B2.2 & B2.3

cytoskeleton

cytoskeleton

network of proteins that provides shape and allows for movement of molecules around the cell

why is the cytoskeleton not considered an organelle?

This is not considered to be an organelle because the proteins are not enclosed by a membrane and are not involved in metabolic processes like other organelles

cell wall

protects against mechanical stresses and provides structural support

why is the cell wall not considered an organelle?

It is not considered to be an organelle because it is not surrounded by a membrane and, like the cytoskeleton, is not involved in metabolic processes

cytoplasm

a matrix that surrounds the organelles and other structures in the cell

why is the cytoplasm not considered an organelle?

It is not a discrete structure with a specific function. Still, it is essential for the cell’s survival

why transcription is kept seperate from translation in eukaryotes?

Eukaryotic mRNAs often need to be modified after synthesis by splicing (a process we will discuss later) before being translated by 80S ribosomes in the cytoplasm

how is prokaryote transcription and translation different from eukaryote?

in prokaryotic cells, transcription and translation both occur in the cytoplasm. the protein is produced soon after the mRNA is finished so no changes can be made.

why is there a difference between prokaryotic and eukaryotic transcription and translation?

-Prokaryotes are not as complex so they don’t need the same level of sophistication of gene regulation as eukaryotes

outline the 4 advantages of compartmentalization:

1.Enzymes and substrates can be more concentrated in a particular area.

2.Substances that could cause damage to the cell can be kept inside the membrane of an organelle. 

3.pH can be maintained at ideal level in a particular area for a particular process.

4.Organelles with their contents can be moved around within the cell.

outline the advantages of comparmentalization relating to lysosomes and phagocytotic vesicles:

-Keeps digestive enzyme harmful to the cell contained and safe

-Allow these enzymes to be at a high concentration for more efficient digestion of targets

-Allows proper pH and other conditions for optimal enzyme activity

single membrane organelles:

• rough er

• smooth er

• golgi apparatus

• lysosomes

• vesicles

• vacuoles

double membrane organelles:

• nucleus

• mitochondria

• chloroplast

5 adaptations of the mitochondria for production of ATP by aerobis respiration:

1. Intermembrane Space: Small space allows H⁺ to quickly accumulate

2.  Inner membrane: Contains ETC and ATP synthase for oxidative phosphorylation (ATP synthesis)

3. Matrix: Has appropriate enzyme and substrates at high concentrations and optimal pH for the Krebs cycle

4. Outer Membrane: Contains transport proteins for shuttling pyruvate into the mitochondrion

5. Cristae: Highly folded to increase the surface area so there can be a lot of the components needed to make ATP

6 adaptations of the chloroplast for photosynthesis:

1. Double membrane: Evidence for endosymbiosis

2. Thylakoid space (lumen): Small space inside the thylakoid allows H⁺ to quickly accumulate

3. Lamella: Connects and separates thylakoid stacks (grana)

4. Granum: Stacks of thylakoids that increase the surface area of thylakoid membrane

5. Thylakoid Membrane: Contains ETC and ATP synthase for photophosphorylation (ATP synthesis)

6. Stroma: Has appropriate enzyme and substrates at high concentrations and optimal pH for the Calvin cycle

outline 2 roles for the nuclear membrane

1. acts as a barrier between the genetic material inside the nucleus and the rest of the cell.

2. has an important role in regulating gene expression

when does the nuclear membrane break down and why?

During cell division, the nuclear envelope breaks down to allow for the separation of the chromosomes

3 parts of the nuclear membrane adn their functions:

1. Outer Membrane: Ribosomes attached to it and is joined with the rough endoplasmic reticulum

2. Inner Membrane: The inner membrane controls the entry and exit of signaling molecules and transcription factors

3. Nuclear Pore: Integral proteins that serve as channel proteins that also regulate mRNA leaving the nucleus for the RER or free ribosomes

the two types of 80S ribosmes:

1. Free: polypeptide is to be used inside the cytoplasm

2. Bound (to the RER): polypeptide is to be transported to a vesicle (lysosome), the Golgi for further processing, the plasma membrane, or outside the cell (secreted).

the role of a signal sequence on a polypeptide being translated

this signal allows the growing polypeptide to enter the lumen of RER so it can be modified and transported where needed

the steps in getting proteins from the RER to the golgi apparatus

•A piece of the RER membrane, with the protein inside, breaks off the RER membrane to form a vesicle.

•Instead of leaving the cell, as would happen in endocytosis, the vesicle travels to the Golgi apparatus.

the 4 common types of vesicles

1.Transport vesicles: transport materials from one part of the cell to another. Transport of proteins from RER to the Golgi apparatus.

2.Secretory vesicles: store and transport molecules to be secreted outside the cell

3.Lysosomes: Contain hydrolytic enzymes that can break down macromolecules such as proteins, carbohydrates and lipids.

•They play a key role in the degradation of cellular waste products and in removing damaged or aged organelles.

