus through nuclear pores

Cytoplasm

1) "Jelly goo" that is within the cell membrane
2) Has organelles/structures in it
3) Found in eukaryotes and prokaryotes

Ribosomes

1) Structures that build proteins during protein synthesis
2) Free-floating or attached to the rough ER
3) Found in eukaryotes and prokaryotes

Rough Endoplasmic Reticulum

1) Helps with protein production and shipping
2) Ribosomes attached make it "rough"

Smooth Endoplasmic Reticulum

1) Synthesis of lipids
2) Detoxification
3) Storage of calcium ions

Golgi Apparatus (body) - Gol-jee

"Warehouse" for receiving, sorting, and shipping of proteins

Vesicles

Small "containers" made from ER or golgi membrane that move products around the cell

Vacuoles

1) Large vesicles for storing products
2) Plant cells have a large central vacuole filled with water

Lysosomes

1) Digestive organelles where macromolecules are broken down
2) Contain hydrolytic enzymes
3) autophagy

Mitochondria (mitochondrion)

1) Site of cell respiration
2) ATP is generated
3) Found in both plants and animals

Chloroplast

1) Site of photosynthesis
2) Converts energy from the sun into sugar molecules
3) PLANTS AND ALGAE ONLY

Centrosomes

1) Helps with cell division (mitosis) in animals
2) Contains centrioles

Cytoskeleton

1) Reinforces cells shape
2) Helps with cell movement
3) Includes microfilaments, intermediate filaments, microtubules

Cell (plasma) membrane

1) Found in plants, animals, and prokaryotes
2) surrounds cytoplasm
3) phospholipid semi-permeable bilayer

cell wall

1) Protects, maintains shape, helps with structure
2) Made of cellulose
3) Found in plant cells and some prokaryotes

Cilia (Cilium)

1) Short appendages containing microtubules present on some eukaryotes
2) Used in locomotion

Flagella (Flagellum)

1) "Tail-like" appendage found on some eukaryotes
2) Used in locomotion

Plant Cell Traits

Shape: Square-ish
Eu or Prokaryote: Eukaryote
Border: Cell wall AND Cell membrane
Mitochondria for cell respiration: Yes
Chloroplast for photosynthesis: Yes
Vacuoles: Large, central, filled with water

Animal Cell Traits

Shape: Varies
Eu or Prokaryote: Eukaryote
Border: Cell membrane
Mitochondria for cell respiration: Yes
Chloroplast for photosynthesis: No
Vacuoles: Small, stores various substances

What Determines Cell Function?

1) Size, shape, and surface area
2) Organelles present or absent
3) Quantity of different organelles

Examples of size, shape, and surface area affecting cell functions

1) Neurons (nerve cells) - spread out; electrical signals
2) Adipose (fat cells) - packed together; only stores fat

Examples of Organelles present or absent affecting cell functions

1) Red blood cells (moves oxygen/waste) - no nucleus
2) Lung cells w/ cilia (hairs) - diffusion of oxygen from lungs to blood stream

Examples of the quantity of different organelles affecting cell functions

Smooth ER: detoxify, liver cells have a lot
muscle cells have extra mitochondria
Endosymbiotic theory

Endosymbiotic theory

theory that eukaryotic cells formed from a symbiosis among several different prokaryotic organisms (mitochondria and chloroplasts)

Evidence for Endosymbiosis

1. Mitochondria and chloroplasts have a double membrane
2. Mitochondria and chloroplasts have their own circular DNA (but no nucleus)
3. Mitochondria and chloroplasts divide like bacteria
4. About the same size as bacteria
5. own ribosomes

Why are Cells small?

Cells are small so their surface area to volume ratio is large, allowing the entrance of oxygen and food to the whole cell and the release of CO2 and wastes from the whole cell. If the cell is too big, it wouldn't be able to release waste properly/fully.

Diffusion

1) Movement of molecules in a fluid (gas or liquid) from where they are more concentrated to where they are less concentrated
2) movement DOWN its concentration gradient
3) Does not require energy

Protein Production Steps (17)

1) DNA in nucleus
2) Specific chunk/segment of ATCGs = gene
3) mRNA built from gene (transcription)
4) mRNA comes out from nucleus via nuclear pore
5) Ribosomes clamps onto mRNA, reads in 3 letter sequences
6) Assembles primary structure of protein (translation)
7) Could be a free ribosome (protein free in cytoplasm), done
8) Or could be a bound ribosome
9) Sticks to rough ER, release protein inside, ribosome free again
10) Protein modified in the ER (folding, addition of carbohydrate side chains)
11) Goes to Golgi apparatus via transport vesicle (little pouch of membrane)
12) Vesicle gets "pulled" along via motor proteins on cytoskeletal fibers
13) Vesicle fuses w/ Golgi membrane, releases proteins
14) Golgi modifies and packages proteins
15) Repackaged in other vesicle
16) Motor proteins take to another organelle, cell membrane, or out of cell
17) If exits our of the cell, vesicle fuses to membrane and releases via exocytosis

Osmosis

Diffusion of water through a selectively permeable membrane

Water balance in cells

Cells can be placed in different solutions
1) Hypotonic: less solute; more water
2) Hypertonic: more solute, less water
3) Isotonic: same solute and water

Osmosis Terms

1) Lysed (burst) (hypotonic)
2) Turgid (normal) (hypotonic)
3) Flaccid (isotonic)
4) Plasmolyzed (hypertonic)

