AP Bio - Unit 2: Cell Structure and Function

Viewing cells

Cells are studied with electron microscopes and fluorescent microscopes

Centrifuges

Cell parts are isolated and examined by cell fractionation using centrifuges

Prokaryotic cells

simple, unicellular organisms without a nucleus or membrane-bound organelles. they contain plasma membrane, cell wall, cytoplasm, chromosomes (genetic material), ribosomes, capsule, nucleoid, pili, plasmids, and flagella

Capsule

A sticky gelatinous layer that helps prokaryotes stick to surfaces, some capsules add extra protection

Cell wall

Supports cell shape, protects cell, permeable to water

Plasma membrane

phospholipid bilayer that regulates what goes in and out of the cell

Pili

Some prokaryotes have these, they help the bacteria stick to surfaces. Other types of pili can be used to “spear and reel in” other bacteria to exchange plasmid DNA

Flagella

used for motion, whips around like a propellor, attached to capsule surrounding the whole cell

Ribosomes

free floating in the cytoplasm, makes proteins

Plasmids

Small circular chunks of DNA, contains a couple of genes that are easily shared with other bacteria 

Nucleoid

One large circular chunk of DNA. Contains rest of the bacteria’s genes. Not enclosed by a nucleus

Eukaryotic cells

Have internal membranes that: compartmentalize their functions (organelles), isolate specialized environments (pH, molecules), and increase internal surface area for reactions

Photo-autotrophic

plant-like cells

Chemo-heterotrophic

animal-like cells

Cell differentiation

cell structures/functions vary among tissues and organs of multicellular organisms due to cell differentiation

Endomembrane system

efficiently coordinates the sending of proteins from ribosomes to their destinations. 

Nucleus

permanently stores DNA, hosts DNA synthesis (replication), hosts RNA synthesis (transcription)

Nucleolus

compartment of nucleus that makes ribosomes

Ribosomes

site of translation for protein synthesis

Free ribosomes

make cytoplasmic proteins

Bound ribosomes

attached to the rough ER, they make membrane and excretory proteins. only found in eukaryotic cells.

Endoplasmic reticulum (ER)

compartmentalizes the cell for protein synthesis, since it has bound ribosomes on its surface. Proteins made by rough ER travel to Smooth ER

Smooth ER

packages proteins into vesicles and sent away to the golgi apparatus. Other proteins stay in the smooth ER to become enzymes that break down macromolecules or poisons (detoxification). It also makes phospholipids for cell membranes.

Golgi apparatus

Sort of like the “finishing” center of the cell. They take vesicles delivered from the smooth ER and make final touches, like adding phosphate groups, etc. and then sends the finished products to the cell membrane to be excreted out of the cell.

Vesicles

small membranous sacs that store material or transport/secrete materials around/out of cells

Secretory vesicles

fuse with the cell membrane to deliver membrane proteins or to release secretory proteins, which is done by a process called exocytosis

Vacuoles - type of vesicle

larger vesicles that function as storage for food, water, or waste

Large central vacuole

found in plant cells. It stores water and exerts an outward force (turgor pressure) on the cell wall to give plants rigidity and structure.

Contractile vacuoles - type of vesicle

In unicellular eukaryotes, a contractile vacuole is used to dispel excess water. It prevents the single-celled organism from absorbing too much water from its environment - which can cause cell death.

Lysosome - type of vesicle

produced by the golgi apparatus. Contains over 50 kinds of hydrolytic enzymes (enzymes that break chemical bonds). It digests old cell parts, large food molecules. In white blood cells, lysosomes destroy engulfed pathogens. Found only in animal cells

Peroxisome - type of vesicle

formed by fusing vesicles from the mitochondria AND the rough ER together. In animals, peroxisomes are mostly found in our liver. In plants peroxisomes are found in greater numbers in seeds, and help break down the fats stored in seeds as the first energy source for the seed to germinate (sprout).

Mitochondria

Eukaryotic organelle that makes the energy molecule ATP through aerobic respiration (meaning oxygen is needed, which is why we breathe in!) It uses glucose to generate ATP. Single-celled organisms usually have 1-2 mitochondria. One of our muscle cells contain THOUSANDS of mitochondria (because it needs MORE energy!)

Mitochondria anatomy

Two layers of membrane. Inner membrane is folded, because it needs more surface area to maximize the amount of chemical reactions occurring. Basically - more surface area=more ATP being made! (these folds are called cristate) The very innermost area of the mitochondria (inside the cristae) is called the matrix. Mitochondria has its own DNA, separate from the rest of the cell

Matrix

the matrix stores enzymes, proteins, ribosomes, and mitochondrial DNA. Mitochondria has its own DNA!

Chloroplasts

function in photosynthesis in plants and algae. Contains the pigment chlorophyll (which gives plants green coloration) Chlorophyll captures energy from the sun and carbon from CO2 in the air to turn into glucose. Chloroplasts are considered plastids.

Plastids

organelles that contain pigments surrounded by a membrane. Plastids have their own DNA and ribosomes.

Chromoplasts

plastids that contain other pigments. chromoplasts do not perform photosynthesis, and are found in leaves, fruits, and flowers. their role is to attract pollinators or seed-spreaders

Thylakoids

flat green pancakes in chloroplasts. They store chlorophyll and collect sun energy for the first part of photosynthesis

Grana

stacks of thylakoids. this is another way to increase surface area

Stroma

fluid that surrounds the thylakoids. It is the site where the second half of photosynthesis occurs. It also contains ribosomes and DNA

Cytoskeleton

network of structural proteins extending throughout the cytoplasm. an interconnected system of many protein filaments - some permanent, some temporary. parts of the cytoskeleton reinforce, organize, and move cell structures, or can even move the whole cell. 

Cilia and flagella - cytoskeleton

Extensions of the cytoskeleton that allow for cell motility

Motor proteins

motor proteins can use the cytoskeleton as highways, and drag important stuff around with it. they move when activated by ATP. they are important in muscle contraction, flagella movement, cilia movement, and the movement of vesicles in the cell. In protists like amoeba, proteins help the cell move.

Centrosomes

made of centrioles. animal cells have centrosomes to organize microtubules, especially during mitosis. microtubules help move DNA around in cell division (mitosis)

Cell wall

cross-linked networks of structural polysaccharides. plant cell walls are made of cellulose. fungal cell walls are made of chitin. bacterial cell walls are made of peptidoglycan

Extracellular matrix

animal cells have an ECM, networks of connective proteins (like collagen) outside the cell membrane. ECM is like an external support scaffold and how cells can adhere together better

Intercellular junctions

proteins also connect cells through intercellular junctions, sometimes creating open channels

Tight junctions

fasten together plasma membranes of adjacent cells, like gluing them together. it helps prevent substances leaking through a membrane layer. Stomach lining has these, so the stomach does not leak.

Adhering junctions

fasten cells to one another. these make tissues strong, they actually connect to the cytoskeletons inside cells, like sewing cells together. heart tissues and the skin have a lot of these, as they are subject to stretching and abrasion due to movement

Gap junctions

closable channels/tubes that connect the cytoplasm of adjoining animal cells. they let water, ions, and SMALL molecules to pass from cell to cell through the cytoplasm. heart muscles and nerve cells have a lot of these, to do coordinated actions

Plasmodesmata

In plants, plasmodesmata are passageways in the cell walls, connecting the cytoplasms of adjacent cells to allow communication