AP Bio: Khan Academy Unit 2 Cell Structure and Function

What do all cells have?

All cells have a membrane, ribosomes, genetic material (DNA/RNA)--most (mature red blood cells don't have DNA)

Cytoplasm: what's inside the cell membrane

- Eukaryotic: membrane bound nucleus

- Prokaryotic: DNA is not enclosed in a nucleus

Where are proteins created in the cell?

Pores of nucleus attached to endoplasmic reticulum—lts of surface area

DNA transcribed into mRNA → ribosome of E.R. → translated into proteins; some ribosomes are free in the cytoplasm

What is the Golgi apparatus?

- Detached from membrane

- Package molecules to be used outside the cell

What is the mitochondria?

- ATP is produced

- Have own DNA—endosymbiosis

What are chloroplasts?

Plants/algae cells have chloroplasts

- Has thylakoids

- Photosynthesis

What are valuoles?

- Water and enzymes

- Storage

- Can contain enzymes to digest things

- Can exist in plants or animals

What are lysosomes?

- Enzymes that break down waste products

What are peroxisomes?

Peroxisomes: carry out chemical reactions called oxidation reactions and produce hydrogen peroxide

How are eukaryotes different from prokaryotes?

Eukaryotes, unlike prokaryotic:

- Have membrane-bound nucleus

- Membrane-bound organelles

- Multiple linear chromosomes (as opposed to the singular chromosome of a prokaryotic cell)

What is the process of creating a protein in a cell?

- Genetic material leaves nucleus through pores

- mRNA goes to ribosome

- mRNA enters RER → enters the inside of the membrane of the RER → ribosome can attach

- In ER lumen

- At some point, can bud off→ enters vesicle, which leave endoplasmic reticulum

- Protein travels to Golgi through vesicle→ protein enters bodies→ maturation process→ ready to be used elsewhere or out of cell

What is the endomembrane system?

A group of membranes and organelles in eukaryotic cells that work together to modify, package, and transport lipids and proteins

Endomembrane system—all the membranes inside a cell

- Cell membrane itself, bilayers of phospholipids

- Same with nucleus membrane

- Endoplasmic reticulum is also part of the endomembrane system

System does not include mitochondria, chloroplasts, or peroxisomes

What does the rough ER do beside making proteins?

The rough ER also makes phospholipids for other cellular membranes, which are transported when the vesicle form

What is the smooth endoplasmic reticulum?

Functions:

- Synthesis of carbohydrates, lipids, and steroid hormones

- Detoxification of medications and poison

- Storage of calcium ions

Some patches within the rough ER; called transitional ER

What is the purpose of the Golgi apparatus (in eukaryotes and prokaryotes)?

In charge of sorting, tagging, packaging, and distributing proteins

Receiving sides is cis, opposite side is trans

Proteins and lipids undergo further modifications

- Short chains of sugar molecules might be added or removed

- Phosphate groups attached as tags

-Carbohydrate processing

Vesicles bud off trans

- Some go to other parts of cell or fuse with the plasma membrane

In plant cells, Golgi apparatus also makes polysaccharides

What is the purpose of lysosomes?

Contains digestive enzymes and acts as the organelle-recycling facility of an animal cell

- Some come from Golgi apparatus

What is phagocytosis?

Phagocytosis—a section of the macrophage's plasma membrane invaginates

- Invaginated section pinches off to form phagosome

- Fuses with lysosome, forming a combined compartment where digestive enzymes destroy the pathogen

What do vacuoles do in plants?

- In plants, the large vacuole stores water and wastes, isolates hazardous materials, and has enzymes that can break down macromolecules and cellular components

- Plant vacuoles also function in water balance and may be used to store compounds like toxins and pigments

What do peroxisomes do?

Peroxisome houses enzymes involved in oxidation reactions, which produce hydrogen peroxide (H2O2)

- The enzymes break down fatty acids and amino acids, and they also detoxify some substances that enter the body

- Are not part of the endomembrane system

- Don't receive vesicles from the Golgi apparatus

What is the structure of mitochondria

Outer membrane—phospholipid bilayer

- Porins in membrane; allow small molecules to pass through

Inner membrane

- Has folds to increase surface area→ processes of electron transport chain occur

- Folds = crista/cristae

- Also phospholipid bilayer

- Does not have porins

Location between membrane = intermembrane space

Inside inner membrane = matrix

- Higher protein concentration than cytosol

- Have their own DNA/mitochondrial DNA—Maternal DNA

- Has ribosomes, synthesizes some proteins

What is the endosymbiotic theory?

Endosymbiosis theory—started as bacteria that were engulfed by larger cells

- Chloroplasts

- Mitochondria

What is the role of chloroplasts in photosynthesis?

Only found in plants and photosynthetic algae

Carries out photosynthesis

- Light energy is collected and used to build sugars from carbon dioxide

- Energy in these sugars is harvested through cellular respiration, which happens in mitochondria

What are thylakoids?

Chloroplast has discs called thylakoids arranged in stacks called grana

- Thylakoid membranes contain light-harvesting complexes that include chlorophyll

- Inside thylakoid is thylakoid space/lumen

- Fluid that surrounds the thylakoids is stroma

How are mitochondria and cellular respiration connected?

Mitochondria

- Make ATP, the cell's main energy-carrying molecule

- Process of making ATP using chemical energy from fuels is called cellular respiration

- Multi-compartment structure→ useful for cellular respiration

What is the significance of the ratio of volume to surface area?

Volume increases faster than surface area.

The important point is that the surface area to the volume ratio gets smaller as the cell gets larger. Thus, if the cell grows beyond a certain limit, not enough material will be able to cross the membrane fast enough to accommodate the increased cellular volume.

What are cilia?

Tiny hair-like projections used to move a cell or to move things past a cell

What are flagella?

Slender, hair-like extensions used by parasites for locomotion

What are pseudopodia?

A pseudopod or pseudopodium is a temporary arm-like projection of a eukaryotic cell membrane that are developed in the direction of movement. Filled with cytoplasm, pseudopodia primarily consist of actin filaments and may also contain microtubules and intermediate filaments.