Water Potential

1) Determined by solute and pressure potential
2) Water moves from regions of high water potential to regions of low water potential

Water potential equation

Ψ = Ψs + Ψp

Solute potential

1) Also called osmotic potential
2) Ψs is pressure from membranes/walls as water moves in or out
3) Can be positive or negative
4) Unit = bars ("in an open beaker" = 0 bars)

Solute potential equation

Ψs = -iCRT
i - ionization constant (NaCl = 2, Sucrose/glucose = 1)
C - molar concentration
R - Pressure constant (.0831 Liter*Bar/Mol*Kelvin)
T - Temperature (in Kelvin)

Components of the Cell (plasma) membrane

1) Phospholipids
2) Proteins
3) Carbohydrates
4) Steroids

Phospholipid Bilayer

1) Hydrophilic head
2) Hydrophobic tails
3) Amphipathic (has hydrophobic and philic parts)

Membrane Proteins

1) Peripheral proteins: bound to the membrane surface
2) Integral proteins: penetrate the hydrophobic core
2a) transmembrane protein: spans entire membrane

Carbohydrate

1) Glycoproteins: oligosaccharides bonded to proteins
2) Glycolipids: oligosaccharides bonded to lipids
Both help with cell to cell recognition

Steroids

Cholesterol: regulates cell membrane fluidity

Fluid Mosaic Model

1) Membrane is a "mosaic" of protein molecules in a semi-fluid bilayer of phospholipids
2) Selectively permeable
3) semi-permeable

Six functions of membrane proteins

1. Transport
2. Enzymatic activity
3. Signal transduction
4. Cell-cell recognition
5. Intercellular joining
6. Attachment to the cytoskeleton and extracellular matrix

Passive transport

1) No energy required
2) diffusion through the phospholipid bilayer of small, nonpolar (hydrophobic) molecules like O2 and CO2

Facilitated Diffusion through transport proteins

Can move larger, polar molecules

Two types of transport proteins

1) Channel proteins
2) Carrier proteins

Active Transport

1) Energy required (ATP)
2) Moves substances AGAINST their concentration gradients through transmembrane proteins

Bulk Transport

1) Requires energy
2) Moves larger molecules across cell membrane
3) Molecules packaged in transport vesicles

Exocytosis

1) Moving molecules from inside to outside the cell membrane
2) Vesicle fuses with cell membrane and releases contents outside

Endocytosis

1) Moving molecules form outside to inside the cell membrane
2) New vesicle formed from cell membrane containing molecules to be moved inside membrane

Endocytosis types

1. Phagocytosis
2. Pinocytosis
3. Receptor-mediated endocytosis

Structures Present in Prokaryotic Cells

1) DNA localized in nucleoid
2) Ribosomes
3) Cell (plasma) membrane
4) cell wall
5) cytoplasm
6) capsule

Difference between nucleoid region and nucleus

Nucleus:
1) Found in eukaryotic cells
2) Stores genetic material
3) Contains several chromosomes
4) Spherically shaped
5) surrounded by double layer membrane

Nucleoid:
1) Found in prokaryotes
2) Stores genetic materials
3) Only one chromosome
4) Irregular shape
5) Doesn't contain any surrounding membrane

Proteins synthesized by free ribosomes

Usually stay in cell

Proteins Synthesized by Bound Ribosomes

Usually travel out of cell

Plant vs. Animal Cells

Shape:
Plant - Square-ish
Animal - Varies
Eukaryote or Prokaryote:
Both Eukaryotes
Border:
Plant - Cell Wall and Membrane
Animal - Cell membrane
Mitochondria:
Plant - Yes
Animal - Yes
Chloroplast:
Plant - Yes
Animal - No
Vacuoles
Plant - Large, central, filled with water
Animal - Small, stores various substances

Organelles only present in plants

1) Chloroplasts
2) Cell Wall
3) central vacuole

Organelles only present in animal cells

centriole

Organelles present in both animal and plant cells

1) Nucleus
2) mitochondrion
3) cell (plasma) membrane
4) endoplasmic reticulum
5) golgi apparatus
6) cytoskeleton

Organelles involved in endosymbiotic theory

mitochondria and chloroplasts

Cell Membrane Components

Phospholipids
Proteins
Glycolipids
Glycoproteins
cholesterol

semi-permeable

membranes that allow some substances through but not others

How do molecules move through the membrane

Passive Transport
Active Transport

concentration gradient

A difference in the concentration of a substance across a distance.

Nonpolar molecules crossing cell membrane

1)Hydrophobic
2) Can cross easily
3) No transport protein required

Polar Molecules crossing cell membrane

1) Hydrophilic
2) Have difficulty crossing hydrophobic portion of lipid bilayer
3) transport protein required

Ions crossing cell membrane

1) Hydrophilic
2) Have difficulty crossing hydrophobic portion of lipid bilayer
3) transport protein required

exocytosis steps

1) molecules to be secreted rest in a secretory vesicle
2) vesicle fuses with cell membrane
3) contents released outside

endocytosis steps

1) molecules to be moved inside cell membrane travel into a new vesicle formed from the cell membrane
2) vesicle detaches from the cell membrane and brings contents inside

Peroxisomes

1) Break down fatty acids and produce hydrogen peroxide
2) located in the cytoplasm

Motor proteins

moves vesicles to other organelles, cell membranes, or out of the cell