4.Peroxisomes: Similar to lysosomes but have a different set of enzymes that are involved in the detoxification of harmful compounds and lipid metabolism.

clathrin definition

a protein that plays an important, but not fully understood, role in the formation of vesicles in cells

fertilization

the fusion of male and female gametes to form a single cell

The fate of a fertilized cell

replicates repeatedly to generate an embryo

The types of cells in early stage embryos

unspecialized cells, as the embryo grows the cells develop along specific pathways and become specialized for different functions

what determines what happens to a cell

gradients of signaling chemicas determine what happens to a cell

2 major properties of stem cells

1. can divide indefinitely

2. may stay stem cells or differentiate into a specialized cell after cell division

stem cell’s niche

provide cells that could be grown outside of the body and used for many restorative purposes

Places where stem cells can be found

bone marrow, skin, liver, hair follicules

three types of stem cells

totipotent, pluripotent, unipotent, and multipotent

totipotent

A stem cell that has the ability to differentiate into any type of cell in the body, and can give rise to a complete organism

pluripotent

can differentiate into all body cells, but cannot give rise to a whole new organism

multipotent

can differentitate into a few closely related types of body cells

unipotent

can differentitate only into their associated cell type

sperm size adaptation

long but narrow to minimize resistance while swimming

egg size adaptation

large diameter and spherical to allow for storage of nutrients

red blood cells size adaptation

small with indented sides making it super skinny in the middle, allows it to squeeze through capillaries but has high SA/V ratio to load and unload O2 quickly

white blood cells size adaptation

10um in diameter but swell to 30um to make and secrete antibodies, extra volume is for cytoplasm with RER and golgi for making and secreting the antibodies

cerebellar granule tubes size adaptation

small in diameter with 2 long axons extended, small volume allows for the cerebellum to contain 50 billion of them

motor nuerons size adaptation

large in diameter, large size allows them to maintain a lot of ptotein synthessi to maintain immensely long axon, th elong axon allows the nuerons to interact with distant muscles

striated muscle fibers size adaptation

very large in diameter with long lengths as well, large size allows for the fiber to exert a greater force and contract by a greater length than smaller muscle cells

why cant a cell just keep growing and growing?

A cell cannot keep growing indefinitely due to limitations imposed by the surface area-to-volume ratio. As a cell grows, its volume increases faster than its surface area. This leads to a decrease in the efficiency of nutrient and waste exchange across the cell membrane. Eventually, the cell would not be able to sustain itself and perform essential functions, leading to cell death. Additionally, the cell's internal structures and organelles may not be able to support the increased volume, resulting in functional limitations.

proximal convolted tubules of the kidney SA/V adaptations

recieve large amounts of fluid filtered out of the kidney, reabsorbed most of the fluid including useful molecules like glucose or amino acids by channels and pumps and send it back to bloodstream

mitochondrion adaptation

cristae, increases electron transport

the two types of endothelial cells in an alveolus

type I pneumocytes and type II pneumocytes

type I pneumocytes SA/V adaptation

thinness of type I reduce distances for diffusion of CO2 and O2

type II pneumocytes SA/V adaptation

have many secretor vesicles in the cytoplasm that discharge surfactant to the alveolar lumen

sarcomeres

form units called myofibrils which in turn make up larger units called muscle fibers

adpatations in cardiac muscles

• single nucleus, lessens the cells energy requirements

• contains many mitochondria, high energy production

• branched fibers that connect cardio myocytes in a three-dimension via intercalating disks, allows electrical impulse to pass efficiently

adaptations in skeletal muscles

• many nuclei within the same cytoplasm, enabes the tissue to conduct mroe protein synthesis and repair

• unbranched fibers, enables precise control of voluntary muscle contractions in only 1 direction, important in controlled movement of the body

• many microfibrils, allows longer for the longer muscles needed for movement

adaptations of sperm cells

• haploid

• moves rapidly

• small, don’t waste energy making ltos of big cells

• no food reserves

adaptations of egg cells:

• haploid

• moves slowly

• large, few of them so don;t spend as much energy making them

• food reserve for embryo growth and development

2 adaptations of the egg that are specific to its function

1. have structures that allow them to receive only 1 sperm cell during fertilization (zona pellicida, binding proteins, cortical granules

2. have structures that allow for them to provide the resources needed for the zygote (yolk, mitochondria, centrioles)

2 adaptations of the sperm that are specific to its function

1. moves quickly (tail, midpiece w mitochondria)

2. have structures that they use to insert nucleus into egg (receptors to glycoproteins, acrosome, binding proteins)

skeletal muscle cells

Skeletal muscle cells, also known as myocytes, are specialized cells that make up skeletal muscle tissue. They are long, cylindrical cells with multiple nuclei and are responsible for voluntary movements of the body. Skeletal muscle cells are striated, meaning they have a striped appearance due to the arrangement of contractile proteins called actin and myosin. These cells are under conscious control and contract in response to signals from the nervous system. They play a crucial role in maintaining posture, generating body heat, and enabling movement.

cardiac muscle cells

Cardiac muscle cells, also known as cardiomyocytes, are specialized cells found in the heart. They are responsible for the contraction and relaxation of the heart, allowing it to pump blood throughout the body. These cells have unique features, such as intercalated discs that allow for synchronized contractions, and a high number of mitochondria to support their energy needs. Cardiac muscle cells are striated, meaning they have a striped appearance due to the arrangement of contractile proteins. They are involuntary muscles, meaning they contract without conscious control.

smooth muscle cells

Smooth muscle cells are a type of muscle cells found in the walls of various organs and structures in the body. They are characterized by their spindle-shaped appearance and lack of striations. Smooth muscle cells are involuntary, meaning they are not under conscious control. They play a crucial role in the contraction and relaxation of organs such as the blood vessels, digestive tract, and respiratory airways. Smooth muscle cells are responsible for various physiological processes, including regulating blood pressure, moving food through the digestive system, and facilitating breathing.