BIO SEM 1 UNIT 1

What are the three key points of cell theory?

Cells are the basic unit of life/structure and function of all living organisms; all living organisms are made up of one or more cells; cells are formed from other cells through cell division (they cannot form in isolation)

What is the difference between a prokaryote and a eukaryote?

Prokaryotes lack a nucleus and membrane-bound organelles (e.g. bacteria); eukaryotes have a nucleus and membrane-bound organelles (e.g. animals, plants, fungi, protists)

What is the difference between membrane-bound and non-membranous organelles?

Membrane-bound organelles are surrounded by a phospholipid bilayer membrane (e.g. nucleus, ER, Golgi, lysosomes, mitochondria, chloroplasts, vacuole); non-membranous organelles are not fully membrane-bound (e.g. ribosomes, centrosomes, cilia/flagella, cell wall)

What surrounds the nucleus, and what allows substances to pass through it?

The nuclear envelope (a double membrane); nuclear pores allow substances to move between the nucleus and cytoplasm

What is chromatin, and what are its two forms?

DNA wrapped around histone proteins; heterochromatin (tightly packed, inactive) and euchromatin (loosely packed, actively transcribed)

Where are ribosome subunits made, and what are the subunit sizes in prokaryotes vs eukaryotes?

Made in the nucleolus, assembled in the cytoplasm; prokaryotes = 30S + 50S (70S ribosome); eukaryotes = 40S + 60S (80S ribosome)

What is the function of rough ER, and what is attached to its surface?

Folds and processes proteins made by ribosomes (attached to its surface); proteins are packaged into vesicles for transport

What is the function of smooth ER?

Synthesises lipids (phospholipids, steroids) and detoxifies harmful organic compounds; no ribosomes attached

What is the Golgi body, and what does it do?

A stack of flattened sacs/membranes that modifies proteins and lipids (e.g. adding carbohydrate to form glycoproteins) and packages them into vesicles; also makes lysosomes

What do lysosomes contain, and what are their two main roles?

Contain lytic (digestive) enzymes; roles: 1) breaking down old cell components/unwanted particles, 2) autolysis (releasing enzymes to break down the cell, causing cell death)

What is the function of mitochondria, and what is ATP?

Site of (aerobic) respiration, producing most of the cell's ATP; ATP = adenosine triphosphate, the cell's energy currency, releasing energy when broken down to ADP + phosphate

What is the function of chloroplasts, and what are thylakoids/grana?

Site of photosynthesis; thylakoids are flattened membrane sacs inside the chloroplast, and a stack of thylakoids is called a granum (plural: grana)

What is a vacuole, what is inside it, and what is its function?

A membrane-bound, fluid-filled plant organelle; contains cell sap (sugars, salts, pigments, waste in water); maintains cell turgor/pressure, stores nutrients/pigments, and isolates waste

What is the cell wall made of in plants, bacteria, and fungi?

Plants = cellulose; bacteria = peptidoglycan/murein; fungi = chitin

How do cellulose molecules build up to form the plant cell wall?

~2000 cellulose molecules group together to form microfibrils; ~400 microfibrils group together to form macrofibrils, which are deposited in layers (primary then secondary cell wall)

What is the middle lamella and what are plasmodesmata?

The middle lamella connects the primary cell walls of two adjacent plant cells; plasmodesmata are pores in the cell wall allowing substances to pass directly between cells

What are centrosomes made of, and what is their function?

Two centrioles (made of microtubules/tubulin) at right angles, surrounded by pericentriolar material (PCM); they form the mitotic spindle and contribute to forming cilia and flagella

What is the "9+2" arrangement found in cilia and flagella?

Nine pairs (doublets) of microtubules arranged around a central pair of microtubules

How do eukaryotic flagella differ from bacterial flagella?

Eukaryotic flagella have the 9+2 microtubule structure and move with a bending motion; bacterial flagella are made of flagellin and rotate

Name the three types of cytoskeleton filament and what each is made of.

Microfilaments (actin), intermediate filaments (fibrous proteins), microtubules (tubulin)

List the main roles of the cytoskeleton.

Maintaining cell shape, supporting/positioning organelles, moving materials (e.g. vesicles) within the cell, and cell motility

What structures do animal cells lack that plant cells have, and vice versa?

Animal cells lack a cell wall, plastids/chloroplasts, and a permanent vacuole; plant cells usually lack cilia/flagella and centrioles

What is a tissue, an organ, and an organ system?

Tissue = group of similar cells working together for a function; organ = different tissues combined for a specific function; organ system = organs working together for a life process (e.g. digestive system)

What are bacterial plasmids and what is the bacterial capsule?

Plasmids = small loops of DNA separate from the main chromosome; capsule = slime layer that prevents drying out and helps evade the host immune system

Compare the size of prokaryotic and eukaryotic cells.

Prokaryotes: 0.1-10 μm; Eukaryotes: 10-100 μm

Compare DNA structure and organisation in prokaryotes vs eukaryotes.

Prokaryotic DNA is circular, free in the cytoplasm, and not associated with histones; eukaryotic DNA is linear, enclosed in a nucleus, and coiled around histone proteins (chromatin); only eukaryotic DNA condenses visibly during division

Do prokaryotes have membrane-bound organelles?

No

Compare ribosome size between prokaryotes and eukaryotes.

Prokaryotes have smaller 70S ribosomes; eukaryotes have larger 80S ribosomes

What is the endosymbiotic theory?

Mitochondria and plastids are descended from free-living prokaryotes that were taken up by ancestral eukaryotic cells, avoided destruction, and formed a mutually beneficial relationship with the host

List three pieces of evidence supporting the endosymbiotic theory.

1) Mitochondria/plastids contain their own DNA; 2) they have their own (70S) ribosomes; 3) they duplicate by binary fission, the same process bacteria use