Cell Review

Cells The Cell Theory All living things are made of one or more CELLS. Cells are the basic unit of structure and function in an organism. New cells are produced from existing cells.

2 types of cells Prokaryotes Eukaryotes Cells without a nucleus or organelles surrounded by membranes Eukaryotes Cells with a nucleus and organelles surrounded by membranes.

Prokaryotes Single celled organism Has DNA that is circular floating all around in the cytoplasm Only has ribosomes and no other membrane bound organelles Most common = bacteria Some can make their own food, most get food from other sources

Eukaryotes There can be singled celled eukaryotes as well as multicellular Highly organized More complex than prokaryotes

Cell membrane (plasma membrane) Made mainly of phospholipids (2 layers) and proteins Outside of cell Inside (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains

Cell membrane made of: Phospholipids have hydrophobic tails made of lipids and hydrophilic heads. 3 kinds of proteins- channel-provides a path for materials to move in and out marker- used for recognition receptor- receive signals

Cell membrane Acts as a boundary Controls what enters and leaves cell Fluid (fluid mosaic model) Molecules in cell membranes are constantly moving and changing (ex. cholesterol and carbohydrates)

Nucleus LARGEST organelle in animal cells Surrounded by nuclear envelope Contains nuclear pores = openings that allow molecules to move in and out of nucleus Contains genetic material (DNA) Control center of the cell

Nucleolus Dark spot in nucleus Assembles RNA and also ribosomes

Cytoskeleton Helps cell maintain shape Help move organelles around Made of proteins Microfilaments Microtubules

Centrioles Made of microtubules Only seen in animal cells during cell division Function: Guide chromosomes during PMAT

Mitochondria “Powerplant of cell” Site of cellular respiration Burns glucose to release energy Stores energy as ATP Surrounded by double membrane Inner membrane = cristae

Ribosomes Can be free in cytoplasm or attached to rough ER Made of rRNA Function: assembles proteins Called the site of protein synthesis

Endoplasmic reticulum (internal network of membranes) Rough ER Attached ribosomes make proteins which are modified and transported to Golgi for export Smooth ER Makes membrane lipids (steroids) Regulates calcium in muscles Breaks down toxins in liver

Golgi Apparatus Looks like a “stack of pancakes” Made of membranes Modify, sort, and package substances from ER for storage or export out of cell

Lysosomes Sac containing digestive enzymes Digests food molecules and unwanted cells/cell parts Plays a role in apoptosis “programed cell death” Cell suicide for the good of the organism

Movement Pseudopodia = “false feet” help amoebas with movement and eating (phagocytosis) Cilia = many and short microtubules (little hairs) Move cells Move substances past cells Flagella = few and long microtubules (like a tail)

What’s special about plant cells? Cell wall HUGE central vacuole Chloroplasts No centrioles!!

Cell wall Found outside the cell membrane Provides support and protection Made of Cellulose (carbohydrate) makes plant sturdy Bacteria have cell walls made of peptidoglycan instead Cell walls of fungi are made of chitin

Vacuoles Storage space for: proteins, carbohydrates, water, waste Contractile vacuoles control excess water in a paramecium (homeostasis) Huge in plant cells, small animal cells, not in bacteria

Chloroplast Surrounded by double membrane Thylakoids = membrane sacs inside Contains chlorophyll where photosynthesis happens Found photosynthetic cells (plants, some bacteria and protozoans)

Molecule Movement and Cells Passive Transport = does not require energy by the cell Active transport = requires energy!

Passive transport No energy required Move due to gradient Differences in concentration, pressure, charge Move to equalize gradient (equilibrium) High concentration moves toward low concentration 3 Types Diffusion, osmosis, facilitated diffusion

Diffusion Molecules move to equalize concentration

Osmosis Special form of diffusion Fluid flows from lower solute concentration Always involves movement of water Into cell Out of cell

Hypotonic = solutes in cell more than outside, fluid will flow into cell

Isotonic = solutes equal inside and out of cell

Hypertonic = solutes greater outside cell, fluid will flow out of cell

Facilitated Diffusion Channels (are specific) help molecule or ions enter or leave the cell Channels usually are transport proteins

Active transport Molecular movement Requires energy (against gradient) Example: sodium-potassium pump

Endocytosis Phagocytosis – cell eating Pinocytosis – cell drinking

Exocytosis Reverse of endocytosis Cell discharge material

Cellular reproduction 5 ways 1. Fission 2. Budding 3. Vegetative propagation 4. Mitosis 5. Meiosis

Binary Fission Prokaryotes (bacteria) Asexual reproduction Cell makes copy of DNA and grows in size Membrane will divide and two new cells formed

Budding Asexual reproduction Hydra bud to form new hydra Yeast cells undergo budding

Vegetative propagation Asexual reproduction in plants Runners will grow off from the parent plant and root to form a new identical plant.